xref: /openbmc/linux/drivers/md/raid5.c (revision fd589a8f)
1 /*
2  * raid5.c : Multiple Devices driver for Linux
3  *	   Copyright (C) 1996, 1997 Ingo Molnar, Miguel de Icaza, Gadi Oxman
4  *	   Copyright (C) 1999, 2000 Ingo Molnar
5  *	   Copyright (C) 2002, 2003 H. Peter Anvin
6  *
7  * RAID-4/5/6 management functions.
8  * Thanks to Penguin Computing for making the RAID-6 development possible
9  * by donating a test server!
10  *
11  * This program is free software; you can redistribute it and/or modify
12  * it under the terms of the GNU General Public License as published by
13  * the Free Software Foundation; either version 2, or (at your option)
14  * any later version.
15  *
16  * You should have received a copy of the GNU General Public License
17  * (for example /usr/src/linux/COPYING); if not, write to the Free
18  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19  */
20 
21 /*
22  * BITMAP UNPLUGGING:
23  *
24  * The sequencing for updating the bitmap reliably is a little
25  * subtle (and I got it wrong the first time) so it deserves some
26  * explanation.
27  *
28  * We group bitmap updates into batches.  Each batch has a number.
29  * We may write out several batches at once, but that isn't very important.
30  * conf->bm_write is the number of the last batch successfully written.
31  * conf->bm_flush is the number of the last batch that was closed to
32  *    new additions.
33  * When we discover that we will need to write to any block in a stripe
34  * (in add_stripe_bio) we update the in-memory bitmap and record in sh->bm_seq
35  * the number of the batch it will be in. This is bm_flush+1.
36  * When we are ready to do a write, if that batch hasn't been written yet,
37  *   we plug the array and queue the stripe for later.
38  * When an unplug happens, we increment bm_flush, thus closing the current
39  *   batch.
40  * When we notice that bm_flush > bm_write, we write out all pending updates
41  * to the bitmap, and advance bm_write to where bm_flush was.
42  * This may occasionally write a bit out twice, but is sure never to
43  * miss any bits.
44  */
45 
46 #include <linux/blkdev.h>
47 #include <linux/kthread.h>
48 #include <linux/raid/pq.h>
49 #include <linux/async_tx.h>
50 #include <linux/seq_file.h>
51 #include "md.h"
52 #include "raid5.h"
53 #include "bitmap.h"
54 
55 /*
56  * Stripe cache
57  */
58 
59 #define NR_STRIPES		256
60 #define STRIPE_SIZE		PAGE_SIZE
61 #define STRIPE_SHIFT		(PAGE_SHIFT - 9)
62 #define STRIPE_SECTORS		(STRIPE_SIZE>>9)
63 #define	IO_THRESHOLD		1
64 #define BYPASS_THRESHOLD	1
65 #define NR_HASH			(PAGE_SIZE / sizeof(struct hlist_head))
66 #define HASH_MASK		(NR_HASH - 1)
67 
68 #define stripe_hash(conf, sect)	(&((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK]))
69 
70 /* bio's attached to a stripe+device for I/O are linked together in bi_sector
71  * order without overlap.  There may be several bio's per stripe+device, and
72  * a bio could span several devices.
73  * When walking this list for a particular stripe+device, we must never proceed
74  * beyond a bio that extends past this device, as the next bio might no longer
75  * be valid.
76  * This macro is used to determine the 'next' bio in the list, given the sector
77  * of the current stripe+device
78  */
79 #define r5_next_bio(bio, sect) ( ( (bio)->bi_sector + ((bio)->bi_size>>9) < sect + STRIPE_SECTORS) ? (bio)->bi_next : NULL)
80 /*
81  * The following can be used to debug the driver
82  */
83 #define RAID5_PARANOIA	1
84 #if RAID5_PARANOIA && defined(CONFIG_SMP)
85 # define CHECK_DEVLOCK() assert_spin_locked(&conf->device_lock)
86 #else
87 # define CHECK_DEVLOCK()
88 #endif
89 
90 #ifdef DEBUG
91 #define inline
92 #define __inline__
93 #endif
94 
95 #define printk_rl(args...) ((void) (printk_ratelimit() && printk(args)))
96 
97 /*
98  * We maintain a biased count of active stripes in the bottom 16 bits of
99  * bi_phys_segments, and a count of processed stripes in the upper 16 bits
100  */
101 static inline int raid5_bi_phys_segments(struct bio *bio)
102 {
103 	return bio->bi_phys_segments & 0xffff;
104 }
105 
106 static inline int raid5_bi_hw_segments(struct bio *bio)
107 {
108 	return (bio->bi_phys_segments >> 16) & 0xffff;
109 }
110 
111 static inline int raid5_dec_bi_phys_segments(struct bio *bio)
112 {
113 	--bio->bi_phys_segments;
114 	return raid5_bi_phys_segments(bio);
115 }
116 
117 static inline int raid5_dec_bi_hw_segments(struct bio *bio)
118 {
119 	unsigned short val = raid5_bi_hw_segments(bio);
120 
121 	--val;
122 	bio->bi_phys_segments = (val << 16) | raid5_bi_phys_segments(bio);
123 	return val;
124 }
125 
126 static inline void raid5_set_bi_hw_segments(struct bio *bio, unsigned int cnt)
127 {
128 	bio->bi_phys_segments = raid5_bi_phys_segments(bio) || (cnt << 16);
129 }
130 
131 /* Find first data disk in a raid6 stripe */
132 static inline int raid6_d0(struct stripe_head *sh)
133 {
134 	if (sh->ddf_layout)
135 		/* ddf always start from first device */
136 		return 0;
137 	/* md starts just after Q block */
138 	if (sh->qd_idx == sh->disks - 1)
139 		return 0;
140 	else
141 		return sh->qd_idx + 1;
142 }
143 static inline int raid6_next_disk(int disk, int raid_disks)
144 {
145 	disk++;
146 	return (disk < raid_disks) ? disk : 0;
147 }
148 
149 /* When walking through the disks in a raid5, starting at raid6_d0,
150  * We need to map each disk to a 'slot', where the data disks are slot
151  * 0 .. raid_disks-3, the parity disk is raid_disks-2 and the Q disk
152  * is raid_disks-1.  This help does that mapping.
153  */
154 static int raid6_idx_to_slot(int idx, struct stripe_head *sh,
155 			     int *count, int syndrome_disks)
156 {
157 	int slot;
158 
159 	if (idx == sh->pd_idx)
160 		return syndrome_disks;
161 	if (idx == sh->qd_idx)
162 		return syndrome_disks + 1;
163 	slot = (*count)++;
164 	return slot;
165 }
166 
167 static void return_io(struct bio *return_bi)
168 {
169 	struct bio *bi = return_bi;
170 	while (bi) {
171 
172 		return_bi = bi->bi_next;
173 		bi->bi_next = NULL;
174 		bi->bi_size = 0;
175 		bio_endio(bi, 0);
176 		bi = return_bi;
177 	}
178 }
179 
180 static void print_raid5_conf (raid5_conf_t *conf);
181 
182 static int stripe_operations_active(struct stripe_head *sh)
183 {
184 	return sh->check_state || sh->reconstruct_state ||
185 	       test_bit(STRIPE_BIOFILL_RUN, &sh->state) ||
186 	       test_bit(STRIPE_COMPUTE_RUN, &sh->state);
187 }
188 
189 static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
190 {
191 	if (atomic_dec_and_test(&sh->count)) {
192 		BUG_ON(!list_empty(&sh->lru));
193 		BUG_ON(atomic_read(&conf->active_stripes)==0);
194 		if (test_bit(STRIPE_HANDLE, &sh->state)) {
195 			if (test_bit(STRIPE_DELAYED, &sh->state)) {
196 				list_add_tail(&sh->lru, &conf->delayed_list);
197 				blk_plug_device(conf->mddev->queue);
198 			} else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
199 				   sh->bm_seq - conf->seq_write > 0) {
200 				list_add_tail(&sh->lru, &conf->bitmap_list);
201 				blk_plug_device(conf->mddev->queue);
202 			} else {
203 				clear_bit(STRIPE_BIT_DELAY, &sh->state);
204 				list_add_tail(&sh->lru, &conf->handle_list);
205 			}
206 			md_wakeup_thread(conf->mddev->thread);
207 		} else {
208 			BUG_ON(stripe_operations_active(sh));
209 			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
210 				atomic_dec(&conf->preread_active_stripes);
211 				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
212 					md_wakeup_thread(conf->mddev->thread);
213 			}
214 			atomic_dec(&conf->active_stripes);
215 			if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
216 				list_add_tail(&sh->lru, &conf->inactive_list);
217 				wake_up(&conf->wait_for_stripe);
218 				if (conf->retry_read_aligned)
219 					md_wakeup_thread(conf->mddev->thread);
220 			}
221 		}
222 	}
223 }
224 
225 static void release_stripe(struct stripe_head *sh)
226 {
227 	raid5_conf_t *conf = sh->raid_conf;
228 	unsigned long flags;
229 
230 	spin_lock_irqsave(&conf->device_lock, flags);
231 	__release_stripe(conf, sh);
232 	spin_unlock_irqrestore(&conf->device_lock, flags);
233 }
234 
235 static inline void remove_hash(struct stripe_head *sh)
236 {
237 	pr_debug("remove_hash(), stripe %llu\n",
238 		(unsigned long long)sh->sector);
239 
240 	hlist_del_init(&sh->hash);
241 }
242 
243 static inline void insert_hash(raid5_conf_t *conf, struct stripe_head *sh)
244 {
245 	struct hlist_head *hp = stripe_hash(conf, sh->sector);
246 
247 	pr_debug("insert_hash(), stripe %llu\n",
248 		(unsigned long long)sh->sector);
249 
250 	CHECK_DEVLOCK();
251 	hlist_add_head(&sh->hash, hp);
252 }
253 
254 
255 /* find an idle stripe, make sure it is unhashed, and return it. */
256 static struct stripe_head *get_free_stripe(raid5_conf_t *conf)
257 {
258 	struct stripe_head *sh = NULL;
259 	struct list_head *first;
260 
261 	CHECK_DEVLOCK();
262 	if (list_empty(&conf->inactive_list))
263 		goto out;
264 	first = conf->inactive_list.next;
265 	sh = list_entry(first, struct stripe_head, lru);
266 	list_del_init(first);
267 	remove_hash(sh);
268 	atomic_inc(&conf->active_stripes);
269 out:
270 	return sh;
271 }
272 
273 static void shrink_buffers(struct stripe_head *sh, int num)
274 {
275 	struct page *p;
276 	int i;
277 
278 	for (i=0; i<num ; i++) {
279 		p = sh->dev[i].page;
280 		if (!p)
281 			continue;
282 		sh->dev[i].page = NULL;
283 		put_page(p);
284 	}
285 }
286 
287 static int grow_buffers(struct stripe_head *sh, int num)
288 {
289 	int i;
290 
291 	for (i=0; i<num; i++) {
292 		struct page *page;
293 
294 		if (!(page = alloc_page(GFP_KERNEL))) {
295 			return 1;
296 		}
297 		sh->dev[i].page = page;
298 	}
299 	return 0;
300 }
301 
302 static void raid5_build_block(struct stripe_head *sh, int i, int previous);
303 static void stripe_set_idx(sector_t stripe, raid5_conf_t *conf, int previous,
304 			    struct stripe_head *sh);
305 
306 static void init_stripe(struct stripe_head *sh, sector_t sector, int previous)
307 {
308 	raid5_conf_t *conf = sh->raid_conf;
309 	int i;
310 
311 	BUG_ON(atomic_read(&sh->count) != 0);
312 	BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
313 	BUG_ON(stripe_operations_active(sh));
314 
315 	CHECK_DEVLOCK();
316 	pr_debug("init_stripe called, stripe %llu\n",
317 		(unsigned long long)sh->sector);
318 
319 	remove_hash(sh);
320 
321 	sh->generation = conf->generation - previous;
322 	sh->disks = previous ? conf->previous_raid_disks : conf->raid_disks;
323 	sh->sector = sector;
324 	stripe_set_idx(sector, conf, previous, sh);
325 	sh->state = 0;
326 
327 
328 	for (i = sh->disks; i--; ) {
329 		struct r5dev *dev = &sh->dev[i];
330 
331 		if (dev->toread || dev->read || dev->towrite || dev->written ||
332 		    test_bit(R5_LOCKED, &dev->flags)) {
333 			printk(KERN_ERR "sector=%llx i=%d %p %p %p %p %d\n",
334 			       (unsigned long long)sh->sector, i, dev->toread,
335 			       dev->read, dev->towrite, dev->written,
336 			       test_bit(R5_LOCKED, &dev->flags));
337 			BUG();
338 		}
339 		dev->flags = 0;
340 		raid5_build_block(sh, i, previous);
341 	}
342 	insert_hash(conf, sh);
343 }
344 
345 static struct stripe_head *__find_stripe(raid5_conf_t *conf, sector_t sector,
346 					 short generation)
347 {
348 	struct stripe_head *sh;
349 	struct hlist_node *hn;
350 
351 	CHECK_DEVLOCK();
352 	pr_debug("__find_stripe, sector %llu\n", (unsigned long long)sector);
353 	hlist_for_each_entry(sh, hn, stripe_hash(conf, sector), hash)
354 		if (sh->sector == sector && sh->generation == generation)
355 			return sh;
356 	pr_debug("__stripe %llu not in cache\n", (unsigned long long)sector);
357 	return NULL;
358 }
359 
360 static void unplug_slaves(mddev_t *mddev);
361 static void raid5_unplug_device(struct request_queue *q);
362 
363 static struct stripe_head *
364 get_active_stripe(raid5_conf_t *conf, sector_t sector,
365 		  int previous, int noblock, int noquiesce)
366 {
367 	struct stripe_head *sh;
368 
369 	pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector);
370 
371 	spin_lock_irq(&conf->device_lock);
372 
373 	do {
374 		wait_event_lock_irq(conf->wait_for_stripe,
375 				    conf->quiesce == 0 || noquiesce,
376 				    conf->device_lock, /* nothing */);
377 		sh = __find_stripe(conf, sector, conf->generation - previous);
378 		if (!sh) {
379 			if (!conf->inactive_blocked)
380 				sh = get_free_stripe(conf);
381 			if (noblock && sh == NULL)
382 				break;
383 			if (!sh) {
384 				conf->inactive_blocked = 1;
385 				wait_event_lock_irq(conf->wait_for_stripe,
386 						    !list_empty(&conf->inactive_list) &&
387 						    (atomic_read(&conf->active_stripes)
388 						     < (conf->max_nr_stripes *3/4)
389 						     || !conf->inactive_blocked),
390 						    conf->device_lock,
391 						    raid5_unplug_device(conf->mddev->queue)
392 					);
393 				conf->inactive_blocked = 0;
394 			} else
395 				init_stripe(sh, sector, previous);
396 		} else {
397 			if (atomic_read(&sh->count)) {
398 				BUG_ON(!list_empty(&sh->lru)
399 				    && !test_bit(STRIPE_EXPANDING, &sh->state));
400 			} else {
401 				if (!test_bit(STRIPE_HANDLE, &sh->state))
402 					atomic_inc(&conf->active_stripes);
403 				if (list_empty(&sh->lru) &&
404 				    !test_bit(STRIPE_EXPANDING, &sh->state))
405 					BUG();
406 				list_del_init(&sh->lru);
407 			}
408 		}
409 	} while (sh == NULL);
410 
411 	if (sh)
412 		atomic_inc(&sh->count);
413 
414 	spin_unlock_irq(&conf->device_lock);
415 	return sh;
416 }
417 
418 static void
419 raid5_end_read_request(struct bio *bi, int error);
420 static void
421 raid5_end_write_request(struct bio *bi, int error);
422 
423 static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
424 {
425 	raid5_conf_t *conf = sh->raid_conf;
426 	int i, disks = sh->disks;
427 
428 	might_sleep();
429 
430 	for (i = disks; i--; ) {
431 		int rw;
432 		struct bio *bi;
433 		mdk_rdev_t *rdev;
434 		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
435 			rw = WRITE;
436 		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
437 			rw = READ;
438 		else
439 			continue;
440 
441 		bi = &sh->dev[i].req;
442 
443 		bi->bi_rw = rw;
444 		if (rw == WRITE)
445 			bi->bi_end_io = raid5_end_write_request;
446 		else
447 			bi->bi_end_io = raid5_end_read_request;
448 
449 		rcu_read_lock();
450 		rdev = rcu_dereference(conf->disks[i].rdev);
451 		if (rdev && test_bit(Faulty, &rdev->flags))
452 			rdev = NULL;
453 		if (rdev)
454 			atomic_inc(&rdev->nr_pending);
455 		rcu_read_unlock();
456 
457 		if (rdev) {
458 			if (s->syncing || s->expanding || s->expanded)
459 				md_sync_acct(rdev->bdev, STRIPE_SECTORS);
460 
461 			set_bit(STRIPE_IO_STARTED, &sh->state);
462 
463 			bi->bi_bdev = rdev->bdev;
464 			pr_debug("%s: for %llu schedule op %ld on disc %d\n",
465 				__func__, (unsigned long long)sh->sector,
466 				bi->bi_rw, i);
467 			atomic_inc(&sh->count);
468 			bi->bi_sector = sh->sector + rdev->data_offset;
469 			bi->bi_flags = 1 << BIO_UPTODATE;
470 			bi->bi_vcnt = 1;
471 			bi->bi_max_vecs = 1;
472 			bi->bi_idx = 0;
473 			bi->bi_io_vec = &sh->dev[i].vec;
474 			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
475 			bi->bi_io_vec[0].bv_offset = 0;
476 			bi->bi_size = STRIPE_SIZE;
477 			bi->bi_next = NULL;
478 			if (rw == WRITE &&
479 			    test_bit(R5_ReWrite, &sh->dev[i].flags))
480 				atomic_add(STRIPE_SECTORS,
481 					&rdev->corrected_errors);
482 			generic_make_request(bi);
483 		} else {
484 			if (rw == WRITE)
485 				set_bit(STRIPE_DEGRADED, &sh->state);
486 			pr_debug("skip op %ld on disc %d for sector %llu\n",
487 				bi->bi_rw, i, (unsigned long long)sh->sector);
488 			clear_bit(R5_LOCKED, &sh->dev[i].flags);
489 			set_bit(STRIPE_HANDLE, &sh->state);
490 		}
491 	}
492 }
493 
494 static struct dma_async_tx_descriptor *
495 async_copy_data(int frombio, struct bio *bio, struct page *page,
496 	sector_t sector, struct dma_async_tx_descriptor *tx)
497 {
498 	struct bio_vec *bvl;
499 	struct page *bio_page;
500 	int i;
501 	int page_offset;
502 
503 	if (bio->bi_sector >= sector)
504 		page_offset = (signed)(bio->bi_sector - sector) * 512;
505 	else
506 		page_offset = (signed)(sector - bio->bi_sector) * -512;
507 	bio_for_each_segment(bvl, bio, i) {
508 		int len = bio_iovec_idx(bio, i)->bv_len;
509 		int clen;
510 		int b_offset = 0;
511 
512 		if (page_offset < 0) {
513 			b_offset = -page_offset;
514 			page_offset += b_offset;
515 			len -= b_offset;
516 		}
517 
518 		if (len > 0 && page_offset + len > STRIPE_SIZE)
519 			clen = STRIPE_SIZE - page_offset;
520 		else
521 			clen = len;
522 
523 		if (clen > 0) {
524 			b_offset += bio_iovec_idx(bio, i)->bv_offset;
525 			bio_page = bio_iovec_idx(bio, i)->bv_page;
526 			if (frombio)
527 				tx = async_memcpy(page, bio_page, page_offset,
528 					b_offset, clen,
529 					ASYNC_TX_DEP_ACK,
530 					tx, NULL, NULL);
531 			else
532 				tx = async_memcpy(bio_page, page, b_offset,
533 					page_offset, clen,
534 					ASYNC_TX_DEP_ACK,
535 					tx, NULL, NULL);
536 		}
537 		if (clen < len) /* hit end of page */
538 			break;
539 		page_offset +=  len;
540 	}
541 
542 	return tx;
543 }
544 
545 static void ops_complete_biofill(void *stripe_head_ref)
546 {
547 	struct stripe_head *sh = stripe_head_ref;
548 	struct bio *return_bi = NULL;
549 	raid5_conf_t *conf = sh->raid_conf;
550 	int i;
551 
552 	pr_debug("%s: stripe %llu\n", __func__,
553 		(unsigned long long)sh->sector);
554 
555 	/* clear completed biofills */
556 	spin_lock_irq(&conf->device_lock);
557 	for (i = sh->disks; i--; ) {
558 		struct r5dev *dev = &sh->dev[i];
559 
560 		/* acknowledge completion of a biofill operation */
561 		/* and check if we need to reply to a read request,
562 		 * new R5_Wantfill requests are held off until
563 		 * !STRIPE_BIOFILL_RUN
564 		 */
565 		if (test_and_clear_bit(R5_Wantfill, &dev->flags)) {
566 			struct bio *rbi, *rbi2;
567 
568 			BUG_ON(!dev->read);
569 			rbi = dev->read;
570 			dev->read = NULL;
571 			while (rbi && rbi->bi_sector <
572 				dev->sector + STRIPE_SECTORS) {
573 				rbi2 = r5_next_bio(rbi, dev->sector);
574 				if (!raid5_dec_bi_phys_segments(rbi)) {
575 					rbi->bi_next = return_bi;
576 					return_bi = rbi;
577 				}
578 				rbi = rbi2;
579 			}
580 		}
581 	}
582 	spin_unlock_irq(&conf->device_lock);
583 	clear_bit(STRIPE_BIOFILL_RUN, &sh->state);
584 
585 	return_io(return_bi);
586 
587 	set_bit(STRIPE_HANDLE, &sh->state);
588 	release_stripe(sh);
589 }
590 
591 static void ops_run_biofill(struct stripe_head *sh)
592 {
593 	struct dma_async_tx_descriptor *tx = NULL;
594 	raid5_conf_t *conf = sh->raid_conf;
595 	int i;
596 
597 	pr_debug("%s: stripe %llu\n", __func__,
598 		(unsigned long long)sh->sector);
599 
600 	for (i = sh->disks; i--; ) {
601 		struct r5dev *dev = &sh->dev[i];
602 		if (test_bit(R5_Wantfill, &dev->flags)) {
603 			struct bio *rbi;
604 			spin_lock_irq(&conf->device_lock);
605 			dev->read = rbi = dev->toread;
606 			dev->toread = NULL;
607 			spin_unlock_irq(&conf->device_lock);
608 			while (rbi && rbi->bi_sector <
609 				dev->sector + STRIPE_SECTORS) {
610 				tx = async_copy_data(0, rbi, dev->page,
611 					dev->sector, tx);
612 				rbi = r5_next_bio(rbi, dev->sector);
613 			}
614 		}
615 	}
616 
617 	atomic_inc(&sh->count);
618 	async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
619 		ops_complete_biofill, sh);
620 }
621 
622 static void ops_complete_compute5(void *stripe_head_ref)
623 {
624 	struct stripe_head *sh = stripe_head_ref;
625 	int target = sh->ops.target;
626 	struct r5dev *tgt = &sh->dev[target];
627 
628 	pr_debug("%s: stripe %llu\n", __func__,
629 		(unsigned long long)sh->sector);
630 
631 	set_bit(R5_UPTODATE, &tgt->flags);
632 	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
633 	clear_bit(R5_Wantcompute, &tgt->flags);
634 	clear_bit(STRIPE_COMPUTE_RUN, &sh->state);
635 	if (sh->check_state == check_state_compute_run)
636 		sh->check_state = check_state_compute_result;
637 	set_bit(STRIPE_HANDLE, &sh->state);
638 	release_stripe(sh);
639 }
640 
641 static struct dma_async_tx_descriptor *ops_run_compute5(struct stripe_head *sh)
642 {
643 	/* kernel stack size limits the total number of disks */
644 	int disks = sh->disks;
645 	struct page *xor_srcs[disks];
646 	int target = sh->ops.target;
647 	struct r5dev *tgt = &sh->dev[target];
648 	struct page *xor_dest = tgt->page;
649 	int count = 0;
650 	struct dma_async_tx_descriptor *tx;
651 	int i;
652 
653 	pr_debug("%s: stripe %llu block: %d\n",
654 		__func__, (unsigned long long)sh->sector, target);
655 	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
656 
657 	for (i = disks; i--; )
658 		if (i != target)
659 			xor_srcs[count++] = sh->dev[i].page;
660 
661 	atomic_inc(&sh->count);
662 
663 	if (unlikely(count == 1))
664 		tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
665 			0, NULL, ops_complete_compute5, sh);
666 	else
667 		tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
668 			ASYNC_TX_XOR_ZERO_DST, NULL,
669 			ops_complete_compute5, sh);
670 
671 	return tx;
672 }
673 
674 static void ops_complete_prexor(void *stripe_head_ref)
675 {
676 	struct stripe_head *sh = stripe_head_ref;
677 
678 	pr_debug("%s: stripe %llu\n", __func__,
679 		(unsigned long long)sh->sector);
680 }
681 
682 static struct dma_async_tx_descriptor *
683 ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
684 {
685 	/* kernel stack size limits the total number of disks */
686 	int disks = sh->disks;
687 	struct page *xor_srcs[disks];
688 	int count = 0, pd_idx = sh->pd_idx, i;
689 
690 	/* existing parity data subtracted */
691 	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
692 
693 	pr_debug("%s: stripe %llu\n", __func__,
694 		(unsigned long long)sh->sector);
695 
696 	for (i = disks; i--; ) {
697 		struct r5dev *dev = &sh->dev[i];
698 		/* Only process blocks that are known to be uptodate */
699 		if (test_bit(R5_Wantdrain, &dev->flags))
700 			xor_srcs[count++] = dev->page;
701 	}
702 
703 	tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
704 		ASYNC_TX_DEP_ACK | ASYNC_TX_XOR_DROP_DST, tx,
705 		ops_complete_prexor, sh);
706 
707 	return tx;
708 }
709 
710 static struct dma_async_tx_descriptor *
711 ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
712 {
713 	int disks = sh->disks;
714 	int i;
715 
716 	pr_debug("%s: stripe %llu\n", __func__,
717 		(unsigned long long)sh->sector);
718 
719 	for (i = disks; i--; ) {
720 		struct r5dev *dev = &sh->dev[i];
721 		struct bio *chosen;
722 
723 		if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
724 			struct bio *wbi;
725 
726 			spin_lock(&sh->lock);
727 			chosen = dev->towrite;
728 			dev->towrite = NULL;
729 			BUG_ON(dev->written);
730 			wbi = dev->written = chosen;
731 			spin_unlock(&sh->lock);
732 
733 			while (wbi && wbi->bi_sector <
734 				dev->sector + STRIPE_SECTORS) {
735 				tx = async_copy_data(1, wbi, dev->page,
736 					dev->sector, tx);
737 				wbi = r5_next_bio(wbi, dev->sector);
738 			}
739 		}
740 	}
741 
742 	return tx;
743 }
744 
745 static void ops_complete_postxor(void *stripe_head_ref)
746 {
747 	struct stripe_head *sh = stripe_head_ref;
748 	int disks = sh->disks, i, pd_idx = sh->pd_idx;
749 
750 	pr_debug("%s: stripe %llu\n", __func__,
751 		(unsigned long long)sh->sector);
752 
753 	for (i = disks; i--; ) {
754 		struct r5dev *dev = &sh->dev[i];
755 		if (dev->written || i == pd_idx)
756 			set_bit(R5_UPTODATE, &dev->flags);
757 	}
758 
759 	if (sh->reconstruct_state == reconstruct_state_drain_run)
760 		sh->reconstruct_state = reconstruct_state_drain_result;
761 	else if (sh->reconstruct_state == reconstruct_state_prexor_drain_run)
762 		sh->reconstruct_state = reconstruct_state_prexor_drain_result;
763 	else {
764 		BUG_ON(sh->reconstruct_state != reconstruct_state_run);
765 		sh->reconstruct_state = reconstruct_state_result;
766 	}
767 
768 	set_bit(STRIPE_HANDLE, &sh->state);
769 	release_stripe(sh);
770 }
771 
772 static void
773 ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
774 {
775 	/* kernel stack size limits the total number of disks */
776 	int disks = sh->disks;
777 	struct page *xor_srcs[disks];
778 
779 	int count = 0, pd_idx = sh->pd_idx, i;
780 	struct page *xor_dest;
781 	int prexor = 0;
782 	unsigned long flags;
783 
784 	pr_debug("%s: stripe %llu\n", __func__,
785 		(unsigned long long)sh->sector);
786 
787 	/* check if prexor is active which means only process blocks
788 	 * that are part of a read-modify-write (written)
789 	 */
790 	if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
791 		prexor = 1;
792 		xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
793 		for (i = disks; i--; ) {
794 			struct r5dev *dev = &sh->dev[i];
795 			if (dev->written)
796 				xor_srcs[count++] = dev->page;
797 		}
798 	} else {
799 		xor_dest = sh->dev[pd_idx].page;
800 		for (i = disks; i--; ) {
801 			struct r5dev *dev = &sh->dev[i];
802 			if (i != pd_idx)
803 				xor_srcs[count++] = dev->page;
804 		}
805 	}
806 
807 	/* 1/ if we prexor'd then the dest is reused as a source
808 	 * 2/ if we did not prexor then we are redoing the parity
809 	 * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
810 	 * for the synchronous xor case
811 	 */
812 	flags = ASYNC_TX_DEP_ACK | ASYNC_TX_ACK |
813 		(prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);
814 
815 	atomic_inc(&sh->count);
816 
817 	if (unlikely(count == 1)) {
818 		flags &= ~(ASYNC_TX_XOR_DROP_DST | ASYNC_TX_XOR_ZERO_DST);
819 		tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
820 			flags, tx, ops_complete_postxor, sh);
821 	} else
822 		tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
823 			flags, tx, ops_complete_postxor, sh);
824 }
825 
826 static void ops_complete_check(void *stripe_head_ref)
827 {
828 	struct stripe_head *sh = stripe_head_ref;
829 
830 	pr_debug("%s: stripe %llu\n", __func__,
831 		(unsigned long long)sh->sector);
832 
833 	sh->check_state = check_state_check_result;
834 	set_bit(STRIPE_HANDLE, &sh->state);
835 	release_stripe(sh);
836 }
837 
838 static void ops_run_check(struct stripe_head *sh)
839 {
840 	/* kernel stack size limits the total number of disks */
841 	int disks = sh->disks;
842 	struct page *xor_srcs[disks];
843 	struct dma_async_tx_descriptor *tx;
844 
845 	int count = 0, pd_idx = sh->pd_idx, i;
846 	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
847 
848 	pr_debug("%s: stripe %llu\n", __func__,
849 		(unsigned long long)sh->sector);
850 
851 	for (i = disks; i--; ) {
852 		struct r5dev *dev = &sh->dev[i];
853 		if (i != pd_idx)
854 			xor_srcs[count++] = dev->page;
855 	}
856 
857 	tx = async_xor_zero_sum(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
858 		&sh->ops.zero_sum_result, 0, NULL, NULL, NULL);
859 
860 	atomic_inc(&sh->count);
861 	tx = async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
862 		ops_complete_check, sh);
863 }
864 
865 static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
866 {
867 	int overlap_clear = 0, i, disks = sh->disks;
868 	struct dma_async_tx_descriptor *tx = NULL;
869 
870 	if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
871 		ops_run_biofill(sh);
872 		overlap_clear++;
873 	}
874 
875 	if (test_bit(STRIPE_OP_COMPUTE_BLK, &ops_request)) {
876 		tx = ops_run_compute5(sh);
877 		/* terminate the chain if postxor is not set to be run */
878 		if (tx && !test_bit(STRIPE_OP_POSTXOR, &ops_request))
879 			async_tx_ack(tx);
880 	}
881 
882 	if (test_bit(STRIPE_OP_PREXOR, &ops_request))
883 		tx = ops_run_prexor(sh, tx);
884 
885 	if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
886 		tx = ops_run_biodrain(sh, tx);
887 		overlap_clear++;
888 	}
889 
890 	if (test_bit(STRIPE_OP_POSTXOR, &ops_request))
891 		ops_run_postxor(sh, tx);
892 
893 	if (test_bit(STRIPE_OP_CHECK, &ops_request))
894 		ops_run_check(sh);
895 
896 	if (overlap_clear)
897 		for (i = disks; i--; ) {
898 			struct r5dev *dev = &sh->dev[i];
899 			if (test_and_clear_bit(R5_Overlap, &dev->flags))
900 				wake_up(&sh->raid_conf->wait_for_overlap);
901 		}
902 }
903 
904 static int grow_one_stripe(raid5_conf_t *conf)
905 {
906 	struct stripe_head *sh;
907 	sh = kmem_cache_alloc(conf->slab_cache, GFP_KERNEL);
908 	if (!sh)
909 		return 0;
910 	memset(sh, 0, sizeof(*sh) + (conf->raid_disks-1)*sizeof(struct r5dev));
911 	sh->raid_conf = conf;
912 	spin_lock_init(&sh->lock);
913 
914 	if (grow_buffers(sh, conf->raid_disks)) {
915 		shrink_buffers(sh, conf->raid_disks);
916 		kmem_cache_free(conf->slab_cache, sh);
917 		return 0;
918 	}
919 	sh->disks = conf->raid_disks;
920 	/* we just created an active stripe so... */
921 	atomic_set(&sh->count, 1);
922 	atomic_inc(&conf->active_stripes);
923 	INIT_LIST_HEAD(&sh->lru);
924 	release_stripe(sh);
925 	return 1;
926 }
927 
928 static int grow_stripes(raid5_conf_t *conf, int num)
929 {
930 	struct kmem_cache *sc;
931 	int devs = conf->raid_disks;
932 
933 	sprintf(conf->cache_name[0],
934 		"raid%d-%s", conf->level, mdname(conf->mddev));
935 	sprintf(conf->cache_name[1],
936 		"raid%d-%s-alt", conf->level, mdname(conf->mddev));
937 	conf->active_name = 0;
938 	sc = kmem_cache_create(conf->cache_name[conf->active_name],
939 			       sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
940 			       0, 0, NULL);
941 	if (!sc)
942 		return 1;
943 	conf->slab_cache = sc;
944 	conf->pool_size = devs;
945 	while (num--)
946 		if (!grow_one_stripe(conf))
947 			return 1;
948 	return 0;
949 }
950 
951 static int resize_stripes(raid5_conf_t *conf, int newsize)
952 {
953 	/* Make all the stripes able to hold 'newsize' devices.
954 	 * New slots in each stripe get 'page' set to a new page.
955 	 *
956 	 * This happens in stages:
957 	 * 1/ create a new kmem_cache and allocate the required number of
958 	 *    stripe_heads.
959 	 * 2/ gather all the old stripe_heads and tranfer the pages across
960 	 *    to the new stripe_heads.  This will have the side effect of
961 	 *    freezing the array as once all stripe_heads have been collected,
962 	 *    no IO will be possible.  Old stripe heads are freed once their
963 	 *    pages have been transferred over, and the old kmem_cache is
964 	 *    freed when all stripes are done.
965 	 * 3/ reallocate conf->disks to be suitable bigger.  If this fails,
966 	 *    we simple return a failre status - no need to clean anything up.
967 	 * 4/ allocate new pages for the new slots in the new stripe_heads.
968 	 *    If this fails, we don't bother trying the shrink the
969 	 *    stripe_heads down again, we just leave them as they are.
970 	 *    As each stripe_head is processed the new one is released into
971 	 *    active service.
972 	 *
973 	 * Once step2 is started, we cannot afford to wait for a write,
974 	 * so we use GFP_NOIO allocations.
975 	 */
976 	struct stripe_head *osh, *nsh;
977 	LIST_HEAD(newstripes);
978 	struct disk_info *ndisks;
979 	int err;
980 	struct kmem_cache *sc;
981 	int i;
982 
983 	if (newsize <= conf->pool_size)
984 		return 0; /* never bother to shrink */
985 
986 	err = md_allow_write(conf->mddev);
987 	if (err)
988 		return err;
989 
990 	/* Step 1 */
991 	sc = kmem_cache_create(conf->cache_name[1-conf->active_name],
992 			       sizeof(struct stripe_head)+(newsize-1)*sizeof(struct r5dev),
993 			       0, 0, NULL);
994 	if (!sc)
995 		return -ENOMEM;
996 
997 	for (i = conf->max_nr_stripes; i; i--) {
998 		nsh = kmem_cache_alloc(sc, GFP_KERNEL);
999 		if (!nsh)
1000 			break;
1001 
1002 		memset(nsh, 0, sizeof(*nsh) + (newsize-1)*sizeof(struct r5dev));
1003 
1004 		nsh->raid_conf = conf;
1005 		spin_lock_init(&nsh->lock);
1006 
1007 		list_add(&nsh->lru, &newstripes);
1008 	}
1009 	if (i) {
1010 		/* didn't get enough, give up */
1011 		while (!list_empty(&newstripes)) {
1012 			nsh = list_entry(newstripes.next, struct stripe_head, lru);
1013 			list_del(&nsh->lru);
1014 			kmem_cache_free(sc, nsh);
1015 		}
1016 		kmem_cache_destroy(sc);
1017 		return -ENOMEM;
1018 	}
1019 	/* Step 2 - Must use GFP_NOIO now.
1020 	 * OK, we have enough stripes, start collecting inactive
1021 	 * stripes and copying them over
1022 	 */
1023 	list_for_each_entry(nsh, &newstripes, lru) {
1024 		spin_lock_irq(&conf->device_lock);
1025 		wait_event_lock_irq(conf->wait_for_stripe,
1026 				    !list_empty(&conf->inactive_list),
1027 				    conf->device_lock,
1028 				    unplug_slaves(conf->mddev)
1029 			);
1030 		osh = get_free_stripe(conf);
1031 		spin_unlock_irq(&conf->device_lock);
1032 		atomic_set(&nsh->count, 1);
1033 		for(i=0; i<conf->pool_size; i++)
1034 			nsh->dev[i].page = osh->dev[i].page;
1035 		for( ; i<newsize; i++)
1036 			nsh->dev[i].page = NULL;
1037 		kmem_cache_free(conf->slab_cache, osh);
1038 	}
1039 	kmem_cache_destroy(conf->slab_cache);
1040 
1041 	/* Step 3.
1042 	 * At this point, we are holding all the stripes so the array
1043 	 * is completely stalled, so now is a good time to resize
1044 	 * conf->disks.
1045 	 */
1046 	ndisks = kzalloc(newsize * sizeof(struct disk_info), GFP_NOIO);
1047 	if (ndisks) {
1048 		for (i=0; i<conf->raid_disks; i++)
1049 			ndisks[i] = conf->disks[i];
1050 		kfree(conf->disks);
1051 		conf->disks = ndisks;
1052 	} else
1053 		err = -ENOMEM;
1054 
1055 	/* Step 4, return new stripes to service */
1056 	while(!list_empty(&newstripes)) {
1057 		nsh = list_entry(newstripes.next, struct stripe_head, lru);
1058 		list_del_init(&nsh->lru);
1059 		for (i=conf->raid_disks; i < newsize; i++)
1060 			if (nsh->dev[i].page == NULL) {
1061 				struct page *p = alloc_page(GFP_NOIO);
1062 				nsh->dev[i].page = p;
1063 				if (!p)
1064 					err = -ENOMEM;
1065 			}
1066 		release_stripe(nsh);
1067 	}
1068 	/* critical section pass, GFP_NOIO no longer needed */
1069 
1070 	conf->slab_cache = sc;
1071 	conf->active_name = 1-conf->active_name;
1072 	conf->pool_size = newsize;
1073 	return err;
1074 }
1075 
1076 static int drop_one_stripe(raid5_conf_t *conf)
1077 {
1078 	struct stripe_head *sh;
1079 
1080 	spin_lock_irq(&conf->device_lock);
1081 	sh = get_free_stripe(conf);
1082 	spin_unlock_irq(&conf->device_lock);
1083 	if (!sh)
1084 		return 0;
1085 	BUG_ON(atomic_read(&sh->count));
1086 	shrink_buffers(sh, conf->pool_size);
1087 	kmem_cache_free(conf->slab_cache, sh);
1088 	atomic_dec(&conf->active_stripes);
1089 	return 1;
1090 }
1091 
1092 static void shrink_stripes(raid5_conf_t *conf)
1093 {
1094 	while (drop_one_stripe(conf))
1095 		;
1096 
1097 	if (conf->slab_cache)
1098 		kmem_cache_destroy(conf->slab_cache);
1099 	conf->slab_cache = NULL;
1100 }
1101 
1102 static void raid5_end_read_request(struct bio * bi, int error)
1103 {
1104 	struct stripe_head *sh = bi->bi_private;
1105 	raid5_conf_t *conf = sh->raid_conf;
1106 	int disks = sh->disks, i;
1107 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
1108 	char b[BDEVNAME_SIZE];
1109 	mdk_rdev_t *rdev;
1110 
1111 
1112 	for (i=0 ; i<disks; i++)
1113 		if (bi == &sh->dev[i].req)
1114 			break;
1115 
1116 	pr_debug("end_read_request %llu/%d, count: %d, uptodate %d.\n",
1117 		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
1118 		uptodate);
1119 	if (i == disks) {
1120 		BUG();
1121 		return;
1122 	}
1123 
1124 	if (uptodate) {
1125 		set_bit(R5_UPTODATE, &sh->dev[i].flags);
1126 		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
1127 			rdev = conf->disks[i].rdev;
1128 			printk_rl(KERN_INFO "raid5:%s: read error corrected"
1129 				  " (%lu sectors at %llu on %s)\n",
1130 				  mdname(conf->mddev), STRIPE_SECTORS,
1131 				  (unsigned long long)(sh->sector
1132 						       + rdev->data_offset),
1133 				  bdevname(rdev->bdev, b));
1134 			clear_bit(R5_ReadError, &sh->dev[i].flags);
1135 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
1136 		}
1137 		if (atomic_read(&conf->disks[i].rdev->read_errors))
1138 			atomic_set(&conf->disks[i].rdev->read_errors, 0);
1139 	} else {
1140 		const char *bdn = bdevname(conf->disks[i].rdev->bdev, b);
1141 		int retry = 0;
1142 		rdev = conf->disks[i].rdev;
1143 
1144 		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
1145 		atomic_inc(&rdev->read_errors);
1146 		if (conf->mddev->degraded)
1147 			printk_rl(KERN_WARNING
1148 				  "raid5:%s: read error not correctable "
1149 				  "(sector %llu on %s).\n",
1150 				  mdname(conf->mddev),
1151 				  (unsigned long long)(sh->sector
1152 						       + rdev->data_offset),
1153 				  bdn);
1154 		else if (test_bit(R5_ReWrite, &sh->dev[i].flags))
1155 			/* Oh, no!!! */
1156 			printk_rl(KERN_WARNING
1157 				  "raid5:%s: read error NOT corrected!! "
1158 				  "(sector %llu on %s).\n",
1159 				  mdname(conf->mddev),
1160 				  (unsigned long long)(sh->sector
1161 						       + rdev->data_offset),
1162 				  bdn);
1163 		else if (atomic_read(&rdev->read_errors)
1164 			 > conf->max_nr_stripes)
1165 			printk(KERN_WARNING
1166 			       "raid5:%s: Too many read errors, failing device %s.\n",
1167 			       mdname(conf->mddev), bdn);
1168 		else
1169 			retry = 1;
1170 		if (retry)
1171 			set_bit(R5_ReadError, &sh->dev[i].flags);
1172 		else {
1173 			clear_bit(R5_ReadError, &sh->dev[i].flags);
1174 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
1175 			md_error(conf->mddev, rdev);
1176 		}
1177 	}
1178 	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
1179 	clear_bit(R5_LOCKED, &sh->dev[i].flags);
1180 	set_bit(STRIPE_HANDLE, &sh->state);
1181 	release_stripe(sh);
1182 }
1183 
1184 static void raid5_end_write_request(struct bio *bi, int error)
1185 {
1186 	struct stripe_head *sh = bi->bi_private;
1187 	raid5_conf_t *conf = sh->raid_conf;
1188 	int disks = sh->disks, i;
1189 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
1190 
1191 	for (i=0 ; i<disks; i++)
1192 		if (bi == &sh->dev[i].req)
1193 			break;
1194 
1195 	pr_debug("end_write_request %llu/%d, count %d, uptodate: %d.\n",
1196 		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
1197 		uptodate);
1198 	if (i == disks) {
1199 		BUG();
1200 		return;
1201 	}
1202 
1203 	if (!uptodate)
1204 		md_error(conf->mddev, conf->disks[i].rdev);
1205 
1206 	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
1207 
1208 	clear_bit(R5_LOCKED, &sh->dev[i].flags);
1209 	set_bit(STRIPE_HANDLE, &sh->state);
1210 	release_stripe(sh);
1211 }
1212 
1213 
1214 static sector_t compute_blocknr(struct stripe_head *sh, int i, int previous);
1215 
1216 static void raid5_build_block(struct stripe_head *sh, int i, int previous)
1217 {
1218 	struct r5dev *dev = &sh->dev[i];
1219 
1220 	bio_init(&dev->req);
1221 	dev->req.bi_io_vec = &dev->vec;
1222 	dev->req.bi_vcnt++;
1223 	dev->req.bi_max_vecs++;
1224 	dev->vec.bv_page = dev->page;
1225 	dev->vec.bv_len = STRIPE_SIZE;
1226 	dev->vec.bv_offset = 0;
1227 
1228 	dev->req.bi_sector = sh->sector;
1229 	dev->req.bi_private = sh;
1230 
1231 	dev->flags = 0;
1232 	dev->sector = compute_blocknr(sh, i, previous);
1233 }
1234 
1235 static void error(mddev_t *mddev, mdk_rdev_t *rdev)
1236 {
1237 	char b[BDEVNAME_SIZE];
1238 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
1239 	pr_debug("raid5: error called\n");
1240 
1241 	if (!test_bit(Faulty, &rdev->flags)) {
1242 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
1243 		if (test_and_clear_bit(In_sync, &rdev->flags)) {
1244 			unsigned long flags;
1245 			spin_lock_irqsave(&conf->device_lock, flags);
1246 			mddev->degraded++;
1247 			spin_unlock_irqrestore(&conf->device_lock, flags);
1248 			/*
1249 			 * if recovery was running, make sure it aborts.
1250 			 */
1251 			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
1252 		}
1253 		set_bit(Faulty, &rdev->flags);
1254 		printk(KERN_ALERT
1255 		       "raid5: Disk failure on %s, disabling device.\n"
1256 		       "raid5: Operation continuing on %d devices.\n",
1257 		       bdevname(rdev->bdev,b), conf->raid_disks - mddev->degraded);
1258 	}
1259 }
1260 
1261 /*
1262  * Input: a 'big' sector number,
1263  * Output: index of the data and parity disk, and the sector # in them.
1264  */
1265 static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector,
1266 				     int previous, int *dd_idx,
1267 				     struct stripe_head *sh)
1268 {
1269 	long stripe;
1270 	unsigned long chunk_number;
1271 	unsigned int chunk_offset;
1272 	int pd_idx, qd_idx;
1273 	int ddf_layout = 0;
1274 	sector_t new_sector;
1275 	int algorithm = previous ? conf->prev_algo
1276 				 : conf->algorithm;
1277 	int sectors_per_chunk = previous ? conf->prev_chunk_sectors
1278 					 : conf->chunk_sectors;
1279 	int raid_disks = previous ? conf->previous_raid_disks
1280 				  : conf->raid_disks;
1281 	int data_disks = raid_disks - conf->max_degraded;
1282 
1283 	/* First compute the information on this sector */
1284 
1285 	/*
1286 	 * Compute the chunk number and the sector offset inside the chunk
1287 	 */
1288 	chunk_offset = sector_div(r_sector, sectors_per_chunk);
1289 	chunk_number = r_sector;
1290 	BUG_ON(r_sector != chunk_number);
1291 
1292 	/*
1293 	 * Compute the stripe number
1294 	 */
1295 	stripe = chunk_number / data_disks;
1296 
1297 	/*
1298 	 * Compute the data disk and parity disk indexes inside the stripe
1299 	 */
1300 	*dd_idx = chunk_number % data_disks;
1301 
1302 	/*
1303 	 * Select the parity disk based on the user selected algorithm.
1304 	 */
1305 	pd_idx = qd_idx = ~0;
1306 	switch(conf->level) {
1307 	case 4:
1308 		pd_idx = data_disks;
1309 		break;
1310 	case 5:
1311 		switch (algorithm) {
1312 		case ALGORITHM_LEFT_ASYMMETRIC:
1313 			pd_idx = data_disks - stripe % raid_disks;
1314 			if (*dd_idx >= pd_idx)
1315 				(*dd_idx)++;
1316 			break;
1317 		case ALGORITHM_RIGHT_ASYMMETRIC:
1318 			pd_idx = stripe % raid_disks;
1319 			if (*dd_idx >= pd_idx)
1320 				(*dd_idx)++;
1321 			break;
1322 		case ALGORITHM_LEFT_SYMMETRIC:
1323 			pd_idx = data_disks - stripe % raid_disks;
1324 			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
1325 			break;
1326 		case ALGORITHM_RIGHT_SYMMETRIC:
1327 			pd_idx = stripe % raid_disks;
1328 			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
1329 			break;
1330 		case ALGORITHM_PARITY_0:
1331 			pd_idx = 0;
1332 			(*dd_idx)++;
1333 			break;
1334 		case ALGORITHM_PARITY_N:
1335 			pd_idx = data_disks;
1336 			break;
1337 		default:
1338 			printk(KERN_ERR "raid5: unsupported algorithm %d\n",
1339 				algorithm);
1340 			BUG();
1341 		}
1342 		break;
1343 	case 6:
1344 
1345 		switch (algorithm) {
1346 		case ALGORITHM_LEFT_ASYMMETRIC:
1347 			pd_idx = raid_disks - 1 - (stripe % raid_disks);
1348 			qd_idx = pd_idx + 1;
1349 			if (pd_idx == raid_disks-1) {
1350 				(*dd_idx)++;	/* Q D D D P */
1351 				qd_idx = 0;
1352 			} else if (*dd_idx >= pd_idx)
1353 				(*dd_idx) += 2; /* D D P Q D */
1354 			break;
1355 		case ALGORITHM_RIGHT_ASYMMETRIC:
1356 			pd_idx = stripe % raid_disks;
1357 			qd_idx = pd_idx + 1;
1358 			if (pd_idx == raid_disks-1) {
1359 				(*dd_idx)++;	/* Q D D D P */
1360 				qd_idx = 0;
1361 			} else if (*dd_idx >= pd_idx)
1362 				(*dd_idx) += 2; /* D D P Q D */
1363 			break;
1364 		case ALGORITHM_LEFT_SYMMETRIC:
1365 			pd_idx = raid_disks - 1 - (stripe % raid_disks);
1366 			qd_idx = (pd_idx + 1) % raid_disks;
1367 			*dd_idx = (pd_idx + 2 + *dd_idx) % raid_disks;
1368 			break;
1369 		case ALGORITHM_RIGHT_SYMMETRIC:
1370 			pd_idx = stripe % raid_disks;
1371 			qd_idx = (pd_idx + 1) % raid_disks;
1372 			*dd_idx = (pd_idx + 2 + *dd_idx) % raid_disks;
1373 			break;
1374 
1375 		case ALGORITHM_PARITY_0:
1376 			pd_idx = 0;
1377 			qd_idx = 1;
1378 			(*dd_idx) += 2;
1379 			break;
1380 		case ALGORITHM_PARITY_N:
1381 			pd_idx = data_disks;
1382 			qd_idx = data_disks + 1;
1383 			break;
1384 
1385 		case ALGORITHM_ROTATING_ZERO_RESTART:
1386 			/* Exactly the same as RIGHT_ASYMMETRIC, but or
1387 			 * of blocks for computing Q is different.
1388 			 */
1389 			pd_idx = stripe % raid_disks;
1390 			qd_idx = pd_idx + 1;
1391 			if (pd_idx == raid_disks-1) {
1392 				(*dd_idx)++;	/* Q D D D P */
1393 				qd_idx = 0;
1394 			} else if (*dd_idx >= pd_idx)
1395 				(*dd_idx) += 2; /* D D P Q D */
1396 			ddf_layout = 1;
1397 			break;
1398 
1399 		case ALGORITHM_ROTATING_N_RESTART:
1400 			/* Same a left_asymmetric, by first stripe is
1401 			 * D D D P Q  rather than
1402 			 * Q D D D P
1403 			 */
1404 			pd_idx = raid_disks - 1 - ((stripe + 1) % raid_disks);
1405 			qd_idx = pd_idx + 1;
1406 			if (pd_idx == raid_disks-1) {
1407 				(*dd_idx)++;	/* Q D D D P */
1408 				qd_idx = 0;
1409 			} else if (*dd_idx >= pd_idx)
1410 				(*dd_idx) += 2; /* D D P Q D */
1411 			ddf_layout = 1;
1412 			break;
1413 
1414 		case ALGORITHM_ROTATING_N_CONTINUE:
1415 			/* Same as left_symmetric but Q is before P */
1416 			pd_idx = raid_disks - 1 - (stripe % raid_disks);
1417 			qd_idx = (pd_idx + raid_disks - 1) % raid_disks;
1418 			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
1419 			ddf_layout = 1;
1420 			break;
1421 
1422 		case ALGORITHM_LEFT_ASYMMETRIC_6:
1423 			/* RAID5 left_asymmetric, with Q on last device */
1424 			pd_idx = data_disks - stripe % (raid_disks-1);
1425 			if (*dd_idx >= pd_idx)
1426 				(*dd_idx)++;
1427 			qd_idx = raid_disks - 1;
1428 			break;
1429 
1430 		case ALGORITHM_RIGHT_ASYMMETRIC_6:
1431 			pd_idx = stripe % (raid_disks-1);
1432 			if (*dd_idx >= pd_idx)
1433 				(*dd_idx)++;
1434 			qd_idx = raid_disks - 1;
1435 			break;
1436 
1437 		case ALGORITHM_LEFT_SYMMETRIC_6:
1438 			pd_idx = data_disks - stripe % (raid_disks-1);
1439 			*dd_idx = (pd_idx + 1 + *dd_idx) % (raid_disks-1);
1440 			qd_idx = raid_disks - 1;
1441 			break;
1442 
1443 		case ALGORITHM_RIGHT_SYMMETRIC_6:
1444 			pd_idx = stripe % (raid_disks-1);
1445 			*dd_idx = (pd_idx + 1 + *dd_idx) % (raid_disks-1);
1446 			qd_idx = raid_disks - 1;
1447 			break;
1448 
1449 		case ALGORITHM_PARITY_0_6:
1450 			pd_idx = 0;
1451 			(*dd_idx)++;
1452 			qd_idx = raid_disks - 1;
1453 			break;
1454 
1455 
1456 		default:
1457 			printk(KERN_CRIT "raid6: unsupported algorithm %d\n",
1458 			       algorithm);
1459 			BUG();
1460 		}
1461 		break;
1462 	}
1463 
1464 	if (sh) {
1465 		sh->pd_idx = pd_idx;
1466 		sh->qd_idx = qd_idx;
1467 		sh->ddf_layout = ddf_layout;
1468 	}
1469 	/*
1470 	 * Finally, compute the new sector number
1471 	 */
1472 	new_sector = (sector_t)stripe * sectors_per_chunk + chunk_offset;
1473 	return new_sector;
1474 }
1475 
1476 
1477 static sector_t compute_blocknr(struct stripe_head *sh, int i, int previous)
1478 {
1479 	raid5_conf_t *conf = sh->raid_conf;
1480 	int raid_disks = sh->disks;
1481 	int data_disks = raid_disks - conf->max_degraded;
1482 	sector_t new_sector = sh->sector, check;
1483 	int sectors_per_chunk = previous ? conf->prev_chunk_sectors
1484 					 : conf->chunk_sectors;
1485 	int algorithm = previous ? conf->prev_algo
1486 				 : conf->algorithm;
1487 	sector_t stripe;
1488 	int chunk_offset;
1489 	int chunk_number, dummy1, dd_idx = i;
1490 	sector_t r_sector;
1491 	struct stripe_head sh2;
1492 
1493 
1494 	chunk_offset = sector_div(new_sector, sectors_per_chunk);
1495 	stripe = new_sector;
1496 	BUG_ON(new_sector != stripe);
1497 
1498 	if (i == sh->pd_idx)
1499 		return 0;
1500 	switch(conf->level) {
1501 	case 4: break;
1502 	case 5:
1503 		switch (algorithm) {
1504 		case ALGORITHM_LEFT_ASYMMETRIC:
1505 		case ALGORITHM_RIGHT_ASYMMETRIC:
1506 			if (i > sh->pd_idx)
1507 				i--;
1508 			break;
1509 		case ALGORITHM_LEFT_SYMMETRIC:
1510 		case ALGORITHM_RIGHT_SYMMETRIC:
1511 			if (i < sh->pd_idx)
1512 				i += raid_disks;
1513 			i -= (sh->pd_idx + 1);
1514 			break;
1515 		case ALGORITHM_PARITY_0:
1516 			i -= 1;
1517 			break;
1518 		case ALGORITHM_PARITY_N:
1519 			break;
1520 		default:
1521 			printk(KERN_ERR "raid5: unsupported algorithm %d\n",
1522 			       algorithm);
1523 			BUG();
1524 		}
1525 		break;
1526 	case 6:
1527 		if (i == sh->qd_idx)
1528 			return 0; /* It is the Q disk */
1529 		switch (algorithm) {
1530 		case ALGORITHM_LEFT_ASYMMETRIC:
1531 		case ALGORITHM_RIGHT_ASYMMETRIC:
1532 		case ALGORITHM_ROTATING_ZERO_RESTART:
1533 		case ALGORITHM_ROTATING_N_RESTART:
1534 			if (sh->pd_idx == raid_disks-1)
1535 				i--;	/* Q D D D P */
1536 			else if (i > sh->pd_idx)
1537 				i -= 2; /* D D P Q D */
1538 			break;
1539 		case ALGORITHM_LEFT_SYMMETRIC:
1540 		case ALGORITHM_RIGHT_SYMMETRIC:
1541 			if (sh->pd_idx == raid_disks-1)
1542 				i--; /* Q D D D P */
1543 			else {
1544 				/* D D P Q D */
1545 				if (i < sh->pd_idx)
1546 					i += raid_disks;
1547 				i -= (sh->pd_idx + 2);
1548 			}
1549 			break;
1550 		case ALGORITHM_PARITY_0:
1551 			i -= 2;
1552 			break;
1553 		case ALGORITHM_PARITY_N:
1554 			break;
1555 		case ALGORITHM_ROTATING_N_CONTINUE:
1556 			if (sh->pd_idx == 0)
1557 				i--;	/* P D D D Q */
1558 			else if (i > sh->pd_idx)
1559 				i -= 2; /* D D Q P D */
1560 			break;
1561 		case ALGORITHM_LEFT_ASYMMETRIC_6:
1562 		case ALGORITHM_RIGHT_ASYMMETRIC_6:
1563 			if (i > sh->pd_idx)
1564 				i--;
1565 			break;
1566 		case ALGORITHM_LEFT_SYMMETRIC_6:
1567 		case ALGORITHM_RIGHT_SYMMETRIC_6:
1568 			if (i < sh->pd_idx)
1569 				i += data_disks + 1;
1570 			i -= (sh->pd_idx + 1);
1571 			break;
1572 		case ALGORITHM_PARITY_0_6:
1573 			i -= 1;
1574 			break;
1575 		default:
1576 			printk(KERN_CRIT "raid6: unsupported algorithm %d\n",
1577 			       algorithm);
1578 			BUG();
1579 		}
1580 		break;
1581 	}
1582 
1583 	chunk_number = stripe * data_disks + i;
1584 	r_sector = (sector_t)chunk_number * sectors_per_chunk + chunk_offset;
1585 
1586 	check = raid5_compute_sector(conf, r_sector,
1587 				     previous, &dummy1, &sh2);
1588 	if (check != sh->sector || dummy1 != dd_idx || sh2.pd_idx != sh->pd_idx
1589 		|| sh2.qd_idx != sh->qd_idx) {
1590 		printk(KERN_ERR "compute_blocknr: map not correct\n");
1591 		return 0;
1592 	}
1593 	return r_sector;
1594 }
1595 
1596 
1597 
1598 /*
1599  * Copy data between a page in the stripe cache, and one or more bion
1600  * The page could align with the middle of the bio, or there could be
1601  * several bion, each with several bio_vecs, which cover part of the page
1602  * Multiple bion are linked together on bi_next.  There may be extras
1603  * at the end of this list.  We ignore them.
1604  */
1605 static void copy_data(int frombio, struct bio *bio,
1606 		     struct page *page,
1607 		     sector_t sector)
1608 {
1609 	char *pa = page_address(page);
1610 	struct bio_vec *bvl;
1611 	int i;
1612 	int page_offset;
1613 
1614 	if (bio->bi_sector >= sector)
1615 		page_offset = (signed)(bio->bi_sector - sector) * 512;
1616 	else
1617 		page_offset = (signed)(sector - bio->bi_sector) * -512;
1618 	bio_for_each_segment(bvl, bio, i) {
1619 		int len = bio_iovec_idx(bio,i)->bv_len;
1620 		int clen;
1621 		int b_offset = 0;
1622 
1623 		if (page_offset < 0) {
1624 			b_offset = -page_offset;
1625 			page_offset += b_offset;
1626 			len -= b_offset;
1627 		}
1628 
1629 		if (len > 0 && page_offset + len > STRIPE_SIZE)
1630 			clen = STRIPE_SIZE - page_offset;
1631 		else clen = len;
1632 
1633 		if (clen > 0) {
1634 			char *ba = __bio_kmap_atomic(bio, i, KM_USER0);
1635 			if (frombio)
1636 				memcpy(pa+page_offset, ba+b_offset, clen);
1637 			else
1638 				memcpy(ba+b_offset, pa+page_offset, clen);
1639 			__bio_kunmap_atomic(ba, KM_USER0);
1640 		}
1641 		if (clen < len) /* hit end of page */
1642 			break;
1643 		page_offset +=  len;
1644 	}
1645 }
1646 
1647 #define check_xor()	do {						  \
1648 				if (count == MAX_XOR_BLOCKS) {		  \
1649 				xor_blocks(count, STRIPE_SIZE, dest, ptr);\
1650 				count = 0;				  \
1651 			   }						  \
1652 			} while(0)
1653 
1654 static void compute_parity6(struct stripe_head *sh, int method)
1655 {
1656 	raid5_conf_t *conf = sh->raid_conf;
1657 	int i, pd_idx, qd_idx, d0_idx, disks = sh->disks, count;
1658 	int syndrome_disks = sh->ddf_layout ? disks : (disks - 2);
1659 	struct bio *chosen;
1660 	/**** FIX THIS: This could be very bad if disks is close to 256 ****/
1661 	void *ptrs[syndrome_disks+2];
1662 
1663 	pd_idx = sh->pd_idx;
1664 	qd_idx = sh->qd_idx;
1665 	d0_idx = raid6_d0(sh);
1666 
1667 	pr_debug("compute_parity, stripe %llu, method %d\n",
1668 		(unsigned long long)sh->sector, method);
1669 
1670 	switch(method) {
1671 	case READ_MODIFY_WRITE:
1672 		BUG();		/* READ_MODIFY_WRITE N/A for RAID-6 */
1673 	case RECONSTRUCT_WRITE:
1674 		for (i= disks; i-- ;)
1675 			if ( i != pd_idx && i != qd_idx && sh->dev[i].towrite ) {
1676 				chosen = sh->dev[i].towrite;
1677 				sh->dev[i].towrite = NULL;
1678 
1679 				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1680 					wake_up(&conf->wait_for_overlap);
1681 
1682 				BUG_ON(sh->dev[i].written);
1683 				sh->dev[i].written = chosen;
1684 			}
1685 		break;
1686 	case CHECK_PARITY:
1687 		BUG();		/* Not implemented yet */
1688 	}
1689 
1690 	for (i = disks; i--;)
1691 		if (sh->dev[i].written) {
1692 			sector_t sector = sh->dev[i].sector;
1693 			struct bio *wbi = sh->dev[i].written;
1694 			while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
1695 				copy_data(1, wbi, sh->dev[i].page, sector);
1696 				wbi = r5_next_bio(wbi, sector);
1697 			}
1698 
1699 			set_bit(R5_LOCKED, &sh->dev[i].flags);
1700 			set_bit(R5_UPTODATE, &sh->dev[i].flags);
1701 		}
1702 
1703 	/* Note that unlike RAID-5, the ordering of the disks matters greatly.*/
1704 
1705 	for (i = 0; i < disks; i++)
1706 		ptrs[i] = (void *)raid6_empty_zero_page;
1707 
1708 	count = 0;
1709 	i = d0_idx;
1710 	do {
1711 		int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
1712 
1713 		ptrs[slot] = page_address(sh->dev[i].page);
1714 		if (slot < syndrome_disks &&
1715 		    !test_bit(R5_UPTODATE, &sh->dev[i].flags)) {
1716 			printk(KERN_ERR "block %d/%d not uptodate "
1717 			       "on parity calc\n", i, count);
1718 			BUG();
1719 		}
1720 
1721 		i = raid6_next_disk(i, disks);
1722 	} while (i != d0_idx);
1723 	BUG_ON(count != syndrome_disks);
1724 
1725 	raid6_call.gen_syndrome(syndrome_disks+2, STRIPE_SIZE, ptrs);
1726 
1727 	switch(method) {
1728 	case RECONSTRUCT_WRITE:
1729 		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1730 		set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
1731 		set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
1732 		set_bit(R5_LOCKED,   &sh->dev[qd_idx].flags);
1733 		break;
1734 	case UPDATE_PARITY:
1735 		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1736 		set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
1737 		break;
1738 	}
1739 }
1740 
1741 
1742 /* Compute one missing block */
1743 static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
1744 {
1745 	int i, count, disks = sh->disks;
1746 	void *ptr[MAX_XOR_BLOCKS], *dest, *p;
1747 	int qd_idx = sh->qd_idx;
1748 
1749 	pr_debug("compute_block_1, stripe %llu, idx %d\n",
1750 		(unsigned long long)sh->sector, dd_idx);
1751 
1752 	if ( dd_idx == qd_idx ) {
1753 		/* We're actually computing the Q drive */
1754 		compute_parity6(sh, UPDATE_PARITY);
1755 	} else {
1756 		dest = page_address(sh->dev[dd_idx].page);
1757 		if (!nozero) memset(dest, 0, STRIPE_SIZE);
1758 		count = 0;
1759 		for (i = disks ; i--; ) {
1760 			if (i == dd_idx || i == qd_idx)
1761 				continue;
1762 			p = page_address(sh->dev[i].page);
1763 			if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
1764 				ptr[count++] = p;
1765 			else
1766 				printk("compute_block() %d, stripe %llu, %d"
1767 				       " not present\n", dd_idx,
1768 				       (unsigned long long)sh->sector, i);
1769 
1770 			check_xor();
1771 		}
1772 		if (count)
1773 			xor_blocks(count, STRIPE_SIZE, dest, ptr);
1774 		if (!nozero) set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
1775 		else clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
1776 	}
1777 }
1778 
1779 /* Compute two missing blocks */
1780 static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
1781 {
1782 	int i, count, disks = sh->disks;
1783 	int syndrome_disks = sh->ddf_layout ? disks : disks-2;
1784 	int d0_idx = raid6_d0(sh);
1785 	int faila = -1, failb = -1;
1786 	/**** FIX THIS: This could be very bad if disks is close to 256 ****/
1787 	void *ptrs[syndrome_disks+2];
1788 
1789 	for (i = 0; i < disks ; i++)
1790 		ptrs[i] = (void *)raid6_empty_zero_page;
1791 	count = 0;
1792 	i = d0_idx;
1793 	do {
1794 		int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
1795 
1796 		ptrs[slot] = page_address(sh->dev[i].page);
1797 
1798 		if (i == dd_idx1)
1799 			faila = slot;
1800 		if (i == dd_idx2)
1801 			failb = slot;
1802 		i = raid6_next_disk(i, disks);
1803 	} while (i != d0_idx);
1804 	BUG_ON(count != syndrome_disks);
1805 
1806 	BUG_ON(faila == failb);
1807 	if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
1808 
1809 	pr_debug("compute_block_2, stripe %llu, idx %d,%d (%d,%d)\n",
1810 		 (unsigned long long)sh->sector, dd_idx1, dd_idx2,
1811 		 faila, failb);
1812 
1813 	if (failb == syndrome_disks+1) {
1814 		/* Q disk is one of the missing disks */
1815 		if (faila == syndrome_disks) {
1816 			/* Missing P+Q, just recompute */
1817 			compute_parity6(sh, UPDATE_PARITY);
1818 			return;
1819 		} else {
1820 			/* We're missing D+Q; recompute D from P */
1821 			compute_block_1(sh, ((dd_idx1 == sh->qd_idx) ?
1822 					     dd_idx2 : dd_idx1),
1823 					0);
1824 			compute_parity6(sh, UPDATE_PARITY); /* Is this necessary? */
1825 			return;
1826 		}
1827 	}
1828 
1829 	/* We're missing D+P or D+D; */
1830 	if (failb == syndrome_disks) {
1831 		/* We're missing D+P. */
1832 		raid6_datap_recov(syndrome_disks+2, STRIPE_SIZE, faila, ptrs);
1833 	} else {
1834 		/* We're missing D+D. */
1835 		raid6_2data_recov(syndrome_disks+2, STRIPE_SIZE, faila, failb,
1836 				  ptrs);
1837 	}
1838 
1839 	/* Both the above update both missing blocks */
1840 	set_bit(R5_UPTODATE, &sh->dev[dd_idx1].flags);
1841 	set_bit(R5_UPTODATE, &sh->dev[dd_idx2].flags);
1842 }
1843 
1844 static void
1845 schedule_reconstruction5(struct stripe_head *sh, struct stripe_head_state *s,
1846 			 int rcw, int expand)
1847 {
1848 	int i, pd_idx = sh->pd_idx, disks = sh->disks;
1849 
1850 	if (rcw) {
1851 		/* if we are not expanding this is a proper write request, and
1852 		 * there will be bios with new data to be drained into the
1853 		 * stripe cache
1854 		 */
1855 		if (!expand) {
1856 			sh->reconstruct_state = reconstruct_state_drain_run;
1857 			set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
1858 		} else
1859 			sh->reconstruct_state = reconstruct_state_run;
1860 
1861 		set_bit(STRIPE_OP_POSTXOR, &s->ops_request);
1862 
1863 		for (i = disks; i--; ) {
1864 			struct r5dev *dev = &sh->dev[i];
1865 
1866 			if (dev->towrite) {
1867 				set_bit(R5_LOCKED, &dev->flags);
1868 				set_bit(R5_Wantdrain, &dev->flags);
1869 				if (!expand)
1870 					clear_bit(R5_UPTODATE, &dev->flags);
1871 				s->locked++;
1872 			}
1873 		}
1874 		if (s->locked + 1 == disks)
1875 			if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
1876 				atomic_inc(&sh->raid_conf->pending_full_writes);
1877 	} else {
1878 		BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
1879 			test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
1880 
1881 		sh->reconstruct_state = reconstruct_state_prexor_drain_run;
1882 		set_bit(STRIPE_OP_PREXOR, &s->ops_request);
1883 		set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
1884 		set_bit(STRIPE_OP_POSTXOR, &s->ops_request);
1885 
1886 		for (i = disks; i--; ) {
1887 			struct r5dev *dev = &sh->dev[i];
1888 			if (i == pd_idx)
1889 				continue;
1890 
1891 			if (dev->towrite &&
1892 			    (test_bit(R5_UPTODATE, &dev->flags) ||
1893 			     test_bit(R5_Wantcompute, &dev->flags))) {
1894 				set_bit(R5_Wantdrain, &dev->flags);
1895 				set_bit(R5_LOCKED, &dev->flags);
1896 				clear_bit(R5_UPTODATE, &dev->flags);
1897 				s->locked++;
1898 			}
1899 		}
1900 	}
1901 
1902 	/* keep the parity disk locked while asynchronous operations
1903 	 * are in flight
1904 	 */
1905 	set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
1906 	clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1907 	s->locked++;
1908 
1909 	pr_debug("%s: stripe %llu locked: %d ops_request: %lx\n",
1910 		__func__, (unsigned long long)sh->sector,
1911 		s->locked, s->ops_request);
1912 }
1913 
1914 /*
1915  * Each stripe/dev can have one or more bion attached.
1916  * toread/towrite point to the first in a chain.
1917  * The bi_next chain must be in order.
1918  */
1919 static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, int forwrite)
1920 {
1921 	struct bio **bip;
1922 	raid5_conf_t *conf = sh->raid_conf;
1923 	int firstwrite=0;
1924 
1925 	pr_debug("adding bh b#%llu to stripe s#%llu\n",
1926 		(unsigned long long)bi->bi_sector,
1927 		(unsigned long long)sh->sector);
1928 
1929 
1930 	spin_lock(&sh->lock);
1931 	spin_lock_irq(&conf->device_lock);
1932 	if (forwrite) {
1933 		bip = &sh->dev[dd_idx].towrite;
1934 		if (*bip == NULL && sh->dev[dd_idx].written == NULL)
1935 			firstwrite = 1;
1936 	} else
1937 		bip = &sh->dev[dd_idx].toread;
1938 	while (*bip && (*bip)->bi_sector < bi->bi_sector) {
1939 		if ((*bip)->bi_sector + ((*bip)->bi_size >> 9) > bi->bi_sector)
1940 			goto overlap;
1941 		bip = & (*bip)->bi_next;
1942 	}
1943 	if (*bip && (*bip)->bi_sector < bi->bi_sector + ((bi->bi_size)>>9))
1944 		goto overlap;
1945 
1946 	BUG_ON(*bip && bi->bi_next && (*bip) != bi->bi_next);
1947 	if (*bip)
1948 		bi->bi_next = *bip;
1949 	*bip = bi;
1950 	bi->bi_phys_segments++;
1951 	spin_unlock_irq(&conf->device_lock);
1952 	spin_unlock(&sh->lock);
1953 
1954 	pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
1955 		(unsigned long long)bi->bi_sector,
1956 		(unsigned long long)sh->sector, dd_idx);
1957 
1958 	if (conf->mddev->bitmap && firstwrite) {
1959 		bitmap_startwrite(conf->mddev->bitmap, sh->sector,
1960 				  STRIPE_SECTORS, 0);
1961 		sh->bm_seq = conf->seq_flush+1;
1962 		set_bit(STRIPE_BIT_DELAY, &sh->state);
1963 	}
1964 
1965 	if (forwrite) {
1966 		/* check if page is covered */
1967 		sector_t sector = sh->dev[dd_idx].sector;
1968 		for (bi=sh->dev[dd_idx].towrite;
1969 		     sector < sh->dev[dd_idx].sector + STRIPE_SECTORS &&
1970 			     bi && bi->bi_sector <= sector;
1971 		     bi = r5_next_bio(bi, sh->dev[dd_idx].sector)) {
1972 			if (bi->bi_sector + (bi->bi_size>>9) >= sector)
1973 				sector = bi->bi_sector + (bi->bi_size>>9);
1974 		}
1975 		if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
1976 			set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
1977 	}
1978 	return 1;
1979 
1980  overlap:
1981 	set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
1982 	spin_unlock_irq(&conf->device_lock);
1983 	spin_unlock(&sh->lock);
1984 	return 0;
1985 }
1986 
1987 static void end_reshape(raid5_conf_t *conf);
1988 
1989 static int page_is_zero(struct page *p)
1990 {
1991 	char *a = page_address(p);
1992 	return ((*(u32*)a) == 0 &&
1993 		memcmp(a, a+4, STRIPE_SIZE-4)==0);
1994 }
1995 
1996 static void stripe_set_idx(sector_t stripe, raid5_conf_t *conf, int previous,
1997 			    struct stripe_head *sh)
1998 {
1999 	int sectors_per_chunk =
2000 		previous ? conf->prev_chunk_sectors : conf->chunk_sectors;
2001 	int dd_idx;
2002 	int chunk_offset = sector_div(stripe, sectors_per_chunk);
2003 	int disks = previous ? conf->previous_raid_disks : conf->raid_disks;
2004 
2005 	raid5_compute_sector(conf,
2006 			     stripe * (disks - conf->max_degraded)
2007 			     *sectors_per_chunk + chunk_offset,
2008 			     previous,
2009 			     &dd_idx, sh);
2010 }
2011 
2012 static void
2013 handle_failed_stripe(raid5_conf_t *conf, struct stripe_head *sh,
2014 				struct stripe_head_state *s, int disks,
2015 				struct bio **return_bi)
2016 {
2017 	int i;
2018 	for (i = disks; i--; ) {
2019 		struct bio *bi;
2020 		int bitmap_end = 0;
2021 
2022 		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
2023 			mdk_rdev_t *rdev;
2024 			rcu_read_lock();
2025 			rdev = rcu_dereference(conf->disks[i].rdev);
2026 			if (rdev && test_bit(In_sync, &rdev->flags))
2027 				/* multiple read failures in one stripe */
2028 				md_error(conf->mddev, rdev);
2029 			rcu_read_unlock();
2030 		}
2031 		spin_lock_irq(&conf->device_lock);
2032 		/* fail all writes first */
2033 		bi = sh->dev[i].towrite;
2034 		sh->dev[i].towrite = NULL;
2035 		if (bi) {
2036 			s->to_write--;
2037 			bitmap_end = 1;
2038 		}
2039 
2040 		if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
2041 			wake_up(&conf->wait_for_overlap);
2042 
2043 		while (bi && bi->bi_sector <
2044 			sh->dev[i].sector + STRIPE_SECTORS) {
2045 			struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
2046 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
2047 			if (!raid5_dec_bi_phys_segments(bi)) {
2048 				md_write_end(conf->mddev);
2049 				bi->bi_next = *return_bi;
2050 				*return_bi = bi;
2051 			}
2052 			bi = nextbi;
2053 		}
2054 		/* and fail all 'written' */
2055 		bi = sh->dev[i].written;
2056 		sh->dev[i].written = NULL;
2057 		if (bi) bitmap_end = 1;
2058 		while (bi && bi->bi_sector <
2059 		       sh->dev[i].sector + STRIPE_SECTORS) {
2060 			struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
2061 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
2062 			if (!raid5_dec_bi_phys_segments(bi)) {
2063 				md_write_end(conf->mddev);
2064 				bi->bi_next = *return_bi;
2065 				*return_bi = bi;
2066 			}
2067 			bi = bi2;
2068 		}
2069 
2070 		/* fail any reads if this device is non-operational and
2071 		 * the data has not reached the cache yet.
2072 		 */
2073 		if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
2074 		    (!test_bit(R5_Insync, &sh->dev[i].flags) ||
2075 		      test_bit(R5_ReadError, &sh->dev[i].flags))) {
2076 			bi = sh->dev[i].toread;
2077 			sh->dev[i].toread = NULL;
2078 			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
2079 				wake_up(&conf->wait_for_overlap);
2080 			if (bi) s->to_read--;
2081 			while (bi && bi->bi_sector <
2082 			       sh->dev[i].sector + STRIPE_SECTORS) {
2083 				struct bio *nextbi =
2084 					r5_next_bio(bi, sh->dev[i].sector);
2085 				clear_bit(BIO_UPTODATE, &bi->bi_flags);
2086 				if (!raid5_dec_bi_phys_segments(bi)) {
2087 					bi->bi_next = *return_bi;
2088 					*return_bi = bi;
2089 				}
2090 				bi = nextbi;
2091 			}
2092 		}
2093 		spin_unlock_irq(&conf->device_lock);
2094 		if (bitmap_end)
2095 			bitmap_endwrite(conf->mddev->bitmap, sh->sector,
2096 					STRIPE_SECTORS, 0, 0);
2097 	}
2098 
2099 	if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
2100 		if (atomic_dec_and_test(&conf->pending_full_writes))
2101 			md_wakeup_thread(conf->mddev->thread);
2102 }
2103 
2104 /* fetch_block5 - checks the given member device to see if its data needs
2105  * to be read or computed to satisfy a request.
2106  *
2107  * Returns 1 when no more member devices need to be checked, otherwise returns
2108  * 0 to tell the loop in handle_stripe_fill5 to continue
2109  */
2110 static int fetch_block5(struct stripe_head *sh, struct stripe_head_state *s,
2111 			int disk_idx, int disks)
2112 {
2113 	struct r5dev *dev = &sh->dev[disk_idx];
2114 	struct r5dev *failed_dev = &sh->dev[s->failed_num];
2115 
2116 	/* is the data in this block needed, and can we get it? */
2117 	if (!test_bit(R5_LOCKED, &dev->flags) &&
2118 	    !test_bit(R5_UPTODATE, &dev->flags) &&
2119 	    (dev->toread ||
2120 	     (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
2121 	     s->syncing || s->expanding ||
2122 	     (s->failed &&
2123 	      (failed_dev->toread ||
2124 	       (failed_dev->towrite &&
2125 		!test_bit(R5_OVERWRITE, &failed_dev->flags)))))) {
2126 		/* We would like to get this block, possibly by computing it,
2127 		 * otherwise read it if the backing disk is insync
2128 		 */
2129 		if ((s->uptodate == disks - 1) &&
2130 		    (s->failed && disk_idx == s->failed_num)) {
2131 			set_bit(STRIPE_COMPUTE_RUN, &sh->state);
2132 			set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
2133 			set_bit(R5_Wantcompute, &dev->flags);
2134 			sh->ops.target = disk_idx;
2135 			s->req_compute = 1;
2136 			/* Careful: from this point on 'uptodate' is in the eye
2137 			 * of raid5_run_ops which services 'compute' operations
2138 			 * before writes. R5_Wantcompute flags a block that will
2139 			 * be R5_UPTODATE by the time it is needed for a
2140 			 * subsequent operation.
2141 			 */
2142 			s->uptodate++;
2143 			return 1; /* uptodate + compute == disks */
2144 		} else if (test_bit(R5_Insync, &dev->flags)) {
2145 			set_bit(R5_LOCKED, &dev->flags);
2146 			set_bit(R5_Wantread, &dev->flags);
2147 			s->locked++;
2148 			pr_debug("Reading block %d (sync=%d)\n", disk_idx,
2149 				s->syncing);
2150 		}
2151 	}
2152 
2153 	return 0;
2154 }
2155 
2156 /**
2157  * handle_stripe_fill5 - read or compute data to satisfy pending requests.
2158  */
2159 static void handle_stripe_fill5(struct stripe_head *sh,
2160 			struct stripe_head_state *s, int disks)
2161 {
2162 	int i;
2163 
2164 	/* look for blocks to read/compute, skip this if a compute
2165 	 * is already in flight, or if the stripe contents are in the
2166 	 * midst of changing due to a write
2167 	 */
2168 	if (!test_bit(STRIPE_COMPUTE_RUN, &sh->state) && !sh->check_state &&
2169 	    !sh->reconstruct_state)
2170 		for (i = disks; i--; )
2171 			if (fetch_block5(sh, s, i, disks))
2172 				break;
2173 	set_bit(STRIPE_HANDLE, &sh->state);
2174 }
2175 
2176 static void handle_stripe_fill6(struct stripe_head *sh,
2177 			struct stripe_head_state *s, struct r6_state *r6s,
2178 			int disks)
2179 {
2180 	int i;
2181 	for (i = disks; i--; ) {
2182 		struct r5dev *dev = &sh->dev[i];
2183 		if (!test_bit(R5_LOCKED, &dev->flags) &&
2184 		    !test_bit(R5_UPTODATE, &dev->flags) &&
2185 		    (dev->toread || (dev->towrite &&
2186 		     !test_bit(R5_OVERWRITE, &dev->flags)) ||
2187 		     s->syncing || s->expanding ||
2188 		     (s->failed >= 1 &&
2189 		      (sh->dev[r6s->failed_num[0]].toread ||
2190 		       s->to_write)) ||
2191 		     (s->failed >= 2 &&
2192 		      (sh->dev[r6s->failed_num[1]].toread ||
2193 		       s->to_write)))) {
2194 			/* we would like to get this block, possibly
2195 			 * by computing it, but we might not be able to
2196 			 */
2197 			if ((s->uptodate == disks - 1) &&
2198 			    (s->failed && (i == r6s->failed_num[0] ||
2199 					   i == r6s->failed_num[1]))) {
2200 				pr_debug("Computing stripe %llu block %d\n",
2201 				       (unsigned long long)sh->sector, i);
2202 				compute_block_1(sh, i, 0);
2203 				s->uptodate++;
2204 			} else if ( s->uptodate == disks-2 && s->failed >= 2 ) {
2205 				/* Computing 2-failure is *very* expensive; only
2206 				 * do it if failed >= 2
2207 				 */
2208 				int other;
2209 				for (other = disks; other--; ) {
2210 					if (other == i)
2211 						continue;
2212 					if (!test_bit(R5_UPTODATE,
2213 					      &sh->dev[other].flags))
2214 						break;
2215 				}
2216 				BUG_ON(other < 0);
2217 				pr_debug("Computing stripe %llu blocks %d,%d\n",
2218 				       (unsigned long long)sh->sector,
2219 				       i, other);
2220 				compute_block_2(sh, i, other);
2221 				s->uptodate += 2;
2222 			} else if (test_bit(R5_Insync, &dev->flags)) {
2223 				set_bit(R5_LOCKED, &dev->flags);
2224 				set_bit(R5_Wantread, &dev->flags);
2225 				s->locked++;
2226 				pr_debug("Reading block %d (sync=%d)\n",
2227 					i, s->syncing);
2228 			}
2229 		}
2230 	}
2231 	set_bit(STRIPE_HANDLE, &sh->state);
2232 }
2233 
2234 
2235 /* handle_stripe_clean_event
2236  * any written block on an uptodate or failed drive can be returned.
2237  * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but
2238  * never LOCKED, so we don't need to test 'failed' directly.
2239  */
2240 static void handle_stripe_clean_event(raid5_conf_t *conf,
2241 	struct stripe_head *sh, int disks, struct bio **return_bi)
2242 {
2243 	int i;
2244 	struct r5dev *dev;
2245 
2246 	for (i = disks; i--; )
2247 		if (sh->dev[i].written) {
2248 			dev = &sh->dev[i];
2249 			if (!test_bit(R5_LOCKED, &dev->flags) &&
2250 				test_bit(R5_UPTODATE, &dev->flags)) {
2251 				/* We can return any write requests */
2252 				struct bio *wbi, *wbi2;
2253 				int bitmap_end = 0;
2254 				pr_debug("Return write for disc %d\n", i);
2255 				spin_lock_irq(&conf->device_lock);
2256 				wbi = dev->written;
2257 				dev->written = NULL;
2258 				while (wbi && wbi->bi_sector <
2259 					dev->sector + STRIPE_SECTORS) {
2260 					wbi2 = r5_next_bio(wbi, dev->sector);
2261 					if (!raid5_dec_bi_phys_segments(wbi)) {
2262 						md_write_end(conf->mddev);
2263 						wbi->bi_next = *return_bi;
2264 						*return_bi = wbi;
2265 					}
2266 					wbi = wbi2;
2267 				}
2268 				if (dev->towrite == NULL)
2269 					bitmap_end = 1;
2270 				spin_unlock_irq(&conf->device_lock);
2271 				if (bitmap_end)
2272 					bitmap_endwrite(conf->mddev->bitmap,
2273 							sh->sector,
2274 							STRIPE_SECTORS,
2275 					 !test_bit(STRIPE_DEGRADED, &sh->state),
2276 							0);
2277 			}
2278 		}
2279 
2280 	if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
2281 		if (atomic_dec_and_test(&conf->pending_full_writes))
2282 			md_wakeup_thread(conf->mddev->thread);
2283 }
2284 
2285 static void handle_stripe_dirtying5(raid5_conf_t *conf,
2286 		struct stripe_head *sh,	struct stripe_head_state *s, int disks)
2287 {
2288 	int rmw = 0, rcw = 0, i;
2289 	for (i = disks; i--; ) {
2290 		/* would I have to read this buffer for read_modify_write */
2291 		struct r5dev *dev = &sh->dev[i];
2292 		if ((dev->towrite || i == sh->pd_idx) &&
2293 		    !test_bit(R5_LOCKED, &dev->flags) &&
2294 		    !(test_bit(R5_UPTODATE, &dev->flags) ||
2295 		      test_bit(R5_Wantcompute, &dev->flags))) {
2296 			if (test_bit(R5_Insync, &dev->flags))
2297 				rmw++;
2298 			else
2299 				rmw += 2*disks;  /* cannot read it */
2300 		}
2301 		/* Would I have to read this buffer for reconstruct_write */
2302 		if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
2303 		    !test_bit(R5_LOCKED, &dev->flags) &&
2304 		    !(test_bit(R5_UPTODATE, &dev->flags) ||
2305 		    test_bit(R5_Wantcompute, &dev->flags))) {
2306 			if (test_bit(R5_Insync, &dev->flags)) rcw++;
2307 			else
2308 				rcw += 2*disks;
2309 		}
2310 	}
2311 	pr_debug("for sector %llu, rmw=%d rcw=%d\n",
2312 		(unsigned long long)sh->sector, rmw, rcw);
2313 	set_bit(STRIPE_HANDLE, &sh->state);
2314 	if (rmw < rcw && rmw > 0)
2315 		/* prefer read-modify-write, but need to get some data */
2316 		for (i = disks; i--; ) {
2317 			struct r5dev *dev = &sh->dev[i];
2318 			if ((dev->towrite || i == sh->pd_idx) &&
2319 			    !test_bit(R5_LOCKED, &dev->flags) &&
2320 			    !(test_bit(R5_UPTODATE, &dev->flags) ||
2321 			    test_bit(R5_Wantcompute, &dev->flags)) &&
2322 			    test_bit(R5_Insync, &dev->flags)) {
2323 				if (
2324 				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2325 					pr_debug("Read_old block "
2326 						"%d for r-m-w\n", i);
2327 					set_bit(R5_LOCKED, &dev->flags);
2328 					set_bit(R5_Wantread, &dev->flags);
2329 					s->locked++;
2330 				} else {
2331 					set_bit(STRIPE_DELAYED, &sh->state);
2332 					set_bit(STRIPE_HANDLE, &sh->state);
2333 				}
2334 			}
2335 		}
2336 	if (rcw <= rmw && rcw > 0)
2337 		/* want reconstruct write, but need to get some data */
2338 		for (i = disks; i--; ) {
2339 			struct r5dev *dev = &sh->dev[i];
2340 			if (!test_bit(R5_OVERWRITE, &dev->flags) &&
2341 			    i != sh->pd_idx &&
2342 			    !test_bit(R5_LOCKED, &dev->flags) &&
2343 			    !(test_bit(R5_UPTODATE, &dev->flags) ||
2344 			    test_bit(R5_Wantcompute, &dev->flags)) &&
2345 			    test_bit(R5_Insync, &dev->flags)) {
2346 				if (
2347 				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2348 					pr_debug("Read_old block "
2349 						"%d for Reconstruct\n", i);
2350 					set_bit(R5_LOCKED, &dev->flags);
2351 					set_bit(R5_Wantread, &dev->flags);
2352 					s->locked++;
2353 				} else {
2354 					set_bit(STRIPE_DELAYED, &sh->state);
2355 					set_bit(STRIPE_HANDLE, &sh->state);
2356 				}
2357 			}
2358 		}
2359 	/* now if nothing is locked, and if we have enough data,
2360 	 * we can start a write request
2361 	 */
2362 	/* since handle_stripe can be called at any time we need to handle the
2363 	 * case where a compute block operation has been submitted and then a
2364 	 * subsequent call wants to start a write request.  raid5_run_ops only
2365 	 * handles the case where compute block and postxor are requested
2366 	 * simultaneously.  If this is not the case then new writes need to be
2367 	 * held off until the compute completes.
2368 	 */
2369 	if ((s->req_compute || !test_bit(STRIPE_COMPUTE_RUN, &sh->state)) &&
2370 	    (s->locked == 0 && (rcw == 0 || rmw == 0) &&
2371 	    !test_bit(STRIPE_BIT_DELAY, &sh->state)))
2372 		schedule_reconstruction5(sh, s, rcw == 0, 0);
2373 }
2374 
2375 static void handle_stripe_dirtying6(raid5_conf_t *conf,
2376 		struct stripe_head *sh,	struct stripe_head_state *s,
2377 		struct r6_state *r6s, int disks)
2378 {
2379 	int rcw = 0, must_compute = 0, pd_idx = sh->pd_idx, i;
2380 	int qd_idx = sh->qd_idx;
2381 	for (i = disks; i--; ) {
2382 		struct r5dev *dev = &sh->dev[i];
2383 		/* Would I have to read this buffer for reconstruct_write */
2384 		if (!test_bit(R5_OVERWRITE, &dev->flags)
2385 		    && i != pd_idx && i != qd_idx
2386 		    && (!test_bit(R5_LOCKED, &dev->flags)
2387 			    ) &&
2388 		    !test_bit(R5_UPTODATE, &dev->flags)) {
2389 			if (test_bit(R5_Insync, &dev->flags)) rcw++;
2390 			else {
2391 				pr_debug("raid6: must_compute: "
2392 					"disk %d flags=%#lx\n", i, dev->flags);
2393 				must_compute++;
2394 			}
2395 		}
2396 	}
2397 	pr_debug("for sector %llu, rcw=%d, must_compute=%d\n",
2398 	       (unsigned long long)sh->sector, rcw, must_compute);
2399 	set_bit(STRIPE_HANDLE, &sh->state);
2400 
2401 	if (rcw > 0)
2402 		/* want reconstruct write, but need to get some data */
2403 		for (i = disks; i--; ) {
2404 			struct r5dev *dev = &sh->dev[i];
2405 			if (!test_bit(R5_OVERWRITE, &dev->flags)
2406 			    && !(s->failed == 0 && (i == pd_idx || i == qd_idx))
2407 			    && !test_bit(R5_LOCKED, &dev->flags) &&
2408 			    !test_bit(R5_UPTODATE, &dev->flags) &&
2409 			    test_bit(R5_Insync, &dev->flags)) {
2410 				if (
2411 				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2412 					pr_debug("Read_old stripe %llu "
2413 						"block %d for Reconstruct\n",
2414 					     (unsigned long long)sh->sector, i);
2415 					set_bit(R5_LOCKED, &dev->flags);
2416 					set_bit(R5_Wantread, &dev->flags);
2417 					s->locked++;
2418 				} else {
2419 					pr_debug("Request delayed stripe %llu "
2420 						"block %d for Reconstruct\n",
2421 					     (unsigned long long)sh->sector, i);
2422 					set_bit(STRIPE_DELAYED, &sh->state);
2423 					set_bit(STRIPE_HANDLE, &sh->state);
2424 				}
2425 			}
2426 		}
2427 	/* now if nothing is locked, and if we have enough data, we can start a
2428 	 * write request
2429 	 */
2430 	if (s->locked == 0 && rcw == 0 &&
2431 	    !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
2432 		if (must_compute > 0) {
2433 			/* We have failed blocks and need to compute them */
2434 			switch (s->failed) {
2435 			case 0:
2436 				BUG();
2437 			case 1:
2438 				compute_block_1(sh, r6s->failed_num[0], 0);
2439 				break;
2440 			case 2:
2441 				compute_block_2(sh, r6s->failed_num[0],
2442 						r6s->failed_num[1]);
2443 				break;
2444 			default: /* This request should have been failed? */
2445 				BUG();
2446 			}
2447 		}
2448 
2449 		pr_debug("Computing parity for stripe %llu\n",
2450 			(unsigned long long)sh->sector);
2451 		compute_parity6(sh, RECONSTRUCT_WRITE);
2452 		/* now every locked buffer is ready to be written */
2453 		for (i = disks; i--; )
2454 			if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
2455 				pr_debug("Writing stripe %llu block %d\n",
2456 				       (unsigned long long)sh->sector, i);
2457 				s->locked++;
2458 				set_bit(R5_Wantwrite, &sh->dev[i].flags);
2459 			}
2460 		if (s->locked == disks)
2461 			if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
2462 				atomic_inc(&conf->pending_full_writes);
2463 		/* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */
2464 		set_bit(STRIPE_INSYNC, &sh->state);
2465 
2466 		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2467 			atomic_dec(&conf->preread_active_stripes);
2468 			if (atomic_read(&conf->preread_active_stripes) <
2469 			    IO_THRESHOLD)
2470 				md_wakeup_thread(conf->mddev->thread);
2471 		}
2472 	}
2473 }
2474 
2475 static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,
2476 				struct stripe_head_state *s, int disks)
2477 {
2478 	struct r5dev *dev = NULL;
2479 
2480 	set_bit(STRIPE_HANDLE, &sh->state);
2481 
2482 	switch (sh->check_state) {
2483 	case check_state_idle:
2484 		/* start a new check operation if there are no failures */
2485 		if (s->failed == 0) {
2486 			BUG_ON(s->uptodate != disks);
2487 			sh->check_state = check_state_run;
2488 			set_bit(STRIPE_OP_CHECK, &s->ops_request);
2489 			clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
2490 			s->uptodate--;
2491 			break;
2492 		}
2493 		dev = &sh->dev[s->failed_num];
2494 		/* fall through */
2495 	case check_state_compute_result:
2496 		sh->check_state = check_state_idle;
2497 		if (!dev)
2498 			dev = &sh->dev[sh->pd_idx];
2499 
2500 		/* check that a write has not made the stripe insync */
2501 		if (test_bit(STRIPE_INSYNC, &sh->state))
2502 			break;
2503 
2504 		/* either failed parity check, or recovery is happening */
2505 		BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
2506 		BUG_ON(s->uptodate != disks);
2507 
2508 		set_bit(R5_LOCKED, &dev->flags);
2509 		s->locked++;
2510 		set_bit(R5_Wantwrite, &dev->flags);
2511 
2512 		clear_bit(STRIPE_DEGRADED, &sh->state);
2513 		set_bit(STRIPE_INSYNC, &sh->state);
2514 		break;
2515 	case check_state_run:
2516 		break; /* we will be called again upon completion */
2517 	case check_state_check_result:
2518 		sh->check_state = check_state_idle;
2519 
2520 		/* if a failure occurred during the check operation, leave
2521 		 * STRIPE_INSYNC not set and let the stripe be handled again
2522 		 */
2523 		if (s->failed)
2524 			break;
2525 
2526 		/* handle a successful check operation, if parity is correct
2527 		 * we are done.  Otherwise update the mismatch count and repair
2528 		 * parity if !MD_RECOVERY_CHECK
2529 		 */
2530 		if (sh->ops.zero_sum_result == 0)
2531 			/* parity is correct (on disc,
2532 			 * not in buffer any more)
2533 			 */
2534 			set_bit(STRIPE_INSYNC, &sh->state);
2535 		else {
2536 			conf->mddev->resync_mismatches += STRIPE_SECTORS;
2537 			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
2538 				/* don't try to repair!! */
2539 				set_bit(STRIPE_INSYNC, &sh->state);
2540 			else {
2541 				sh->check_state = check_state_compute_run;
2542 				set_bit(STRIPE_COMPUTE_RUN, &sh->state);
2543 				set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
2544 				set_bit(R5_Wantcompute,
2545 					&sh->dev[sh->pd_idx].flags);
2546 				sh->ops.target = sh->pd_idx;
2547 				s->uptodate++;
2548 			}
2549 		}
2550 		break;
2551 	case check_state_compute_run:
2552 		break;
2553 	default:
2554 		printk(KERN_ERR "%s: unknown check_state: %d sector: %llu\n",
2555 		       __func__, sh->check_state,
2556 		       (unsigned long long) sh->sector);
2557 		BUG();
2558 	}
2559 }
2560 
2561 
2562 static void handle_parity_checks6(raid5_conf_t *conf, struct stripe_head *sh,
2563 				struct stripe_head_state *s,
2564 				struct r6_state *r6s, struct page *tmp_page,
2565 				int disks)
2566 {
2567 	int update_p = 0, update_q = 0;
2568 	struct r5dev *dev;
2569 	int pd_idx = sh->pd_idx;
2570 	int qd_idx = sh->qd_idx;
2571 
2572 	set_bit(STRIPE_HANDLE, &sh->state);
2573 
2574 	BUG_ON(s->failed > 2);
2575 	BUG_ON(s->uptodate < disks);
2576 	/* Want to check and possibly repair P and Q.
2577 	 * However there could be one 'failed' device, in which
2578 	 * case we can only check one of them, possibly using the
2579 	 * other to generate missing data
2580 	 */
2581 
2582 	/* If !tmp_page, we cannot do the calculations,
2583 	 * but as we have set STRIPE_HANDLE, we will soon be called
2584 	 * by stripe_handle with a tmp_page - just wait until then.
2585 	 */
2586 	if (tmp_page) {
2587 		if (s->failed == r6s->q_failed) {
2588 			/* The only possible failed device holds 'Q', so it
2589 			 * makes sense to check P (If anything else were failed,
2590 			 * we would have used P to recreate it).
2591 			 */
2592 			compute_block_1(sh, pd_idx, 1);
2593 			if (!page_is_zero(sh->dev[pd_idx].page)) {
2594 				compute_block_1(sh, pd_idx, 0);
2595 				update_p = 1;
2596 			}
2597 		}
2598 		if (!r6s->q_failed && s->failed < 2) {
2599 			/* q is not failed, and we didn't use it to generate
2600 			 * anything, so it makes sense to check it
2601 			 */
2602 			memcpy(page_address(tmp_page),
2603 			       page_address(sh->dev[qd_idx].page),
2604 			       STRIPE_SIZE);
2605 			compute_parity6(sh, UPDATE_PARITY);
2606 			if (memcmp(page_address(tmp_page),
2607 				   page_address(sh->dev[qd_idx].page),
2608 				   STRIPE_SIZE) != 0) {
2609 				clear_bit(STRIPE_INSYNC, &sh->state);
2610 				update_q = 1;
2611 			}
2612 		}
2613 		if (update_p || update_q) {
2614 			conf->mddev->resync_mismatches += STRIPE_SECTORS;
2615 			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
2616 				/* don't try to repair!! */
2617 				update_p = update_q = 0;
2618 		}
2619 
2620 		/* now write out any block on a failed drive,
2621 		 * or P or Q if they need it
2622 		 */
2623 
2624 		if (s->failed == 2) {
2625 			dev = &sh->dev[r6s->failed_num[1]];
2626 			s->locked++;
2627 			set_bit(R5_LOCKED, &dev->flags);
2628 			set_bit(R5_Wantwrite, &dev->flags);
2629 		}
2630 		if (s->failed >= 1) {
2631 			dev = &sh->dev[r6s->failed_num[0]];
2632 			s->locked++;
2633 			set_bit(R5_LOCKED, &dev->flags);
2634 			set_bit(R5_Wantwrite, &dev->flags);
2635 		}
2636 
2637 		if (update_p) {
2638 			dev = &sh->dev[pd_idx];
2639 			s->locked++;
2640 			set_bit(R5_LOCKED, &dev->flags);
2641 			set_bit(R5_Wantwrite, &dev->flags);
2642 		}
2643 		if (update_q) {
2644 			dev = &sh->dev[qd_idx];
2645 			s->locked++;
2646 			set_bit(R5_LOCKED, &dev->flags);
2647 			set_bit(R5_Wantwrite, &dev->flags);
2648 		}
2649 		clear_bit(STRIPE_DEGRADED, &sh->state);
2650 
2651 		set_bit(STRIPE_INSYNC, &sh->state);
2652 	}
2653 }
2654 
2655 static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
2656 				struct r6_state *r6s)
2657 {
2658 	int i;
2659 
2660 	/* We have read all the blocks in this stripe and now we need to
2661 	 * copy some of them into a target stripe for expand.
2662 	 */
2663 	struct dma_async_tx_descriptor *tx = NULL;
2664 	clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
2665 	for (i = 0; i < sh->disks; i++)
2666 		if (i != sh->pd_idx && i != sh->qd_idx) {
2667 			int dd_idx, j;
2668 			struct stripe_head *sh2;
2669 
2670 			sector_t bn = compute_blocknr(sh, i, 1);
2671 			sector_t s = raid5_compute_sector(conf, bn, 0,
2672 							  &dd_idx, NULL);
2673 			sh2 = get_active_stripe(conf, s, 0, 1, 1);
2674 			if (sh2 == NULL)
2675 				/* so far only the early blocks of this stripe
2676 				 * have been requested.  When later blocks
2677 				 * get requested, we will try again
2678 				 */
2679 				continue;
2680 			if (!test_bit(STRIPE_EXPANDING, &sh2->state) ||
2681 			   test_bit(R5_Expanded, &sh2->dev[dd_idx].flags)) {
2682 				/* must have already done this block */
2683 				release_stripe(sh2);
2684 				continue;
2685 			}
2686 
2687 			/* place all the copies on one channel */
2688 			tx = async_memcpy(sh2->dev[dd_idx].page,
2689 				sh->dev[i].page, 0, 0, STRIPE_SIZE,
2690 				ASYNC_TX_DEP_ACK, tx, NULL, NULL);
2691 
2692 			set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
2693 			set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
2694 			for (j = 0; j < conf->raid_disks; j++)
2695 				if (j != sh2->pd_idx &&
2696 				    (!r6s || j != sh2->qd_idx) &&
2697 				    !test_bit(R5_Expanded, &sh2->dev[j].flags))
2698 					break;
2699 			if (j == conf->raid_disks) {
2700 				set_bit(STRIPE_EXPAND_READY, &sh2->state);
2701 				set_bit(STRIPE_HANDLE, &sh2->state);
2702 			}
2703 			release_stripe(sh2);
2704 
2705 		}
2706 	/* done submitting copies, wait for them to complete */
2707 	if (tx) {
2708 		async_tx_ack(tx);
2709 		dma_wait_for_async_tx(tx);
2710 	}
2711 }
2712 
2713 
2714 /*
2715  * handle_stripe - do things to a stripe.
2716  *
2717  * We lock the stripe and then examine the state of various bits
2718  * to see what needs to be done.
2719  * Possible results:
2720  *    return some read request which now have data
2721  *    return some write requests which are safely on disc
2722  *    schedule a read on some buffers
2723  *    schedule a write of some buffers
2724  *    return confirmation of parity correctness
2725  *
2726  * buffers are taken off read_list or write_list, and bh_cache buffers
2727  * get BH_Lock set before the stripe lock is released.
2728  *
2729  */
2730 
2731 static bool handle_stripe5(struct stripe_head *sh)
2732 {
2733 	raid5_conf_t *conf = sh->raid_conf;
2734 	int disks = sh->disks, i;
2735 	struct bio *return_bi = NULL;
2736 	struct stripe_head_state s;
2737 	struct r5dev *dev;
2738 	mdk_rdev_t *blocked_rdev = NULL;
2739 	int prexor;
2740 
2741 	memset(&s, 0, sizeof(s));
2742 	pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d check:%d "
2743 		 "reconstruct:%d\n", (unsigned long long)sh->sector, sh->state,
2744 		 atomic_read(&sh->count), sh->pd_idx, sh->check_state,
2745 		 sh->reconstruct_state);
2746 
2747 	spin_lock(&sh->lock);
2748 	clear_bit(STRIPE_HANDLE, &sh->state);
2749 	clear_bit(STRIPE_DELAYED, &sh->state);
2750 
2751 	s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
2752 	s.expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
2753 	s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
2754 
2755 	/* Now to look around and see what can be done */
2756 	rcu_read_lock();
2757 	for (i=disks; i--; ) {
2758 		mdk_rdev_t *rdev;
2759 		struct r5dev *dev = &sh->dev[i];
2760 		clear_bit(R5_Insync, &dev->flags);
2761 
2762 		pr_debug("check %d: state 0x%lx toread %p read %p write %p "
2763 			"written %p\n",	i, dev->flags, dev->toread, dev->read,
2764 			dev->towrite, dev->written);
2765 
2766 		/* maybe we can request a biofill operation
2767 		 *
2768 		 * new wantfill requests are only permitted while
2769 		 * ops_complete_biofill is guaranteed to be inactive
2770 		 */
2771 		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
2772 		    !test_bit(STRIPE_BIOFILL_RUN, &sh->state))
2773 			set_bit(R5_Wantfill, &dev->flags);
2774 
2775 		/* now count some things */
2776 		if (test_bit(R5_LOCKED, &dev->flags)) s.locked++;
2777 		if (test_bit(R5_UPTODATE, &dev->flags)) s.uptodate++;
2778 		if (test_bit(R5_Wantcompute, &dev->flags)) s.compute++;
2779 
2780 		if (test_bit(R5_Wantfill, &dev->flags))
2781 			s.to_fill++;
2782 		else if (dev->toread)
2783 			s.to_read++;
2784 		if (dev->towrite) {
2785 			s.to_write++;
2786 			if (!test_bit(R5_OVERWRITE, &dev->flags))
2787 				s.non_overwrite++;
2788 		}
2789 		if (dev->written)
2790 			s.written++;
2791 		rdev = rcu_dereference(conf->disks[i].rdev);
2792 		if (blocked_rdev == NULL &&
2793 		    rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
2794 			blocked_rdev = rdev;
2795 			atomic_inc(&rdev->nr_pending);
2796 		}
2797 		if (!rdev || !test_bit(In_sync, &rdev->flags)) {
2798 			/* The ReadError flag will just be confusing now */
2799 			clear_bit(R5_ReadError, &dev->flags);
2800 			clear_bit(R5_ReWrite, &dev->flags);
2801 		}
2802 		if (!rdev || !test_bit(In_sync, &rdev->flags)
2803 		    || test_bit(R5_ReadError, &dev->flags)) {
2804 			s.failed++;
2805 			s.failed_num = i;
2806 		} else
2807 			set_bit(R5_Insync, &dev->flags);
2808 	}
2809 	rcu_read_unlock();
2810 
2811 	if (unlikely(blocked_rdev)) {
2812 		if (s.syncing || s.expanding || s.expanded ||
2813 		    s.to_write || s.written) {
2814 			set_bit(STRIPE_HANDLE, &sh->state);
2815 			goto unlock;
2816 		}
2817 		/* There is nothing for the blocked_rdev to block */
2818 		rdev_dec_pending(blocked_rdev, conf->mddev);
2819 		blocked_rdev = NULL;
2820 	}
2821 
2822 	if (s.to_fill && !test_bit(STRIPE_BIOFILL_RUN, &sh->state)) {
2823 		set_bit(STRIPE_OP_BIOFILL, &s.ops_request);
2824 		set_bit(STRIPE_BIOFILL_RUN, &sh->state);
2825 	}
2826 
2827 	pr_debug("locked=%d uptodate=%d to_read=%d"
2828 		" to_write=%d failed=%d failed_num=%d\n",
2829 		s.locked, s.uptodate, s.to_read, s.to_write,
2830 		s.failed, s.failed_num);
2831 	/* check if the array has lost two devices and, if so, some requests might
2832 	 * need to be failed
2833 	 */
2834 	if (s.failed > 1 && s.to_read+s.to_write+s.written)
2835 		handle_failed_stripe(conf, sh, &s, disks, &return_bi);
2836 	if (s.failed > 1 && s.syncing) {
2837 		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
2838 		clear_bit(STRIPE_SYNCING, &sh->state);
2839 		s.syncing = 0;
2840 	}
2841 
2842 	/* might be able to return some write requests if the parity block
2843 	 * is safe, or on a failed drive
2844 	 */
2845 	dev = &sh->dev[sh->pd_idx];
2846 	if ( s.written &&
2847 	     ((test_bit(R5_Insync, &dev->flags) &&
2848 	       !test_bit(R5_LOCKED, &dev->flags) &&
2849 	       test_bit(R5_UPTODATE, &dev->flags)) ||
2850 	       (s.failed == 1 && s.failed_num == sh->pd_idx)))
2851 		handle_stripe_clean_event(conf, sh, disks, &return_bi);
2852 
2853 	/* Now we might consider reading some blocks, either to check/generate
2854 	 * parity, or to satisfy requests
2855 	 * or to load a block that is being partially written.
2856 	 */
2857 	if (s.to_read || s.non_overwrite ||
2858 	    (s.syncing && (s.uptodate + s.compute < disks)) || s.expanding)
2859 		handle_stripe_fill5(sh, &s, disks);
2860 
2861 	/* Now we check to see if any write operations have recently
2862 	 * completed
2863 	 */
2864 	prexor = 0;
2865 	if (sh->reconstruct_state == reconstruct_state_prexor_drain_result)
2866 		prexor = 1;
2867 	if (sh->reconstruct_state == reconstruct_state_drain_result ||
2868 	    sh->reconstruct_state == reconstruct_state_prexor_drain_result) {
2869 		sh->reconstruct_state = reconstruct_state_idle;
2870 
2871 		/* All the 'written' buffers and the parity block are ready to
2872 		 * be written back to disk
2873 		 */
2874 		BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
2875 		for (i = disks; i--; ) {
2876 			dev = &sh->dev[i];
2877 			if (test_bit(R5_LOCKED, &dev->flags) &&
2878 				(i == sh->pd_idx || dev->written)) {
2879 				pr_debug("Writing block %d\n", i);
2880 				set_bit(R5_Wantwrite, &dev->flags);
2881 				if (prexor)
2882 					continue;
2883 				if (!test_bit(R5_Insync, &dev->flags) ||
2884 				    (i == sh->pd_idx && s.failed == 0))
2885 					set_bit(STRIPE_INSYNC, &sh->state);
2886 			}
2887 		}
2888 		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2889 			atomic_dec(&conf->preread_active_stripes);
2890 			if (atomic_read(&conf->preread_active_stripes) <
2891 				IO_THRESHOLD)
2892 				md_wakeup_thread(conf->mddev->thread);
2893 		}
2894 	}
2895 
2896 	/* Now to consider new write requests and what else, if anything
2897 	 * should be read.  We do not handle new writes when:
2898 	 * 1/ A 'write' operation (copy+xor) is already in flight.
2899 	 * 2/ A 'check' operation is in flight, as it may clobber the parity
2900 	 *    block.
2901 	 */
2902 	if (s.to_write && !sh->reconstruct_state && !sh->check_state)
2903 		handle_stripe_dirtying5(conf, sh, &s, disks);
2904 
2905 	/* maybe we need to check and possibly fix the parity for this stripe
2906 	 * Any reads will already have been scheduled, so we just see if enough
2907 	 * data is available.  The parity check is held off while parity
2908 	 * dependent operations are in flight.
2909 	 */
2910 	if (sh->check_state ||
2911 	    (s.syncing && s.locked == 0 &&
2912 	     !test_bit(STRIPE_COMPUTE_RUN, &sh->state) &&
2913 	     !test_bit(STRIPE_INSYNC, &sh->state)))
2914 		handle_parity_checks5(conf, sh, &s, disks);
2915 
2916 	if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
2917 		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
2918 		clear_bit(STRIPE_SYNCING, &sh->state);
2919 	}
2920 
2921 	/* If the failed drive is just a ReadError, then we might need to progress
2922 	 * the repair/check process
2923 	 */
2924 	if (s.failed == 1 && !conf->mddev->ro &&
2925 	    test_bit(R5_ReadError, &sh->dev[s.failed_num].flags)
2926 	    && !test_bit(R5_LOCKED, &sh->dev[s.failed_num].flags)
2927 	    && test_bit(R5_UPTODATE, &sh->dev[s.failed_num].flags)
2928 		) {
2929 		dev = &sh->dev[s.failed_num];
2930 		if (!test_bit(R5_ReWrite, &dev->flags)) {
2931 			set_bit(R5_Wantwrite, &dev->flags);
2932 			set_bit(R5_ReWrite, &dev->flags);
2933 			set_bit(R5_LOCKED, &dev->flags);
2934 			s.locked++;
2935 		} else {
2936 			/* let's read it back */
2937 			set_bit(R5_Wantread, &dev->flags);
2938 			set_bit(R5_LOCKED, &dev->flags);
2939 			s.locked++;
2940 		}
2941 	}
2942 
2943 	/* Finish reconstruct operations initiated by the expansion process */
2944 	if (sh->reconstruct_state == reconstruct_state_result) {
2945 		struct stripe_head *sh2
2946 			= get_active_stripe(conf, sh->sector, 1, 1, 1);
2947 		if (sh2 && test_bit(STRIPE_EXPAND_SOURCE, &sh2->state)) {
2948 			/* sh cannot be written until sh2 has been read.
2949 			 * so arrange for sh to be delayed a little
2950 			 */
2951 			set_bit(STRIPE_DELAYED, &sh->state);
2952 			set_bit(STRIPE_HANDLE, &sh->state);
2953 			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE,
2954 					      &sh2->state))
2955 				atomic_inc(&conf->preread_active_stripes);
2956 			release_stripe(sh2);
2957 			goto unlock;
2958 		}
2959 		if (sh2)
2960 			release_stripe(sh2);
2961 
2962 		sh->reconstruct_state = reconstruct_state_idle;
2963 		clear_bit(STRIPE_EXPANDING, &sh->state);
2964 		for (i = conf->raid_disks; i--; ) {
2965 			set_bit(R5_Wantwrite, &sh->dev[i].flags);
2966 			set_bit(R5_LOCKED, &sh->dev[i].flags);
2967 			s.locked++;
2968 		}
2969 	}
2970 
2971 	if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state) &&
2972 	    !sh->reconstruct_state) {
2973 		/* Need to write out all blocks after computing parity */
2974 		sh->disks = conf->raid_disks;
2975 		stripe_set_idx(sh->sector, conf, 0, sh);
2976 		schedule_reconstruction5(sh, &s, 1, 1);
2977 	} else if (s.expanded && !sh->reconstruct_state && s.locked == 0) {
2978 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
2979 		atomic_dec(&conf->reshape_stripes);
2980 		wake_up(&conf->wait_for_overlap);
2981 		md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
2982 	}
2983 
2984 	if (s.expanding && s.locked == 0 &&
2985 	    !test_bit(STRIPE_COMPUTE_RUN, &sh->state))
2986 		handle_stripe_expansion(conf, sh, NULL);
2987 
2988  unlock:
2989 	spin_unlock(&sh->lock);
2990 
2991 	/* wait for this device to become unblocked */
2992 	if (unlikely(blocked_rdev))
2993 		md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
2994 
2995 	if (s.ops_request)
2996 		raid5_run_ops(sh, s.ops_request);
2997 
2998 	ops_run_io(sh, &s);
2999 
3000 	return_io(return_bi);
3001 
3002 	return blocked_rdev == NULL;
3003 }
3004 
3005 static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
3006 {
3007 	raid5_conf_t *conf = sh->raid_conf;
3008 	int disks = sh->disks;
3009 	struct bio *return_bi = NULL;
3010 	int i, pd_idx = sh->pd_idx, qd_idx = sh->qd_idx;
3011 	struct stripe_head_state s;
3012 	struct r6_state r6s;
3013 	struct r5dev *dev, *pdev, *qdev;
3014 	mdk_rdev_t *blocked_rdev = NULL;
3015 
3016 	pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
3017 		"pd_idx=%d, qd_idx=%d\n",
3018 	       (unsigned long long)sh->sector, sh->state,
3019 	       atomic_read(&sh->count), pd_idx, qd_idx);
3020 	memset(&s, 0, sizeof(s));
3021 
3022 	spin_lock(&sh->lock);
3023 	clear_bit(STRIPE_HANDLE, &sh->state);
3024 	clear_bit(STRIPE_DELAYED, &sh->state);
3025 
3026 	s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
3027 	s.expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
3028 	s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
3029 	/* Now to look around and see what can be done */
3030 
3031 	rcu_read_lock();
3032 	for (i=disks; i--; ) {
3033 		mdk_rdev_t *rdev;
3034 		dev = &sh->dev[i];
3035 		clear_bit(R5_Insync, &dev->flags);
3036 
3037 		pr_debug("check %d: state 0x%lx read %p write %p written %p\n",
3038 			i, dev->flags, dev->toread, dev->towrite, dev->written);
3039 		/* maybe we can reply to a read */
3040 		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
3041 			struct bio *rbi, *rbi2;
3042 			pr_debug("Return read for disc %d\n", i);
3043 			spin_lock_irq(&conf->device_lock);
3044 			rbi = dev->toread;
3045 			dev->toread = NULL;
3046 			if (test_and_clear_bit(R5_Overlap, &dev->flags))
3047 				wake_up(&conf->wait_for_overlap);
3048 			spin_unlock_irq(&conf->device_lock);
3049 			while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
3050 				copy_data(0, rbi, dev->page, dev->sector);
3051 				rbi2 = r5_next_bio(rbi, dev->sector);
3052 				spin_lock_irq(&conf->device_lock);
3053 				if (!raid5_dec_bi_phys_segments(rbi)) {
3054 					rbi->bi_next = return_bi;
3055 					return_bi = rbi;
3056 				}
3057 				spin_unlock_irq(&conf->device_lock);
3058 				rbi = rbi2;
3059 			}
3060 		}
3061 
3062 		/* now count some things */
3063 		if (test_bit(R5_LOCKED, &dev->flags)) s.locked++;
3064 		if (test_bit(R5_UPTODATE, &dev->flags)) s.uptodate++;
3065 
3066 
3067 		if (dev->toread)
3068 			s.to_read++;
3069 		if (dev->towrite) {
3070 			s.to_write++;
3071 			if (!test_bit(R5_OVERWRITE, &dev->flags))
3072 				s.non_overwrite++;
3073 		}
3074 		if (dev->written)
3075 			s.written++;
3076 		rdev = rcu_dereference(conf->disks[i].rdev);
3077 		if (blocked_rdev == NULL &&
3078 		    rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
3079 			blocked_rdev = rdev;
3080 			atomic_inc(&rdev->nr_pending);
3081 		}
3082 		if (!rdev || !test_bit(In_sync, &rdev->flags)) {
3083 			/* The ReadError flag will just be confusing now */
3084 			clear_bit(R5_ReadError, &dev->flags);
3085 			clear_bit(R5_ReWrite, &dev->flags);
3086 		}
3087 		if (!rdev || !test_bit(In_sync, &rdev->flags)
3088 		    || test_bit(R5_ReadError, &dev->flags)) {
3089 			if (s.failed < 2)
3090 				r6s.failed_num[s.failed] = i;
3091 			s.failed++;
3092 		} else
3093 			set_bit(R5_Insync, &dev->flags);
3094 	}
3095 	rcu_read_unlock();
3096 
3097 	if (unlikely(blocked_rdev)) {
3098 		if (s.syncing || s.expanding || s.expanded ||
3099 		    s.to_write || s.written) {
3100 			set_bit(STRIPE_HANDLE, &sh->state);
3101 			goto unlock;
3102 		}
3103 		/* There is nothing for the blocked_rdev to block */
3104 		rdev_dec_pending(blocked_rdev, conf->mddev);
3105 		blocked_rdev = NULL;
3106 	}
3107 
3108 	pr_debug("locked=%d uptodate=%d to_read=%d"
3109 	       " to_write=%d failed=%d failed_num=%d,%d\n",
3110 	       s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
3111 	       r6s.failed_num[0], r6s.failed_num[1]);
3112 	/* check if the array has lost >2 devices and, if so, some requests
3113 	 * might need to be failed
3114 	 */
3115 	if (s.failed > 2 && s.to_read+s.to_write+s.written)
3116 		handle_failed_stripe(conf, sh, &s, disks, &return_bi);
3117 	if (s.failed > 2 && s.syncing) {
3118 		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
3119 		clear_bit(STRIPE_SYNCING, &sh->state);
3120 		s.syncing = 0;
3121 	}
3122 
3123 	/*
3124 	 * might be able to return some write requests if the parity blocks
3125 	 * are safe, or on a failed drive
3126 	 */
3127 	pdev = &sh->dev[pd_idx];
3128 	r6s.p_failed = (s.failed >= 1 && r6s.failed_num[0] == pd_idx)
3129 		|| (s.failed >= 2 && r6s.failed_num[1] == pd_idx);
3130 	qdev = &sh->dev[qd_idx];
3131 	r6s.q_failed = (s.failed >= 1 && r6s.failed_num[0] == qd_idx)
3132 		|| (s.failed >= 2 && r6s.failed_num[1] == qd_idx);
3133 
3134 	if ( s.written &&
3135 	     ( r6s.p_failed || ((test_bit(R5_Insync, &pdev->flags)
3136 			     && !test_bit(R5_LOCKED, &pdev->flags)
3137 			     && test_bit(R5_UPTODATE, &pdev->flags)))) &&
3138 	     ( r6s.q_failed || ((test_bit(R5_Insync, &qdev->flags)
3139 			     && !test_bit(R5_LOCKED, &qdev->flags)
3140 			     && test_bit(R5_UPTODATE, &qdev->flags)))))
3141 		handle_stripe_clean_event(conf, sh, disks, &return_bi);
3142 
3143 	/* Now we might consider reading some blocks, either to check/generate
3144 	 * parity, or to satisfy requests
3145 	 * or to load a block that is being partially written.
3146 	 */
3147 	if (s.to_read || s.non_overwrite || (s.to_write && s.failed) ||
3148 	    (s.syncing && (s.uptodate < disks)) || s.expanding)
3149 		handle_stripe_fill6(sh, &s, &r6s, disks);
3150 
3151 	/* now to consider writing and what else, if anything should be read */
3152 	if (s.to_write)
3153 		handle_stripe_dirtying6(conf, sh, &s, &r6s, disks);
3154 
3155 	/* maybe we need to check and possibly fix the parity for this stripe
3156 	 * Any reads will already have been scheduled, so we just see if enough
3157 	 * data is available
3158 	 */
3159 	if (s.syncing && s.locked == 0 && !test_bit(STRIPE_INSYNC, &sh->state))
3160 		handle_parity_checks6(conf, sh, &s, &r6s, tmp_page, disks);
3161 
3162 	if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
3163 		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
3164 		clear_bit(STRIPE_SYNCING, &sh->state);
3165 	}
3166 
3167 	/* If the failed drives are just a ReadError, then we might need
3168 	 * to progress the repair/check process
3169 	 */
3170 	if (s.failed <= 2 && !conf->mddev->ro)
3171 		for (i = 0; i < s.failed; i++) {
3172 			dev = &sh->dev[r6s.failed_num[i]];
3173 			if (test_bit(R5_ReadError, &dev->flags)
3174 			    && !test_bit(R5_LOCKED, &dev->flags)
3175 			    && test_bit(R5_UPTODATE, &dev->flags)
3176 				) {
3177 				if (!test_bit(R5_ReWrite, &dev->flags)) {
3178 					set_bit(R5_Wantwrite, &dev->flags);
3179 					set_bit(R5_ReWrite, &dev->flags);
3180 					set_bit(R5_LOCKED, &dev->flags);
3181 				} else {
3182 					/* let's read it back */
3183 					set_bit(R5_Wantread, &dev->flags);
3184 					set_bit(R5_LOCKED, &dev->flags);
3185 				}
3186 			}
3187 		}
3188 
3189 	if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
3190 		struct stripe_head *sh2
3191 			= get_active_stripe(conf, sh->sector, 1, 1, 1);
3192 		if (sh2 && test_bit(STRIPE_EXPAND_SOURCE, &sh2->state)) {
3193 			/* sh cannot be written until sh2 has been read.
3194 			 * so arrange for sh to be delayed a little
3195 			 */
3196 			set_bit(STRIPE_DELAYED, &sh->state);
3197 			set_bit(STRIPE_HANDLE, &sh->state);
3198 			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE,
3199 					      &sh2->state))
3200 				atomic_inc(&conf->preread_active_stripes);
3201 			release_stripe(sh2);
3202 			goto unlock;
3203 		}
3204 		if (sh2)
3205 			release_stripe(sh2);
3206 
3207 		/* Need to write out all blocks after computing P&Q */
3208 		sh->disks = conf->raid_disks;
3209 		stripe_set_idx(sh->sector, conf, 0, sh);
3210 		compute_parity6(sh, RECONSTRUCT_WRITE);
3211 		for (i = conf->raid_disks ; i-- ;  ) {
3212 			set_bit(R5_LOCKED, &sh->dev[i].flags);
3213 			s.locked++;
3214 			set_bit(R5_Wantwrite, &sh->dev[i].flags);
3215 		}
3216 		clear_bit(STRIPE_EXPANDING, &sh->state);
3217 	} else if (s.expanded) {
3218 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
3219 		atomic_dec(&conf->reshape_stripes);
3220 		wake_up(&conf->wait_for_overlap);
3221 		md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
3222 	}
3223 
3224 	if (s.expanding && s.locked == 0 &&
3225 	    !test_bit(STRIPE_COMPUTE_RUN, &sh->state))
3226 		handle_stripe_expansion(conf, sh, &r6s);
3227 
3228  unlock:
3229 	spin_unlock(&sh->lock);
3230 
3231 	/* wait for this device to become unblocked */
3232 	if (unlikely(blocked_rdev))
3233 		md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
3234 
3235 	ops_run_io(sh, &s);
3236 
3237 	return_io(return_bi);
3238 
3239 	return blocked_rdev == NULL;
3240 }
3241 
3242 /* returns true if the stripe was handled */
3243 static bool handle_stripe(struct stripe_head *sh, struct page *tmp_page)
3244 {
3245 	if (sh->raid_conf->level == 6)
3246 		return handle_stripe6(sh, tmp_page);
3247 	else
3248 		return handle_stripe5(sh);
3249 }
3250 
3251 
3252 
3253 static void raid5_activate_delayed(raid5_conf_t *conf)
3254 {
3255 	if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
3256 		while (!list_empty(&conf->delayed_list)) {
3257 			struct list_head *l = conf->delayed_list.next;
3258 			struct stripe_head *sh;
3259 			sh = list_entry(l, struct stripe_head, lru);
3260 			list_del_init(l);
3261 			clear_bit(STRIPE_DELAYED, &sh->state);
3262 			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
3263 				atomic_inc(&conf->preread_active_stripes);
3264 			list_add_tail(&sh->lru, &conf->hold_list);
3265 		}
3266 	} else
3267 		blk_plug_device(conf->mddev->queue);
3268 }
3269 
3270 static void activate_bit_delay(raid5_conf_t *conf)
3271 {
3272 	/* device_lock is held */
3273 	struct list_head head;
3274 	list_add(&head, &conf->bitmap_list);
3275 	list_del_init(&conf->bitmap_list);
3276 	while (!list_empty(&head)) {
3277 		struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
3278 		list_del_init(&sh->lru);
3279 		atomic_inc(&sh->count);
3280 		__release_stripe(conf, sh);
3281 	}
3282 }
3283 
3284 static void unplug_slaves(mddev_t *mddev)
3285 {
3286 	raid5_conf_t *conf = mddev->private;
3287 	int i;
3288 
3289 	rcu_read_lock();
3290 	for (i = 0; i < conf->raid_disks; i++) {
3291 		mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
3292 		if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
3293 			struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
3294 
3295 			atomic_inc(&rdev->nr_pending);
3296 			rcu_read_unlock();
3297 
3298 			blk_unplug(r_queue);
3299 
3300 			rdev_dec_pending(rdev, mddev);
3301 			rcu_read_lock();
3302 		}
3303 	}
3304 	rcu_read_unlock();
3305 }
3306 
3307 static void raid5_unplug_device(struct request_queue *q)
3308 {
3309 	mddev_t *mddev = q->queuedata;
3310 	raid5_conf_t *conf = mddev->private;
3311 	unsigned long flags;
3312 
3313 	spin_lock_irqsave(&conf->device_lock, flags);
3314 
3315 	if (blk_remove_plug(q)) {
3316 		conf->seq_flush++;
3317 		raid5_activate_delayed(conf);
3318 	}
3319 	md_wakeup_thread(mddev->thread);
3320 
3321 	spin_unlock_irqrestore(&conf->device_lock, flags);
3322 
3323 	unplug_slaves(mddev);
3324 }
3325 
3326 static int raid5_congested(void *data, int bits)
3327 {
3328 	mddev_t *mddev = data;
3329 	raid5_conf_t *conf = mddev->private;
3330 
3331 	/* No difference between reads and writes.  Just check
3332 	 * how busy the stripe_cache is
3333 	 */
3334 	if (conf->inactive_blocked)
3335 		return 1;
3336 	if (conf->quiesce)
3337 		return 1;
3338 	if (list_empty_careful(&conf->inactive_list))
3339 		return 1;
3340 
3341 	return 0;
3342 }
3343 
3344 /* We want read requests to align with chunks where possible,
3345  * but write requests don't need to.
3346  */
3347 static int raid5_mergeable_bvec(struct request_queue *q,
3348 				struct bvec_merge_data *bvm,
3349 				struct bio_vec *biovec)
3350 {
3351 	mddev_t *mddev = q->queuedata;
3352 	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
3353 	int max;
3354 	unsigned int chunk_sectors = mddev->chunk_sectors;
3355 	unsigned int bio_sectors = bvm->bi_size >> 9;
3356 
3357 	if ((bvm->bi_rw & 1) == WRITE)
3358 		return biovec->bv_len; /* always allow writes to be mergeable */
3359 
3360 	if (mddev->new_chunk_sectors < mddev->chunk_sectors)
3361 		chunk_sectors = mddev->new_chunk_sectors;
3362 	max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
3363 	if (max < 0) max = 0;
3364 	if (max <= biovec->bv_len && bio_sectors == 0)
3365 		return biovec->bv_len;
3366 	else
3367 		return max;
3368 }
3369 
3370 
3371 static int in_chunk_boundary(mddev_t *mddev, struct bio *bio)
3372 {
3373 	sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
3374 	unsigned int chunk_sectors = mddev->chunk_sectors;
3375 	unsigned int bio_sectors = bio->bi_size >> 9;
3376 
3377 	if (mddev->new_chunk_sectors < mddev->chunk_sectors)
3378 		chunk_sectors = mddev->new_chunk_sectors;
3379 	return  chunk_sectors >=
3380 		((sector & (chunk_sectors - 1)) + bio_sectors);
3381 }
3382 
3383 /*
3384  *  add bio to the retry LIFO  ( in O(1) ... we are in interrupt )
3385  *  later sampled by raid5d.
3386  */
3387 static void add_bio_to_retry(struct bio *bi,raid5_conf_t *conf)
3388 {
3389 	unsigned long flags;
3390 
3391 	spin_lock_irqsave(&conf->device_lock, flags);
3392 
3393 	bi->bi_next = conf->retry_read_aligned_list;
3394 	conf->retry_read_aligned_list = bi;
3395 
3396 	spin_unlock_irqrestore(&conf->device_lock, flags);
3397 	md_wakeup_thread(conf->mddev->thread);
3398 }
3399 
3400 
3401 static struct bio *remove_bio_from_retry(raid5_conf_t *conf)
3402 {
3403 	struct bio *bi;
3404 
3405 	bi = conf->retry_read_aligned;
3406 	if (bi) {
3407 		conf->retry_read_aligned = NULL;
3408 		return bi;
3409 	}
3410 	bi = conf->retry_read_aligned_list;
3411 	if(bi) {
3412 		conf->retry_read_aligned_list = bi->bi_next;
3413 		bi->bi_next = NULL;
3414 		/*
3415 		 * this sets the active strip count to 1 and the processed
3416 		 * strip count to zero (upper 8 bits)
3417 		 */
3418 		bi->bi_phys_segments = 1; /* biased count of active stripes */
3419 	}
3420 
3421 	return bi;
3422 }
3423 
3424 
3425 /*
3426  *  The "raid5_align_endio" should check if the read succeeded and if it
3427  *  did, call bio_endio on the original bio (having bio_put the new bio
3428  *  first).
3429  *  If the read failed..
3430  */
3431 static void raid5_align_endio(struct bio *bi, int error)
3432 {
3433 	struct bio* raid_bi  = bi->bi_private;
3434 	mddev_t *mddev;
3435 	raid5_conf_t *conf;
3436 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
3437 	mdk_rdev_t *rdev;
3438 
3439 	bio_put(bi);
3440 
3441 	mddev = raid_bi->bi_bdev->bd_disk->queue->queuedata;
3442 	conf = mddev->private;
3443 	rdev = (void*)raid_bi->bi_next;
3444 	raid_bi->bi_next = NULL;
3445 
3446 	rdev_dec_pending(rdev, conf->mddev);
3447 
3448 	if (!error && uptodate) {
3449 		bio_endio(raid_bi, 0);
3450 		if (atomic_dec_and_test(&conf->active_aligned_reads))
3451 			wake_up(&conf->wait_for_stripe);
3452 		return;
3453 	}
3454 
3455 
3456 	pr_debug("raid5_align_endio : io error...handing IO for a retry\n");
3457 
3458 	add_bio_to_retry(raid_bi, conf);
3459 }
3460 
3461 static int bio_fits_rdev(struct bio *bi)
3462 {
3463 	struct request_queue *q = bdev_get_queue(bi->bi_bdev);
3464 
3465 	if ((bi->bi_size>>9) > queue_max_sectors(q))
3466 		return 0;
3467 	blk_recount_segments(q, bi);
3468 	if (bi->bi_phys_segments > queue_max_phys_segments(q))
3469 		return 0;
3470 
3471 	if (q->merge_bvec_fn)
3472 		/* it's too hard to apply the merge_bvec_fn at this stage,
3473 		 * just just give up
3474 		 */
3475 		return 0;
3476 
3477 	return 1;
3478 }
3479 
3480 
3481 static int chunk_aligned_read(struct request_queue *q, struct bio * raid_bio)
3482 {
3483 	mddev_t *mddev = q->queuedata;
3484 	raid5_conf_t *conf = mddev->private;
3485 	unsigned int dd_idx;
3486 	struct bio* align_bi;
3487 	mdk_rdev_t *rdev;
3488 
3489 	if (!in_chunk_boundary(mddev, raid_bio)) {
3490 		pr_debug("chunk_aligned_read : non aligned\n");
3491 		return 0;
3492 	}
3493 	/*
3494 	 * use bio_clone to make a copy of the bio
3495 	 */
3496 	align_bi = bio_clone(raid_bio, GFP_NOIO);
3497 	if (!align_bi)
3498 		return 0;
3499 	/*
3500 	 *   set bi_end_io to a new function, and set bi_private to the
3501 	 *     original bio.
3502 	 */
3503 	align_bi->bi_end_io  = raid5_align_endio;
3504 	align_bi->bi_private = raid_bio;
3505 	/*
3506 	 *	compute position
3507 	 */
3508 	align_bi->bi_sector =  raid5_compute_sector(conf, raid_bio->bi_sector,
3509 						    0,
3510 						    &dd_idx, NULL);
3511 
3512 	rcu_read_lock();
3513 	rdev = rcu_dereference(conf->disks[dd_idx].rdev);
3514 	if (rdev && test_bit(In_sync, &rdev->flags)) {
3515 		atomic_inc(&rdev->nr_pending);
3516 		rcu_read_unlock();
3517 		raid_bio->bi_next = (void*)rdev;
3518 		align_bi->bi_bdev =  rdev->bdev;
3519 		align_bi->bi_flags &= ~(1 << BIO_SEG_VALID);
3520 		align_bi->bi_sector += rdev->data_offset;
3521 
3522 		if (!bio_fits_rdev(align_bi)) {
3523 			/* too big in some way */
3524 			bio_put(align_bi);
3525 			rdev_dec_pending(rdev, mddev);
3526 			return 0;
3527 		}
3528 
3529 		spin_lock_irq(&conf->device_lock);
3530 		wait_event_lock_irq(conf->wait_for_stripe,
3531 				    conf->quiesce == 0,
3532 				    conf->device_lock, /* nothing */);
3533 		atomic_inc(&conf->active_aligned_reads);
3534 		spin_unlock_irq(&conf->device_lock);
3535 
3536 		generic_make_request(align_bi);
3537 		return 1;
3538 	} else {
3539 		rcu_read_unlock();
3540 		bio_put(align_bi);
3541 		return 0;
3542 	}
3543 }
3544 
3545 /* __get_priority_stripe - get the next stripe to process
3546  *
3547  * Full stripe writes are allowed to pass preread active stripes up until
3548  * the bypass_threshold is exceeded.  In general the bypass_count
3549  * increments when the handle_list is handled before the hold_list; however, it
3550  * will not be incremented when STRIPE_IO_STARTED is sampled set signifying a
3551  * stripe with in flight i/o.  The bypass_count will be reset when the
3552  * head of the hold_list has changed, i.e. the head was promoted to the
3553  * handle_list.
3554  */
3555 static struct stripe_head *__get_priority_stripe(raid5_conf_t *conf)
3556 {
3557 	struct stripe_head *sh;
3558 
3559 	pr_debug("%s: handle: %s hold: %s full_writes: %d bypass_count: %d\n",
3560 		  __func__,
3561 		  list_empty(&conf->handle_list) ? "empty" : "busy",
3562 		  list_empty(&conf->hold_list) ? "empty" : "busy",
3563 		  atomic_read(&conf->pending_full_writes), conf->bypass_count);
3564 
3565 	if (!list_empty(&conf->handle_list)) {
3566 		sh = list_entry(conf->handle_list.next, typeof(*sh), lru);
3567 
3568 		if (list_empty(&conf->hold_list))
3569 			conf->bypass_count = 0;
3570 		else if (!test_bit(STRIPE_IO_STARTED, &sh->state)) {
3571 			if (conf->hold_list.next == conf->last_hold)
3572 				conf->bypass_count++;
3573 			else {
3574 				conf->last_hold = conf->hold_list.next;
3575 				conf->bypass_count -= conf->bypass_threshold;
3576 				if (conf->bypass_count < 0)
3577 					conf->bypass_count = 0;
3578 			}
3579 		}
3580 	} else if (!list_empty(&conf->hold_list) &&
3581 		   ((conf->bypass_threshold &&
3582 		     conf->bypass_count > conf->bypass_threshold) ||
3583 		    atomic_read(&conf->pending_full_writes) == 0)) {
3584 		sh = list_entry(conf->hold_list.next,
3585 				typeof(*sh), lru);
3586 		conf->bypass_count -= conf->bypass_threshold;
3587 		if (conf->bypass_count < 0)
3588 			conf->bypass_count = 0;
3589 	} else
3590 		return NULL;
3591 
3592 	list_del_init(&sh->lru);
3593 	atomic_inc(&sh->count);
3594 	BUG_ON(atomic_read(&sh->count) != 1);
3595 	return sh;
3596 }
3597 
3598 static int make_request(struct request_queue *q, struct bio * bi)
3599 {
3600 	mddev_t *mddev = q->queuedata;
3601 	raid5_conf_t *conf = mddev->private;
3602 	int dd_idx;
3603 	sector_t new_sector;
3604 	sector_t logical_sector, last_sector;
3605 	struct stripe_head *sh;
3606 	const int rw = bio_data_dir(bi);
3607 	int cpu, remaining;
3608 
3609 	if (unlikely(bio_rw_flagged(bi, BIO_RW_BARRIER))) {
3610 		bio_endio(bi, -EOPNOTSUPP);
3611 		return 0;
3612 	}
3613 
3614 	md_write_start(mddev, bi);
3615 
3616 	cpu = part_stat_lock();
3617 	part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
3618 	part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
3619 		      bio_sectors(bi));
3620 	part_stat_unlock();
3621 
3622 	if (rw == READ &&
3623 	     mddev->reshape_position == MaxSector &&
3624 	     chunk_aligned_read(q,bi))
3625 		return 0;
3626 
3627 	logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
3628 	last_sector = bi->bi_sector + (bi->bi_size>>9);
3629 	bi->bi_next = NULL;
3630 	bi->bi_phys_segments = 1;	/* over-loaded to count active stripes */
3631 
3632 	for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
3633 		DEFINE_WAIT(w);
3634 		int disks, data_disks;
3635 		int previous;
3636 
3637 	retry:
3638 		previous = 0;
3639 		disks = conf->raid_disks;
3640 		prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
3641 		if (unlikely(conf->reshape_progress != MaxSector)) {
3642 			/* spinlock is needed as reshape_progress may be
3643 			 * 64bit on a 32bit platform, and so it might be
3644 			 * possible to see a half-updated value
3645 			 * Ofcourse reshape_progress could change after
3646 			 * the lock is dropped, so once we get a reference
3647 			 * to the stripe that we think it is, we will have
3648 			 * to check again.
3649 			 */
3650 			spin_lock_irq(&conf->device_lock);
3651 			if (mddev->delta_disks < 0
3652 			    ? logical_sector < conf->reshape_progress
3653 			    : logical_sector >= conf->reshape_progress) {
3654 				disks = conf->previous_raid_disks;
3655 				previous = 1;
3656 			} else {
3657 				if (mddev->delta_disks < 0
3658 				    ? logical_sector < conf->reshape_safe
3659 				    : logical_sector >= conf->reshape_safe) {
3660 					spin_unlock_irq(&conf->device_lock);
3661 					schedule();
3662 					goto retry;
3663 				}
3664 			}
3665 			spin_unlock_irq(&conf->device_lock);
3666 		}
3667 		data_disks = disks - conf->max_degraded;
3668 
3669 		new_sector = raid5_compute_sector(conf, logical_sector,
3670 						  previous,
3671 						  &dd_idx, NULL);
3672 		pr_debug("raid5: make_request, sector %llu logical %llu\n",
3673 			(unsigned long long)new_sector,
3674 			(unsigned long long)logical_sector);
3675 
3676 		sh = get_active_stripe(conf, new_sector, previous,
3677 				       (bi->bi_rw&RWA_MASK), 0);
3678 		if (sh) {
3679 			if (unlikely(previous)) {
3680 				/* expansion might have moved on while waiting for a
3681 				 * stripe, so we must do the range check again.
3682 				 * Expansion could still move past after this
3683 				 * test, but as we are holding a reference to
3684 				 * 'sh', we know that if that happens,
3685 				 *  STRIPE_EXPANDING will get set and the expansion
3686 				 * won't proceed until we finish with the stripe.
3687 				 */
3688 				int must_retry = 0;
3689 				spin_lock_irq(&conf->device_lock);
3690 				if (mddev->delta_disks < 0
3691 				    ? logical_sector >= conf->reshape_progress
3692 				    : logical_sector < conf->reshape_progress)
3693 					/* mismatch, need to try again */
3694 					must_retry = 1;
3695 				spin_unlock_irq(&conf->device_lock);
3696 				if (must_retry) {
3697 					release_stripe(sh);
3698 					schedule();
3699 					goto retry;
3700 				}
3701 			}
3702 
3703 			if (bio_data_dir(bi) == WRITE &&
3704 			    logical_sector >= mddev->suspend_lo &&
3705 			    logical_sector < mddev->suspend_hi) {
3706 				release_stripe(sh);
3707 				/* As the suspend_* range is controlled by
3708 				 * userspace, we want an interruptible
3709 				 * wait.
3710 				 */
3711 				flush_signals(current);
3712 				prepare_to_wait(&conf->wait_for_overlap,
3713 						&w, TASK_INTERRUPTIBLE);
3714 				if (logical_sector >= mddev->suspend_lo &&
3715 				    logical_sector < mddev->suspend_hi)
3716 					schedule();
3717 				goto retry;
3718 			}
3719 
3720 			if (test_bit(STRIPE_EXPANDING, &sh->state) ||
3721 			    !add_stripe_bio(sh, bi, dd_idx, (bi->bi_rw&RW_MASK))) {
3722 				/* Stripe is busy expanding or
3723 				 * add failed due to overlap.  Flush everything
3724 				 * and wait a while
3725 				 */
3726 				raid5_unplug_device(mddev->queue);
3727 				release_stripe(sh);
3728 				schedule();
3729 				goto retry;
3730 			}
3731 			finish_wait(&conf->wait_for_overlap, &w);
3732 			set_bit(STRIPE_HANDLE, &sh->state);
3733 			clear_bit(STRIPE_DELAYED, &sh->state);
3734 			release_stripe(sh);
3735 		} else {
3736 			/* cannot get stripe for read-ahead, just give-up */
3737 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
3738 			finish_wait(&conf->wait_for_overlap, &w);
3739 			break;
3740 		}
3741 
3742 	}
3743 	spin_lock_irq(&conf->device_lock);
3744 	remaining = raid5_dec_bi_phys_segments(bi);
3745 	spin_unlock_irq(&conf->device_lock);
3746 	if (remaining == 0) {
3747 
3748 		if ( rw == WRITE )
3749 			md_write_end(mddev);
3750 
3751 		bio_endio(bi, 0);
3752 	}
3753 	return 0;
3754 }
3755 
3756 static sector_t raid5_size(mddev_t *mddev, sector_t sectors, int raid_disks);
3757 
3758 static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped)
3759 {
3760 	/* reshaping is quite different to recovery/resync so it is
3761 	 * handled quite separately ... here.
3762 	 *
3763 	 * On each call to sync_request, we gather one chunk worth of
3764 	 * destination stripes and flag them as expanding.
3765 	 * Then we find all the source stripes and request reads.
3766 	 * As the reads complete, handle_stripe will copy the data
3767 	 * into the destination stripe and release that stripe.
3768 	 */
3769 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
3770 	struct stripe_head *sh;
3771 	sector_t first_sector, last_sector;
3772 	int raid_disks = conf->previous_raid_disks;
3773 	int data_disks = raid_disks - conf->max_degraded;
3774 	int new_data_disks = conf->raid_disks - conf->max_degraded;
3775 	int i;
3776 	int dd_idx;
3777 	sector_t writepos, readpos, safepos;
3778 	sector_t stripe_addr;
3779 	int reshape_sectors;
3780 	struct list_head stripes;
3781 
3782 	if (sector_nr == 0) {
3783 		/* If restarting in the middle, skip the initial sectors */
3784 		if (mddev->delta_disks < 0 &&
3785 		    conf->reshape_progress < raid5_size(mddev, 0, 0)) {
3786 			sector_nr = raid5_size(mddev, 0, 0)
3787 				- conf->reshape_progress;
3788 		} else if (mddev->delta_disks >= 0 &&
3789 			   conf->reshape_progress > 0)
3790 			sector_nr = conf->reshape_progress;
3791 		sector_div(sector_nr, new_data_disks);
3792 		if (sector_nr) {
3793 			*skipped = 1;
3794 			return sector_nr;
3795 		}
3796 	}
3797 
3798 	/* We need to process a full chunk at a time.
3799 	 * If old and new chunk sizes differ, we need to process the
3800 	 * largest of these
3801 	 */
3802 	if (mddev->new_chunk_sectors > mddev->chunk_sectors)
3803 		reshape_sectors = mddev->new_chunk_sectors;
3804 	else
3805 		reshape_sectors = mddev->chunk_sectors;
3806 
3807 	/* we update the metadata when there is more than 3Meg
3808 	 * in the block range (that is rather arbitrary, should
3809 	 * probably be time based) or when the data about to be
3810 	 * copied would over-write the source of the data at
3811 	 * the front of the range.
3812 	 * i.e. one new_stripe along from reshape_progress new_maps
3813 	 * to after where reshape_safe old_maps to
3814 	 */
3815 	writepos = conf->reshape_progress;
3816 	sector_div(writepos, new_data_disks);
3817 	readpos = conf->reshape_progress;
3818 	sector_div(readpos, data_disks);
3819 	safepos = conf->reshape_safe;
3820 	sector_div(safepos, data_disks);
3821 	if (mddev->delta_disks < 0) {
3822 		writepos -= min_t(sector_t, reshape_sectors, writepos);
3823 		readpos += reshape_sectors;
3824 		safepos += reshape_sectors;
3825 	} else {
3826 		writepos += reshape_sectors;
3827 		readpos -= min_t(sector_t, reshape_sectors, readpos);
3828 		safepos -= min_t(sector_t, reshape_sectors, safepos);
3829 	}
3830 
3831 	/* 'writepos' is the most advanced device address we might write.
3832 	 * 'readpos' is the least advanced device address we might read.
3833 	 * 'safepos' is the least address recorded in the metadata as having
3834 	 *     been reshaped.
3835 	 * If 'readpos' is behind 'writepos', then there is no way that we can
3836 	 * ensure safety in the face of a crash - that must be done by userspace
3837 	 * making a backup of the data.  So in that case there is no particular
3838 	 * rush to update metadata.
3839 	 * Otherwise if 'safepos' is behind 'writepos', then we really need to
3840 	 * update the metadata to advance 'safepos' to match 'readpos' so that
3841 	 * we can be safe in the event of a crash.
3842 	 * So we insist on updating metadata if safepos is behind writepos and
3843 	 * readpos is beyond writepos.
3844 	 * In any case, update the metadata every 10 seconds.
3845 	 * Maybe that number should be configurable, but I'm not sure it is
3846 	 * worth it.... maybe it could be a multiple of safemode_delay???
3847 	 */
3848 	if ((mddev->delta_disks < 0
3849 	     ? (safepos > writepos && readpos < writepos)
3850 	     : (safepos < writepos && readpos > writepos)) ||
3851 	    time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
3852 		/* Cannot proceed until we've updated the superblock... */
3853 		wait_event(conf->wait_for_overlap,
3854 			   atomic_read(&conf->reshape_stripes)==0);
3855 		mddev->reshape_position = conf->reshape_progress;
3856 		mddev->curr_resync_completed = mddev->curr_resync;
3857 		conf->reshape_checkpoint = jiffies;
3858 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
3859 		md_wakeup_thread(mddev->thread);
3860 		wait_event(mddev->sb_wait, mddev->flags == 0 ||
3861 			   kthread_should_stop());
3862 		spin_lock_irq(&conf->device_lock);
3863 		conf->reshape_safe = mddev->reshape_position;
3864 		spin_unlock_irq(&conf->device_lock);
3865 		wake_up(&conf->wait_for_overlap);
3866 		sysfs_notify(&mddev->kobj, NULL, "sync_completed");
3867 	}
3868 
3869 	if (mddev->delta_disks < 0) {
3870 		BUG_ON(conf->reshape_progress == 0);
3871 		stripe_addr = writepos;
3872 		BUG_ON((mddev->dev_sectors &
3873 			~((sector_t)reshape_sectors - 1))
3874 		       - reshape_sectors - stripe_addr
3875 		       != sector_nr);
3876 	} else {
3877 		BUG_ON(writepos != sector_nr + reshape_sectors);
3878 		stripe_addr = sector_nr;
3879 	}
3880 	INIT_LIST_HEAD(&stripes);
3881 	for (i = 0; i < reshape_sectors; i += STRIPE_SECTORS) {
3882 		int j;
3883 		int skipped = 0;
3884 		sh = get_active_stripe(conf, stripe_addr+i, 0, 0, 1);
3885 		set_bit(STRIPE_EXPANDING, &sh->state);
3886 		atomic_inc(&conf->reshape_stripes);
3887 		/* If any of this stripe is beyond the end of the old
3888 		 * array, then we need to zero those blocks
3889 		 */
3890 		for (j=sh->disks; j--;) {
3891 			sector_t s;
3892 			if (j == sh->pd_idx)
3893 				continue;
3894 			if (conf->level == 6 &&
3895 			    j == sh->qd_idx)
3896 				continue;
3897 			s = compute_blocknr(sh, j, 0);
3898 			if (s < raid5_size(mddev, 0, 0)) {
3899 				skipped = 1;
3900 				continue;
3901 			}
3902 			memset(page_address(sh->dev[j].page), 0, STRIPE_SIZE);
3903 			set_bit(R5_Expanded, &sh->dev[j].flags);
3904 			set_bit(R5_UPTODATE, &sh->dev[j].flags);
3905 		}
3906 		if (!skipped) {
3907 			set_bit(STRIPE_EXPAND_READY, &sh->state);
3908 			set_bit(STRIPE_HANDLE, &sh->state);
3909 		}
3910 		list_add(&sh->lru, &stripes);
3911 	}
3912 	spin_lock_irq(&conf->device_lock);
3913 	if (mddev->delta_disks < 0)
3914 		conf->reshape_progress -= reshape_sectors * new_data_disks;
3915 	else
3916 		conf->reshape_progress += reshape_sectors * new_data_disks;
3917 	spin_unlock_irq(&conf->device_lock);
3918 	/* Ok, those stripe are ready. We can start scheduling
3919 	 * reads on the source stripes.
3920 	 * The source stripes are determined by mapping the first and last
3921 	 * block on the destination stripes.
3922 	 */
3923 	first_sector =
3924 		raid5_compute_sector(conf, stripe_addr*(new_data_disks),
3925 				     1, &dd_idx, NULL);
3926 	last_sector =
3927 		raid5_compute_sector(conf, ((stripe_addr+reshape_sectors)
3928 					    * new_data_disks - 1),
3929 				     1, &dd_idx, NULL);
3930 	if (last_sector >= mddev->dev_sectors)
3931 		last_sector = mddev->dev_sectors - 1;
3932 	while (first_sector <= last_sector) {
3933 		sh = get_active_stripe(conf, first_sector, 1, 0, 1);
3934 		set_bit(STRIPE_EXPAND_SOURCE, &sh->state);
3935 		set_bit(STRIPE_HANDLE, &sh->state);
3936 		release_stripe(sh);
3937 		first_sector += STRIPE_SECTORS;
3938 	}
3939 	/* Now that the sources are clearly marked, we can release
3940 	 * the destination stripes
3941 	 */
3942 	while (!list_empty(&stripes)) {
3943 		sh = list_entry(stripes.next, struct stripe_head, lru);
3944 		list_del_init(&sh->lru);
3945 		release_stripe(sh);
3946 	}
3947 	/* If this takes us to the resync_max point where we have to pause,
3948 	 * then we need to write out the superblock.
3949 	 */
3950 	sector_nr += reshape_sectors;
3951 	if ((sector_nr - mddev->curr_resync_completed) * 2
3952 	    >= mddev->resync_max - mddev->curr_resync_completed) {
3953 		/* Cannot proceed until we've updated the superblock... */
3954 		wait_event(conf->wait_for_overlap,
3955 			   atomic_read(&conf->reshape_stripes) == 0);
3956 		mddev->reshape_position = conf->reshape_progress;
3957 		mddev->curr_resync_completed = mddev->curr_resync + reshape_sectors;
3958 		conf->reshape_checkpoint = jiffies;
3959 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
3960 		md_wakeup_thread(mddev->thread);
3961 		wait_event(mddev->sb_wait,
3962 			   !test_bit(MD_CHANGE_DEVS, &mddev->flags)
3963 			   || kthread_should_stop());
3964 		spin_lock_irq(&conf->device_lock);
3965 		conf->reshape_safe = mddev->reshape_position;
3966 		spin_unlock_irq(&conf->device_lock);
3967 		wake_up(&conf->wait_for_overlap);
3968 		sysfs_notify(&mddev->kobj, NULL, "sync_completed");
3969 	}
3970 	return reshape_sectors;
3971 }
3972 
3973 /* FIXME go_faster isn't used */
3974 static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster)
3975 {
3976 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
3977 	struct stripe_head *sh;
3978 	sector_t max_sector = mddev->dev_sectors;
3979 	int sync_blocks;
3980 	int still_degraded = 0;
3981 	int i;
3982 
3983 	if (sector_nr >= max_sector) {
3984 		/* just being told to finish up .. nothing much to do */
3985 		unplug_slaves(mddev);
3986 
3987 		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) {
3988 			end_reshape(conf);
3989 			return 0;
3990 		}
3991 
3992 		if (mddev->curr_resync < max_sector) /* aborted */
3993 			bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
3994 					&sync_blocks, 1);
3995 		else /* completed sync */
3996 			conf->fullsync = 0;
3997 		bitmap_close_sync(mddev->bitmap);
3998 
3999 		return 0;
4000 	}
4001 
4002 	/* Allow raid5_quiesce to complete */
4003 	wait_event(conf->wait_for_overlap, conf->quiesce != 2);
4004 
4005 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
4006 		return reshape_request(mddev, sector_nr, skipped);
4007 
4008 	/* No need to check resync_max as we never do more than one
4009 	 * stripe, and as resync_max will always be on a chunk boundary,
4010 	 * if the check in md_do_sync didn't fire, there is no chance
4011 	 * of overstepping resync_max here
4012 	 */
4013 
4014 	/* if there is too many failed drives and we are trying
4015 	 * to resync, then assert that we are finished, because there is
4016 	 * nothing we can do.
4017 	 */
4018 	if (mddev->degraded >= conf->max_degraded &&
4019 	    test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
4020 		sector_t rv = mddev->dev_sectors - sector_nr;
4021 		*skipped = 1;
4022 		return rv;
4023 	}
4024 	if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
4025 	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
4026 	    !conf->fullsync && sync_blocks >= STRIPE_SECTORS) {
4027 		/* we can skip this block, and probably more */
4028 		sync_blocks /= STRIPE_SECTORS;
4029 		*skipped = 1;
4030 		return sync_blocks * STRIPE_SECTORS; /* keep things rounded to whole stripes */
4031 	}
4032 
4033 
4034 	bitmap_cond_end_sync(mddev->bitmap, sector_nr);
4035 
4036 	sh = get_active_stripe(conf, sector_nr, 0, 1, 0);
4037 	if (sh == NULL) {
4038 		sh = get_active_stripe(conf, sector_nr, 0, 0, 0);
4039 		/* make sure we don't swamp the stripe cache if someone else
4040 		 * is trying to get access
4041 		 */
4042 		schedule_timeout_uninterruptible(1);
4043 	}
4044 	/* Need to check if array will still be degraded after recovery/resync
4045 	 * We don't need to check the 'failed' flag as when that gets set,
4046 	 * recovery aborts.
4047 	 */
4048 	for (i = 0; i < conf->raid_disks; i++)
4049 		if (conf->disks[i].rdev == NULL)
4050 			still_degraded = 1;
4051 
4052 	bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);
4053 
4054 	spin_lock(&sh->lock);
4055 	set_bit(STRIPE_SYNCING, &sh->state);
4056 	clear_bit(STRIPE_INSYNC, &sh->state);
4057 	spin_unlock(&sh->lock);
4058 
4059 	/* wait for any blocked device to be handled */
4060 	while(unlikely(!handle_stripe(sh, NULL)))
4061 		;
4062 	release_stripe(sh);
4063 
4064 	return STRIPE_SECTORS;
4065 }
4066 
4067 static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
4068 {
4069 	/* We may not be able to submit a whole bio at once as there
4070 	 * may not be enough stripe_heads available.
4071 	 * We cannot pre-allocate enough stripe_heads as we may need
4072 	 * more than exist in the cache (if we allow ever large chunks).
4073 	 * So we do one stripe head at a time and record in
4074 	 * ->bi_hw_segments how many have been done.
4075 	 *
4076 	 * We *know* that this entire raid_bio is in one chunk, so
4077 	 * it will be only one 'dd_idx' and only need one call to raid5_compute_sector.
4078 	 */
4079 	struct stripe_head *sh;
4080 	int dd_idx;
4081 	sector_t sector, logical_sector, last_sector;
4082 	int scnt = 0;
4083 	int remaining;
4084 	int handled = 0;
4085 
4086 	logical_sector = raid_bio->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
4087 	sector = raid5_compute_sector(conf, logical_sector,
4088 				      0, &dd_idx, NULL);
4089 	last_sector = raid_bio->bi_sector + (raid_bio->bi_size>>9);
4090 
4091 	for (; logical_sector < last_sector;
4092 	     logical_sector += STRIPE_SECTORS,
4093 		     sector += STRIPE_SECTORS,
4094 		     scnt++) {
4095 
4096 		if (scnt < raid5_bi_hw_segments(raid_bio))
4097 			/* already done this stripe */
4098 			continue;
4099 
4100 		sh = get_active_stripe(conf, sector, 0, 1, 0);
4101 
4102 		if (!sh) {
4103 			/* failed to get a stripe - must wait */
4104 			raid5_set_bi_hw_segments(raid_bio, scnt);
4105 			conf->retry_read_aligned = raid_bio;
4106 			return handled;
4107 		}
4108 
4109 		set_bit(R5_ReadError, &sh->dev[dd_idx].flags);
4110 		if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
4111 			release_stripe(sh);
4112 			raid5_set_bi_hw_segments(raid_bio, scnt);
4113 			conf->retry_read_aligned = raid_bio;
4114 			return handled;
4115 		}
4116 
4117 		handle_stripe(sh, NULL);
4118 		release_stripe(sh);
4119 		handled++;
4120 	}
4121 	spin_lock_irq(&conf->device_lock);
4122 	remaining = raid5_dec_bi_phys_segments(raid_bio);
4123 	spin_unlock_irq(&conf->device_lock);
4124 	if (remaining == 0)
4125 		bio_endio(raid_bio, 0);
4126 	if (atomic_dec_and_test(&conf->active_aligned_reads))
4127 		wake_up(&conf->wait_for_stripe);
4128 	return handled;
4129 }
4130 
4131 
4132 
4133 /*
4134  * This is our raid5 kernel thread.
4135  *
4136  * We scan the hash table for stripes which can be handled now.
4137  * During the scan, completed stripes are saved for us by the interrupt
4138  * handler, so that they will not have to wait for our next wakeup.
4139  */
4140 static void raid5d(mddev_t *mddev)
4141 {
4142 	struct stripe_head *sh;
4143 	raid5_conf_t *conf = mddev->private;
4144 	int handled;
4145 
4146 	pr_debug("+++ raid5d active\n");
4147 
4148 	md_check_recovery(mddev);
4149 
4150 	handled = 0;
4151 	spin_lock_irq(&conf->device_lock);
4152 	while (1) {
4153 		struct bio *bio;
4154 
4155 		if (conf->seq_flush != conf->seq_write) {
4156 			int seq = conf->seq_flush;
4157 			spin_unlock_irq(&conf->device_lock);
4158 			bitmap_unplug(mddev->bitmap);
4159 			spin_lock_irq(&conf->device_lock);
4160 			conf->seq_write = seq;
4161 			activate_bit_delay(conf);
4162 		}
4163 
4164 		while ((bio = remove_bio_from_retry(conf))) {
4165 			int ok;
4166 			spin_unlock_irq(&conf->device_lock);
4167 			ok = retry_aligned_read(conf, bio);
4168 			spin_lock_irq(&conf->device_lock);
4169 			if (!ok)
4170 				break;
4171 			handled++;
4172 		}
4173 
4174 		sh = __get_priority_stripe(conf);
4175 
4176 		if (!sh)
4177 			break;
4178 		spin_unlock_irq(&conf->device_lock);
4179 
4180 		handled++;
4181 		handle_stripe(sh, conf->spare_page);
4182 		release_stripe(sh);
4183 
4184 		spin_lock_irq(&conf->device_lock);
4185 	}
4186 	pr_debug("%d stripes handled\n", handled);
4187 
4188 	spin_unlock_irq(&conf->device_lock);
4189 
4190 	async_tx_issue_pending_all();
4191 	unplug_slaves(mddev);
4192 
4193 	pr_debug("--- raid5d inactive\n");
4194 }
4195 
4196 static ssize_t
4197 raid5_show_stripe_cache_size(mddev_t *mddev, char *page)
4198 {
4199 	raid5_conf_t *conf = mddev->private;
4200 	if (conf)
4201 		return sprintf(page, "%d\n", conf->max_nr_stripes);
4202 	else
4203 		return 0;
4204 }
4205 
4206 static ssize_t
4207 raid5_store_stripe_cache_size(mddev_t *mddev, const char *page, size_t len)
4208 {
4209 	raid5_conf_t *conf = mddev->private;
4210 	unsigned long new;
4211 	int err;
4212 
4213 	if (len >= PAGE_SIZE)
4214 		return -EINVAL;
4215 	if (!conf)
4216 		return -ENODEV;
4217 
4218 	if (strict_strtoul(page, 10, &new))
4219 		return -EINVAL;
4220 	if (new <= 16 || new > 32768)
4221 		return -EINVAL;
4222 	while (new < conf->max_nr_stripes) {
4223 		if (drop_one_stripe(conf))
4224 			conf->max_nr_stripes--;
4225 		else
4226 			break;
4227 	}
4228 	err = md_allow_write(mddev);
4229 	if (err)
4230 		return err;
4231 	while (new > conf->max_nr_stripes) {
4232 		if (grow_one_stripe(conf))
4233 			conf->max_nr_stripes++;
4234 		else break;
4235 	}
4236 	return len;
4237 }
4238 
4239 static struct md_sysfs_entry
4240 raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
4241 				raid5_show_stripe_cache_size,
4242 				raid5_store_stripe_cache_size);
4243 
4244 static ssize_t
4245 raid5_show_preread_threshold(mddev_t *mddev, char *page)
4246 {
4247 	raid5_conf_t *conf = mddev->private;
4248 	if (conf)
4249 		return sprintf(page, "%d\n", conf->bypass_threshold);
4250 	else
4251 		return 0;
4252 }
4253 
4254 static ssize_t
4255 raid5_store_preread_threshold(mddev_t *mddev, const char *page, size_t len)
4256 {
4257 	raid5_conf_t *conf = mddev->private;
4258 	unsigned long new;
4259 	if (len >= PAGE_SIZE)
4260 		return -EINVAL;
4261 	if (!conf)
4262 		return -ENODEV;
4263 
4264 	if (strict_strtoul(page, 10, &new))
4265 		return -EINVAL;
4266 	if (new > conf->max_nr_stripes)
4267 		return -EINVAL;
4268 	conf->bypass_threshold = new;
4269 	return len;
4270 }
4271 
4272 static struct md_sysfs_entry
4273 raid5_preread_bypass_threshold = __ATTR(preread_bypass_threshold,
4274 					S_IRUGO | S_IWUSR,
4275 					raid5_show_preread_threshold,
4276 					raid5_store_preread_threshold);
4277 
4278 static ssize_t
4279 stripe_cache_active_show(mddev_t *mddev, char *page)
4280 {
4281 	raid5_conf_t *conf = mddev->private;
4282 	if (conf)
4283 		return sprintf(page, "%d\n", atomic_read(&conf->active_stripes));
4284 	else
4285 		return 0;
4286 }
4287 
4288 static struct md_sysfs_entry
4289 raid5_stripecache_active = __ATTR_RO(stripe_cache_active);
4290 
4291 static struct attribute *raid5_attrs[] =  {
4292 	&raid5_stripecache_size.attr,
4293 	&raid5_stripecache_active.attr,
4294 	&raid5_preread_bypass_threshold.attr,
4295 	NULL,
4296 };
4297 static struct attribute_group raid5_attrs_group = {
4298 	.name = NULL,
4299 	.attrs = raid5_attrs,
4300 };
4301 
4302 static sector_t
4303 raid5_size(mddev_t *mddev, sector_t sectors, int raid_disks)
4304 {
4305 	raid5_conf_t *conf = mddev->private;
4306 
4307 	if (!sectors)
4308 		sectors = mddev->dev_sectors;
4309 	if (!raid_disks) {
4310 		/* size is defined by the smallest of previous and new size */
4311 		if (conf->raid_disks < conf->previous_raid_disks)
4312 			raid_disks = conf->raid_disks;
4313 		else
4314 			raid_disks = conf->previous_raid_disks;
4315 	}
4316 
4317 	sectors &= ~((sector_t)mddev->chunk_sectors - 1);
4318 	sectors &= ~((sector_t)mddev->new_chunk_sectors - 1);
4319 	return sectors * (raid_disks - conf->max_degraded);
4320 }
4321 
4322 static void free_conf(raid5_conf_t *conf)
4323 {
4324 	shrink_stripes(conf);
4325 	safe_put_page(conf->spare_page);
4326 	kfree(conf->disks);
4327 	kfree(conf->stripe_hashtbl);
4328 	kfree(conf);
4329 }
4330 
4331 static raid5_conf_t *setup_conf(mddev_t *mddev)
4332 {
4333 	raid5_conf_t *conf;
4334 	int raid_disk, memory;
4335 	mdk_rdev_t *rdev;
4336 	struct disk_info *disk;
4337 
4338 	if (mddev->new_level != 5
4339 	    && mddev->new_level != 4
4340 	    && mddev->new_level != 6) {
4341 		printk(KERN_ERR "raid5: %s: raid level not set to 4/5/6 (%d)\n",
4342 		       mdname(mddev), mddev->new_level);
4343 		return ERR_PTR(-EIO);
4344 	}
4345 	if ((mddev->new_level == 5
4346 	     && !algorithm_valid_raid5(mddev->new_layout)) ||
4347 	    (mddev->new_level == 6
4348 	     && !algorithm_valid_raid6(mddev->new_layout))) {
4349 		printk(KERN_ERR "raid5: %s: layout %d not supported\n",
4350 		       mdname(mddev), mddev->new_layout);
4351 		return ERR_PTR(-EIO);
4352 	}
4353 	if (mddev->new_level == 6 && mddev->raid_disks < 4) {
4354 		printk(KERN_ERR "raid6: not enough configured devices for %s (%d, minimum 4)\n",
4355 		       mdname(mddev), mddev->raid_disks);
4356 		return ERR_PTR(-EINVAL);
4357 	}
4358 
4359 	if (!mddev->new_chunk_sectors ||
4360 	    (mddev->new_chunk_sectors << 9) % PAGE_SIZE ||
4361 	    !is_power_of_2(mddev->new_chunk_sectors)) {
4362 		printk(KERN_ERR "raid5: invalid chunk size %d for %s\n",
4363 		       mddev->new_chunk_sectors << 9, mdname(mddev));
4364 		return ERR_PTR(-EINVAL);
4365 	}
4366 
4367 	conf = kzalloc(sizeof(raid5_conf_t), GFP_KERNEL);
4368 	if (conf == NULL)
4369 		goto abort;
4370 
4371 	conf->raid_disks = mddev->raid_disks;
4372 	if (mddev->reshape_position == MaxSector)
4373 		conf->previous_raid_disks = mddev->raid_disks;
4374 	else
4375 		conf->previous_raid_disks = mddev->raid_disks - mddev->delta_disks;
4376 
4377 	conf->disks = kzalloc(conf->raid_disks * sizeof(struct disk_info),
4378 			      GFP_KERNEL);
4379 	if (!conf->disks)
4380 		goto abort;
4381 
4382 	conf->mddev = mddev;
4383 
4384 	if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
4385 		goto abort;
4386 
4387 	if (mddev->new_level == 6) {
4388 		conf->spare_page = alloc_page(GFP_KERNEL);
4389 		if (!conf->spare_page)
4390 			goto abort;
4391 	}
4392 	spin_lock_init(&conf->device_lock);
4393 	init_waitqueue_head(&conf->wait_for_stripe);
4394 	init_waitqueue_head(&conf->wait_for_overlap);
4395 	INIT_LIST_HEAD(&conf->handle_list);
4396 	INIT_LIST_HEAD(&conf->hold_list);
4397 	INIT_LIST_HEAD(&conf->delayed_list);
4398 	INIT_LIST_HEAD(&conf->bitmap_list);
4399 	INIT_LIST_HEAD(&conf->inactive_list);
4400 	atomic_set(&conf->active_stripes, 0);
4401 	atomic_set(&conf->preread_active_stripes, 0);
4402 	atomic_set(&conf->active_aligned_reads, 0);
4403 	conf->bypass_threshold = BYPASS_THRESHOLD;
4404 
4405 	pr_debug("raid5: run(%s) called.\n", mdname(mddev));
4406 
4407 	list_for_each_entry(rdev, &mddev->disks, same_set) {
4408 		raid_disk = rdev->raid_disk;
4409 		if (raid_disk >= conf->raid_disks
4410 		    || raid_disk < 0)
4411 			continue;
4412 		disk = conf->disks + raid_disk;
4413 
4414 		disk->rdev = rdev;
4415 
4416 		if (test_bit(In_sync, &rdev->flags)) {
4417 			char b[BDEVNAME_SIZE];
4418 			printk(KERN_INFO "raid5: device %s operational as raid"
4419 				" disk %d\n", bdevname(rdev->bdev,b),
4420 				raid_disk);
4421 		} else
4422 			/* Cannot rely on bitmap to complete recovery */
4423 			conf->fullsync = 1;
4424 	}
4425 
4426 	conf->chunk_sectors = mddev->new_chunk_sectors;
4427 	conf->level = mddev->new_level;
4428 	if (conf->level == 6)
4429 		conf->max_degraded = 2;
4430 	else
4431 		conf->max_degraded = 1;
4432 	conf->algorithm = mddev->new_layout;
4433 	conf->max_nr_stripes = NR_STRIPES;
4434 	conf->reshape_progress = mddev->reshape_position;
4435 	if (conf->reshape_progress != MaxSector) {
4436 		conf->prev_chunk_sectors = mddev->chunk_sectors;
4437 		conf->prev_algo = mddev->layout;
4438 	}
4439 
4440 	memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
4441 		 conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
4442 	if (grow_stripes(conf, conf->max_nr_stripes)) {
4443 		printk(KERN_ERR
4444 			"raid5: couldn't allocate %dkB for buffers\n", memory);
4445 		goto abort;
4446 	} else
4447 		printk(KERN_INFO "raid5: allocated %dkB for %s\n",
4448 			memory, mdname(mddev));
4449 
4450 	conf->thread = md_register_thread(raid5d, mddev, "%s_raid5");
4451 	if (!conf->thread) {
4452 		printk(KERN_ERR
4453 		       "raid5: couldn't allocate thread for %s\n",
4454 		       mdname(mddev));
4455 		goto abort;
4456 	}
4457 
4458 	return conf;
4459 
4460  abort:
4461 	if (conf) {
4462 		free_conf(conf);
4463 		return ERR_PTR(-EIO);
4464 	} else
4465 		return ERR_PTR(-ENOMEM);
4466 }
4467 
4468 static int run(mddev_t *mddev)
4469 {
4470 	raid5_conf_t *conf;
4471 	int working_disks = 0, chunk_size;
4472 	mdk_rdev_t *rdev;
4473 
4474 	if (mddev->recovery_cp != MaxSector)
4475 		printk(KERN_NOTICE "raid5: %s is not clean"
4476 		       " -- starting background reconstruction\n",
4477 		       mdname(mddev));
4478 	if (mddev->reshape_position != MaxSector) {
4479 		/* Check that we can continue the reshape.
4480 		 * Currently only disks can change, it must
4481 		 * increase, and we must be past the point where
4482 		 * a stripe over-writes itself
4483 		 */
4484 		sector_t here_new, here_old;
4485 		int old_disks;
4486 		int max_degraded = (mddev->level == 6 ? 2 : 1);
4487 
4488 		if (mddev->new_level != mddev->level) {
4489 			printk(KERN_ERR "raid5: %s: unsupported reshape "
4490 			       "required - aborting.\n",
4491 			       mdname(mddev));
4492 			return -EINVAL;
4493 		}
4494 		old_disks = mddev->raid_disks - mddev->delta_disks;
4495 		/* reshape_position must be on a new-stripe boundary, and one
4496 		 * further up in new geometry must map after here in old
4497 		 * geometry.
4498 		 */
4499 		here_new = mddev->reshape_position;
4500 		if (sector_div(here_new, mddev->new_chunk_sectors *
4501 			       (mddev->raid_disks - max_degraded))) {
4502 			printk(KERN_ERR "raid5: reshape_position not "
4503 			       "on a stripe boundary\n");
4504 			return -EINVAL;
4505 		}
4506 		/* here_new is the stripe we will write to */
4507 		here_old = mddev->reshape_position;
4508 		sector_div(here_old, mddev->chunk_sectors *
4509 			   (old_disks-max_degraded));
4510 		/* here_old is the first stripe that we might need to read
4511 		 * from */
4512 		if (mddev->delta_disks == 0) {
4513 			/* We cannot be sure it is safe to start an in-place
4514 			 * reshape.  It is only safe if user-space if monitoring
4515 			 * and taking constant backups.
4516 			 * mdadm always starts a situation like this in
4517 			 * readonly mode so it can take control before
4518 			 * allowing any writes.  So just check for that.
4519 			 */
4520 			if ((here_new * mddev->new_chunk_sectors !=
4521 			     here_old * mddev->chunk_sectors) ||
4522 			    mddev->ro == 0) {
4523 				printk(KERN_ERR "raid5: in-place reshape must be started"
4524 				       " in read-only mode - aborting\n");
4525 				return -EINVAL;
4526 			}
4527 		} else if (mddev->delta_disks < 0
4528 		    ? (here_new * mddev->new_chunk_sectors <=
4529 		       here_old * mddev->chunk_sectors)
4530 		    : (here_new * mddev->new_chunk_sectors >=
4531 		       here_old * mddev->chunk_sectors)) {
4532 			/* Reading from the same stripe as writing to - bad */
4533 			printk(KERN_ERR "raid5: reshape_position too early for "
4534 			       "auto-recovery - aborting.\n");
4535 			return -EINVAL;
4536 		}
4537 		printk(KERN_INFO "raid5: reshape will continue\n");
4538 		/* OK, we should be able to continue; */
4539 	} else {
4540 		BUG_ON(mddev->level != mddev->new_level);
4541 		BUG_ON(mddev->layout != mddev->new_layout);
4542 		BUG_ON(mddev->chunk_sectors != mddev->new_chunk_sectors);
4543 		BUG_ON(mddev->delta_disks != 0);
4544 	}
4545 
4546 	if (mddev->private == NULL)
4547 		conf = setup_conf(mddev);
4548 	else
4549 		conf = mddev->private;
4550 
4551 	if (IS_ERR(conf))
4552 		return PTR_ERR(conf);
4553 
4554 	mddev->thread = conf->thread;
4555 	conf->thread = NULL;
4556 	mddev->private = conf;
4557 
4558 	/*
4559 	 * 0 for a fully functional array, 1 or 2 for a degraded array.
4560 	 */
4561 	list_for_each_entry(rdev, &mddev->disks, same_set)
4562 		if (rdev->raid_disk >= 0 &&
4563 		    test_bit(In_sync, &rdev->flags))
4564 			working_disks++;
4565 
4566 	mddev->degraded = conf->raid_disks - working_disks;
4567 
4568 	if (mddev->degraded > conf->max_degraded) {
4569 		printk(KERN_ERR "raid5: not enough operational devices for %s"
4570 			" (%d/%d failed)\n",
4571 			mdname(mddev), mddev->degraded, conf->raid_disks);
4572 		goto abort;
4573 	}
4574 
4575 	/* device size must be a multiple of chunk size */
4576 	mddev->dev_sectors &= ~(mddev->chunk_sectors - 1);
4577 	mddev->resync_max_sectors = mddev->dev_sectors;
4578 
4579 	if (mddev->degraded > 0 &&
4580 	    mddev->recovery_cp != MaxSector) {
4581 		if (mddev->ok_start_degraded)
4582 			printk(KERN_WARNING
4583 			       "raid5: starting dirty degraded array: %s"
4584 			       "- data corruption possible.\n",
4585 			       mdname(mddev));
4586 		else {
4587 			printk(KERN_ERR
4588 			       "raid5: cannot start dirty degraded array for %s\n",
4589 			       mdname(mddev));
4590 			goto abort;
4591 		}
4592 	}
4593 
4594 	if (mddev->degraded == 0)
4595 		printk("raid5: raid level %d set %s active with %d out of %d"
4596 		       " devices, algorithm %d\n", conf->level, mdname(mddev),
4597 		       mddev->raid_disks-mddev->degraded, mddev->raid_disks,
4598 		       mddev->new_layout);
4599 	else
4600 		printk(KERN_ALERT "raid5: raid level %d set %s active with %d"
4601 			" out of %d devices, algorithm %d\n", conf->level,
4602 			mdname(mddev), mddev->raid_disks - mddev->degraded,
4603 			mddev->raid_disks, mddev->new_layout);
4604 
4605 	print_raid5_conf(conf);
4606 
4607 	if (conf->reshape_progress != MaxSector) {
4608 		printk("...ok start reshape thread\n");
4609 		conf->reshape_safe = conf->reshape_progress;
4610 		atomic_set(&conf->reshape_stripes, 0);
4611 		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
4612 		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
4613 		set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
4614 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
4615 		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
4616 							"%s_reshape");
4617 	}
4618 
4619 	/* read-ahead size must cover two whole stripes, which is
4620 	 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
4621 	 */
4622 	{
4623 		int data_disks = conf->previous_raid_disks - conf->max_degraded;
4624 		int stripe = data_disks *
4625 			((mddev->chunk_sectors << 9) / PAGE_SIZE);
4626 		if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
4627 			mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
4628 	}
4629 
4630 	/* Ok, everything is just fine now */
4631 	if (sysfs_create_group(&mddev->kobj, &raid5_attrs_group))
4632 		printk(KERN_WARNING
4633 		       "raid5: failed to create sysfs attributes for %s\n",
4634 		       mdname(mddev));
4635 
4636 	mddev->queue->queue_lock = &conf->device_lock;
4637 
4638 	mddev->queue->unplug_fn = raid5_unplug_device;
4639 	mddev->queue->backing_dev_info.congested_data = mddev;
4640 	mddev->queue->backing_dev_info.congested_fn = raid5_congested;
4641 
4642 	md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));
4643 
4644 	blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);
4645 	chunk_size = mddev->chunk_sectors << 9;
4646 	blk_queue_io_min(mddev->queue, chunk_size);
4647 	blk_queue_io_opt(mddev->queue, chunk_size *
4648 			 (conf->raid_disks - conf->max_degraded));
4649 
4650 	list_for_each_entry(rdev, &mddev->disks, same_set)
4651 		disk_stack_limits(mddev->gendisk, rdev->bdev,
4652 				  rdev->data_offset << 9);
4653 
4654 	return 0;
4655 abort:
4656 	md_unregister_thread(mddev->thread);
4657 	mddev->thread = NULL;
4658 	if (conf) {
4659 		print_raid5_conf(conf);
4660 		free_conf(conf);
4661 	}
4662 	mddev->private = NULL;
4663 	printk(KERN_ALERT "raid5: failed to run raid set %s\n", mdname(mddev));
4664 	return -EIO;
4665 }
4666 
4667 
4668 
4669 static int stop(mddev_t *mddev)
4670 {
4671 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
4672 
4673 	md_unregister_thread(mddev->thread);
4674 	mddev->thread = NULL;
4675 	mddev->queue->backing_dev_info.congested_fn = NULL;
4676 	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
4677 	sysfs_remove_group(&mddev->kobj, &raid5_attrs_group);
4678 	free_conf(conf);
4679 	mddev->private = NULL;
4680 	return 0;
4681 }
4682 
4683 #ifdef DEBUG
4684 static void print_sh(struct seq_file *seq, struct stripe_head *sh)
4685 {
4686 	int i;
4687 
4688 	seq_printf(seq, "sh %llu, pd_idx %d, state %ld.\n",
4689 		   (unsigned long long)sh->sector, sh->pd_idx, sh->state);
4690 	seq_printf(seq, "sh %llu,  count %d.\n",
4691 		   (unsigned long long)sh->sector, atomic_read(&sh->count));
4692 	seq_printf(seq, "sh %llu, ", (unsigned long long)sh->sector);
4693 	for (i = 0; i < sh->disks; i++) {
4694 		seq_printf(seq, "(cache%d: %p %ld) ",
4695 			   i, sh->dev[i].page, sh->dev[i].flags);
4696 	}
4697 	seq_printf(seq, "\n");
4698 }
4699 
4700 static void printall(struct seq_file *seq, raid5_conf_t *conf)
4701 {
4702 	struct stripe_head *sh;
4703 	struct hlist_node *hn;
4704 	int i;
4705 
4706 	spin_lock_irq(&conf->device_lock);
4707 	for (i = 0; i < NR_HASH; i++) {
4708 		hlist_for_each_entry(sh, hn, &conf->stripe_hashtbl[i], hash) {
4709 			if (sh->raid_conf != conf)
4710 				continue;
4711 			print_sh(seq, sh);
4712 		}
4713 	}
4714 	spin_unlock_irq(&conf->device_lock);
4715 }
4716 #endif
4717 
4718 static void status(struct seq_file *seq, mddev_t *mddev)
4719 {
4720 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
4721 	int i;
4722 
4723 	seq_printf(seq, " level %d, %dk chunk, algorithm %d", mddev->level,
4724 		mddev->chunk_sectors / 2, mddev->layout);
4725 	seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->raid_disks - mddev->degraded);
4726 	for (i = 0; i < conf->raid_disks; i++)
4727 		seq_printf (seq, "%s",
4728 			       conf->disks[i].rdev &&
4729 			       test_bit(In_sync, &conf->disks[i].rdev->flags) ? "U" : "_");
4730 	seq_printf (seq, "]");
4731 #ifdef DEBUG
4732 	seq_printf (seq, "\n");
4733 	printall(seq, conf);
4734 #endif
4735 }
4736 
4737 static void print_raid5_conf (raid5_conf_t *conf)
4738 {
4739 	int i;
4740 	struct disk_info *tmp;
4741 
4742 	printk("RAID5 conf printout:\n");
4743 	if (!conf) {
4744 		printk("(conf==NULL)\n");
4745 		return;
4746 	}
4747 	printk(" --- rd:%d wd:%d\n", conf->raid_disks,
4748 		 conf->raid_disks - conf->mddev->degraded);
4749 
4750 	for (i = 0; i < conf->raid_disks; i++) {
4751 		char b[BDEVNAME_SIZE];
4752 		tmp = conf->disks + i;
4753 		if (tmp->rdev)
4754 		printk(" disk %d, o:%d, dev:%s\n",
4755 			i, !test_bit(Faulty, &tmp->rdev->flags),
4756 			bdevname(tmp->rdev->bdev,b));
4757 	}
4758 }
4759 
4760 static int raid5_spare_active(mddev_t *mddev)
4761 {
4762 	int i;
4763 	raid5_conf_t *conf = mddev->private;
4764 	struct disk_info *tmp;
4765 
4766 	for (i = 0; i < conf->raid_disks; i++) {
4767 		tmp = conf->disks + i;
4768 		if (tmp->rdev
4769 		    && !test_bit(Faulty, &tmp->rdev->flags)
4770 		    && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
4771 			unsigned long flags;
4772 			spin_lock_irqsave(&conf->device_lock, flags);
4773 			mddev->degraded--;
4774 			spin_unlock_irqrestore(&conf->device_lock, flags);
4775 		}
4776 	}
4777 	print_raid5_conf(conf);
4778 	return 0;
4779 }
4780 
4781 static int raid5_remove_disk(mddev_t *mddev, int number)
4782 {
4783 	raid5_conf_t *conf = mddev->private;
4784 	int err = 0;
4785 	mdk_rdev_t *rdev;
4786 	struct disk_info *p = conf->disks + number;
4787 
4788 	print_raid5_conf(conf);
4789 	rdev = p->rdev;
4790 	if (rdev) {
4791 		if (number >= conf->raid_disks &&
4792 		    conf->reshape_progress == MaxSector)
4793 			clear_bit(In_sync, &rdev->flags);
4794 
4795 		if (test_bit(In_sync, &rdev->flags) ||
4796 		    atomic_read(&rdev->nr_pending)) {
4797 			err = -EBUSY;
4798 			goto abort;
4799 		}
4800 		/* Only remove non-faulty devices if recovery
4801 		 * isn't possible.
4802 		 */
4803 		if (!test_bit(Faulty, &rdev->flags) &&
4804 		    mddev->degraded <= conf->max_degraded &&
4805 		    number < conf->raid_disks) {
4806 			err = -EBUSY;
4807 			goto abort;
4808 		}
4809 		p->rdev = NULL;
4810 		synchronize_rcu();
4811 		if (atomic_read(&rdev->nr_pending)) {
4812 			/* lost the race, try later */
4813 			err = -EBUSY;
4814 			p->rdev = rdev;
4815 		}
4816 	}
4817 abort:
4818 
4819 	print_raid5_conf(conf);
4820 	return err;
4821 }
4822 
4823 static int raid5_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
4824 {
4825 	raid5_conf_t *conf = mddev->private;
4826 	int err = -EEXIST;
4827 	int disk;
4828 	struct disk_info *p;
4829 	int first = 0;
4830 	int last = conf->raid_disks - 1;
4831 
4832 	if (mddev->degraded > conf->max_degraded)
4833 		/* no point adding a device */
4834 		return -EINVAL;
4835 
4836 	if (rdev->raid_disk >= 0)
4837 		first = last = rdev->raid_disk;
4838 
4839 	/*
4840 	 * find the disk ... but prefer rdev->saved_raid_disk
4841 	 * if possible.
4842 	 */
4843 	if (rdev->saved_raid_disk >= 0 &&
4844 	    rdev->saved_raid_disk >= first &&
4845 	    conf->disks[rdev->saved_raid_disk].rdev == NULL)
4846 		disk = rdev->saved_raid_disk;
4847 	else
4848 		disk = first;
4849 	for ( ; disk <= last ; disk++)
4850 		if ((p=conf->disks + disk)->rdev == NULL) {
4851 			clear_bit(In_sync, &rdev->flags);
4852 			rdev->raid_disk = disk;
4853 			err = 0;
4854 			if (rdev->saved_raid_disk != disk)
4855 				conf->fullsync = 1;
4856 			rcu_assign_pointer(p->rdev, rdev);
4857 			break;
4858 		}
4859 	print_raid5_conf(conf);
4860 	return err;
4861 }
4862 
4863 static int raid5_resize(mddev_t *mddev, sector_t sectors)
4864 {
4865 	/* no resync is happening, and there is enough space
4866 	 * on all devices, so we can resize.
4867 	 * We need to make sure resync covers any new space.
4868 	 * If the array is shrinking we should possibly wait until
4869 	 * any io in the removed space completes, but it hardly seems
4870 	 * worth it.
4871 	 */
4872 	sectors &= ~((sector_t)mddev->chunk_sectors - 1);
4873 	md_set_array_sectors(mddev, raid5_size(mddev, sectors,
4874 					       mddev->raid_disks));
4875 	if (mddev->array_sectors >
4876 	    raid5_size(mddev, sectors, mddev->raid_disks))
4877 		return -EINVAL;
4878 	set_capacity(mddev->gendisk, mddev->array_sectors);
4879 	mddev->changed = 1;
4880 	revalidate_disk(mddev->gendisk);
4881 	if (sectors > mddev->dev_sectors && mddev->recovery_cp == MaxSector) {
4882 		mddev->recovery_cp = mddev->dev_sectors;
4883 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
4884 	}
4885 	mddev->dev_sectors = sectors;
4886 	mddev->resync_max_sectors = sectors;
4887 	return 0;
4888 }
4889 
4890 static int check_stripe_cache(mddev_t *mddev)
4891 {
4892 	/* Can only proceed if there are plenty of stripe_heads.
4893 	 * We need a minimum of one full stripe,, and for sensible progress
4894 	 * it is best to have about 4 times that.
4895 	 * If we require 4 times, then the default 256 4K stripe_heads will
4896 	 * allow for chunk sizes up to 256K, which is probably OK.
4897 	 * If the chunk size is greater, user-space should request more
4898 	 * stripe_heads first.
4899 	 */
4900 	raid5_conf_t *conf = mddev->private;
4901 	if (((mddev->chunk_sectors << 9) / STRIPE_SIZE) * 4
4902 	    > conf->max_nr_stripes ||
4903 	    ((mddev->new_chunk_sectors << 9) / STRIPE_SIZE) * 4
4904 	    > conf->max_nr_stripes) {
4905 		printk(KERN_WARNING "raid5: reshape: not enough stripes.  Needed %lu\n",
4906 		       ((max(mddev->chunk_sectors, mddev->new_chunk_sectors) << 9)
4907 			/ STRIPE_SIZE)*4);
4908 		return 0;
4909 	}
4910 	return 1;
4911 }
4912 
4913 static int check_reshape(mddev_t *mddev)
4914 {
4915 	raid5_conf_t *conf = mddev->private;
4916 
4917 	if (mddev->delta_disks == 0 &&
4918 	    mddev->new_layout == mddev->layout &&
4919 	    mddev->new_chunk_sectors == mddev->chunk_sectors)
4920 		return 0; /* nothing to do */
4921 	if (mddev->bitmap)
4922 		/* Cannot grow a bitmap yet */
4923 		return -EBUSY;
4924 	if (mddev->degraded > conf->max_degraded)
4925 		return -EINVAL;
4926 	if (mddev->delta_disks < 0) {
4927 		/* We might be able to shrink, but the devices must
4928 		 * be made bigger first.
4929 		 * For raid6, 4 is the minimum size.
4930 		 * Otherwise 2 is the minimum
4931 		 */
4932 		int min = 2;
4933 		if (mddev->level == 6)
4934 			min = 4;
4935 		if (mddev->raid_disks + mddev->delta_disks < min)
4936 			return -EINVAL;
4937 	}
4938 
4939 	if (!check_stripe_cache(mddev))
4940 		return -ENOSPC;
4941 
4942 	return resize_stripes(conf, conf->raid_disks + mddev->delta_disks);
4943 }
4944 
4945 static int raid5_start_reshape(mddev_t *mddev)
4946 {
4947 	raid5_conf_t *conf = mddev->private;
4948 	mdk_rdev_t *rdev;
4949 	int spares = 0;
4950 	int added_devices = 0;
4951 	unsigned long flags;
4952 
4953 	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
4954 		return -EBUSY;
4955 
4956 	if (!check_stripe_cache(mddev))
4957 		return -ENOSPC;
4958 
4959 	list_for_each_entry(rdev, &mddev->disks, same_set)
4960 		if (rdev->raid_disk < 0 &&
4961 		    !test_bit(Faulty, &rdev->flags))
4962 			spares++;
4963 
4964 	if (spares - mddev->degraded < mddev->delta_disks - conf->max_degraded)
4965 		/* Not enough devices even to make a degraded array
4966 		 * of that size
4967 		 */
4968 		return -EINVAL;
4969 
4970 	/* Refuse to reduce size of the array.  Any reductions in
4971 	 * array size must be through explicit setting of array_size
4972 	 * attribute.
4973 	 */
4974 	if (raid5_size(mddev, 0, conf->raid_disks + mddev->delta_disks)
4975 	    < mddev->array_sectors) {
4976 		printk(KERN_ERR "md: %s: array size must be reduced "
4977 		       "before number of disks\n", mdname(mddev));
4978 		return -EINVAL;
4979 	}
4980 
4981 	atomic_set(&conf->reshape_stripes, 0);
4982 	spin_lock_irq(&conf->device_lock);
4983 	conf->previous_raid_disks = conf->raid_disks;
4984 	conf->raid_disks += mddev->delta_disks;
4985 	conf->prev_chunk_sectors = conf->chunk_sectors;
4986 	conf->chunk_sectors = mddev->new_chunk_sectors;
4987 	conf->prev_algo = conf->algorithm;
4988 	conf->algorithm = mddev->new_layout;
4989 	if (mddev->delta_disks < 0)
4990 		conf->reshape_progress = raid5_size(mddev, 0, 0);
4991 	else
4992 		conf->reshape_progress = 0;
4993 	conf->reshape_safe = conf->reshape_progress;
4994 	conf->generation++;
4995 	spin_unlock_irq(&conf->device_lock);
4996 
4997 	/* Add some new drives, as many as will fit.
4998 	 * We know there are enough to make the newly sized array work.
4999 	 */
5000 	list_for_each_entry(rdev, &mddev->disks, same_set)
5001 		if (rdev->raid_disk < 0 &&
5002 		    !test_bit(Faulty, &rdev->flags)) {
5003 			if (raid5_add_disk(mddev, rdev) == 0) {
5004 				char nm[20];
5005 				set_bit(In_sync, &rdev->flags);
5006 				added_devices++;
5007 				rdev->recovery_offset = 0;
5008 				sprintf(nm, "rd%d", rdev->raid_disk);
5009 				if (sysfs_create_link(&mddev->kobj,
5010 						      &rdev->kobj, nm))
5011 					printk(KERN_WARNING
5012 					       "raid5: failed to create "
5013 					       " link %s for %s\n",
5014 					       nm, mdname(mddev));
5015 			} else
5016 				break;
5017 		}
5018 
5019 	if (mddev->delta_disks > 0) {
5020 		spin_lock_irqsave(&conf->device_lock, flags);
5021 		mddev->degraded = (conf->raid_disks - conf->previous_raid_disks)
5022 			- added_devices;
5023 		spin_unlock_irqrestore(&conf->device_lock, flags);
5024 	}
5025 	mddev->raid_disks = conf->raid_disks;
5026 	mddev->reshape_position = conf->reshape_progress;
5027 	set_bit(MD_CHANGE_DEVS, &mddev->flags);
5028 
5029 	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
5030 	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
5031 	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
5032 	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
5033 	mddev->sync_thread = md_register_thread(md_do_sync, mddev,
5034 						"%s_reshape");
5035 	if (!mddev->sync_thread) {
5036 		mddev->recovery = 0;
5037 		spin_lock_irq(&conf->device_lock);
5038 		mddev->raid_disks = conf->raid_disks = conf->previous_raid_disks;
5039 		conf->reshape_progress = MaxSector;
5040 		spin_unlock_irq(&conf->device_lock);
5041 		return -EAGAIN;
5042 	}
5043 	conf->reshape_checkpoint = jiffies;
5044 	md_wakeup_thread(mddev->sync_thread);
5045 	md_new_event(mddev);
5046 	return 0;
5047 }
5048 
5049 /* This is called from the reshape thread and should make any
5050  * changes needed in 'conf'
5051  */
5052 static void end_reshape(raid5_conf_t *conf)
5053 {
5054 
5055 	if (!test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
5056 
5057 		spin_lock_irq(&conf->device_lock);
5058 		conf->previous_raid_disks = conf->raid_disks;
5059 		conf->reshape_progress = MaxSector;
5060 		spin_unlock_irq(&conf->device_lock);
5061 		wake_up(&conf->wait_for_overlap);
5062 
5063 		/* read-ahead size must cover two whole stripes, which is
5064 		 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
5065 		 */
5066 		{
5067 			int data_disks = conf->raid_disks - conf->max_degraded;
5068 			int stripe = data_disks * ((conf->chunk_sectors << 9)
5069 						   / PAGE_SIZE);
5070 			if (conf->mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
5071 				conf->mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
5072 		}
5073 	}
5074 }
5075 
5076 /* This is called from the raid5d thread with mddev_lock held.
5077  * It makes config changes to the device.
5078  */
5079 static void raid5_finish_reshape(mddev_t *mddev)
5080 {
5081 	raid5_conf_t *conf = mddev->private;
5082 
5083 	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
5084 
5085 		if (mddev->delta_disks > 0) {
5086 			md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));
5087 			set_capacity(mddev->gendisk, mddev->array_sectors);
5088 			mddev->changed = 1;
5089 			revalidate_disk(mddev->gendisk);
5090 		} else {
5091 			int d;
5092 			mddev->degraded = conf->raid_disks;
5093 			for (d = 0; d < conf->raid_disks ; d++)
5094 				if (conf->disks[d].rdev &&
5095 				    test_bit(In_sync,
5096 					     &conf->disks[d].rdev->flags))
5097 					mddev->degraded--;
5098 			for (d = conf->raid_disks ;
5099 			     d < conf->raid_disks - mddev->delta_disks;
5100 			     d++) {
5101 				mdk_rdev_t *rdev = conf->disks[d].rdev;
5102 				if (rdev && raid5_remove_disk(mddev, d) == 0) {
5103 					char nm[20];
5104 					sprintf(nm, "rd%d", rdev->raid_disk);
5105 					sysfs_remove_link(&mddev->kobj, nm);
5106 					rdev->raid_disk = -1;
5107 				}
5108 			}
5109 		}
5110 		mddev->layout = conf->algorithm;
5111 		mddev->chunk_sectors = conf->chunk_sectors;
5112 		mddev->reshape_position = MaxSector;
5113 		mddev->delta_disks = 0;
5114 	}
5115 }
5116 
5117 static void raid5_quiesce(mddev_t *mddev, int state)
5118 {
5119 	raid5_conf_t *conf = mddev->private;
5120 
5121 	switch(state) {
5122 	case 2: /* resume for a suspend */
5123 		wake_up(&conf->wait_for_overlap);
5124 		break;
5125 
5126 	case 1: /* stop all writes */
5127 		spin_lock_irq(&conf->device_lock);
5128 		/* '2' tells resync/reshape to pause so that all
5129 		 * active stripes can drain
5130 		 */
5131 		conf->quiesce = 2;
5132 		wait_event_lock_irq(conf->wait_for_stripe,
5133 				    atomic_read(&conf->active_stripes) == 0 &&
5134 				    atomic_read(&conf->active_aligned_reads) == 0,
5135 				    conf->device_lock, /* nothing */);
5136 		conf->quiesce = 1;
5137 		spin_unlock_irq(&conf->device_lock);
5138 		/* allow reshape to continue */
5139 		wake_up(&conf->wait_for_overlap);
5140 		break;
5141 
5142 	case 0: /* re-enable writes */
5143 		spin_lock_irq(&conf->device_lock);
5144 		conf->quiesce = 0;
5145 		wake_up(&conf->wait_for_stripe);
5146 		wake_up(&conf->wait_for_overlap);
5147 		spin_unlock_irq(&conf->device_lock);
5148 		break;
5149 	}
5150 }
5151 
5152 
5153 static void *raid5_takeover_raid1(mddev_t *mddev)
5154 {
5155 	int chunksect;
5156 
5157 	if (mddev->raid_disks != 2 ||
5158 	    mddev->degraded > 1)
5159 		return ERR_PTR(-EINVAL);
5160 
5161 	/* Should check if there are write-behind devices? */
5162 
5163 	chunksect = 64*2; /* 64K by default */
5164 
5165 	/* The array must be an exact multiple of chunksize */
5166 	while (chunksect && (mddev->array_sectors & (chunksect-1)))
5167 		chunksect >>= 1;
5168 
5169 	if ((chunksect<<9) < STRIPE_SIZE)
5170 		/* array size does not allow a suitable chunk size */
5171 		return ERR_PTR(-EINVAL);
5172 
5173 	mddev->new_level = 5;
5174 	mddev->new_layout = ALGORITHM_LEFT_SYMMETRIC;
5175 	mddev->new_chunk_sectors = chunksect;
5176 
5177 	return setup_conf(mddev);
5178 }
5179 
5180 static void *raid5_takeover_raid6(mddev_t *mddev)
5181 {
5182 	int new_layout;
5183 
5184 	switch (mddev->layout) {
5185 	case ALGORITHM_LEFT_ASYMMETRIC_6:
5186 		new_layout = ALGORITHM_LEFT_ASYMMETRIC;
5187 		break;
5188 	case ALGORITHM_RIGHT_ASYMMETRIC_6:
5189 		new_layout = ALGORITHM_RIGHT_ASYMMETRIC;
5190 		break;
5191 	case ALGORITHM_LEFT_SYMMETRIC_6:
5192 		new_layout = ALGORITHM_LEFT_SYMMETRIC;
5193 		break;
5194 	case ALGORITHM_RIGHT_SYMMETRIC_6:
5195 		new_layout = ALGORITHM_RIGHT_SYMMETRIC;
5196 		break;
5197 	case ALGORITHM_PARITY_0_6:
5198 		new_layout = ALGORITHM_PARITY_0;
5199 		break;
5200 	case ALGORITHM_PARITY_N:
5201 		new_layout = ALGORITHM_PARITY_N;
5202 		break;
5203 	default:
5204 		return ERR_PTR(-EINVAL);
5205 	}
5206 	mddev->new_level = 5;
5207 	mddev->new_layout = new_layout;
5208 	mddev->delta_disks = -1;
5209 	mddev->raid_disks -= 1;
5210 	return setup_conf(mddev);
5211 }
5212 
5213 
5214 static int raid5_check_reshape(mddev_t *mddev)
5215 {
5216 	/* For a 2-drive array, the layout and chunk size can be changed
5217 	 * immediately as not restriping is needed.
5218 	 * For larger arrays we record the new value - after validation
5219 	 * to be used by a reshape pass.
5220 	 */
5221 	raid5_conf_t *conf = mddev->private;
5222 	int new_chunk = mddev->new_chunk_sectors;
5223 
5224 	if (mddev->new_layout >= 0 && !algorithm_valid_raid5(mddev->new_layout))
5225 		return -EINVAL;
5226 	if (new_chunk > 0) {
5227 		if (!is_power_of_2(new_chunk))
5228 			return -EINVAL;
5229 		if (new_chunk < (PAGE_SIZE>>9))
5230 			return -EINVAL;
5231 		if (mddev->array_sectors & (new_chunk-1))
5232 			/* not factor of array size */
5233 			return -EINVAL;
5234 	}
5235 
5236 	/* They look valid */
5237 
5238 	if (mddev->raid_disks == 2) {
5239 		/* can make the change immediately */
5240 		if (mddev->new_layout >= 0) {
5241 			conf->algorithm = mddev->new_layout;
5242 			mddev->layout = mddev->new_layout;
5243 		}
5244 		if (new_chunk > 0) {
5245 			conf->chunk_sectors = new_chunk ;
5246 			mddev->chunk_sectors = new_chunk;
5247 		}
5248 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
5249 		md_wakeup_thread(mddev->thread);
5250 	}
5251 	return check_reshape(mddev);
5252 }
5253 
5254 static int raid6_check_reshape(mddev_t *mddev)
5255 {
5256 	int new_chunk = mddev->new_chunk_sectors;
5257 
5258 	if (mddev->new_layout >= 0 && !algorithm_valid_raid6(mddev->new_layout))
5259 		return -EINVAL;
5260 	if (new_chunk > 0) {
5261 		if (!is_power_of_2(new_chunk))
5262 			return -EINVAL;
5263 		if (new_chunk < (PAGE_SIZE >> 9))
5264 			return -EINVAL;
5265 		if (mddev->array_sectors & (new_chunk-1))
5266 			/* not factor of array size */
5267 			return -EINVAL;
5268 	}
5269 
5270 	/* They look valid */
5271 	return check_reshape(mddev);
5272 }
5273 
5274 static void *raid5_takeover(mddev_t *mddev)
5275 {
5276 	/* raid5 can take over:
5277 	 *  raid0 - if all devices are the same - make it a raid4 layout
5278 	 *  raid1 - if there are two drives.  We need to know the chunk size
5279 	 *  raid4 - trivial - just use a raid4 layout.
5280 	 *  raid6 - Providing it is a *_6 layout
5281 	 */
5282 
5283 	if (mddev->level == 1)
5284 		return raid5_takeover_raid1(mddev);
5285 	if (mddev->level == 4) {
5286 		mddev->new_layout = ALGORITHM_PARITY_N;
5287 		mddev->new_level = 5;
5288 		return setup_conf(mddev);
5289 	}
5290 	if (mddev->level == 6)
5291 		return raid5_takeover_raid6(mddev);
5292 
5293 	return ERR_PTR(-EINVAL);
5294 }
5295 
5296 
5297 static struct mdk_personality raid5_personality;
5298 
5299 static void *raid6_takeover(mddev_t *mddev)
5300 {
5301 	/* Currently can only take over a raid5.  We map the
5302 	 * personality to an equivalent raid6 personality
5303 	 * with the Q block at the end.
5304 	 */
5305 	int new_layout;
5306 
5307 	if (mddev->pers != &raid5_personality)
5308 		return ERR_PTR(-EINVAL);
5309 	if (mddev->degraded > 1)
5310 		return ERR_PTR(-EINVAL);
5311 	if (mddev->raid_disks > 253)
5312 		return ERR_PTR(-EINVAL);
5313 	if (mddev->raid_disks < 3)
5314 		return ERR_PTR(-EINVAL);
5315 
5316 	switch (mddev->layout) {
5317 	case ALGORITHM_LEFT_ASYMMETRIC:
5318 		new_layout = ALGORITHM_LEFT_ASYMMETRIC_6;
5319 		break;
5320 	case ALGORITHM_RIGHT_ASYMMETRIC:
5321 		new_layout = ALGORITHM_RIGHT_ASYMMETRIC_6;
5322 		break;
5323 	case ALGORITHM_LEFT_SYMMETRIC:
5324 		new_layout = ALGORITHM_LEFT_SYMMETRIC_6;
5325 		break;
5326 	case ALGORITHM_RIGHT_SYMMETRIC:
5327 		new_layout = ALGORITHM_RIGHT_SYMMETRIC_6;
5328 		break;
5329 	case ALGORITHM_PARITY_0:
5330 		new_layout = ALGORITHM_PARITY_0_6;
5331 		break;
5332 	case ALGORITHM_PARITY_N:
5333 		new_layout = ALGORITHM_PARITY_N;
5334 		break;
5335 	default:
5336 		return ERR_PTR(-EINVAL);
5337 	}
5338 	mddev->new_level = 6;
5339 	mddev->new_layout = new_layout;
5340 	mddev->delta_disks = 1;
5341 	mddev->raid_disks += 1;
5342 	return setup_conf(mddev);
5343 }
5344 
5345 
5346 static struct mdk_personality raid6_personality =
5347 {
5348 	.name		= "raid6",
5349 	.level		= 6,
5350 	.owner		= THIS_MODULE,
5351 	.make_request	= make_request,
5352 	.run		= run,
5353 	.stop		= stop,
5354 	.status		= status,
5355 	.error_handler	= error,
5356 	.hot_add_disk	= raid5_add_disk,
5357 	.hot_remove_disk= raid5_remove_disk,
5358 	.spare_active	= raid5_spare_active,
5359 	.sync_request	= sync_request,
5360 	.resize		= raid5_resize,
5361 	.size		= raid5_size,
5362 	.check_reshape	= raid6_check_reshape,
5363 	.start_reshape  = raid5_start_reshape,
5364 	.finish_reshape = raid5_finish_reshape,
5365 	.quiesce	= raid5_quiesce,
5366 	.takeover	= raid6_takeover,
5367 };
5368 static struct mdk_personality raid5_personality =
5369 {
5370 	.name		= "raid5",
5371 	.level		= 5,
5372 	.owner		= THIS_MODULE,
5373 	.make_request	= make_request,
5374 	.run		= run,
5375 	.stop		= stop,
5376 	.status		= status,
5377 	.error_handler	= error,
5378 	.hot_add_disk	= raid5_add_disk,
5379 	.hot_remove_disk= raid5_remove_disk,
5380 	.spare_active	= raid5_spare_active,
5381 	.sync_request	= sync_request,
5382 	.resize		= raid5_resize,
5383 	.size		= raid5_size,
5384 	.check_reshape	= raid5_check_reshape,
5385 	.start_reshape  = raid5_start_reshape,
5386 	.finish_reshape = raid5_finish_reshape,
5387 	.quiesce	= raid5_quiesce,
5388 	.takeover	= raid5_takeover,
5389 };
5390 
5391 static struct mdk_personality raid4_personality =
5392 {
5393 	.name		= "raid4",
5394 	.level		= 4,
5395 	.owner		= THIS_MODULE,
5396 	.make_request	= make_request,
5397 	.run		= run,
5398 	.stop		= stop,
5399 	.status		= status,
5400 	.error_handler	= error,
5401 	.hot_add_disk	= raid5_add_disk,
5402 	.hot_remove_disk= raid5_remove_disk,
5403 	.spare_active	= raid5_spare_active,
5404 	.sync_request	= sync_request,
5405 	.resize		= raid5_resize,
5406 	.size		= raid5_size,
5407 	.check_reshape	= raid5_check_reshape,
5408 	.start_reshape  = raid5_start_reshape,
5409 	.finish_reshape = raid5_finish_reshape,
5410 	.quiesce	= raid5_quiesce,
5411 };
5412 
5413 static int __init raid5_init(void)
5414 {
5415 	register_md_personality(&raid6_personality);
5416 	register_md_personality(&raid5_personality);
5417 	register_md_personality(&raid4_personality);
5418 	return 0;
5419 }
5420 
5421 static void raid5_exit(void)
5422 {
5423 	unregister_md_personality(&raid6_personality);
5424 	unregister_md_personality(&raid5_personality);
5425 	unregister_md_personality(&raid4_personality);
5426 }
5427 
5428 module_init(raid5_init);
5429 module_exit(raid5_exit);
5430 MODULE_LICENSE("GPL");
5431 MODULE_ALIAS("md-personality-4"); /* RAID5 */
5432 MODULE_ALIAS("md-raid5");
5433 MODULE_ALIAS("md-raid4");
5434 MODULE_ALIAS("md-level-5");
5435 MODULE_ALIAS("md-level-4");
5436 MODULE_ALIAS("md-personality-8"); /* RAID6 */
5437 MODULE_ALIAS("md-raid6");
5438 MODULE_ALIAS("md-level-6");
5439 
5440 /* This used to be two separate modules, they were: */
5441 MODULE_ALIAS("raid5");
5442 MODULE_ALIAS("raid6");
5443