xref: /openbmc/linux/drivers/md/raid5.c (revision 643d1f7f)
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/module.h>
47 #include <linux/slab.h>
48 #include <linux/highmem.h>
49 #include <linux/bitops.h>
50 #include <linux/kthread.h>
51 #include <asm/atomic.h>
52 #include "raid6.h"
53 
54 #include <linux/raid/bitmap.h>
55 #include <linux/async_tx.h>
56 
57 /*
58  * Stripe cache
59  */
60 
61 #define NR_STRIPES		256
62 #define STRIPE_SIZE		PAGE_SIZE
63 #define STRIPE_SHIFT		(PAGE_SHIFT - 9)
64 #define STRIPE_SECTORS		(STRIPE_SIZE>>9)
65 #define	IO_THRESHOLD		1
66 #define NR_HASH			(PAGE_SIZE / sizeof(struct hlist_head))
67 #define HASH_MASK		(NR_HASH - 1)
68 
69 #define stripe_hash(conf, sect)	(&((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK]))
70 
71 /* bio's attached to a stripe+device for I/O are linked together in bi_sector
72  * order without overlap.  There may be several bio's per stripe+device, and
73  * a bio could span several devices.
74  * When walking this list for a particular stripe+device, we must never proceed
75  * beyond a bio that extends past this device, as the next bio might no longer
76  * be valid.
77  * This macro is used to determine the 'next' bio in the list, given the sector
78  * of the current stripe+device
79  */
80 #define r5_next_bio(bio, sect) ( ( (bio)->bi_sector + ((bio)->bi_size>>9) < sect + STRIPE_SECTORS) ? (bio)->bi_next : NULL)
81 /*
82  * The following can be used to debug the driver
83  */
84 #define RAID5_PARANOIA	1
85 #if RAID5_PARANOIA && defined(CONFIG_SMP)
86 # define CHECK_DEVLOCK() assert_spin_locked(&conf->device_lock)
87 #else
88 # define CHECK_DEVLOCK()
89 #endif
90 
91 #ifdef DEBUG
92 #define inline
93 #define __inline__
94 #endif
95 
96 #if !RAID6_USE_EMPTY_ZERO_PAGE
97 /* In .bss so it's zeroed */
98 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
99 #endif
100 
101 static inline int raid6_next_disk(int disk, int raid_disks)
102 {
103 	disk++;
104 	return (disk < raid_disks) ? disk : 0;
105 }
106 
107 static void return_io(struct bio *return_bi)
108 {
109 	struct bio *bi = return_bi;
110 	while (bi) {
111 
112 		return_bi = bi->bi_next;
113 		bi->bi_next = NULL;
114 		bi->bi_size = 0;
115 		bi->bi_end_io(bi,
116 			      test_bit(BIO_UPTODATE, &bi->bi_flags)
117 			        ? 0 : -EIO);
118 		bi = return_bi;
119 	}
120 }
121 
122 static void print_raid5_conf (raid5_conf_t *conf);
123 
124 static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
125 {
126 	if (atomic_dec_and_test(&sh->count)) {
127 		BUG_ON(!list_empty(&sh->lru));
128 		BUG_ON(atomic_read(&conf->active_stripes)==0);
129 		if (test_bit(STRIPE_HANDLE, &sh->state)) {
130 			if (test_bit(STRIPE_DELAYED, &sh->state)) {
131 				list_add_tail(&sh->lru, &conf->delayed_list);
132 				blk_plug_device(conf->mddev->queue);
133 			} else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
134 				   sh->bm_seq - conf->seq_write > 0) {
135 				list_add_tail(&sh->lru, &conf->bitmap_list);
136 				blk_plug_device(conf->mddev->queue);
137 			} else {
138 				clear_bit(STRIPE_BIT_DELAY, &sh->state);
139 				list_add_tail(&sh->lru, &conf->handle_list);
140 			}
141 			md_wakeup_thread(conf->mddev->thread);
142 		} else {
143 			BUG_ON(sh->ops.pending);
144 			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
145 				atomic_dec(&conf->preread_active_stripes);
146 				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
147 					md_wakeup_thread(conf->mddev->thread);
148 			}
149 			atomic_dec(&conf->active_stripes);
150 			if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
151 				list_add_tail(&sh->lru, &conf->inactive_list);
152 				wake_up(&conf->wait_for_stripe);
153 				if (conf->retry_read_aligned)
154 					md_wakeup_thread(conf->mddev->thread);
155 			}
156 		}
157 	}
158 }
159 static void release_stripe(struct stripe_head *sh)
160 {
161 	raid5_conf_t *conf = sh->raid_conf;
162 	unsigned long flags;
163 
164 	spin_lock_irqsave(&conf->device_lock, flags);
165 	__release_stripe(conf, sh);
166 	spin_unlock_irqrestore(&conf->device_lock, flags);
167 }
168 
169 static inline void remove_hash(struct stripe_head *sh)
170 {
171 	pr_debug("remove_hash(), stripe %llu\n",
172 		(unsigned long long)sh->sector);
173 
174 	hlist_del_init(&sh->hash);
175 }
176 
177 static inline void insert_hash(raid5_conf_t *conf, struct stripe_head *sh)
178 {
179 	struct hlist_head *hp = stripe_hash(conf, sh->sector);
180 
181 	pr_debug("insert_hash(), stripe %llu\n",
182 		(unsigned long long)sh->sector);
183 
184 	CHECK_DEVLOCK();
185 	hlist_add_head(&sh->hash, hp);
186 }
187 
188 
189 /* find an idle stripe, make sure it is unhashed, and return it. */
190 static struct stripe_head *get_free_stripe(raid5_conf_t *conf)
191 {
192 	struct stripe_head *sh = NULL;
193 	struct list_head *first;
194 
195 	CHECK_DEVLOCK();
196 	if (list_empty(&conf->inactive_list))
197 		goto out;
198 	first = conf->inactive_list.next;
199 	sh = list_entry(first, struct stripe_head, lru);
200 	list_del_init(first);
201 	remove_hash(sh);
202 	atomic_inc(&conf->active_stripes);
203 out:
204 	return sh;
205 }
206 
207 static void shrink_buffers(struct stripe_head *sh, int num)
208 {
209 	struct page *p;
210 	int i;
211 
212 	for (i=0; i<num ; i++) {
213 		p = sh->dev[i].page;
214 		if (!p)
215 			continue;
216 		sh->dev[i].page = NULL;
217 		put_page(p);
218 	}
219 }
220 
221 static int grow_buffers(struct stripe_head *sh, int num)
222 {
223 	int i;
224 
225 	for (i=0; i<num; i++) {
226 		struct page *page;
227 
228 		if (!(page = alloc_page(GFP_KERNEL))) {
229 			return 1;
230 		}
231 		sh->dev[i].page = page;
232 	}
233 	return 0;
234 }
235 
236 static void raid5_build_block (struct stripe_head *sh, int i);
237 
238 static void init_stripe(struct stripe_head *sh, sector_t sector, int pd_idx, int disks)
239 {
240 	raid5_conf_t *conf = sh->raid_conf;
241 	int i;
242 
243 	BUG_ON(atomic_read(&sh->count) != 0);
244 	BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
245 	BUG_ON(sh->ops.pending || sh->ops.ack || sh->ops.complete);
246 
247 	CHECK_DEVLOCK();
248 	pr_debug("init_stripe called, stripe %llu\n",
249 		(unsigned long long)sh->sector);
250 
251 	remove_hash(sh);
252 
253 	sh->sector = sector;
254 	sh->pd_idx = pd_idx;
255 	sh->state = 0;
256 
257 	sh->disks = disks;
258 
259 	for (i = sh->disks; i--; ) {
260 		struct r5dev *dev = &sh->dev[i];
261 
262 		if (dev->toread || dev->read || dev->towrite || dev->written ||
263 		    test_bit(R5_LOCKED, &dev->flags)) {
264 			printk(KERN_ERR "sector=%llx i=%d %p %p %p %p %d\n",
265 			       (unsigned long long)sh->sector, i, dev->toread,
266 			       dev->read, dev->towrite, dev->written,
267 			       test_bit(R5_LOCKED, &dev->flags));
268 			BUG();
269 		}
270 		dev->flags = 0;
271 		raid5_build_block(sh, i);
272 	}
273 	insert_hash(conf, sh);
274 }
275 
276 static struct stripe_head *__find_stripe(raid5_conf_t *conf, sector_t sector, int disks)
277 {
278 	struct stripe_head *sh;
279 	struct hlist_node *hn;
280 
281 	CHECK_DEVLOCK();
282 	pr_debug("__find_stripe, sector %llu\n", (unsigned long long)sector);
283 	hlist_for_each_entry(sh, hn, stripe_hash(conf, sector), hash)
284 		if (sh->sector == sector && sh->disks == disks)
285 			return sh;
286 	pr_debug("__stripe %llu not in cache\n", (unsigned long long)sector);
287 	return NULL;
288 }
289 
290 static void unplug_slaves(mddev_t *mddev);
291 static void raid5_unplug_device(struct request_queue *q);
292 
293 static struct stripe_head *get_active_stripe(raid5_conf_t *conf, sector_t sector, int disks,
294 					     int pd_idx, int noblock)
295 {
296 	struct stripe_head *sh;
297 
298 	pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector);
299 
300 	spin_lock_irq(&conf->device_lock);
301 
302 	do {
303 		wait_event_lock_irq(conf->wait_for_stripe,
304 				    conf->quiesce == 0,
305 				    conf->device_lock, /* nothing */);
306 		sh = __find_stripe(conf, sector, disks);
307 		if (!sh) {
308 			if (!conf->inactive_blocked)
309 				sh = get_free_stripe(conf);
310 			if (noblock && sh == NULL)
311 				break;
312 			if (!sh) {
313 				conf->inactive_blocked = 1;
314 				wait_event_lock_irq(conf->wait_for_stripe,
315 						    !list_empty(&conf->inactive_list) &&
316 						    (atomic_read(&conf->active_stripes)
317 						     < (conf->max_nr_stripes *3/4)
318 						     || !conf->inactive_blocked),
319 						    conf->device_lock,
320 						    raid5_unplug_device(conf->mddev->queue)
321 					);
322 				conf->inactive_blocked = 0;
323 			} else
324 				init_stripe(sh, sector, pd_idx, disks);
325 		} else {
326 			if (atomic_read(&sh->count)) {
327 			  BUG_ON(!list_empty(&sh->lru));
328 			} else {
329 				if (!test_bit(STRIPE_HANDLE, &sh->state))
330 					atomic_inc(&conf->active_stripes);
331 				if (list_empty(&sh->lru) &&
332 				    !test_bit(STRIPE_EXPANDING, &sh->state))
333 					BUG();
334 				list_del_init(&sh->lru);
335 			}
336 		}
337 	} while (sh == NULL);
338 
339 	if (sh)
340 		atomic_inc(&sh->count);
341 
342 	spin_unlock_irq(&conf->device_lock);
343 	return sh;
344 }
345 
346 /* test_and_ack_op() ensures that we only dequeue an operation once */
347 #define test_and_ack_op(op, pend) \
348 do {							\
349 	if (test_bit(op, &sh->ops.pending) &&		\
350 		!test_bit(op, &sh->ops.complete)) {	\
351 		if (test_and_set_bit(op, &sh->ops.ack)) \
352 			clear_bit(op, &pend);		\
353 		else					\
354 			ack++;				\
355 	} else						\
356 		clear_bit(op, &pend);			\
357 } while (0)
358 
359 /* find new work to run, do not resubmit work that is already
360  * in flight
361  */
362 static unsigned long get_stripe_work(struct stripe_head *sh)
363 {
364 	unsigned long pending;
365 	int ack = 0;
366 
367 	pending = sh->ops.pending;
368 
369 	test_and_ack_op(STRIPE_OP_BIOFILL, pending);
370 	test_and_ack_op(STRIPE_OP_COMPUTE_BLK, pending);
371 	test_and_ack_op(STRIPE_OP_PREXOR, pending);
372 	test_and_ack_op(STRIPE_OP_BIODRAIN, pending);
373 	test_and_ack_op(STRIPE_OP_POSTXOR, pending);
374 	test_and_ack_op(STRIPE_OP_CHECK, pending);
375 	if (test_and_clear_bit(STRIPE_OP_IO, &sh->ops.pending))
376 		ack++;
377 
378 	sh->ops.count -= ack;
379 	if (unlikely(sh->ops.count < 0)) {
380 		printk(KERN_ERR "pending: %#lx ops.pending: %#lx ops.ack: %#lx "
381 			"ops.complete: %#lx\n", pending, sh->ops.pending,
382 			sh->ops.ack, sh->ops.complete);
383 		BUG();
384 	}
385 
386 	return pending;
387 }
388 
389 static void
390 raid5_end_read_request(struct bio *bi, int error);
391 static void
392 raid5_end_write_request(struct bio *bi, int error);
393 
394 static void ops_run_io(struct stripe_head *sh)
395 {
396 	raid5_conf_t *conf = sh->raid_conf;
397 	int i, disks = sh->disks;
398 
399 	might_sleep();
400 
401 	for (i = disks; i--; ) {
402 		int rw;
403 		struct bio *bi;
404 		mdk_rdev_t *rdev;
405 		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
406 			rw = WRITE;
407 		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
408 			rw = READ;
409 		else
410 			continue;
411 
412 		bi = &sh->dev[i].req;
413 
414 		bi->bi_rw = rw;
415 		if (rw == WRITE)
416 			bi->bi_end_io = raid5_end_write_request;
417 		else
418 			bi->bi_end_io = raid5_end_read_request;
419 
420 		rcu_read_lock();
421 		rdev = rcu_dereference(conf->disks[i].rdev);
422 		if (rdev && test_bit(Faulty, &rdev->flags))
423 			rdev = NULL;
424 		if (rdev)
425 			atomic_inc(&rdev->nr_pending);
426 		rcu_read_unlock();
427 
428 		if (rdev) {
429 			if (test_bit(STRIPE_SYNCING, &sh->state) ||
430 				test_bit(STRIPE_EXPAND_SOURCE, &sh->state) ||
431 				test_bit(STRIPE_EXPAND_READY, &sh->state))
432 				md_sync_acct(rdev->bdev, STRIPE_SECTORS);
433 
434 			bi->bi_bdev = rdev->bdev;
435 			pr_debug("%s: for %llu schedule op %ld on disc %d\n",
436 				__FUNCTION__, (unsigned long long)sh->sector,
437 				bi->bi_rw, i);
438 			atomic_inc(&sh->count);
439 			bi->bi_sector = sh->sector + rdev->data_offset;
440 			bi->bi_flags = 1 << BIO_UPTODATE;
441 			bi->bi_vcnt = 1;
442 			bi->bi_max_vecs = 1;
443 			bi->bi_idx = 0;
444 			bi->bi_io_vec = &sh->dev[i].vec;
445 			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
446 			bi->bi_io_vec[0].bv_offset = 0;
447 			bi->bi_size = STRIPE_SIZE;
448 			bi->bi_next = NULL;
449 			if (rw == WRITE &&
450 			    test_bit(R5_ReWrite, &sh->dev[i].flags))
451 				atomic_add(STRIPE_SECTORS,
452 					&rdev->corrected_errors);
453 			generic_make_request(bi);
454 		} else {
455 			if (rw == WRITE)
456 				set_bit(STRIPE_DEGRADED, &sh->state);
457 			pr_debug("skip op %ld on disc %d for sector %llu\n",
458 				bi->bi_rw, i, (unsigned long long)sh->sector);
459 			clear_bit(R5_LOCKED, &sh->dev[i].flags);
460 			set_bit(STRIPE_HANDLE, &sh->state);
461 		}
462 	}
463 }
464 
465 static struct dma_async_tx_descriptor *
466 async_copy_data(int frombio, struct bio *bio, struct page *page,
467 	sector_t sector, struct dma_async_tx_descriptor *tx)
468 {
469 	struct bio_vec *bvl;
470 	struct page *bio_page;
471 	int i;
472 	int page_offset;
473 
474 	if (bio->bi_sector >= sector)
475 		page_offset = (signed)(bio->bi_sector - sector) * 512;
476 	else
477 		page_offset = (signed)(sector - bio->bi_sector) * -512;
478 	bio_for_each_segment(bvl, bio, i) {
479 		int len = bio_iovec_idx(bio, i)->bv_len;
480 		int clen;
481 		int b_offset = 0;
482 
483 		if (page_offset < 0) {
484 			b_offset = -page_offset;
485 			page_offset += b_offset;
486 			len -= b_offset;
487 		}
488 
489 		if (len > 0 && page_offset + len > STRIPE_SIZE)
490 			clen = STRIPE_SIZE - page_offset;
491 		else
492 			clen = len;
493 
494 		if (clen > 0) {
495 			b_offset += bio_iovec_idx(bio, i)->bv_offset;
496 			bio_page = bio_iovec_idx(bio, i)->bv_page;
497 			if (frombio)
498 				tx = async_memcpy(page, bio_page, page_offset,
499 					b_offset, clen,
500 					ASYNC_TX_DEP_ACK,
501 					tx, NULL, NULL);
502 			else
503 				tx = async_memcpy(bio_page, page, b_offset,
504 					page_offset, clen,
505 					ASYNC_TX_DEP_ACK,
506 					tx, NULL, NULL);
507 		}
508 		if (clen < len) /* hit end of page */
509 			break;
510 		page_offset +=  len;
511 	}
512 
513 	return tx;
514 }
515 
516 static void ops_complete_biofill(void *stripe_head_ref)
517 {
518 	struct stripe_head *sh = stripe_head_ref;
519 	struct bio *return_bi = NULL;
520 	raid5_conf_t *conf = sh->raid_conf;
521 	int i;
522 
523 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
524 		(unsigned long long)sh->sector);
525 
526 	/* clear completed biofills */
527 	for (i = sh->disks; i--; ) {
528 		struct r5dev *dev = &sh->dev[i];
529 
530 		/* acknowledge completion of a biofill operation */
531 		/* and check if we need to reply to a read request,
532 		 * new R5_Wantfill requests are held off until
533 		 * !test_bit(STRIPE_OP_BIOFILL, &sh->ops.pending)
534 		 */
535 		if (test_and_clear_bit(R5_Wantfill, &dev->flags)) {
536 			struct bio *rbi, *rbi2;
537 
538 			/* The access to dev->read is outside of the
539 			 * spin_lock_irq(&conf->device_lock), but is protected
540 			 * by the STRIPE_OP_BIOFILL pending bit
541 			 */
542 			BUG_ON(!dev->read);
543 			rbi = dev->read;
544 			dev->read = NULL;
545 			while (rbi && rbi->bi_sector <
546 				dev->sector + STRIPE_SECTORS) {
547 				rbi2 = r5_next_bio(rbi, dev->sector);
548 				spin_lock_irq(&conf->device_lock);
549 				if (--rbi->bi_phys_segments == 0) {
550 					rbi->bi_next = return_bi;
551 					return_bi = rbi;
552 				}
553 				spin_unlock_irq(&conf->device_lock);
554 				rbi = rbi2;
555 			}
556 		}
557 	}
558 	set_bit(STRIPE_OP_BIOFILL, &sh->ops.complete);
559 
560 	return_io(return_bi);
561 
562 	set_bit(STRIPE_HANDLE, &sh->state);
563 	release_stripe(sh);
564 }
565 
566 static void ops_run_biofill(struct stripe_head *sh)
567 {
568 	struct dma_async_tx_descriptor *tx = NULL;
569 	raid5_conf_t *conf = sh->raid_conf;
570 	int i;
571 
572 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
573 		(unsigned long long)sh->sector);
574 
575 	for (i = sh->disks; i--; ) {
576 		struct r5dev *dev = &sh->dev[i];
577 		if (test_bit(R5_Wantfill, &dev->flags)) {
578 			struct bio *rbi;
579 			spin_lock_irq(&conf->device_lock);
580 			dev->read = rbi = dev->toread;
581 			dev->toread = NULL;
582 			spin_unlock_irq(&conf->device_lock);
583 			while (rbi && rbi->bi_sector <
584 				dev->sector + STRIPE_SECTORS) {
585 				tx = async_copy_data(0, rbi, dev->page,
586 					dev->sector, tx);
587 				rbi = r5_next_bio(rbi, dev->sector);
588 			}
589 		}
590 	}
591 
592 	atomic_inc(&sh->count);
593 	async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
594 		ops_complete_biofill, sh);
595 }
596 
597 static void ops_complete_compute5(void *stripe_head_ref)
598 {
599 	struct stripe_head *sh = stripe_head_ref;
600 	int target = sh->ops.target;
601 	struct r5dev *tgt = &sh->dev[target];
602 
603 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
604 		(unsigned long long)sh->sector);
605 
606 	set_bit(R5_UPTODATE, &tgt->flags);
607 	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
608 	clear_bit(R5_Wantcompute, &tgt->flags);
609 	set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete);
610 	set_bit(STRIPE_HANDLE, &sh->state);
611 	release_stripe(sh);
612 }
613 
614 static struct dma_async_tx_descriptor *
615 ops_run_compute5(struct stripe_head *sh, unsigned long pending)
616 {
617 	/* kernel stack size limits the total number of disks */
618 	int disks = sh->disks;
619 	struct page *xor_srcs[disks];
620 	int target = sh->ops.target;
621 	struct r5dev *tgt = &sh->dev[target];
622 	struct page *xor_dest = tgt->page;
623 	int count = 0;
624 	struct dma_async_tx_descriptor *tx;
625 	int i;
626 
627 	pr_debug("%s: stripe %llu block: %d\n",
628 		__FUNCTION__, (unsigned long long)sh->sector, target);
629 	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
630 
631 	for (i = disks; i--; )
632 		if (i != target)
633 			xor_srcs[count++] = sh->dev[i].page;
634 
635 	atomic_inc(&sh->count);
636 
637 	if (unlikely(count == 1))
638 		tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
639 			0, NULL, ops_complete_compute5, sh);
640 	else
641 		tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
642 			ASYNC_TX_XOR_ZERO_DST, NULL,
643 			ops_complete_compute5, sh);
644 
645 	/* ack now if postxor is not set to be run */
646 	if (tx && !test_bit(STRIPE_OP_POSTXOR, &pending))
647 		async_tx_ack(tx);
648 
649 	return tx;
650 }
651 
652 static void ops_complete_prexor(void *stripe_head_ref)
653 {
654 	struct stripe_head *sh = stripe_head_ref;
655 
656 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
657 		(unsigned long long)sh->sector);
658 
659 	set_bit(STRIPE_OP_PREXOR, &sh->ops.complete);
660 }
661 
662 static struct dma_async_tx_descriptor *
663 ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
664 {
665 	/* kernel stack size limits the total number of disks */
666 	int disks = sh->disks;
667 	struct page *xor_srcs[disks];
668 	int count = 0, pd_idx = sh->pd_idx, i;
669 
670 	/* existing parity data subtracted */
671 	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
672 
673 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
674 		(unsigned long long)sh->sector);
675 
676 	for (i = disks; i--; ) {
677 		struct r5dev *dev = &sh->dev[i];
678 		/* Only process blocks that are known to be uptodate */
679 		if (dev->towrite && test_bit(R5_Wantprexor, &dev->flags))
680 			xor_srcs[count++] = dev->page;
681 	}
682 
683 	tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
684 		ASYNC_TX_DEP_ACK | ASYNC_TX_XOR_DROP_DST, tx,
685 		ops_complete_prexor, sh);
686 
687 	return tx;
688 }
689 
690 static struct dma_async_tx_descriptor *
691 ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
692 		 unsigned long pending)
693 {
694 	int disks = sh->disks;
695 	int pd_idx = sh->pd_idx, i;
696 
697 	/* check if prexor is active which means only process blocks
698 	 * that are part of a read-modify-write (Wantprexor)
699 	 */
700 	int prexor = test_bit(STRIPE_OP_PREXOR, &pending);
701 
702 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
703 		(unsigned long long)sh->sector);
704 
705 	for (i = disks; i--; ) {
706 		struct r5dev *dev = &sh->dev[i];
707 		struct bio *chosen;
708 		int towrite;
709 
710 		towrite = 0;
711 		if (prexor) { /* rmw */
712 			if (dev->towrite &&
713 			    test_bit(R5_Wantprexor, &dev->flags))
714 				towrite = 1;
715 		} else { /* rcw */
716 			if (i != pd_idx && dev->towrite &&
717 				test_bit(R5_LOCKED, &dev->flags))
718 				towrite = 1;
719 		}
720 
721 		if (towrite) {
722 			struct bio *wbi;
723 
724 			spin_lock(&sh->lock);
725 			chosen = dev->towrite;
726 			dev->towrite = NULL;
727 			BUG_ON(dev->written);
728 			wbi = dev->written = chosen;
729 			spin_unlock(&sh->lock);
730 
731 			while (wbi && wbi->bi_sector <
732 				dev->sector + STRIPE_SECTORS) {
733 				tx = async_copy_data(1, wbi, dev->page,
734 					dev->sector, tx);
735 				wbi = r5_next_bio(wbi, dev->sector);
736 			}
737 		}
738 	}
739 
740 	return tx;
741 }
742 
743 static void ops_complete_postxor(void *stripe_head_ref)
744 {
745 	struct stripe_head *sh = stripe_head_ref;
746 
747 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
748 		(unsigned long long)sh->sector);
749 
750 	set_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
751 	set_bit(STRIPE_HANDLE, &sh->state);
752 	release_stripe(sh);
753 }
754 
755 static void ops_complete_write(void *stripe_head_ref)
756 {
757 	struct stripe_head *sh = stripe_head_ref;
758 	int disks = sh->disks, i, pd_idx = sh->pd_idx;
759 
760 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
761 		(unsigned long long)sh->sector);
762 
763 	for (i = disks; i--; ) {
764 		struct r5dev *dev = &sh->dev[i];
765 		if (dev->written || i == pd_idx)
766 			set_bit(R5_UPTODATE, &dev->flags);
767 	}
768 
769 	set_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete);
770 	set_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
771 
772 	set_bit(STRIPE_HANDLE, &sh->state);
773 	release_stripe(sh);
774 }
775 
776 static void
777 ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx,
778 		unsigned long pending)
779 {
780 	/* kernel stack size limits the total number of disks */
781 	int disks = sh->disks;
782 	struct page *xor_srcs[disks];
783 
784 	int count = 0, pd_idx = sh->pd_idx, i;
785 	struct page *xor_dest;
786 	int prexor = test_bit(STRIPE_OP_PREXOR, &pending);
787 	unsigned long flags;
788 	dma_async_tx_callback callback;
789 
790 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
791 		(unsigned long long)sh->sector);
792 
793 	/* check if prexor is active which means only process blocks
794 	 * that are part of a read-modify-write (written)
795 	 */
796 	if (prexor) {
797 		xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
798 		for (i = disks; i--; ) {
799 			struct r5dev *dev = &sh->dev[i];
800 			if (dev->written)
801 				xor_srcs[count++] = dev->page;
802 		}
803 	} else {
804 		xor_dest = sh->dev[pd_idx].page;
805 		for (i = disks; i--; ) {
806 			struct r5dev *dev = &sh->dev[i];
807 			if (i != pd_idx)
808 				xor_srcs[count++] = dev->page;
809 		}
810 	}
811 
812 	/* check whether this postxor is part of a write */
813 	callback = test_bit(STRIPE_OP_BIODRAIN, &pending) ?
814 		ops_complete_write : ops_complete_postxor;
815 
816 	/* 1/ if we prexor'd then the dest is reused as a source
817 	 * 2/ if we did not prexor then we are redoing the parity
818 	 * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
819 	 * for the synchronous xor case
820 	 */
821 	flags = ASYNC_TX_DEP_ACK | ASYNC_TX_ACK |
822 		(prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);
823 
824 	atomic_inc(&sh->count);
825 
826 	if (unlikely(count == 1)) {
827 		flags &= ~(ASYNC_TX_XOR_DROP_DST | ASYNC_TX_XOR_ZERO_DST);
828 		tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
829 			flags, tx, callback, sh);
830 	} else
831 		tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
832 			flags, tx, callback, sh);
833 }
834 
835 static void ops_complete_check(void *stripe_head_ref)
836 {
837 	struct stripe_head *sh = stripe_head_ref;
838 	int pd_idx = sh->pd_idx;
839 
840 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
841 		(unsigned long long)sh->sector);
842 
843 	if (test_and_clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending) &&
844 		sh->ops.zero_sum_result == 0)
845 		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
846 
847 	set_bit(STRIPE_OP_CHECK, &sh->ops.complete);
848 	set_bit(STRIPE_HANDLE, &sh->state);
849 	release_stripe(sh);
850 }
851 
852 static void ops_run_check(struct stripe_head *sh)
853 {
854 	/* kernel stack size limits the total number of disks */
855 	int disks = sh->disks;
856 	struct page *xor_srcs[disks];
857 	struct dma_async_tx_descriptor *tx;
858 
859 	int count = 0, pd_idx = sh->pd_idx, i;
860 	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
861 
862 	pr_debug("%s: stripe %llu\n", __FUNCTION__,
863 		(unsigned long long)sh->sector);
864 
865 	for (i = disks; i--; ) {
866 		struct r5dev *dev = &sh->dev[i];
867 		if (i != pd_idx)
868 			xor_srcs[count++] = dev->page;
869 	}
870 
871 	tx = async_xor_zero_sum(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
872 		&sh->ops.zero_sum_result, 0, NULL, NULL, NULL);
873 
874 	if (tx)
875 		set_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
876 	else
877 		clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
878 
879 	atomic_inc(&sh->count);
880 	tx = async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
881 		ops_complete_check, sh);
882 }
883 
884 static void raid5_run_ops(struct stripe_head *sh, unsigned long pending)
885 {
886 	int overlap_clear = 0, i, disks = sh->disks;
887 	struct dma_async_tx_descriptor *tx = NULL;
888 
889 	if (test_bit(STRIPE_OP_BIOFILL, &pending)) {
890 		ops_run_biofill(sh);
891 		overlap_clear++;
892 	}
893 
894 	if (test_bit(STRIPE_OP_COMPUTE_BLK, &pending))
895 		tx = ops_run_compute5(sh, pending);
896 
897 	if (test_bit(STRIPE_OP_PREXOR, &pending))
898 		tx = ops_run_prexor(sh, tx);
899 
900 	if (test_bit(STRIPE_OP_BIODRAIN, &pending)) {
901 		tx = ops_run_biodrain(sh, tx, pending);
902 		overlap_clear++;
903 	}
904 
905 	if (test_bit(STRIPE_OP_POSTXOR, &pending))
906 		ops_run_postxor(sh, tx, pending);
907 
908 	if (test_bit(STRIPE_OP_CHECK, &pending))
909 		ops_run_check(sh);
910 
911 	if (test_bit(STRIPE_OP_IO, &pending))
912 		ops_run_io(sh);
913 
914 	if (overlap_clear)
915 		for (i = disks; i--; ) {
916 			struct r5dev *dev = &sh->dev[i];
917 			if (test_and_clear_bit(R5_Overlap, &dev->flags))
918 				wake_up(&sh->raid_conf->wait_for_overlap);
919 		}
920 }
921 
922 static int grow_one_stripe(raid5_conf_t *conf)
923 {
924 	struct stripe_head *sh;
925 	sh = kmem_cache_alloc(conf->slab_cache, GFP_KERNEL);
926 	if (!sh)
927 		return 0;
928 	memset(sh, 0, sizeof(*sh) + (conf->raid_disks-1)*sizeof(struct r5dev));
929 	sh->raid_conf = conf;
930 	spin_lock_init(&sh->lock);
931 
932 	if (grow_buffers(sh, conf->raid_disks)) {
933 		shrink_buffers(sh, conf->raid_disks);
934 		kmem_cache_free(conf->slab_cache, sh);
935 		return 0;
936 	}
937 	sh->disks = conf->raid_disks;
938 	/* we just created an active stripe so... */
939 	atomic_set(&sh->count, 1);
940 	atomic_inc(&conf->active_stripes);
941 	INIT_LIST_HEAD(&sh->lru);
942 	release_stripe(sh);
943 	return 1;
944 }
945 
946 static int grow_stripes(raid5_conf_t *conf, int num)
947 {
948 	struct kmem_cache *sc;
949 	int devs = conf->raid_disks;
950 
951 	sprintf(conf->cache_name[0], "raid5-%s", mdname(conf->mddev));
952 	sprintf(conf->cache_name[1], "raid5-%s-alt", mdname(conf->mddev));
953 	conf->active_name = 0;
954 	sc = kmem_cache_create(conf->cache_name[conf->active_name],
955 			       sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
956 			       0, 0, NULL);
957 	if (!sc)
958 		return 1;
959 	conf->slab_cache = sc;
960 	conf->pool_size = devs;
961 	while (num--)
962 		if (!grow_one_stripe(conf))
963 			return 1;
964 	return 0;
965 }
966 
967 #ifdef CONFIG_MD_RAID5_RESHAPE
968 static int resize_stripes(raid5_conf_t *conf, int newsize)
969 {
970 	/* Make all the stripes able to hold 'newsize' devices.
971 	 * New slots in each stripe get 'page' set to a new page.
972 	 *
973 	 * This happens in stages:
974 	 * 1/ create a new kmem_cache and allocate the required number of
975 	 *    stripe_heads.
976 	 * 2/ gather all the old stripe_heads and tranfer the pages across
977 	 *    to the new stripe_heads.  This will have the side effect of
978 	 *    freezing the array as once all stripe_heads have been collected,
979 	 *    no IO will be possible.  Old stripe heads are freed once their
980 	 *    pages have been transferred over, and the old kmem_cache is
981 	 *    freed when all stripes are done.
982 	 * 3/ reallocate conf->disks to be suitable bigger.  If this fails,
983 	 *    we simple return a failre status - no need to clean anything up.
984 	 * 4/ allocate new pages for the new slots in the new stripe_heads.
985 	 *    If this fails, we don't bother trying the shrink the
986 	 *    stripe_heads down again, we just leave them as they are.
987 	 *    As each stripe_head is processed the new one is released into
988 	 *    active service.
989 	 *
990 	 * Once step2 is started, we cannot afford to wait for a write,
991 	 * so we use GFP_NOIO allocations.
992 	 */
993 	struct stripe_head *osh, *nsh;
994 	LIST_HEAD(newstripes);
995 	struct disk_info *ndisks;
996 	int err = 0;
997 	struct kmem_cache *sc;
998 	int i;
999 
1000 	if (newsize <= conf->pool_size)
1001 		return 0; /* never bother to shrink */
1002 
1003 	md_allow_write(conf->mddev);
1004 
1005 	/* Step 1 */
1006 	sc = kmem_cache_create(conf->cache_name[1-conf->active_name],
1007 			       sizeof(struct stripe_head)+(newsize-1)*sizeof(struct r5dev),
1008 			       0, 0, NULL);
1009 	if (!sc)
1010 		return -ENOMEM;
1011 
1012 	for (i = conf->max_nr_stripes; i; i--) {
1013 		nsh = kmem_cache_alloc(sc, GFP_KERNEL);
1014 		if (!nsh)
1015 			break;
1016 
1017 		memset(nsh, 0, sizeof(*nsh) + (newsize-1)*sizeof(struct r5dev));
1018 
1019 		nsh->raid_conf = conf;
1020 		spin_lock_init(&nsh->lock);
1021 
1022 		list_add(&nsh->lru, &newstripes);
1023 	}
1024 	if (i) {
1025 		/* didn't get enough, give up */
1026 		while (!list_empty(&newstripes)) {
1027 			nsh = list_entry(newstripes.next, struct stripe_head, lru);
1028 			list_del(&nsh->lru);
1029 			kmem_cache_free(sc, nsh);
1030 		}
1031 		kmem_cache_destroy(sc);
1032 		return -ENOMEM;
1033 	}
1034 	/* Step 2 - Must use GFP_NOIO now.
1035 	 * OK, we have enough stripes, start collecting inactive
1036 	 * stripes and copying them over
1037 	 */
1038 	list_for_each_entry(nsh, &newstripes, lru) {
1039 		spin_lock_irq(&conf->device_lock);
1040 		wait_event_lock_irq(conf->wait_for_stripe,
1041 				    !list_empty(&conf->inactive_list),
1042 				    conf->device_lock,
1043 				    unplug_slaves(conf->mddev)
1044 			);
1045 		osh = get_free_stripe(conf);
1046 		spin_unlock_irq(&conf->device_lock);
1047 		atomic_set(&nsh->count, 1);
1048 		for(i=0; i<conf->pool_size; i++)
1049 			nsh->dev[i].page = osh->dev[i].page;
1050 		for( ; i<newsize; i++)
1051 			nsh->dev[i].page = NULL;
1052 		kmem_cache_free(conf->slab_cache, osh);
1053 	}
1054 	kmem_cache_destroy(conf->slab_cache);
1055 
1056 	/* Step 3.
1057 	 * At this point, we are holding all the stripes so the array
1058 	 * is completely stalled, so now is a good time to resize
1059 	 * conf->disks.
1060 	 */
1061 	ndisks = kzalloc(newsize * sizeof(struct disk_info), GFP_NOIO);
1062 	if (ndisks) {
1063 		for (i=0; i<conf->raid_disks; i++)
1064 			ndisks[i] = conf->disks[i];
1065 		kfree(conf->disks);
1066 		conf->disks = ndisks;
1067 	} else
1068 		err = -ENOMEM;
1069 
1070 	/* Step 4, return new stripes to service */
1071 	while(!list_empty(&newstripes)) {
1072 		nsh = list_entry(newstripes.next, struct stripe_head, lru);
1073 		list_del_init(&nsh->lru);
1074 		for (i=conf->raid_disks; i < newsize; i++)
1075 			if (nsh->dev[i].page == NULL) {
1076 				struct page *p = alloc_page(GFP_NOIO);
1077 				nsh->dev[i].page = p;
1078 				if (!p)
1079 					err = -ENOMEM;
1080 			}
1081 		release_stripe(nsh);
1082 	}
1083 	/* critical section pass, GFP_NOIO no longer needed */
1084 
1085 	conf->slab_cache = sc;
1086 	conf->active_name = 1-conf->active_name;
1087 	conf->pool_size = newsize;
1088 	return err;
1089 }
1090 #endif
1091 
1092 static int drop_one_stripe(raid5_conf_t *conf)
1093 {
1094 	struct stripe_head *sh;
1095 
1096 	spin_lock_irq(&conf->device_lock);
1097 	sh = get_free_stripe(conf);
1098 	spin_unlock_irq(&conf->device_lock);
1099 	if (!sh)
1100 		return 0;
1101 	BUG_ON(atomic_read(&sh->count));
1102 	shrink_buffers(sh, conf->pool_size);
1103 	kmem_cache_free(conf->slab_cache, sh);
1104 	atomic_dec(&conf->active_stripes);
1105 	return 1;
1106 }
1107 
1108 static void shrink_stripes(raid5_conf_t *conf)
1109 {
1110 	while (drop_one_stripe(conf))
1111 		;
1112 
1113 	if (conf->slab_cache)
1114 		kmem_cache_destroy(conf->slab_cache);
1115 	conf->slab_cache = NULL;
1116 }
1117 
1118 static void raid5_end_read_request(struct bio * bi, int error)
1119 {
1120  	struct stripe_head *sh = bi->bi_private;
1121 	raid5_conf_t *conf = sh->raid_conf;
1122 	int disks = sh->disks, i;
1123 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
1124 	char b[BDEVNAME_SIZE];
1125 	mdk_rdev_t *rdev;
1126 
1127 
1128 	for (i=0 ; i<disks; i++)
1129 		if (bi == &sh->dev[i].req)
1130 			break;
1131 
1132 	pr_debug("end_read_request %llu/%d, count: %d, uptodate %d.\n",
1133 		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
1134 		uptodate);
1135 	if (i == disks) {
1136 		BUG();
1137 		return;
1138 	}
1139 
1140 	if (uptodate) {
1141 		set_bit(R5_UPTODATE, &sh->dev[i].flags);
1142 		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
1143 			rdev = conf->disks[i].rdev;
1144 			printk(KERN_INFO "raid5:%s: read error corrected (%lu sectors at %llu on %s)\n",
1145 			       mdname(conf->mddev), STRIPE_SECTORS,
1146 			       (unsigned long long)sh->sector + rdev->data_offset,
1147 			       bdevname(rdev->bdev, b));
1148 			clear_bit(R5_ReadError, &sh->dev[i].flags);
1149 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
1150 		}
1151 		if (atomic_read(&conf->disks[i].rdev->read_errors))
1152 			atomic_set(&conf->disks[i].rdev->read_errors, 0);
1153 	} else {
1154 		const char *bdn = bdevname(conf->disks[i].rdev->bdev, b);
1155 		int retry = 0;
1156 		rdev = conf->disks[i].rdev;
1157 
1158 		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
1159 		atomic_inc(&rdev->read_errors);
1160 		if (conf->mddev->degraded)
1161 			printk(KERN_WARNING "raid5:%s: read error not correctable (sector %llu on %s).\n",
1162 			       mdname(conf->mddev),
1163 			       (unsigned long long)sh->sector + rdev->data_offset,
1164 			       bdn);
1165 		else if (test_bit(R5_ReWrite, &sh->dev[i].flags))
1166 			/* Oh, no!!! */
1167 			printk(KERN_WARNING "raid5:%s: read error NOT corrected!! (sector %llu on %s).\n",
1168 			       mdname(conf->mddev),
1169 			       (unsigned long long)sh->sector + rdev->data_offset,
1170 			       bdn);
1171 		else if (atomic_read(&rdev->read_errors)
1172 			 > conf->max_nr_stripes)
1173 			printk(KERN_WARNING
1174 			       "raid5:%s: Too many read errors, failing device %s.\n",
1175 			       mdname(conf->mddev), bdn);
1176 		else
1177 			retry = 1;
1178 		if (retry)
1179 			set_bit(R5_ReadError, &sh->dev[i].flags);
1180 		else {
1181 			clear_bit(R5_ReadError, &sh->dev[i].flags);
1182 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
1183 			md_error(conf->mddev, rdev);
1184 		}
1185 	}
1186 	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
1187 	clear_bit(R5_LOCKED, &sh->dev[i].flags);
1188 	set_bit(STRIPE_HANDLE, &sh->state);
1189 	release_stripe(sh);
1190 }
1191 
1192 static void raid5_end_write_request (struct bio *bi, int error)
1193 {
1194  	struct stripe_head *sh = bi->bi_private;
1195 	raid5_conf_t *conf = sh->raid_conf;
1196 	int disks = sh->disks, i;
1197 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
1198 
1199 	for (i=0 ; i<disks; i++)
1200 		if (bi == &sh->dev[i].req)
1201 			break;
1202 
1203 	pr_debug("end_write_request %llu/%d, count %d, uptodate: %d.\n",
1204 		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
1205 		uptodate);
1206 	if (i == disks) {
1207 		BUG();
1208 		return;
1209 	}
1210 
1211 	if (!uptodate)
1212 		md_error(conf->mddev, conf->disks[i].rdev);
1213 
1214 	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
1215 
1216 	clear_bit(R5_LOCKED, &sh->dev[i].flags);
1217 	set_bit(STRIPE_HANDLE, &sh->state);
1218 	release_stripe(sh);
1219 }
1220 
1221 
1222 static sector_t compute_blocknr(struct stripe_head *sh, int i);
1223 
1224 static void raid5_build_block (struct stripe_head *sh, int i)
1225 {
1226 	struct r5dev *dev = &sh->dev[i];
1227 
1228 	bio_init(&dev->req);
1229 	dev->req.bi_io_vec = &dev->vec;
1230 	dev->req.bi_vcnt++;
1231 	dev->req.bi_max_vecs++;
1232 	dev->vec.bv_page = dev->page;
1233 	dev->vec.bv_len = STRIPE_SIZE;
1234 	dev->vec.bv_offset = 0;
1235 
1236 	dev->req.bi_sector = sh->sector;
1237 	dev->req.bi_private = sh;
1238 
1239 	dev->flags = 0;
1240 	dev->sector = compute_blocknr(sh, i);
1241 }
1242 
1243 static void error(mddev_t *mddev, mdk_rdev_t *rdev)
1244 {
1245 	char b[BDEVNAME_SIZE];
1246 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
1247 	pr_debug("raid5: error called\n");
1248 
1249 	if (!test_bit(Faulty, &rdev->flags)) {
1250 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
1251 		if (test_and_clear_bit(In_sync, &rdev->flags)) {
1252 			unsigned long flags;
1253 			spin_lock_irqsave(&conf->device_lock, flags);
1254 			mddev->degraded++;
1255 			spin_unlock_irqrestore(&conf->device_lock, flags);
1256 			/*
1257 			 * if recovery was running, make sure it aborts.
1258 			 */
1259 			set_bit(MD_RECOVERY_ERR, &mddev->recovery);
1260 		}
1261 		set_bit(Faulty, &rdev->flags);
1262 		printk (KERN_ALERT
1263 			"raid5: Disk failure on %s, disabling device."
1264 			" Operation continuing on %d devices\n",
1265 			bdevname(rdev->bdev,b), conf->raid_disks - mddev->degraded);
1266 	}
1267 }
1268 
1269 /*
1270  * Input: a 'big' sector number,
1271  * Output: index of the data and parity disk, and the sector # in them.
1272  */
1273 static sector_t raid5_compute_sector(sector_t r_sector, unsigned int raid_disks,
1274 			unsigned int data_disks, unsigned int * dd_idx,
1275 			unsigned int * pd_idx, raid5_conf_t *conf)
1276 {
1277 	long stripe;
1278 	unsigned long chunk_number;
1279 	unsigned int chunk_offset;
1280 	sector_t new_sector;
1281 	int sectors_per_chunk = conf->chunk_size >> 9;
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 	switch(conf->level) {
1306 	case 4:
1307 		*pd_idx = data_disks;
1308 		break;
1309 	case 5:
1310 		switch (conf->algorithm) {
1311 		case ALGORITHM_LEFT_ASYMMETRIC:
1312 			*pd_idx = data_disks - stripe % raid_disks;
1313 			if (*dd_idx >= *pd_idx)
1314 				(*dd_idx)++;
1315 			break;
1316 		case ALGORITHM_RIGHT_ASYMMETRIC:
1317 			*pd_idx = stripe % raid_disks;
1318 			if (*dd_idx >= *pd_idx)
1319 				(*dd_idx)++;
1320 			break;
1321 		case ALGORITHM_LEFT_SYMMETRIC:
1322 			*pd_idx = data_disks - stripe % raid_disks;
1323 			*dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;
1324 			break;
1325 		case ALGORITHM_RIGHT_SYMMETRIC:
1326 			*pd_idx = stripe % raid_disks;
1327 			*dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;
1328 			break;
1329 		default:
1330 			printk(KERN_ERR "raid5: unsupported algorithm %d\n",
1331 				conf->algorithm);
1332 		}
1333 		break;
1334 	case 6:
1335 
1336 		/**** FIX THIS ****/
1337 		switch (conf->algorithm) {
1338 		case ALGORITHM_LEFT_ASYMMETRIC:
1339 			*pd_idx = raid_disks - 1 - (stripe % raid_disks);
1340 			if (*pd_idx == raid_disks-1)
1341 				(*dd_idx)++; 	/* Q D D D P */
1342 			else if (*dd_idx >= *pd_idx)
1343 				(*dd_idx) += 2; /* D D P Q D */
1344 			break;
1345 		case ALGORITHM_RIGHT_ASYMMETRIC:
1346 			*pd_idx = stripe % raid_disks;
1347 			if (*pd_idx == raid_disks-1)
1348 				(*dd_idx)++; 	/* Q D D D P */
1349 			else if (*dd_idx >= *pd_idx)
1350 				(*dd_idx) += 2; /* D D P Q D */
1351 			break;
1352 		case ALGORITHM_LEFT_SYMMETRIC:
1353 			*pd_idx = raid_disks - 1 - (stripe % raid_disks);
1354 			*dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
1355 			break;
1356 		case ALGORITHM_RIGHT_SYMMETRIC:
1357 			*pd_idx = stripe % raid_disks;
1358 			*dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
1359 			break;
1360 		default:
1361 			printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
1362 				conf->algorithm);
1363 		}
1364 		break;
1365 	}
1366 
1367 	/*
1368 	 * Finally, compute the new sector number
1369 	 */
1370 	new_sector = (sector_t)stripe * sectors_per_chunk + chunk_offset;
1371 	return new_sector;
1372 }
1373 
1374 
1375 static sector_t compute_blocknr(struct stripe_head *sh, int i)
1376 {
1377 	raid5_conf_t *conf = sh->raid_conf;
1378 	int raid_disks = sh->disks;
1379 	int data_disks = raid_disks - conf->max_degraded;
1380 	sector_t new_sector = sh->sector, check;
1381 	int sectors_per_chunk = conf->chunk_size >> 9;
1382 	sector_t stripe;
1383 	int chunk_offset;
1384 	int chunk_number, dummy1, dummy2, dd_idx = i;
1385 	sector_t r_sector;
1386 
1387 
1388 	chunk_offset = sector_div(new_sector, sectors_per_chunk);
1389 	stripe = new_sector;
1390 	BUG_ON(new_sector != stripe);
1391 
1392 	if (i == sh->pd_idx)
1393 		return 0;
1394 	switch(conf->level) {
1395 	case 4: break;
1396 	case 5:
1397 		switch (conf->algorithm) {
1398 		case ALGORITHM_LEFT_ASYMMETRIC:
1399 		case ALGORITHM_RIGHT_ASYMMETRIC:
1400 			if (i > sh->pd_idx)
1401 				i--;
1402 			break;
1403 		case ALGORITHM_LEFT_SYMMETRIC:
1404 		case ALGORITHM_RIGHT_SYMMETRIC:
1405 			if (i < sh->pd_idx)
1406 				i += raid_disks;
1407 			i -= (sh->pd_idx + 1);
1408 			break;
1409 		default:
1410 			printk(KERN_ERR "raid5: unsupported algorithm %d\n",
1411 			       conf->algorithm);
1412 		}
1413 		break;
1414 	case 6:
1415 		if (i == raid6_next_disk(sh->pd_idx, raid_disks))
1416 			return 0; /* It is the Q disk */
1417 		switch (conf->algorithm) {
1418 		case ALGORITHM_LEFT_ASYMMETRIC:
1419 		case ALGORITHM_RIGHT_ASYMMETRIC:
1420 		  	if (sh->pd_idx == raid_disks-1)
1421 				i--; 	/* Q D D D P */
1422 			else if (i > sh->pd_idx)
1423 				i -= 2; /* D D P Q D */
1424 			break;
1425 		case ALGORITHM_LEFT_SYMMETRIC:
1426 		case ALGORITHM_RIGHT_SYMMETRIC:
1427 			if (sh->pd_idx == raid_disks-1)
1428 				i--; /* Q D D D P */
1429 			else {
1430 				/* D D P Q D */
1431 				if (i < sh->pd_idx)
1432 					i += raid_disks;
1433 				i -= (sh->pd_idx + 2);
1434 			}
1435 			break;
1436 		default:
1437 			printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
1438 				conf->algorithm);
1439 		}
1440 		break;
1441 	}
1442 
1443 	chunk_number = stripe * data_disks + i;
1444 	r_sector = (sector_t)chunk_number * sectors_per_chunk + chunk_offset;
1445 
1446 	check = raid5_compute_sector (r_sector, raid_disks, data_disks, &dummy1, &dummy2, conf);
1447 	if (check != sh->sector || dummy1 != dd_idx || dummy2 != sh->pd_idx) {
1448 		printk(KERN_ERR "compute_blocknr: map not correct\n");
1449 		return 0;
1450 	}
1451 	return r_sector;
1452 }
1453 
1454 
1455 
1456 /*
1457  * Copy data between a page in the stripe cache, and one or more bion
1458  * The page could align with the middle of the bio, or there could be
1459  * several bion, each with several bio_vecs, which cover part of the page
1460  * Multiple bion are linked together on bi_next.  There may be extras
1461  * at the end of this list.  We ignore them.
1462  */
1463 static void copy_data(int frombio, struct bio *bio,
1464 		     struct page *page,
1465 		     sector_t sector)
1466 {
1467 	char *pa = page_address(page);
1468 	struct bio_vec *bvl;
1469 	int i;
1470 	int page_offset;
1471 
1472 	if (bio->bi_sector >= sector)
1473 		page_offset = (signed)(bio->bi_sector - sector) * 512;
1474 	else
1475 		page_offset = (signed)(sector - bio->bi_sector) * -512;
1476 	bio_for_each_segment(bvl, bio, i) {
1477 		int len = bio_iovec_idx(bio,i)->bv_len;
1478 		int clen;
1479 		int b_offset = 0;
1480 
1481 		if (page_offset < 0) {
1482 			b_offset = -page_offset;
1483 			page_offset += b_offset;
1484 			len -= b_offset;
1485 		}
1486 
1487 		if (len > 0 && page_offset + len > STRIPE_SIZE)
1488 			clen = STRIPE_SIZE - page_offset;
1489 		else clen = len;
1490 
1491 		if (clen > 0) {
1492 			char *ba = __bio_kmap_atomic(bio, i, KM_USER0);
1493 			if (frombio)
1494 				memcpy(pa+page_offset, ba+b_offset, clen);
1495 			else
1496 				memcpy(ba+b_offset, pa+page_offset, clen);
1497 			__bio_kunmap_atomic(ba, KM_USER0);
1498 		}
1499 		if (clen < len) /* hit end of page */
1500 			break;
1501 		page_offset +=  len;
1502 	}
1503 }
1504 
1505 #define check_xor()	do {						  \
1506 				if (count == MAX_XOR_BLOCKS) {		  \
1507 				xor_blocks(count, STRIPE_SIZE, dest, ptr);\
1508 				count = 0;				  \
1509 			   }						  \
1510 			} while(0)
1511 
1512 static void compute_parity6(struct stripe_head *sh, int method)
1513 {
1514 	raid6_conf_t *conf = sh->raid_conf;
1515 	int i, pd_idx = sh->pd_idx, qd_idx, d0_idx, disks = sh->disks, count;
1516 	struct bio *chosen;
1517 	/**** FIX THIS: This could be very bad if disks is close to 256 ****/
1518 	void *ptrs[disks];
1519 
1520 	qd_idx = raid6_next_disk(pd_idx, disks);
1521 	d0_idx = raid6_next_disk(qd_idx, disks);
1522 
1523 	pr_debug("compute_parity, stripe %llu, method %d\n",
1524 		(unsigned long long)sh->sector, method);
1525 
1526 	switch(method) {
1527 	case READ_MODIFY_WRITE:
1528 		BUG();		/* READ_MODIFY_WRITE N/A for RAID-6 */
1529 	case RECONSTRUCT_WRITE:
1530 		for (i= disks; i-- ;)
1531 			if ( i != pd_idx && i != qd_idx && sh->dev[i].towrite ) {
1532 				chosen = sh->dev[i].towrite;
1533 				sh->dev[i].towrite = NULL;
1534 
1535 				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1536 					wake_up(&conf->wait_for_overlap);
1537 
1538 				BUG_ON(sh->dev[i].written);
1539 				sh->dev[i].written = chosen;
1540 			}
1541 		break;
1542 	case CHECK_PARITY:
1543 		BUG();		/* Not implemented yet */
1544 	}
1545 
1546 	for (i = disks; i--;)
1547 		if (sh->dev[i].written) {
1548 			sector_t sector = sh->dev[i].sector;
1549 			struct bio *wbi = sh->dev[i].written;
1550 			while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
1551 				copy_data(1, wbi, sh->dev[i].page, sector);
1552 				wbi = r5_next_bio(wbi, sector);
1553 			}
1554 
1555 			set_bit(R5_LOCKED, &sh->dev[i].flags);
1556 			set_bit(R5_UPTODATE, &sh->dev[i].flags);
1557 		}
1558 
1559 //	switch(method) {
1560 //	case RECONSTRUCT_WRITE:
1561 //	case CHECK_PARITY:
1562 //	case UPDATE_PARITY:
1563 		/* Note that unlike RAID-5, the ordering of the disks matters greatly. */
1564 		/* FIX: Is this ordering of drives even remotely optimal? */
1565 		count = 0;
1566 		i = d0_idx;
1567 		do {
1568 			ptrs[count++] = page_address(sh->dev[i].page);
1569 			if (count <= disks-2 && !test_bit(R5_UPTODATE, &sh->dev[i].flags))
1570 				printk("block %d/%d not uptodate on parity calc\n", i,count);
1571 			i = raid6_next_disk(i, disks);
1572 		} while ( i != d0_idx );
1573 //		break;
1574 //	}
1575 
1576 	raid6_call.gen_syndrome(disks, STRIPE_SIZE, ptrs);
1577 
1578 	switch(method) {
1579 	case RECONSTRUCT_WRITE:
1580 		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1581 		set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
1582 		set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
1583 		set_bit(R5_LOCKED,   &sh->dev[qd_idx].flags);
1584 		break;
1585 	case UPDATE_PARITY:
1586 		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1587 		set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
1588 		break;
1589 	}
1590 }
1591 
1592 
1593 /* Compute one missing block */
1594 static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
1595 {
1596 	int i, count, disks = sh->disks;
1597 	void *ptr[MAX_XOR_BLOCKS], *dest, *p;
1598 	int pd_idx = sh->pd_idx;
1599 	int qd_idx = raid6_next_disk(pd_idx, disks);
1600 
1601 	pr_debug("compute_block_1, stripe %llu, idx %d\n",
1602 		(unsigned long long)sh->sector, dd_idx);
1603 
1604 	if ( dd_idx == qd_idx ) {
1605 		/* We're actually computing the Q drive */
1606 		compute_parity6(sh, UPDATE_PARITY);
1607 	} else {
1608 		dest = page_address(sh->dev[dd_idx].page);
1609 		if (!nozero) memset(dest, 0, STRIPE_SIZE);
1610 		count = 0;
1611 		for (i = disks ; i--; ) {
1612 			if (i == dd_idx || i == qd_idx)
1613 				continue;
1614 			p = page_address(sh->dev[i].page);
1615 			if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
1616 				ptr[count++] = p;
1617 			else
1618 				printk("compute_block() %d, stripe %llu, %d"
1619 				       " not present\n", dd_idx,
1620 				       (unsigned long long)sh->sector, i);
1621 
1622 			check_xor();
1623 		}
1624 		if (count)
1625 			xor_blocks(count, STRIPE_SIZE, dest, ptr);
1626 		if (!nozero) set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
1627 		else clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
1628 	}
1629 }
1630 
1631 /* Compute two missing blocks */
1632 static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
1633 {
1634 	int i, count, disks = sh->disks;
1635 	int pd_idx = sh->pd_idx;
1636 	int qd_idx = raid6_next_disk(pd_idx, disks);
1637 	int d0_idx = raid6_next_disk(qd_idx, disks);
1638 	int faila, failb;
1639 
1640 	/* faila and failb are disk numbers relative to d0_idx */
1641 	/* pd_idx become disks-2 and qd_idx become disks-1 */
1642 	faila = (dd_idx1 < d0_idx) ? dd_idx1+(disks-d0_idx) : dd_idx1-d0_idx;
1643 	failb = (dd_idx2 < d0_idx) ? dd_idx2+(disks-d0_idx) : dd_idx2-d0_idx;
1644 
1645 	BUG_ON(faila == failb);
1646 	if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
1647 
1648 	pr_debug("compute_block_2, stripe %llu, idx %d,%d (%d,%d)\n",
1649 	       (unsigned long long)sh->sector, dd_idx1, dd_idx2, faila, failb);
1650 
1651 	if ( failb == disks-1 ) {
1652 		/* Q disk is one of the missing disks */
1653 		if ( faila == disks-2 ) {
1654 			/* Missing P+Q, just recompute */
1655 			compute_parity6(sh, UPDATE_PARITY);
1656 			return;
1657 		} else {
1658 			/* We're missing D+Q; recompute D from P */
1659 			compute_block_1(sh, (dd_idx1 == qd_idx) ? dd_idx2 : dd_idx1, 0);
1660 			compute_parity6(sh, UPDATE_PARITY); /* Is this necessary? */
1661 			return;
1662 		}
1663 	}
1664 
1665 	/* We're missing D+P or D+D; build pointer table */
1666 	{
1667 		/**** FIX THIS: This could be very bad if disks is close to 256 ****/
1668 		void *ptrs[disks];
1669 
1670 		count = 0;
1671 		i = d0_idx;
1672 		do {
1673 			ptrs[count++] = page_address(sh->dev[i].page);
1674 			i = raid6_next_disk(i, disks);
1675 			if (i != dd_idx1 && i != dd_idx2 &&
1676 			    !test_bit(R5_UPTODATE, &sh->dev[i].flags))
1677 				printk("compute_2 with missing block %d/%d\n", count, i);
1678 		} while ( i != d0_idx );
1679 
1680 		if ( failb == disks-2 ) {
1681 			/* We're missing D+P. */
1682 			raid6_datap_recov(disks, STRIPE_SIZE, faila, ptrs);
1683 		} else {
1684 			/* We're missing D+D. */
1685 			raid6_2data_recov(disks, STRIPE_SIZE, faila, failb, ptrs);
1686 		}
1687 
1688 		/* Both the above update both missing blocks */
1689 		set_bit(R5_UPTODATE, &sh->dev[dd_idx1].flags);
1690 		set_bit(R5_UPTODATE, &sh->dev[dd_idx2].flags);
1691 	}
1692 }
1693 
1694 static int
1695 handle_write_operations5(struct stripe_head *sh, int rcw, int expand)
1696 {
1697 	int i, pd_idx = sh->pd_idx, disks = sh->disks;
1698 	int locked = 0;
1699 
1700 	if (rcw) {
1701 		/* if we are not expanding this is a proper write request, and
1702 		 * there will be bios with new data to be drained into the
1703 		 * stripe cache
1704 		 */
1705 		if (!expand) {
1706 			set_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
1707 			sh->ops.count++;
1708 		}
1709 
1710 		set_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
1711 		sh->ops.count++;
1712 
1713 		for (i = disks; i--; ) {
1714 			struct r5dev *dev = &sh->dev[i];
1715 
1716 			if (dev->towrite) {
1717 				set_bit(R5_LOCKED, &dev->flags);
1718 				if (!expand)
1719 					clear_bit(R5_UPTODATE, &dev->flags);
1720 				locked++;
1721 			}
1722 		}
1723 	} else {
1724 		BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
1725 			test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
1726 
1727 		set_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
1728 		set_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
1729 		set_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
1730 
1731 		sh->ops.count += 3;
1732 
1733 		for (i = disks; i--; ) {
1734 			struct r5dev *dev = &sh->dev[i];
1735 			if (i == pd_idx)
1736 				continue;
1737 
1738 			/* For a read-modify write there may be blocks that are
1739 			 * locked for reading while others are ready to be
1740 			 * written so we distinguish these blocks by the
1741 			 * R5_Wantprexor bit
1742 			 */
1743 			if (dev->towrite &&
1744 			    (test_bit(R5_UPTODATE, &dev->flags) ||
1745 			    test_bit(R5_Wantcompute, &dev->flags))) {
1746 				set_bit(R5_Wantprexor, &dev->flags);
1747 				set_bit(R5_LOCKED, &dev->flags);
1748 				clear_bit(R5_UPTODATE, &dev->flags);
1749 				locked++;
1750 			}
1751 		}
1752 	}
1753 
1754 	/* keep the parity disk locked while asynchronous operations
1755 	 * are in flight
1756 	 */
1757 	set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
1758 	clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1759 	locked++;
1760 
1761 	pr_debug("%s: stripe %llu locked: %d pending: %lx\n",
1762 		__FUNCTION__, (unsigned long long)sh->sector,
1763 		locked, sh->ops.pending);
1764 
1765 	return locked;
1766 }
1767 
1768 /*
1769  * Each stripe/dev can have one or more bion attached.
1770  * toread/towrite point to the first in a chain.
1771  * The bi_next chain must be in order.
1772  */
1773 static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, int forwrite)
1774 {
1775 	struct bio **bip;
1776 	raid5_conf_t *conf = sh->raid_conf;
1777 	int firstwrite=0;
1778 
1779 	pr_debug("adding bh b#%llu to stripe s#%llu\n",
1780 		(unsigned long long)bi->bi_sector,
1781 		(unsigned long long)sh->sector);
1782 
1783 
1784 	spin_lock(&sh->lock);
1785 	spin_lock_irq(&conf->device_lock);
1786 	if (forwrite) {
1787 		bip = &sh->dev[dd_idx].towrite;
1788 		if (*bip == NULL && sh->dev[dd_idx].written == NULL)
1789 			firstwrite = 1;
1790 	} else
1791 		bip = &sh->dev[dd_idx].toread;
1792 	while (*bip && (*bip)->bi_sector < bi->bi_sector) {
1793 		if ((*bip)->bi_sector + ((*bip)->bi_size >> 9) > bi->bi_sector)
1794 			goto overlap;
1795 		bip = & (*bip)->bi_next;
1796 	}
1797 	if (*bip && (*bip)->bi_sector < bi->bi_sector + ((bi->bi_size)>>9))
1798 		goto overlap;
1799 
1800 	BUG_ON(*bip && bi->bi_next && (*bip) != bi->bi_next);
1801 	if (*bip)
1802 		bi->bi_next = *bip;
1803 	*bip = bi;
1804 	bi->bi_phys_segments ++;
1805 	spin_unlock_irq(&conf->device_lock);
1806 	spin_unlock(&sh->lock);
1807 
1808 	pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
1809 		(unsigned long long)bi->bi_sector,
1810 		(unsigned long long)sh->sector, dd_idx);
1811 
1812 	if (conf->mddev->bitmap && firstwrite) {
1813 		bitmap_startwrite(conf->mddev->bitmap, sh->sector,
1814 				  STRIPE_SECTORS, 0);
1815 		sh->bm_seq = conf->seq_flush+1;
1816 		set_bit(STRIPE_BIT_DELAY, &sh->state);
1817 	}
1818 
1819 	if (forwrite) {
1820 		/* check if page is covered */
1821 		sector_t sector = sh->dev[dd_idx].sector;
1822 		for (bi=sh->dev[dd_idx].towrite;
1823 		     sector < sh->dev[dd_idx].sector + STRIPE_SECTORS &&
1824 			     bi && bi->bi_sector <= sector;
1825 		     bi = r5_next_bio(bi, sh->dev[dd_idx].sector)) {
1826 			if (bi->bi_sector + (bi->bi_size>>9) >= sector)
1827 				sector = bi->bi_sector + (bi->bi_size>>9);
1828 		}
1829 		if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
1830 			set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
1831 	}
1832 	return 1;
1833 
1834  overlap:
1835 	set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
1836 	spin_unlock_irq(&conf->device_lock);
1837 	spin_unlock(&sh->lock);
1838 	return 0;
1839 }
1840 
1841 static void end_reshape(raid5_conf_t *conf);
1842 
1843 static int page_is_zero(struct page *p)
1844 {
1845 	char *a = page_address(p);
1846 	return ((*(u32*)a) == 0 &&
1847 		memcmp(a, a+4, STRIPE_SIZE-4)==0);
1848 }
1849 
1850 static int stripe_to_pdidx(sector_t stripe, raid5_conf_t *conf, int disks)
1851 {
1852 	int sectors_per_chunk = conf->chunk_size >> 9;
1853 	int pd_idx, dd_idx;
1854 	int chunk_offset = sector_div(stripe, sectors_per_chunk);
1855 
1856 	raid5_compute_sector(stripe * (disks - conf->max_degraded)
1857 			     *sectors_per_chunk + chunk_offset,
1858 			     disks, disks - conf->max_degraded,
1859 			     &dd_idx, &pd_idx, conf);
1860 	return pd_idx;
1861 }
1862 
1863 static void
1864 handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
1865 				struct stripe_head_state *s, int disks,
1866 				struct bio **return_bi)
1867 {
1868 	int i;
1869 	for (i = disks; i--; ) {
1870 		struct bio *bi;
1871 		int bitmap_end = 0;
1872 
1873 		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
1874 			mdk_rdev_t *rdev;
1875 			rcu_read_lock();
1876 			rdev = rcu_dereference(conf->disks[i].rdev);
1877 			if (rdev && test_bit(In_sync, &rdev->flags))
1878 				/* multiple read failures in one stripe */
1879 				md_error(conf->mddev, rdev);
1880 			rcu_read_unlock();
1881 		}
1882 		spin_lock_irq(&conf->device_lock);
1883 		/* fail all writes first */
1884 		bi = sh->dev[i].towrite;
1885 		sh->dev[i].towrite = NULL;
1886 		if (bi) {
1887 			s->to_write--;
1888 			bitmap_end = 1;
1889 		}
1890 
1891 		if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1892 			wake_up(&conf->wait_for_overlap);
1893 
1894 		while (bi && bi->bi_sector <
1895 			sh->dev[i].sector + STRIPE_SECTORS) {
1896 			struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
1897 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
1898 			if (--bi->bi_phys_segments == 0) {
1899 				md_write_end(conf->mddev);
1900 				bi->bi_next = *return_bi;
1901 				*return_bi = bi;
1902 			}
1903 			bi = nextbi;
1904 		}
1905 		/* and fail all 'written' */
1906 		bi = sh->dev[i].written;
1907 		sh->dev[i].written = NULL;
1908 		if (bi) bitmap_end = 1;
1909 		while (bi && bi->bi_sector <
1910 		       sh->dev[i].sector + STRIPE_SECTORS) {
1911 			struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
1912 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
1913 			if (--bi->bi_phys_segments == 0) {
1914 				md_write_end(conf->mddev);
1915 				bi->bi_next = *return_bi;
1916 				*return_bi = bi;
1917 			}
1918 			bi = bi2;
1919 		}
1920 
1921 		/* fail any reads if this device is non-operational and
1922 		 * the data has not reached the cache yet.
1923 		 */
1924 		if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
1925 		    (!test_bit(R5_Insync, &sh->dev[i].flags) ||
1926 		      test_bit(R5_ReadError, &sh->dev[i].flags))) {
1927 			bi = sh->dev[i].toread;
1928 			sh->dev[i].toread = NULL;
1929 			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1930 				wake_up(&conf->wait_for_overlap);
1931 			if (bi) s->to_read--;
1932 			while (bi && bi->bi_sector <
1933 			       sh->dev[i].sector + STRIPE_SECTORS) {
1934 				struct bio *nextbi =
1935 					r5_next_bio(bi, sh->dev[i].sector);
1936 				clear_bit(BIO_UPTODATE, &bi->bi_flags);
1937 				if (--bi->bi_phys_segments == 0) {
1938 					bi->bi_next = *return_bi;
1939 					*return_bi = bi;
1940 				}
1941 				bi = nextbi;
1942 			}
1943 		}
1944 		spin_unlock_irq(&conf->device_lock);
1945 		if (bitmap_end)
1946 			bitmap_endwrite(conf->mddev->bitmap, sh->sector,
1947 					STRIPE_SECTORS, 0, 0);
1948 	}
1949 
1950 }
1951 
1952 /* __handle_issuing_new_read_requests5 - returns 0 if there are no more disks
1953  * to process
1954  */
1955 static int __handle_issuing_new_read_requests5(struct stripe_head *sh,
1956 			struct stripe_head_state *s, int disk_idx, int disks)
1957 {
1958 	struct r5dev *dev = &sh->dev[disk_idx];
1959 	struct r5dev *failed_dev = &sh->dev[s->failed_num];
1960 
1961 	/* don't schedule compute operations or reads on the parity block while
1962 	 * a check is in flight
1963 	 */
1964 	if ((disk_idx == sh->pd_idx) &&
1965 	     test_bit(STRIPE_OP_CHECK, &sh->ops.pending))
1966 		return ~0;
1967 
1968 	/* is the data in this block needed, and can we get it? */
1969 	if (!test_bit(R5_LOCKED, &dev->flags) &&
1970 	    !test_bit(R5_UPTODATE, &dev->flags) && (dev->toread ||
1971 	    (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
1972 	     s->syncing || s->expanding || (s->failed &&
1973 	     (failed_dev->toread || (failed_dev->towrite &&
1974 	     !test_bit(R5_OVERWRITE, &failed_dev->flags)
1975 	     ))))) {
1976 		/* 1/ We would like to get this block, possibly by computing it,
1977 		 * but we might not be able to.
1978 		 *
1979 		 * 2/ Since parity check operations potentially make the parity
1980 		 * block !uptodate it will need to be refreshed before any
1981 		 * compute operations on data disks are scheduled.
1982 		 *
1983 		 * 3/ We hold off parity block re-reads until check operations
1984 		 * have quiesced.
1985 		 */
1986 		if ((s->uptodate == disks - 1) &&
1987 		    !test_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {
1988 			set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
1989 			set_bit(R5_Wantcompute, &dev->flags);
1990 			sh->ops.target = disk_idx;
1991 			s->req_compute = 1;
1992 			sh->ops.count++;
1993 			/* Careful: from this point on 'uptodate' is in the eye
1994 			 * of raid5_run_ops which services 'compute' operations
1995 			 * before writes. R5_Wantcompute flags a block that will
1996 			 * be R5_UPTODATE by the time it is needed for a
1997 			 * subsequent operation.
1998 			 */
1999 			s->uptodate++;
2000 			return 0; /* uptodate + compute == disks */
2001 		} else if ((s->uptodate < disks - 1) &&
2002 			test_bit(R5_Insync, &dev->flags)) {
2003 			/* Note: we hold off compute operations while checks are
2004 			 * in flight, but we still prefer 'compute' over 'read'
2005 			 * hence we only read if (uptodate < * disks-1)
2006 			 */
2007 			set_bit(R5_LOCKED, &dev->flags);
2008 			set_bit(R5_Wantread, &dev->flags);
2009 			if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
2010 				sh->ops.count++;
2011 			s->locked++;
2012 			pr_debug("Reading block %d (sync=%d)\n", disk_idx,
2013 				s->syncing);
2014 		}
2015 	}
2016 
2017 	return ~0;
2018 }
2019 
2020 static void handle_issuing_new_read_requests5(struct stripe_head *sh,
2021 			struct stripe_head_state *s, int disks)
2022 {
2023 	int i;
2024 
2025 	/* Clear completed compute operations.  Parity recovery
2026 	 * (STRIPE_OP_MOD_REPAIR_PD) implies a write-back which is handled
2027 	 * later on in this routine
2028 	 */
2029 	if (test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete) &&
2030 		!test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {
2031 		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete);
2032 		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.ack);
2033 		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
2034 	}
2035 
2036 	/* look for blocks to read/compute, skip this if a compute
2037 	 * is already in flight, or if the stripe contents are in the
2038 	 * midst of changing due to a write
2039 	 */
2040 	if (!test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending) &&
2041 		!test_bit(STRIPE_OP_PREXOR, &sh->ops.pending) &&
2042 		!test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
2043 		for (i = disks; i--; )
2044 			if (__handle_issuing_new_read_requests5(
2045 				sh, s, i, disks) == 0)
2046 				break;
2047 	}
2048 	set_bit(STRIPE_HANDLE, &sh->state);
2049 }
2050 
2051 static void handle_issuing_new_read_requests6(struct stripe_head *sh,
2052 			struct stripe_head_state *s, struct r6_state *r6s,
2053 			int disks)
2054 {
2055 	int i;
2056 	for (i = disks; i--; ) {
2057 		struct r5dev *dev = &sh->dev[i];
2058 		if (!test_bit(R5_LOCKED, &dev->flags) &&
2059 		    !test_bit(R5_UPTODATE, &dev->flags) &&
2060 		    (dev->toread || (dev->towrite &&
2061 		     !test_bit(R5_OVERWRITE, &dev->flags)) ||
2062 		     s->syncing || s->expanding ||
2063 		     (s->failed >= 1 &&
2064 		      (sh->dev[r6s->failed_num[0]].toread ||
2065 		       s->to_write)) ||
2066 		     (s->failed >= 2 &&
2067 		      (sh->dev[r6s->failed_num[1]].toread ||
2068 		       s->to_write)))) {
2069 			/* we would like to get this block, possibly
2070 			 * by computing it, but we might not be able to
2071 			 */
2072 			if (s->uptodate == disks-1) {
2073 				pr_debug("Computing stripe %llu block %d\n",
2074 				       (unsigned long long)sh->sector, i);
2075 				compute_block_1(sh, i, 0);
2076 				s->uptodate++;
2077 			} else if ( s->uptodate == disks-2 && s->failed >= 2 ) {
2078 				/* Computing 2-failure is *very* expensive; only
2079 				 * do it if failed >= 2
2080 				 */
2081 				int other;
2082 				for (other = disks; other--; ) {
2083 					if (other == i)
2084 						continue;
2085 					if (!test_bit(R5_UPTODATE,
2086 					      &sh->dev[other].flags))
2087 						break;
2088 				}
2089 				BUG_ON(other < 0);
2090 				pr_debug("Computing stripe %llu blocks %d,%d\n",
2091 				       (unsigned long long)sh->sector,
2092 				       i, other);
2093 				compute_block_2(sh, i, other);
2094 				s->uptodate += 2;
2095 			} else if (test_bit(R5_Insync, &dev->flags)) {
2096 				set_bit(R5_LOCKED, &dev->flags);
2097 				set_bit(R5_Wantread, &dev->flags);
2098 				s->locked++;
2099 				pr_debug("Reading block %d (sync=%d)\n",
2100 					i, s->syncing);
2101 			}
2102 		}
2103 	}
2104 	set_bit(STRIPE_HANDLE, &sh->state);
2105 }
2106 
2107 
2108 /* handle_completed_write_requests
2109  * any written block on an uptodate or failed drive can be returned.
2110  * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but
2111  * never LOCKED, so we don't need to test 'failed' directly.
2112  */
2113 static void handle_completed_write_requests(raid5_conf_t *conf,
2114 	struct stripe_head *sh, int disks, struct bio **return_bi)
2115 {
2116 	int i;
2117 	struct r5dev *dev;
2118 
2119 	for (i = disks; i--; )
2120 		if (sh->dev[i].written) {
2121 			dev = &sh->dev[i];
2122 			if (!test_bit(R5_LOCKED, &dev->flags) &&
2123 				test_bit(R5_UPTODATE, &dev->flags)) {
2124 				/* We can return any write requests */
2125 				struct bio *wbi, *wbi2;
2126 				int bitmap_end = 0;
2127 				pr_debug("Return write for disc %d\n", i);
2128 				spin_lock_irq(&conf->device_lock);
2129 				wbi = dev->written;
2130 				dev->written = NULL;
2131 				while (wbi && wbi->bi_sector <
2132 					dev->sector + STRIPE_SECTORS) {
2133 					wbi2 = r5_next_bio(wbi, dev->sector);
2134 					if (--wbi->bi_phys_segments == 0) {
2135 						md_write_end(conf->mddev);
2136 						wbi->bi_next = *return_bi;
2137 						*return_bi = wbi;
2138 					}
2139 					wbi = wbi2;
2140 				}
2141 				if (dev->towrite == NULL)
2142 					bitmap_end = 1;
2143 				spin_unlock_irq(&conf->device_lock);
2144 				if (bitmap_end)
2145 					bitmap_endwrite(conf->mddev->bitmap,
2146 							sh->sector,
2147 							STRIPE_SECTORS,
2148 					 !test_bit(STRIPE_DEGRADED, &sh->state),
2149 							0);
2150 			}
2151 		}
2152 }
2153 
2154 static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
2155 		struct stripe_head *sh,	struct stripe_head_state *s, int disks)
2156 {
2157 	int rmw = 0, rcw = 0, i;
2158 	for (i = disks; i--; ) {
2159 		/* would I have to read this buffer for read_modify_write */
2160 		struct r5dev *dev = &sh->dev[i];
2161 		if ((dev->towrite || i == sh->pd_idx) &&
2162 		    !test_bit(R5_LOCKED, &dev->flags) &&
2163 		    !(test_bit(R5_UPTODATE, &dev->flags) ||
2164 		      test_bit(R5_Wantcompute, &dev->flags))) {
2165 			if (test_bit(R5_Insync, &dev->flags))
2166 				rmw++;
2167 			else
2168 				rmw += 2*disks;  /* cannot read it */
2169 		}
2170 		/* Would I have to read this buffer for reconstruct_write */
2171 		if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
2172 		    !test_bit(R5_LOCKED, &dev->flags) &&
2173 		    !(test_bit(R5_UPTODATE, &dev->flags) ||
2174 		    test_bit(R5_Wantcompute, &dev->flags))) {
2175 			if (test_bit(R5_Insync, &dev->flags)) rcw++;
2176 			else
2177 				rcw += 2*disks;
2178 		}
2179 	}
2180 	pr_debug("for sector %llu, rmw=%d rcw=%d\n",
2181 		(unsigned long long)sh->sector, rmw, rcw);
2182 	set_bit(STRIPE_HANDLE, &sh->state);
2183 	if (rmw < rcw && rmw > 0)
2184 		/* prefer read-modify-write, but need to get some data */
2185 		for (i = disks; i--; ) {
2186 			struct r5dev *dev = &sh->dev[i];
2187 			if ((dev->towrite || i == sh->pd_idx) &&
2188 			    !test_bit(R5_LOCKED, &dev->flags) &&
2189 			    !(test_bit(R5_UPTODATE, &dev->flags) ||
2190 			    test_bit(R5_Wantcompute, &dev->flags)) &&
2191 			    test_bit(R5_Insync, &dev->flags)) {
2192 				if (
2193 				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2194 					pr_debug("Read_old block "
2195 						"%d for r-m-w\n", i);
2196 					set_bit(R5_LOCKED, &dev->flags);
2197 					set_bit(R5_Wantread, &dev->flags);
2198 					if (!test_and_set_bit(
2199 						STRIPE_OP_IO, &sh->ops.pending))
2200 						sh->ops.count++;
2201 					s->locked++;
2202 				} else {
2203 					set_bit(STRIPE_DELAYED, &sh->state);
2204 					set_bit(STRIPE_HANDLE, &sh->state);
2205 				}
2206 			}
2207 		}
2208 	if (rcw <= rmw && rcw > 0)
2209 		/* want reconstruct write, but need to get some data */
2210 		for (i = disks; i--; ) {
2211 			struct r5dev *dev = &sh->dev[i];
2212 			if (!test_bit(R5_OVERWRITE, &dev->flags) &&
2213 			    i != sh->pd_idx &&
2214 			    !test_bit(R5_LOCKED, &dev->flags) &&
2215 			    !(test_bit(R5_UPTODATE, &dev->flags) ||
2216 			    test_bit(R5_Wantcompute, &dev->flags)) &&
2217 			    test_bit(R5_Insync, &dev->flags)) {
2218 				if (
2219 				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2220 					pr_debug("Read_old block "
2221 						"%d for Reconstruct\n", i);
2222 					set_bit(R5_LOCKED, &dev->flags);
2223 					set_bit(R5_Wantread, &dev->flags);
2224 					if (!test_and_set_bit(
2225 						STRIPE_OP_IO, &sh->ops.pending))
2226 						sh->ops.count++;
2227 					s->locked++;
2228 				} else {
2229 					set_bit(STRIPE_DELAYED, &sh->state);
2230 					set_bit(STRIPE_HANDLE, &sh->state);
2231 				}
2232 			}
2233 		}
2234 	/* now if nothing is locked, and if we have enough data,
2235 	 * we can start a write request
2236 	 */
2237 	/* since handle_stripe can be called at any time we need to handle the
2238 	 * case where a compute block operation has been submitted and then a
2239 	 * subsequent call wants to start a write request.  raid5_run_ops only
2240 	 * handles the case where compute block and postxor are requested
2241 	 * simultaneously.  If this is not the case then new writes need to be
2242 	 * held off until the compute completes.
2243 	 */
2244 	if ((s->req_compute ||
2245 	    !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending)) &&
2246 		(s->locked == 0 && (rcw == 0 || rmw == 0) &&
2247 		!test_bit(STRIPE_BIT_DELAY, &sh->state)))
2248 		s->locked += handle_write_operations5(sh, rcw == 0, 0);
2249 }
2250 
2251 static void handle_issuing_new_write_requests6(raid5_conf_t *conf,
2252 		struct stripe_head *sh,	struct stripe_head_state *s,
2253 		struct r6_state *r6s, int disks)
2254 {
2255 	int rcw = 0, must_compute = 0, pd_idx = sh->pd_idx, i;
2256 	int qd_idx = r6s->qd_idx;
2257 	for (i = disks; i--; ) {
2258 		struct r5dev *dev = &sh->dev[i];
2259 		/* Would I have to read this buffer for reconstruct_write */
2260 		if (!test_bit(R5_OVERWRITE, &dev->flags)
2261 		    && i != pd_idx && i != qd_idx
2262 		    && (!test_bit(R5_LOCKED, &dev->flags)
2263 			    ) &&
2264 		    !test_bit(R5_UPTODATE, &dev->flags)) {
2265 			if (test_bit(R5_Insync, &dev->flags)) rcw++;
2266 			else {
2267 				pr_debug("raid6: must_compute: "
2268 					"disk %d flags=%#lx\n", i, dev->flags);
2269 				must_compute++;
2270 			}
2271 		}
2272 	}
2273 	pr_debug("for sector %llu, rcw=%d, must_compute=%d\n",
2274 	       (unsigned long long)sh->sector, rcw, must_compute);
2275 	set_bit(STRIPE_HANDLE, &sh->state);
2276 
2277 	if (rcw > 0)
2278 		/* want reconstruct write, but need to get some data */
2279 		for (i = disks; i--; ) {
2280 			struct r5dev *dev = &sh->dev[i];
2281 			if (!test_bit(R5_OVERWRITE, &dev->flags)
2282 			    && !(s->failed == 0 && (i == pd_idx || i == qd_idx))
2283 			    && !test_bit(R5_LOCKED, &dev->flags) &&
2284 			    !test_bit(R5_UPTODATE, &dev->flags) &&
2285 			    test_bit(R5_Insync, &dev->flags)) {
2286 				if (
2287 				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2288 					pr_debug("Read_old stripe %llu "
2289 						"block %d for Reconstruct\n",
2290 					     (unsigned long long)sh->sector, i);
2291 					set_bit(R5_LOCKED, &dev->flags);
2292 					set_bit(R5_Wantread, &dev->flags);
2293 					s->locked++;
2294 				} else {
2295 					pr_debug("Request delayed stripe %llu "
2296 						"block %d for Reconstruct\n",
2297 					     (unsigned long long)sh->sector, i);
2298 					set_bit(STRIPE_DELAYED, &sh->state);
2299 					set_bit(STRIPE_HANDLE, &sh->state);
2300 				}
2301 			}
2302 		}
2303 	/* now if nothing is locked, and if we have enough data, we can start a
2304 	 * write request
2305 	 */
2306 	if (s->locked == 0 && rcw == 0 &&
2307 	    !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
2308 		if (must_compute > 0) {
2309 			/* We have failed blocks and need to compute them */
2310 			switch (s->failed) {
2311 			case 0:
2312 				BUG();
2313 			case 1:
2314 				compute_block_1(sh, r6s->failed_num[0], 0);
2315 				break;
2316 			case 2:
2317 				compute_block_2(sh, r6s->failed_num[0],
2318 						r6s->failed_num[1]);
2319 				break;
2320 			default: /* This request should have been failed? */
2321 				BUG();
2322 			}
2323 		}
2324 
2325 		pr_debug("Computing parity for stripe %llu\n",
2326 			(unsigned long long)sh->sector);
2327 		compute_parity6(sh, RECONSTRUCT_WRITE);
2328 		/* now every locked buffer is ready to be written */
2329 		for (i = disks; i--; )
2330 			if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
2331 				pr_debug("Writing stripe %llu block %d\n",
2332 				       (unsigned long long)sh->sector, i);
2333 				s->locked++;
2334 				set_bit(R5_Wantwrite, &sh->dev[i].flags);
2335 			}
2336 		/* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */
2337 		set_bit(STRIPE_INSYNC, &sh->state);
2338 
2339 		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2340 			atomic_dec(&conf->preread_active_stripes);
2341 			if (atomic_read(&conf->preread_active_stripes) <
2342 			    IO_THRESHOLD)
2343 				md_wakeup_thread(conf->mddev->thread);
2344 		}
2345 	}
2346 }
2347 
2348 static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,
2349 				struct stripe_head_state *s, int disks)
2350 {
2351 	set_bit(STRIPE_HANDLE, &sh->state);
2352 	/* Take one of the following actions:
2353 	 * 1/ start a check parity operation if (uptodate == disks)
2354 	 * 2/ finish a check parity operation and act on the result
2355 	 * 3/ skip to the writeback section if we previously
2356 	 *    initiated a recovery operation
2357 	 */
2358 	if (s->failed == 0 &&
2359 	    !test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {
2360 		if (!test_and_set_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {
2361 			BUG_ON(s->uptodate != disks);
2362 			clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
2363 			sh->ops.count++;
2364 			s->uptodate--;
2365 		} else if (
2366 		       test_and_clear_bit(STRIPE_OP_CHECK, &sh->ops.complete)) {
2367 			clear_bit(STRIPE_OP_CHECK, &sh->ops.ack);
2368 			clear_bit(STRIPE_OP_CHECK, &sh->ops.pending);
2369 
2370 			if (sh->ops.zero_sum_result == 0)
2371 				/* parity is correct (on disc,
2372 				 * not in buffer any more)
2373 				 */
2374 				set_bit(STRIPE_INSYNC, &sh->state);
2375 			else {
2376 				conf->mddev->resync_mismatches +=
2377 					STRIPE_SECTORS;
2378 				if (test_bit(
2379 				     MD_RECOVERY_CHECK, &conf->mddev->recovery))
2380 					/* don't try to repair!! */
2381 					set_bit(STRIPE_INSYNC, &sh->state);
2382 				else {
2383 					set_bit(STRIPE_OP_COMPUTE_BLK,
2384 						&sh->ops.pending);
2385 					set_bit(STRIPE_OP_MOD_REPAIR_PD,
2386 						&sh->ops.pending);
2387 					set_bit(R5_Wantcompute,
2388 						&sh->dev[sh->pd_idx].flags);
2389 					sh->ops.target = sh->pd_idx;
2390 					sh->ops.count++;
2391 					s->uptodate++;
2392 				}
2393 			}
2394 		}
2395 	}
2396 
2397 	/* check if we can clear a parity disk reconstruct */
2398 	if (test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete) &&
2399 		test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {
2400 
2401 		clear_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending);
2402 		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete);
2403 		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.ack);
2404 		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
2405 	}
2406 
2407 	/* Wait for check parity and compute block operations to complete
2408 	 * before write-back
2409 	 */
2410 	if (!test_bit(STRIPE_INSYNC, &sh->state) &&
2411 		!test_bit(STRIPE_OP_CHECK, &sh->ops.pending) &&
2412 		!test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending)) {
2413 		struct r5dev *dev;
2414 		/* either failed parity check, or recovery is happening */
2415 		if (s->failed == 0)
2416 			s->failed_num = sh->pd_idx;
2417 		dev = &sh->dev[s->failed_num];
2418 		BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
2419 		BUG_ON(s->uptodate != disks);
2420 
2421 		set_bit(R5_LOCKED, &dev->flags);
2422 		set_bit(R5_Wantwrite, &dev->flags);
2423 		if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
2424 			sh->ops.count++;
2425 
2426 		clear_bit(STRIPE_DEGRADED, &sh->state);
2427 		s->locked++;
2428 		set_bit(STRIPE_INSYNC, &sh->state);
2429 	}
2430 }
2431 
2432 
2433 static void handle_parity_checks6(raid5_conf_t *conf, struct stripe_head *sh,
2434 				struct stripe_head_state *s,
2435 				struct r6_state *r6s, struct page *tmp_page,
2436 				int disks)
2437 {
2438 	int update_p = 0, update_q = 0;
2439 	struct r5dev *dev;
2440 	int pd_idx = sh->pd_idx;
2441 	int qd_idx = r6s->qd_idx;
2442 
2443 	set_bit(STRIPE_HANDLE, &sh->state);
2444 
2445 	BUG_ON(s->failed > 2);
2446 	BUG_ON(s->uptodate < disks);
2447 	/* Want to check and possibly repair P and Q.
2448 	 * However there could be one 'failed' device, in which
2449 	 * case we can only check one of them, possibly using the
2450 	 * other to generate missing data
2451 	 */
2452 
2453 	/* If !tmp_page, we cannot do the calculations,
2454 	 * but as we have set STRIPE_HANDLE, we will soon be called
2455 	 * by stripe_handle with a tmp_page - just wait until then.
2456 	 */
2457 	if (tmp_page) {
2458 		if (s->failed == r6s->q_failed) {
2459 			/* The only possible failed device holds 'Q', so it
2460 			 * makes sense to check P (If anything else were failed,
2461 			 * we would have used P to recreate it).
2462 			 */
2463 			compute_block_1(sh, pd_idx, 1);
2464 			if (!page_is_zero(sh->dev[pd_idx].page)) {
2465 				compute_block_1(sh, pd_idx, 0);
2466 				update_p = 1;
2467 			}
2468 		}
2469 		if (!r6s->q_failed && s->failed < 2) {
2470 			/* q is not failed, and we didn't use it to generate
2471 			 * anything, so it makes sense to check it
2472 			 */
2473 			memcpy(page_address(tmp_page),
2474 			       page_address(sh->dev[qd_idx].page),
2475 			       STRIPE_SIZE);
2476 			compute_parity6(sh, UPDATE_PARITY);
2477 			if (memcmp(page_address(tmp_page),
2478 				   page_address(sh->dev[qd_idx].page),
2479 				   STRIPE_SIZE) != 0) {
2480 				clear_bit(STRIPE_INSYNC, &sh->state);
2481 				update_q = 1;
2482 			}
2483 		}
2484 		if (update_p || update_q) {
2485 			conf->mddev->resync_mismatches += STRIPE_SECTORS;
2486 			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
2487 				/* don't try to repair!! */
2488 				update_p = update_q = 0;
2489 		}
2490 
2491 		/* now write out any block on a failed drive,
2492 		 * or P or Q if they need it
2493 		 */
2494 
2495 		if (s->failed == 2) {
2496 			dev = &sh->dev[r6s->failed_num[1]];
2497 			s->locked++;
2498 			set_bit(R5_LOCKED, &dev->flags);
2499 			set_bit(R5_Wantwrite, &dev->flags);
2500 		}
2501 		if (s->failed >= 1) {
2502 			dev = &sh->dev[r6s->failed_num[0]];
2503 			s->locked++;
2504 			set_bit(R5_LOCKED, &dev->flags);
2505 			set_bit(R5_Wantwrite, &dev->flags);
2506 		}
2507 
2508 		if (update_p) {
2509 			dev = &sh->dev[pd_idx];
2510 			s->locked++;
2511 			set_bit(R5_LOCKED, &dev->flags);
2512 			set_bit(R5_Wantwrite, &dev->flags);
2513 		}
2514 		if (update_q) {
2515 			dev = &sh->dev[qd_idx];
2516 			s->locked++;
2517 			set_bit(R5_LOCKED, &dev->flags);
2518 			set_bit(R5_Wantwrite, &dev->flags);
2519 		}
2520 		clear_bit(STRIPE_DEGRADED, &sh->state);
2521 
2522 		set_bit(STRIPE_INSYNC, &sh->state);
2523 	}
2524 }
2525 
2526 static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
2527 				struct r6_state *r6s)
2528 {
2529 	int i;
2530 
2531 	/* We have read all the blocks in this stripe and now we need to
2532 	 * copy some of them into a target stripe for expand.
2533 	 */
2534 	struct dma_async_tx_descriptor *tx = NULL;
2535 	clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
2536 	for (i = 0; i < sh->disks; i++)
2537 		if (i != sh->pd_idx && (!r6s || i != r6s->qd_idx)) {
2538 			int dd_idx, pd_idx, j;
2539 			struct stripe_head *sh2;
2540 
2541 			sector_t bn = compute_blocknr(sh, i);
2542 			sector_t s = raid5_compute_sector(bn, conf->raid_disks,
2543 						conf->raid_disks -
2544 						conf->max_degraded, &dd_idx,
2545 						&pd_idx, conf);
2546 			sh2 = get_active_stripe(conf, s, conf->raid_disks,
2547 						pd_idx, 1);
2548 			if (sh2 == NULL)
2549 				/* so far only the early blocks of this stripe
2550 				 * have been requested.  When later blocks
2551 				 * get requested, we will try again
2552 				 */
2553 				continue;
2554 			if (!test_bit(STRIPE_EXPANDING, &sh2->state) ||
2555 			   test_bit(R5_Expanded, &sh2->dev[dd_idx].flags)) {
2556 				/* must have already done this block */
2557 				release_stripe(sh2);
2558 				continue;
2559 			}
2560 
2561 			/* place all the copies on one channel */
2562 			tx = async_memcpy(sh2->dev[dd_idx].page,
2563 				sh->dev[i].page, 0, 0, STRIPE_SIZE,
2564 				ASYNC_TX_DEP_ACK, tx, NULL, NULL);
2565 
2566 			set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
2567 			set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
2568 			for (j = 0; j < conf->raid_disks; j++)
2569 				if (j != sh2->pd_idx &&
2570 				    (!r6s || j != raid6_next_disk(sh2->pd_idx,
2571 								 sh2->disks)) &&
2572 				    !test_bit(R5_Expanded, &sh2->dev[j].flags))
2573 					break;
2574 			if (j == conf->raid_disks) {
2575 				set_bit(STRIPE_EXPAND_READY, &sh2->state);
2576 				set_bit(STRIPE_HANDLE, &sh2->state);
2577 			}
2578 			release_stripe(sh2);
2579 
2580 		}
2581 	/* done submitting copies, wait for them to complete */
2582 	if (tx) {
2583 		async_tx_ack(tx);
2584 		dma_wait_for_async_tx(tx);
2585 	}
2586 }
2587 
2588 /*
2589  * handle_stripe - do things to a stripe.
2590  *
2591  * We lock the stripe and then examine the state of various bits
2592  * to see what needs to be done.
2593  * Possible results:
2594  *    return some read request which now have data
2595  *    return some write requests which are safely on disc
2596  *    schedule a read on some buffers
2597  *    schedule a write of some buffers
2598  *    return confirmation of parity correctness
2599  *
2600  * buffers are taken off read_list or write_list, and bh_cache buffers
2601  * get BH_Lock set before the stripe lock is released.
2602  *
2603  */
2604 
2605 static void handle_stripe5(struct stripe_head *sh)
2606 {
2607 	raid5_conf_t *conf = sh->raid_conf;
2608 	int disks = sh->disks, i;
2609 	struct bio *return_bi = NULL;
2610 	struct stripe_head_state s;
2611 	struct r5dev *dev;
2612 	unsigned long pending = 0;
2613 
2614 	memset(&s, 0, sizeof(s));
2615 	pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d "
2616 		"ops=%lx:%lx:%lx\n", (unsigned long long)sh->sector, sh->state,
2617 		atomic_read(&sh->count), sh->pd_idx,
2618 		sh->ops.pending, sh->ops.ack, sh->ops.complete);
2619 
2620 	spin_lock(&sh->lock);
2621 	clear_bit(STRIPE_HANDLE, &sh->state);
2622 	clear_bit(STRIPE_DELAYED, &sh->state);
2623 
2624 	s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
2625 	s.expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
2626 	s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
2627 	/* Now to look around and see what can be done */
2628 
2629 	/* clean-up completed biofill operations */
2630 	if (test_bit(STRIPE_OP_BIOFILL, &sh->ops.complete)) {
2631 		clear_bit(STRIPE_OP_BIOFILL, &sh->ops.pending);
2632 		clear_bit(STRIPE_OP_BIOFILL, &sh->ops.ack);
2633 		clear_bit(STRIPE_OP_BIOFILL, &sh->ops.complete);
2634 	}
2635 
2636 	rcu_read_lock();
2637 	for (i=disks; i--; ) {
2638 		mdk_rdev_t *rdev;
2639 		struct r5dev *dev = &sh->dev[i];
2640 		clear_bit(R5_Insync, &dev->flags);
2641 
2642 		pr_debug("check %d: state 0x%lx toread %p read %p write %p "
2643 			"written %p\n",	i, dev->flags, dev->toread, dev->read,
2644 			dev->towrite, dev->written);
2645 
2646 		/* maybe we can request a biofill operation
2647 		 *
2648 		 * new wantfill requests are only permitted while
2649 		 * STRIPE_OP_BIOFILL is clear
2650 		 */
2651 		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
2652 			!test_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
2653 			set_bit(R5_Wantfill, &dev->flags);
2654 
2655 		/* now count some things */
2656 		if (test_bit(R5_LOCKED, &dev->flags)) s.locked++;
2657 		if (test_bit(R5_UPTODATE, &dev->flags)) s.uptodate++;
2658 		if (test_bit(R5_Wantcompute, &dev->flags)) s.compute++;
2659 
2660 		if (test_bit(R5_Wantfill, &dev->flags))
2661 			s.to_fill++;
2662 		else if (dev->toread)
2663 			s.to_read++;
2664 		if (dev->towrite) {
2665 			s.to_write++;
2666 			if (!test_bit(R5_OVERWRITE, &dev->flags))
2667 				s.non_overwrite++;
2668 		}
2669 		if (dev->written)
2670 			s.written++;
2671 		rdev = rcu_dereference(conf->disks[i].rdev);
2672 		if (!rdev || !test_bit(In_sync, &rdev->flags)) {
2673 			/* The ReadError flag will just be confusing now */
2674 			clear_bit(R5_ReadError, &dev->flags);
2675 			clear_bit(R5_ReWrite, &dev->flags);
2676 		}
2677 		if (!rdev || !test_bit(In_sync, &rdev->flags)
2678 		    || test_bit(R5_ReadError, &dev->flags)) {
2679 			s.failed++;
2680 			s.failed_num = i;
2681 		} else
2682 			set_bit(R5_Insync, &dev->flags);
2683 	}
2684 	rcu_read_unlock();
2685 
2686 	if (s.to_fill && !test_and_set_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
2687 		sh->ops.count++;
2688 
2689 	pr_debug("locked=%d uptodate=%d to_read=%d"
2690 		" to_write=%d failed=%d failed_num=%d\n",
2691 		s.locked, s.uptodate, s.to_read, s.to_write,
2692 		s.failed, s.failed_num);
2693 	/* check if the array has lost two devices and, if so, some requests might
2694 	 * need to be failed
2695 	 */
2696 	if (s.failed > 1 && s.to_read+s.to_write+s.written)
2697 		handle_requests_to_failed_array(conf, sh, &s, disks,
2698 						&return_bi);
2699 	if (s.failed > 1 && s.syncing) {
2700 		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
2701 		clear_bit(STRIPE_SYNCING, &sh->state);
2702 		s.syncing = 0;
2703 	}
2704 
2705 	/* might be able to return some write requests if the parity block
2706 	 * is safe, or on a failed drive
2707 	 */
2708 	dev = &sh->dev[sh->pd_idx];
2709 	if ( s.written &&
2710 	     ((test_bit(R5_Insync, &dev->flags) &&
2711 	       !test_bit(R5_LOCKED, &dev->flags) &&
2712 	       test_bit(R5_UPTODATE, &dev->flags)) ||
2713 	       (s.failed == 1 && s.failed_num == sh->pd_idx)))
2714 		handle_completed_write_requests(conf, sh, disks, &return_bi);
2715 
2716 	/* Now we might consider reading some blocks, either to check/generate
2717 	 * parity, or to satisfy requests
2718 	 * or to load a block that is being partially written.
2719 	 */
2720 	if (s.to_read || s.non_overwrite ||
2721 	    (s.syncing && (s.uptodate + s.compute < disks)) || s.expanding ||
2722 	    test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending))
2723 		handle_issuing_new_read_requests5(sh, &s, disks);
2724 
2725 	/* Now we check to see if any write operations have recently
2726 	 * completed
2727 	 */
2728 
2729 	/* leave prexor set until postxor is done, allows us to distinguish
2730 	 * a rmw from a rcw during biodrain
2731 	 */
2732 	if (test_bit(STRIPE_OP_PREXOR, &sh->ops.complete) &&
2733 		test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) {
2734 
2735 		clear_bit(STRIPE_OP_PREXOR, &sh->ops.complete);
2736 		clear_bit(STRIPE_OP_PREXOR, &sh->ops.ack);
2737 		clear_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
2738 
2739 		for (i = disks; i--; )
2740 			clear_bit(R5_Wantprexor, &sh->dev[i].flags);
2741 	}
2742 
2743 	/* if only POSTXOR is set then this is an 'expand' postxor */
2744 	if (test_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete) &&
2745 		test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) {
2746 
2747 		clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete);
2748 		clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.ack);
2749 		clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
2750 
2751 		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
2752 		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.ack);
2753 		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
2754 
2755 		/* All the 'written' buffers and the parity block are ready to
2756 		 * be written back to disk
2757 		 */
2758 		BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
2759 		for (i = disks; i--; ) {
2760 			dev = &sh->dev[i];
2761 			if (test_bit(R5_LOCKED, &dev->flags) &&
2762 				(i == sh->pd_idx || dev->written)) {
2763 				pr_debug("Writing block %d\n", i);
2764 				set_bit(R5_Wantwrite, &dev->flags);
2765 				if (!test_and_set_bit(
2766 				    STRIPE_OP_IO, &sh->ops.pending))
2767 					sh->ops.count++;
2768 				if (!test_bit(R5_Insync, &dev->flags) ||
2769 				    (i == sh->pd_idx && s.failed == 0))
2770 					set_bit(STRIPE_INSYNC, &sh->state);
2771 			}
2772 		}
2773 		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2774 			atomic_dec(&conf->preread_active_stripes);
2775 			if (atomic_read(&conf->preread_active_stripes) <
2776 				IO_THRESHOLD)
2777 				md_wakeup_thread(conf->mddev->thread);
2778 		}
2779 	}
2780 
2781 	/* Now to consider new write requests and what else, if anything
2782 	 * should be read.  We do not handle new writes when:
2783 	 * 1/ A 'write' operation (copy+xor) is already in flight.
2784 	 * 2/ A 'check' operation is in flight, as it may clobber the parity
2785 	 *    block.
2786 	 */
2787 	if (s.to_write && !test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending) &&
2788 			  !test_bit(STRIPE_OP_CHECK, &sh->ops.pending))
2789 		handle_issuing_new_write_requests5(conf, sh, &s, disks);
2790 
2791 	/* maybe we need to check and possibly fix the parity for this stripe
2792 	 * Any reads will already have been scheduled, so we just see if enough
2793 	 * data is available.  The parity check is held off while parity
2794 	 * dependent operations are in flight.
2795 	 */
2796 	if ((s.syncing && s.locked == 0 &&
2797 	     !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending) &&
2798 	     !test_bit(STRIPE_INSYNC, &sh->state)) ||
2799 	      test_bit(STRIPE_OP_CHECK, &sh->ops.pending) ||
2800 	      test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending))
2801 		handle_parity_checks5(conf, sh, &s, disks);
2802 
2803 	if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
2804 		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
2805 		clear_bit(STRIPE_SYNCING, &sh->state);
2806 	}
2807 
2808 	/* If the failed drive is just a ReadError, then we might need to progress
2809 	 * the repair/check process
2810 	 */
2811 	if (s.failed == 1 && !conf->mddev->ro &&
2812 	    test_bit(R5_ReadError, &sh->dev[s.failed_num].flags)
2813 	    && !test_bit(R5_LOCKED, &sh->dev[s.failed_num].flags)
2814 	    && test_bit(R5_UPTODATE, &sh->dev[s.failed_num].flags)
2815 		) {
2816 		dev = &sh->dev[s.failed_num];
2817 		if (!test_bit(R5_ReWrite, &dev->flags)) {
2818 			set_bit(R5_Wantwrite, &dev->flags);
2819 			if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
2820 				sh->ops.count++;
2821 			set_bit(R5_ReWrite, &dev->flags);
2822 			set_bit(R5_LOCKED, &dev->flags);
2823 			s.locked++;
2824 		} else {
2825 			/* let's read it back */
2826 			set_bit(R5_Wantread, &dev->flags);
2827 			if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
2828 				sh->ops.count++;
2829 			set_bit(R5_LOCKED, &dev->flags);
2830 			s.locked++;
2831 		}
2832 	}
2833 
2834 	/* Finish postxor operations initiated by the expansion
2835 	 * process
2836 	 */
2837 	if (test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete) &&
2838 		!test_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending)) {
2839 
2840 		clear_bit(STRIPE_EXPANDING, &sh->state);
2841 
2842 		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
2843 		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.ack);
2844 		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
2845 
2846 		for (i = conf->raid_disks; i--; ) {
2847 			set_bit(R5_Wantwrite, &sh->dev[i].flags);
2848 			if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
2849 				sh->ops.count++;
2850 		}
2851 	}
2852 
2853 	if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state) &&
2854 		!test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
2855 		/* Need to write out all blocks after computing parity */
2856 		sh->disks = conf->raid_disks;
2857 		sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
2858 			conf->raid_disks);
2859 		s.locked += handle_write_operations5(sh, 1, 1);
2860 	} else if (s.expanded &&
2861 		!test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
2862 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
2863 		atomic_dec(&conf->reshape_stripes);
2864 		wake_up(&conf->wait_for_overlap);
2865 		md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
2866 	}
2867 
2868 	if (s.expanding && s.locked == 0 &&
2869 	    !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending))
2870 		handle_stripe_expansion(conf, sh, NULL);
2871 
2872 	if (sh->ops.count)
2873 		pending = get_stripe_work(sh);
2874 
2875 	spin_unlock(&sh->lock);
2876 
2877 	if (pending)
2878 		raid5_run_ops(sh, pending);
2879 
2880 	return_io(return_bi);
2881 
2882 }
2883 
2884 static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
2885 {
2886 	raid6_conf_t *conf = sh->raid_conf;
2887 	int disks = sh->disks;
2888 	struct bio *return_bi = NULL;
2889 	int i, pd_idx = sh->pd_idx;
2890 	struct stripe_head_state s;
2891 	struct r6_state r6s;
2892 	struct r5dev *dev, *pdev, *qdev;
2893 
2894 	r6s.qd_idx = raid6_next_disk(pd_idx, disks);
2895 	pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
2896 		"pd_idx=%d, qd_idx=%d\n",
2897 	       (unsigned long long)sh->sector, sh->state,
2898 	       atomic_read(&sh->count), pd_idx, r6s.qd_idx);
2899 	memset(&s, 0, sizeof(s));
2900 
2901 	spin_lock(&sh->lock);
2902 	clear_bit(STRIPE_HANDLE, &sh->state);
2903 	clear_bit(STRIPE_DELAYED, &sh->state);
2904 
2905 	s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
2906 	s.expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
2907 	s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
2908 	/* Now to look around and see what can be done */
2909 
2910 	rcu_read_lock();
2911 	for (i=disks; i--; ) {
2912 		mdk_rdev_t *rdev;
2913 		dev = &sh->dev[i];
2914 		clear_bit(R5_Insync, &dev->flags);
2915 
2916 		pr_debug("check %d: state 0x%lx read %p write %p written %p\n",
2917 			i, dev->flags, dev->toread, dev->towrite, dev->written);
2918 		/* maybe we can reply to a read */
2919 		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
2920 			struct bio *rbi, *rbi2;
2921 			pr_debug("Return read for disc %d\n", i);
2922 			spin_lock_irq(&conf->device_lock);
2923 			rbi = dev->toread;
2924 			dev->toread = NULL;
2925 			if (test_and_clear_bit(R5_Overlap, &dev->flags))
2926 				wake_up(&conf->wait_for_overlap);
2927 			spin_unlock_irq(&conf->device_lock);
2928 			while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
2929 				copy_data(0, rbi, dev->page, dev->sector);
2930 				rbi2 = r5_next_bio(rbi, dev->sector);
2931 				spin_lock_irq(&conf->device_lock);
2932 				if (--rbi->bi_phys_segments == 0) {
2933 					rbi->bi_next = return_bi;
2934 					return_bi = rbi;
2935 				}
2936 				spin_unlock_irq(&conf->device_lock);
2937 				rbi = rbi2;
2938 			}
2939 		}
2940 
2941 		/* now count some things */
2942 		if (test_bit(R5_LOCKED, &dev->flags)) s.locked++;
2943 		if (test_bit(R5_UPTODATE, &dev->flags)) s.uptodate++;
2944 
2945 
2946 		if (dev->toread)
2947 			s.to_read++;
2948 		if (dev->towrite) {
2949 			s.to_write++;
2950 			if (!test_bit(R5_OVERWRITE, &dev->flags))
2951 				s.non_overwrite++;
2952 		}
2953 		if (dev->written)
2954 			s.written++;
2955 		rdev = rcu_dereference(conf->disks[i].rdev);
2956 		if (!rdev || !test_bit(In_sync, &rdev->flags)) {
2957 			/* The ReadError flag will just be confusing now */
2958 			clear_bit(R5_ReadError, &dev->flags);
2959 			clear_bit(R5_ReWrite, &dev->flags);
2960 		}
2961 		if (!rdev || !test_bit(In_sync, &rdev->flags)
2962 		    || test_bit(R5_ReadError, &dev->flags)) {
2963 			if (s.failed < 2)
2964 				r6s.failed_num[s.failed] = i;
2965 			s.failed++;
2966 		} else
2967 			set_bit(R5_Insync, &dev->flags);
2968 	}
2969 	rcu_read_unlock();
2970 	pr_debug("locked=%d uptodate=%d to_read=%d"
2971 	       " to_write=%d failed=%d failed_num=%d,%d\n",
2972 	       s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
2973 	       r6s.failed_num[0], r6s.failed_num[1]);
2974 	/* check if the array has lost >2 devices and, if so, some requests
2975 	 * might need to be failed
2976 	 */
2977 	if (s.failed > 2 && s.to_read+s.to_write+s.written)
2978 		handle_requests_to_failed_array(conf, sh, &s, disks,
2979 						&return_bi);
2980 	if (s.failed > 2 && s.syncing) {
2981 		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
2982 		clear_bit(STRIPE_SYNCING, &sh->state);
2983 		s.syncing = 0;
2984 	}
2985 
2986 	/*
2987 	 * might be able to return some write requests if the parity blocks
2988 	 * are safe, or on a failed drive
2989 	 */
2990 	pdev = &sh->dev[pd_idx];
2991 	r6s.p_failed = (s.failed >= 1 && r6s.failed_num[0] == pd_idx)
2992 		|| (s.failed >= 2 && r6s.failed_num[1] == pd_idx);
2993 	qdev = &sh->dev[r6s.qd_idx];
2994 	r6s.q_failed = (s.failed >= 1 && r6s.failed_num[0] == r6s.qd_idx)
2995 		|| (s.failed >= 2 && r6s.failed_num[1] == r6s.qd_idx);
2996 
2997 	if ( s.written &&
2998 	     ( r6s.p_failed || ((test_bit(R5_Insync, &pdev->flags)
2999 			     && !test_bit(R5_LOCKED, &pdev->flags)
3000 			     && test_bit(R5_UPTODATE, &pdev->flags)))) &&
3001 	     ( r6s.q_failed || ((test_bit(R5_Insync, &qdev->flags)
3002 			     && !test_bit(R5_LOCKED, &qdev->flags)
3003 			     && test_bit(R5_UPTODATE, &qdev->flags)))))
3004 		handle_completed_write_requests(conf, sh, disks, &return_bi);
3005 
3006 	/* Now we might consider reading some blocks, either to check/generate
3007 	 * parity, or to satisfy requests
3008 	 * or to load a block that is being partially written.
3009 	 */
3010 	if (s.to_read || s.non_overwrite || (s.to_write && s.failed) ||
3011 	    (s.syncing && (s.uptodate < disks)) || s.expanding)
3012 		handle_issuing_new_read_requests6(sh, &s, &r6s, disks);
3013 
3014 	/* now to consider writing and what else, if anything should be read */
3015 	if (s.to_write)
3016 		handle_issuing_new_write_requests6(conf, sh, &s, &r6s, disks);
3017 
3018 	/* maybe we need to check and possibly fix the parity for this stripe
3019 	 * Any reads will already have been scheduled, so we just see if enough
3020 	 * data is available
3021 	 */
3022 	if (s.syncing && s.locked == 0 && !test_bit(STRIPE_INSYNC, &sh->state))
3023 		handle_parity_checks6(conf, sh, &s, &r6s, tmp_page, disks);
3024 
3025 	if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
3026 		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
3027 		clear_bit(STRIPE_SYNCING, &sh->state);
3028 	}
3029 
3030 	/* If the failed drives are just a ReadError, then we might need
3031 	 * to progress the repair/check process
3032 	 */
3033 	if (s.failed <= 2 && !conf->mddev->ro)
3034 		for (i = 0; i < s.failed; i++) {
3035 			dev = &sh->dev[r6s.failed_num[i]];
3036 			if (test_bit(R5_ReadError, &dev->flags)
3037 			    && !test_bit(R5_LOCKED, &dev->flags)
3038 			    && test_bit(R5_UPTODATE, &dev->flags)
3039 				) {
3040 				if (!test_bit(R5_ReWrite, &dev->flags)) {
3041 					set_bit(R5_Wantwrite, &dev->flags);
3042 					set_bit(R5_ReWrite, &dev->flags);
3043 					set_bit(R5_LOCKED, &dev->flags);
3044 				} else {
3045 					/* let's read it back */
3046 					set_bit(R5_Wantread, &dev->flags);
3047 					set_bit(R5_LOCKED, &dev->flags);
3048 				}
3049 			}
3050 		}
3051 
3052 	if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
3053 		/* Need to write out all blocks after computing P&Q */
3054 		sh->disks = conf->raid_disks;
3055 		sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
3056 					     conf->raid_disks);
3057 		compute_parity6(sh, RECONSTRUCT_WRITE);
3058 		for (i = conf->raid_disks ; i-- ;  ) {
3059 			set_bit(R5_LOCKED, &sh->dev[i].flags);
3060 			s.locked++;
3061 			set_bit(R5_Wantwrite, &sh->dev[i].flags);
3062 		}
3063 		clear_bit(STRIPE_EXPANDING, &sh->state);
3064 	} else if (s.expanded) {
3065 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
3066 		atomic_dec(&conf->reshape_stripes);
3067 		wake_up(&conf->wait_for_overlap);
3068 		md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
3069 	}
3070 
3071 	if (s.expanding && s.locked == 0 &&
3072 	    !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending))
3073 		handle_stripe_expansion(conf, sh, &r6s);
3074 
3075 	spin_unlock(&sh->lock);
3076 
3077 	return_io(return_bi);
3078 
3079 	for (i=disks; i-- ;) {
3080 		int rw;
3081 		struct bio *bi;
3082 		mdk_rdev_t *rdev;
3083 		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
3084 			rw = WRITE;
3085 		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
3086 			rw = READ;
3087 		else
3088 			continue;
3089 
3090 		bi = &sh->dev[i].req;
3091 
3092 		bi->bi_rw = rw;
3093 		if (rw == WRITE)
3094 			bi->bi_end_io = raid5_end_write_request;
3095 		else
3096 			bi->bi_end_io = raid5_end_read_request;
3097 
3098 		rcu_read_lock();
3099 		rdev = rcu_dereference(conf->disks[i].rdev);
3100 		if (rdev && test_bit(Faulty, &rdev->flags))
3101 			rdev = NULL;
3102 		if (rdev)
3103 			atomic_inc(&rdev->nr_pending);
3104 		rcu_read_unlock();
3105 
3106 		if (rdev) {
3107 			if (s.syncing || s.expanding || s.expanded)
3108 				md_sync_acct(rdev->bdev, STRIPE_SECTORS);
3109 
3110 			bi->bi_bdev = rdev->bdev;
3111 			pr_debug("for %llu schedule op %ld on disc %d\n",
3112 				(unsigned long long)sh->sector, bi->bi_rw, i);
3113 			atomic_inc(&sh->count);
3114 			bi->bi_sector = sh->sector + rdev->data_offset;
3115 			bi->bi_flags = 1 << BIO_UPTODATE;
3116 			bi->bi_vcnt = 1;
3117 			bi->bi_max_vecs = 1;
3118 			bi->bi_idx = 0;
3119 			bi->bi_io_vec = &sh->dev[i].vec;
3120 			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
3121 			bi->bi_io_vec[0].bv_offset = 0;
3122 			bi->bi_size = STRIPE_SIZE;
3123 			bi->bi_next = NULL;
3124 			if (rw == WRITE &&
3125 			    test_bit(R5_ReWrite, &sh->dev[i].flags))
3126 				atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
3127 			generic_make_request(bi);
3128 		} else {
3129 			if (rw == WRITE)
3130 				set_bit(STRIPE_DEGRADED, &sh->state);
3131 			pr_debug("skip op %ld on disc %d for sector %llu\n",
3132 				bi->bi_rw, i, (unsigned long long)sh->sector);
3133 			clear_bit(R5_LOCKED, &sh->dev[i].flags);
3134 			set_bit(STRIPE_HANDLE, &sh->state);
3135 		}
3136 	}
3137 }
3138 
3139 static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
3140 {
3141 	if (sh->raid_conf->level == 6)
3142 		handle_stripe6(sh, tmp_page);
3143 	else
3144 		handle_stripe5(sh);
3145 }
3146 
3147 
3148 
3149 static void raid5_activate_delayed(raid5_conf_t *conf)
3150 {
3151 	if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
3152 		while (!list_empty(&conf->delayed_list)) {
3153 			struct list_head *l = conf->delayed_list.next;
3154 			struct stripe_head *sh;
3155 			sh = list_entry(l, struct stripe_head, lru);
3156 			list_del_init(l);
3157 			clear_bit(STRIPE_DELAYED, &sh->state);
3158 			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
3159 				atomic_inc(&conf->preread_active_stripes);
3160 			list_add_tail(&sh->lru, &conf->handle_list);
3161 		}
3162 	}
3163 }
3164 
3165 static void activate_bit_delay(raid5_conf_t *conf)
3166 {
3167 	/* device_lock is held */
3168 	struct list_head head;
3169 	list_add(&head, &conf->bitmap_list);
3170 	list_del_init(&conf->bitmap_list);
3171 	while (!list_empty(&head)) {
3172 		struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
3173 		list_del_init(&sh->lru);
3174 		atomic_inc(&sh->count);
3175 		__release_stripe(conf, sh);
3176 	}
3177 }
3178 
3179 static void unplug_slaves(mddev_t *mddev)
3180 {
3181 	raid5_conf_t *conf = mddev_to_conf(mddev);
3182 	int i;
3183 
3184 	rcu_read_lock();
3185 	for (i=0; i<mddev->raid_disks; i++) {
3186 		mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
3187 		if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
3188 			struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
3189 
3190 			atomic_inc(&rdev->nr_pending);
3191 			rcu_read_unlock();
3192 
3193 			blk_unplug(r_queue);
3194 
3195 			rdev_dec_pending(rdev, mddev);
3196 			rcu_read_lock();
3197 		}
3198 	}
3199 	rcu_read_unlock();
3200 }
3201 
3202 static void raid5_unplug_device(struct request_queue *q)
3203 {
3204 	mddev_t *mddev = q->queuedata;
3205 	raid5_conf_t *conf = mddev_to_conf(mddev);
3206 	unsigned long flags;
3207 
3208 	spin_lock_irqsave(&conf->device_lock, flags);
3209 
3210 	if (blk_remove_plug(q)) {
3211 		conf->seq_flush++;
3212 		raid5_activate_delayed(conf);
3213 	}
3214 	md_wakeup_thread(mddev->thread);
3215 
3216 	spin_unlock_irqrestore(&conf->device_lock, flags);
3217 
3218 	unplug_slaves(mddev);
3219 }
3220 
3221 static int raid5_congested(void *data, int bits)
3222 {
3223 	mddev_t *mddev = data;
3224 	raid5_conf_t *conf = mddev_to_conf(mddev);
3225 
3226 	/* No difference between reads and writes.  Just check
3227 	 * how busy the stripe_cache is
3228 	 */
3229 	if (conf->inactive_blocked)
3230 		return 1;
3231 	if (conf->quiesce)
3232 		return 1;
3233 	if (list_empty_careful(&conf->inactive_list))
3234 		return 1;
3235 
3236 	return 0;
3237 }
3238 
3239 /* We want read requests to align with chunks where possible,
3240  * but write requests don't need to.
3241  */
3242 static int raid5_mergeable_bvec(struct request_queue *q, struct bio *bio, struct bio_vec *biovec)
3243 {
3244 	mddev_t *mddev = q->queuedata;
3245 	sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
3246 	int max;
3247 	unsigned int chunk_sectors = mddev->chunk_size >> 9;
3248 	unsigned int bio_sectors = bio->bi_size >> 9;
3249 
3250 	if (bio_data_dir(bio) == WRITE)
3251 		return biovec->bv_len; /* always allow writes to be mergeable */
3252 
3253 	max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
3254 	if (max < 0) max = 0;
3255 	if (max <= biovec->bv_len && bio_sectors == 0)
3256 		return biovec->bv_len;
3257 	else
3258 		return max;
3259 }
3260 
3261 
3262 static int in_chunk_boundary(mddev_t *mddev, struct bio *bio)
3263 {
3264 	sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
3265 	unsigned int chunk_sectors = mddev->chunk_size >> 9;
3266 	unsigned int bio_sectors = bio->bi_size >> 9;
3267 
3268 	return  chunk_sectors >=
3269 		((sector & (chunk_sectors - 1)) + bio_sectors);
3270 }
3271 
3272 /*
3273  *  add bio to the retry LIFO  ( in O(1) ... we are in interrupt )
3274  *  later sampled by raid5d.
3275  */
3276 static void add_bio_to_retry(struct bio *bi,raid5_conf_t *conf)
3277 {
3278 	unsigned long flags;
3279 
3280 	spin_lock_irqsave(&conf->device_lock, flags);
3281 
3282 	bi->bi_next = conf->retry_read_aligned_list;
3283 	conf->retry_read_aligned_list = bi;
3284 
3285 	spin_unlock_irqrestore(&conf->device_lock, flags);
3286 	md_wakeup_thread(conf->mddev->thread);
3287 }
3288 
3289 
3290 static struct bio *remove_bio_from_retry(raid5_conf_t *conf)
3291 {
3292 	struct bio *bi;
3293 
3294 	bi = conf->retry_read_aligned;
3295 	if (bi) {
3296 		conf->retry_read_aligned = NULL;
3297 		return bi;
3298 	}
3299 	bi = conf->retry_read_aligned_list;
3300 	if(bi) {
3301 		conf->retry_read_aligned_list = bi->bi_next;
3302 		bi->bi_next = NULL;
3303 		bi->bi_phys_segments = 1; /* biased count of active stripes */
3304 		bi->bi_hw_segments = 0; /* count of processed stripes */
3305 	}
3306 
3307 	return bi;
3308 }
3309 
3310 
3311 /*
3312  *  The "raid5_align_endio" should check if the read succeeded and if it
3313  *  did, call bio_endio on the original bio (having bio_put the new bio
3314  *  first).
3315  *  If the read failed..
3316  */
3317 static void raid5_align_endio(struct bio *bi, int error)
3318 {
3319 	struct bio* raid_bi  = bi->bi_private;
3320 	mddev_t *mddev;
3321 	raid5_conf_t *conf;
3322 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
3323 	mdk_rdev_t *rdev;
3324 
3325 	bio_put(bi);
3326 
3327 	mddev = raid_bi->bi_bdev->bd_disk->queue->queuedata;
3328 	conf = mddev_to_conf(mddev);
3329 	rdev = (void*)raid_bi->bi_next;
3330 	raid_bi->bi_next = NULL;
3331 
3332 	rdev_dec_pending(rdev, conf->mddev);
3333 
3334 	if (!error && uptodate) {
3335 		bio_endio(raid_bi, 0);
3336 		if (atomic_dec_and_test(&conf->active_aligned_reads))
3337 			wake_up(&conf->wait_for_stripe);
3338 		return;
3339 	}
3340 
3341 
3342 	pr_debug("raid5_align_endio : io error...handing IO for a retry\n");
3343 
3344 	add_bio_to_retry(raid_bi, conf);
3345 }
3346 
3347 static int bio_fits_rdev(struct bio *bi)
3348 {
3349 	struct request_queue *q = bdev_get_queue(bi->bi_bdev);
3350 
3351 	if ((bi->bi_size>>9) > q->max_sectors)
3352 		return 0;
3353 	blk_recount_segments(q, bi);
3354 	if (bi->bi_phys_segments > q->max_phys_segments ||
3355 	    bi->bi_hw_segments > q->max_hw_segments)
3356 		return 0;
3357 
3358 	if (q->merge_bvec_fn)
3359 		/* it's too hard to apply the merge_bvec_fn at this stage,
3360 		 * just just give up
3361 		 */
3362 		return 0;
3363 
3364 	return 1;
3365 }
3366 
3367 
3368 static int chunk_aligned_read(struct request_queue *q, struct bio * raid_bio)
3369 {
3370 	mddev_t *mddev = q->queuedata;
3371 	raid5_conf_t *conf = mddev_to_conf(mddev);
3372 	const unsigned int raid_disks = conf->raid_disks;
3373 	const unsigned int data_disks = raid_disks - conf->max_degraded;
3374 	unsigned int dd_idx, pd_idx;
3375 	struct bio* align_bi;
3376 	mdk_rdev_t *rdev;
3377 
3378 	if (!in_chunk_boundary(mddev, raid_bio)) {
3379 		pr_debug("chunk_aligned_read : non aligned\n");
3380 		return 0;
3381 	}
3382 	/*
3383  	 * use bio_clone to make a copy of the bio
3384 	 */
3385 	align_bi = bio_clone(raid_bio, GFP_NOIO);
3386 	if (!align_bi)
3387 		return 0;
3388 	/*
3389 	 *   set bi_end_io to a new function, and set bi_private to the
3390 	 *     original bio.
3391 	 */
3392 	align_bi->bi_end_io  = raid5_align_endio;
3393 	align_bi->bi_private = raid_bio;
3394 	/*
3395 	 *	compute position
3396 	 */
3397 	align_bi->bi_sector =  raid5_compute_sector(raid_bio->bi_sector,
3398 					raid_disks,
3399 					data_disks,
3400 					&dd_idx,
3401 					&pd_idx,
3402 					conf);
3403 
3404 	rcu_read_lock();
3405 	rdev = rcu_dereference(conf->disks[dd_idx].rdev);
3406 	if (rdev && test_bit(In_sync, &rdev->flags)) {
3407 		atomic_inc(&rdev->nr_pending);
3408 		rcu_read_unlock();
3409 		raid_bio->bi_next = (void*)rdev;
3410 		align_bi->bi_bdev =  rdev->bdev;
3411 		align_bi->bi_flags &= ~(1 << BIO_SEG_VALID);
3412 		align_bi->bi_sector += rdev->data_offset;
3413 
3414 		if (!bio_fits_rdev(align_bi)) {
3415 			/* too big in some way */
3416 			bio_put(align_bi);
3417 			rdev_dec_pending(rdev, mddev);
3418 			return 0;
3419 		}
3420 
3421 		spin_lock_irq(&conf->device_lock);
3422 		wait_event_lock_irq(conf->wait_for_stripe,
3423 				    conf->quiesce == 0,
3424 				    conf->device_lock, /* nothing */);
3425 		atomic_inc(&conf->active_aligned_reads);
3426 		spin_unlock_irq(&conf->device_lock);
3427 
3428 		generic_make_request(align_bi);
3429 		return 1;
3430 	} else {
3431 		rcu_read_unlock();
3432 		bio_put(align_bi);
3433 		return 0;
3434 	}
3435 }
3436 
3437 
3438 static int make_request(struct request_queue *q, struct bio * bi)
3439 {
3440 	mddev_t *mddev = q->queuedata;
3441 	raid5_conf_t *conf = mddev_to_conf(mddev);
3442 	unsigned int dd_idx, pd_idx;
3443 	sector_t new_sector;
3444 	sector_t logical_sector, last_sector;
3445 	struct stripe_head *sh;
3446 	const int rw = bio_data_dir(bi);
3447 	int remaining;
3448 
3449 	if (unlikely(bio_barrier(bi))) {
3450 		bio_endio(bi, -EOPNOTSUPP);
3451 		return 0;
3452 	}
3453 
3454 	md_write_start(mddev, bi);
3455 
3456 	disk_stat_inc(mddev->gendisk, ios[rw]);
3457 	disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bi));
3458 
3459 	if (rw == READ &&
3460 	     mddev->reshape_position == MaxSector &&
3461 	     chunk_aligned_read(q,bi))
3462             	return 0;
3463 
3464 	logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
3465 	last_sector = bi->bi_sector + (bi->bi_size>>9);
3466 	bi->bi_next = NULL;
3467 	bi->bi_phys_segments = 1;	/* over-loaded to count active stripes */
3468 
3469 	for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
3470 		DEFINE_WAIT(w);
3471 		int disks, data_disks;
3472 
3473 	retry:
3474 		prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
3475 		if (likely(conf->expand_progress == MaxSector))
3476 			disks = conf->raid_disks;
3477 		else {
3478 			/* spinlock is needed as expand_progress may be
3479 			 * 64bit on a 32bit platform, and so it might be
3480 			 * possible to see a half-updated value
3481 			 * Ofcourse expand_progress could change after
3482 			 * the lock is dropped, so once we get a reference
3483 			 * to the stripe that we think it is, we will have
3484 			 * to check again.
3485 			 */
3486 			spin_lock_irq(&conf->device_lock);
3487 			disks = conf->raid_disks;
3488 			if (logical_sector >= conf->expand_progress)
3489 				disks = conf->previous_raid_disks;
3490 			else {
3491 				if (logical_sector >= conf->expand_lo) {
3492 					spin_unlock_irq(&conf->device_lock);
3493 					schedule();
3494 					goto retry;
3495 				}
3496 			}
3497 			spin_unlock_irq(&conf->device_lock);
3498 		}
3499 		data_disks = disks - conf->max_degraded;
3500 
3501  		new_sector = raid5_compute_sector(logical_sector, disks, data_disks,
3502 						  &dd_idx, &pd_idx, conf);
3503 		pr_debug("raid5: make_request, sector %llu logical %llu\n",
3504 			(unsigned long long)new_sector,
3505 			(unsigned long long)logical_sector);
3506 
3507 		sh = get_active_stripe(conf, new_sector, disks, pd_idx, (bi->bi_rw&RWA_MASK));
3508 		if (sh) {
3509 			if (unlikely(conf->expand_progress != MaxSector)) {
3510 				/* expansion might have moved on while waiting for a
3511 				 * stripe, so we must do the range check again.
3512 				 * Expansion could still move past after this
3513 				 * test, but as we are holding a reference to
3514 				 * 'sh', we know that if that happens,
3515 				 *  STRIPE_EXPANDING will get set and the expansion
3516 				 * won't proceed until we finish with the stripe.
3517 				 */
3518 				int must_retry = 0;
3519 				spin_lock_irq(&conf->device_lock);
3520 				if (logical_sector <  conf->expand_progress &&
3521 				    disks == conf->previous_raid_disks)
3522 					/* mismatch, need to try again */
3523 					must_retry = 1;
3524 				spin_unlock_irq(&conf->device_lock);
3525 				if (must_retry) {
3526 					release_stripe(sh);
3527 					goto retry;
3528 				}
3529 			}
3530 			/* FIXME what if we get a false positive because these
3531 			 * are being updated.
3532 			 */
3533 			if (logical_sector >= mddev->suspend_lo &&
3534 			    logical_sector < mddev->suspend_hi) {
3535 				release_stripe(sh);
3536 				schedule();
3537 				goto retry;
3538 			}
3539 
3540 			if (test_bit(STRIPE_EXPANDING, &sh->state) ||
3541 			    !add_stripe_bio(sh, bi, dd_idx, (bi->bi_rw&RW_MASK))) {
3542 				/* Stripe is busy expanding or
3543 				 * add failed due to overlap.  Flush everything
3544 				 * and wait a while
3545 				 */
3546 				raid5_unplug_device(mddev->queue);
3547 				release_stripe(sh);
3548 				schedule();
3549 				goto retry;
3550 			}
3551 			finish_wait(&conf->wait_for_overlap, &w);
3552 			handle_stripe(sh, NULL);
3553 			release_stripe(sh);
3554 		} else {
3555 			/* cannot get stripe for read-ahead, just give-up */
3556 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
3557 			finish_wait(&conf->wait_for_overlap, &w);
3558 			break;
3559 		}
3560 
3561 	}
3562 	spin_lock_irq(&conf->device_lock);
3563 	remaining = --bi->bi_phys_segments;
3564 	spin_unlock_irq(&conf->device_lock);
3565 	if (remaining == 0) {
3566 
3567 		if ( rw == WRITE )
3568 			md_write_end(mddev);
3569 
3570 		bi->bi_end_io(bi,
3571 			      test_bit(BIO_UPTODATE, &bi->bi_flags)
3572 			        ? 0 : -EIO);
3573 	}
3574 	return 0;
3575 }
3576 
3577 static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped)
3578 {
3579 	/* reshaping is quite different to recovery/resync so it is
3580 	 * handled quite separately ... here.
3581 	 *
3582 	 * On each call to sync_request, we gather one chunk worth of
3583 	 * destination stripes and flag them as expanding.
3584 	 * Then we find all the source stripes and request reads.
3585 	 * As the reads complete, handle_stripe will copy the data
3586 	 * into the destination stripe and release that stripe.
3587 	 */
3588 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
3589 	struct stripe_head *sh;
3590 	int pd_idx;
3591 	sector_t first_sector, last_sector;
3592 	int raid_disks = conf->previous_raid_disks;
3593 	int data_disks = raid_disks - conf->max_degraded;
3594 	int new_data_disks = conf->raid_disks - conf->max_degraded;
3595 	int i;
3596 	int dd_idx;
3597 	sector_t writepos, safepos, gap;
3598 
3599 	if (sector_nr == 0 &&
3600 	    conf->expand_progress != 0) {
3601 		/* restarting in the middle, skip the initial sectors */
3602 		sector_nr = conf->expand_progress;
3603 		sector_div(sector_nr, new_data_disks);
3604 		*skipped = 1;
3605 		return sector_nr;
3606 	}
3607 
3608 	/* we update the metadata when there is more than 3Meg
3609 	 * in the block range (that is rather arbitrary, should
3610 	 * probably be time based) or when the data about to be
3611 	 * copied would over-write the source of the data at
3612 	 * the front of the range.
3613 	 * i.e. one new_stripe forward from expand_progress new_maps
3614 	 * to after where expand_lo old_maps to
3615 	 */
3616 	writepos = conf->expand_progress +
3617 		conf->chunk_size/512*(new_data_disks);
3618 	sector_div(writepos, new_data_disks);
3619 	safepos = conf->expand_lo;
3620 	sector_div(safepos, data_disks);
3621 	gap = conf->expand_progress - conf->expand_lo;
3622 
3623 	if (writepos >= safepos ||
3624 	    gap > (new_data_disks)*3000*2 /*3Meg*/) {
3625 		/* Cannot proceed until we've updated the superblock... */
3626 		wait_event(conf->wait_for_overlap,
3627 			   atomic_read(&conf->reshape_stripes)==0);
3628 		mddev->reshape_position = conf->expand_progress;
3629 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
3630 		md_wakeup_thread(mddev->thread);
3631 		wait_event(mddev->sb_wait, mddev->flags == 0 ||
3632 			   kthread_should_stop());
3633 		spin_lock_irq(&conf->device_lock);
3634 		conf->expand_lo = mddev->reshape_position;
3635 		spin_unlock_irq(&conf->device_lock);
3636 		wake_up(&conf->wait_for_overlap);
3637 	}
3638 
3639 	for (i=0; i < conf->chunk_size/512; i+= STRIPE_SECTORS) {
3640 		int j;
3641 		int skipped = 0;
3642 		pd_idx = stripe_to_pdidx(sector_nr+i, conf, conf->raid_disks);
3643 		sh = get_active_stripe(conf, sector_nr+i,
3644 				       conf->raid_disks, pd_idx, 0);
3645 		set_bit(STRIPE_EXPANDING, &sh->state);
3646 		atomic_inc(&conf->reshape_stripes);
3647 		/* If any of this stripe is beyond the end of the old
3648 		 * array, then we need to zero those blocks
3649 		 */
3650 		for (j=sh->disks; j--;) {
3651 			sector_t s;
3652 			if (j == sh->pd_idx)
3653 				continue;
3654 			if (conf->level == 6 &&
3655 			    j == raid6_next_disk(sh->pd_idx, sh->disks))
3656 				continue;
3657 			s = compute_blocknr(sh, j);
3658 			if (s < (mddev->array_size<<1)) {
3659 				skipped = 1;
3660 				continue;
3661 			}
3662 			memset(page_address(sh->dev[j].page), 0, STRIPE_SIZE);
3663 			set_bit(R5_Expanded, &sh->dev[j].flags);
3664 			set_bit(R5_UPTODATE, &sh->dev[j].flags);
3665 		}
3666 		if (!skipped) {
3667 			set_bit(STRIPE_EXPAND_READY, &sh->state);
3668 			set_bit(STRIPE_HANDLE, &sh->state);
3669 		}
3670 		release_stripe(sh);
3671 	}
3672 	spin_lock_irq(&conf->device_lock);
3673 	conf->expand_progress = (sector_nr + i) * new_data_disks;
3674 	spin_unlock_irq(&conf->device_lock);
3675 	/* Ok, those stripe are ready. We can start scheduling
3676 	 * reads on the source stripes.
3677 	 * The source stripes are determined by mapping the first and last
3678 	 * block on the destination stripes.
3679 	 */
3680 	first_sector =
3681 		raid5_compute_sector(sector_nr*(new_data_disks),
3682 				     raid_disks, data_disks,
3683 				     &dd_idx, &pd_idx, conf);
3684 	last_sector =
3685 		raid5_compute_sector((sector_nr+conf->chunk_size/512)
3686 				     *(new_data_disks) -1,
3687 				     raid_disks, data_disks,
3688 				     &dd_idx, &pd_idx, conf);
3689 	if (last_sector >= (mddev->size<<1))
3690 		last_sector = (mddev->size<<1)-1;
3691 	while (first_sector <= last_sector) {
3692 		pd_idx = stripe_to_pdidx(first_sector, conf,
3693 					 conf->previous_raid_disks);
3694 		sh = get_active_stripe(conf, first_sector,
3695 				       conf->previous_raid_disks, pd_idx, 0);
3696 		set_bit(STRIPE_EXPAND_SOURCE, &sh->state);
3697 		set_bit(STRIPE_HANDLE, &sh->state);
3698 		release_stripe(sh);
3699 		first_sector += STRIPE_SECTORS;
3700 	}
3701 	return conf->chunk_size>>9;
3702 }
3703 
3704 /* FIXME go_faster isn't used */
3705 static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster)
3706 {
3707 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
3708 	struct stripe_head *sh;
3709 	int pd_idx;
3710 	int raid_disks = conf->raid_disks;
3711 	sector_t max_sector = mddev->size << 1;
3712 	int sync_blocks;
3713 	int still_degraded = 0;
3714 	int i;
3715 
3716 	if (sector_nr >= max_sector) {
3717 		/* just being told to finish up .. nothing much to do */
3718 		unplug_slaves(mddev);
3719 		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) {
3720 			end_reshape(conf);
3721 			return 0;
3722 		}
3723 
3724 		if (mddev->curr_resync < max_sector) /* aborted */
3725 			bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
3726 					&sync_blocks, 1);
3727 		else /* completed sync */
3728 			conf->fullsync = 0;
3729 		bitmap_close_sync(mddev->bitmap);
3730 
3731 		return 0;
3732 	}
3733 
3734 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
3735 		return reshape_request(mddev, sector_nr, skipped);
3736 
3737 	/* if there is too many failed drives and we are trying
3738 	 * to resync, then assert that we are finished, because there is
3739 	 * nothing we can do.
3740 	 */
3741 	if (mddev->degraded >= conf->max_degraded &&
3742 	    test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
3743 		sector_t rv = (mddev->size << 1) - sector_nr;
3744 		*skipped = 1;
3745 		return rv;
3746 	}
3747 	if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
3748 	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
3749 	    !conf->fullsync && sync_blocks >= STRIPE_SECTORS) {
3750 		/* we can skip this block, and probably more */
3751 		sync_blocks /= STRIPE_SECTORS;
3752 		*skipped = 1;
3753 		return sync_blocks * STRIPE_SECTORS; /* keep things rounded to whole stripes */
3754 	}
3755 
3756 	pd_idx = stripe_to_pdidx(sector_nr, conf, raid_disks);
3757 	sh = get_active_stripe(conf, sector_nr, raid_disks, pd_idx, 1);
3758 	if (sh == NULL) {
3759 		sh = get_active_stripe(conf, sector_nr, raid_disks, pd_idx, 0);
3760 		/* make sure we don't swamp the stripe cache if someone else
3761 		 * is trying to get access
3762 		 */
3763 		schedule_timeout_uninterruptible(1);
3764 	}
3765 	/* Need to check if array will still be degraded after recovery/resync
3766 	 * We don't need to check the 'failed' flag as when that gets set,
3767 	 * recovery aborts.
3768 	 */
3769 	for (i=0; i<mddev->raid_disks; i++)
3770 		if (conf->disks[i].rdev == NULL)
3771 			still_degraded = 1;
3772 
3773 	bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);
3774 
3775 	spin_lock(&sh->lock);
3776 	set_bit(STRIPE_SYNCING, &sh->state);
3777 	clear_bit(STRIPE_INSYNC, &sh->state);
3778 	spin_unlock(&sh->lock);
3779 
3780 	handle_stripe(sh, NULL);
3781 	release_stripe(sh);
3782 
3783 	return STRIPE_SECTORS;
3784 }
3785 
3786 static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
3787 {
3788 	/* We may not be able to submit a whole bio at once as there
3789 	 * may not be enough stripe_heads available.
3790 	 * We cannot pre-allocate enough stripe_heads as we may need
3791 	 * more than exist in the cache (if we allow ever large chunks).
3792 	 * So we do one stripe head at a time and record in
3793 	 * ->bi_hw_segments how many have been done.
3794 	 *
3795 	 * We *know* that this entire raid_bio is in one chunk, so
3796 	 * it will be only one 'dd_idx' and only need one call to raid5_compute_sector.
3797 	 */
3798 	struct stripe_head *sh;
3799 	int dd_idx, pd_idx;
3800 	sector_t sector, logical_sector, last_sector;
3801 	int scnt = 0;
3802 	int remaining;
3803 	int handled = 0;
3804 
3805 	logical_sector = raid_bio->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
3806 	sector = raid5_compute_sector(	logical_sector,
3807 					conf->raid_disks,
3808 					conf->raid_disks - conf->max_degraded,
3809 					&dd_idx,
3810 					&pd_idx,
3811 					conf);
3812 	last_sector = raid_bio->bi_sector + (raid_bio->bi_size>>9);
3813 
3814 	for (; logical_sector < last_sector;
3815 	     logical_sector += STRIPE_SECTORS,
3816 		     sector += STRIPE_SECTORS,
3817 		     scnt++) {
3818 
3819 		if (scnt < raid_bio->bi_hw_segments)
3820 			/* already done this stripe */
3821 			continue;
3822 
3823 		sh = get_active_stripe(conf, sector, conf->raid_disks, pd_idx, 1);
3824 
3825 		if (!sh) {
3826 			/* failed to get a stripe - must wait */
3827 			raid_bio->bi_hw_segments = scnt;
3828 			conf->retry_read_aligned = raid_bio;
3829 			return handled;
3830 		}
3831 
3832 		set_bit(R5_ReadError, &sh->dev[dd_idx].flags);
3833 		if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
3834 			release_stripe(sh);
3835 			raid_bio->bi_hw_segments = scnt;
3836 			conf->retry_read_aligned = raid_bio;
3837 			return handled;
3838 		}
3839 
3840 		handle_stripe(sh, NULL);
3841 		release_stripe(sh);
3842 		handled++;
3843 	}
3844 	spin_lock_irq(&conf->device_lock);
3845 	remaining = --raid_bio->bi_phys_segments;
3846 	spin_unlock_irq(&conf->device_lock);
3847 	if (remaining == 0) {
3848 
3849 		raid_bio->bi_end_io(raid_bio,
3850 			      test_bit(BIO_UPTODATE, &raid_bio->bi_flags)
3851 			        ? 0 : -EIO);
3852 	}
3853 	if (atomic_dec_and_test(&conf->active_aligned_reads))
3854 		wake_up(&conf->wait_for_stripe);
3855 	return handled;
3856 }
3857 
3858 
3859 
3860 /*
3861  * This is our raid5 kernel thread.
3862  *
3863  * We scan the hash table for stripes which can be handled now.
3864  * During the scan, completed stripes are saved for us by the interrupt
3865  * handler, so that they will not have to wait for our next wakeup.
3866  */
3867 static void raid5d (mddev_t *mddev)
3868 {
3869 	struct stripe_head *sh;
3870 	raid5_conf_t *conf = mddev_to_conf(mddev);
3871 	int handled;
3872 
3873 	pr_debug("+++ raid5d active\n");
3874 
3875 	md_check_recovery(mddev);
3876 
3877 	handled = 0;
3878 	spin_lock_irq(&conf->device_lock);
3879 	while (1) {
3880 		struct list_head *first;
3881 		struct bio *bio;
3882 
3883 		if (conf->seq_flush != conf->seq_write) {
3884 			int seq = conf->seq_flush;
3885 			spin_unlock_irq(&conf->device_lock);
3886 			bitmap_unplug(mddev->bitmap);
3887 			spin_lock_irq(&conf->device_lock);
3888 			conf->seq_write = seq;
3889 			activate_bit_delay(conf);
3890 		}
3891 
3892 		if (list_empty(&conf->handle_list) &&
3893 		    atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD &&
3894 		    !blk_queue_plugged(mddev->queue) &&
3895 		    !list_empty(&conf->delayed_list))
3896 			raid5_activate_delayed(conf);
3897 
3898 		while ((bio = remove_bio_from_retry(conf))) {
3899 			int ok;
3900 			spin_unlock_irq(&conf->device_lock);
3901 			ok = retry_aligned_read(conf, bio);
3902 			spin_lock_irq(&conf->device_lock);
3903 			if (!ok)
3904 				break;
3905 			handled++;
3906 		}
3907 
3908 		if (list_empty(&conf->handle_list)) {
3909 			async_tx_issue_pending_all();
3910 			break;
3911 		}
3912 
3913 		first = conf->handle_list.next;
3914 		sh = list_entry(first, struct stripe_head, lru);
3915 
3916 		list_del_init(first);
3917 		atomic_inc(&sh->count);
3918 		BUG_ON(atomic_read(&sh->count)!= 1);
3919 		spin_unlock_irq(&conf->device_lock);
3920 
3921 		handled++;
3922 		handle_stripe(sh, conf->spare_page);
3923 		release_stripe(sh);
3924 
3925 		spin_lock_irq(&conf->device_lock);
3926 	}
3927 	pr_debug("%d stripes handled\n", handled);
3928 
3929 	spin_unlock_irq(&conf->device_lock);
3930 
3931 	unplug_slaves(mddev);
3932 
3933 	pr_debug("--- raid5d inactive\n");
3934 }
3935 
3936 static ssize_t
3937 raid5_show_stripe_cache_size(mddev_t *mddev, char *page)
3938 {
3939 	raid5_conf_t *conf = mddev_to_conf(mddev);
3940 	if (conf)
3941 		return sprintf(page, "%d\n", conf->max_nr_stripes);
3942 	else
3943 		return 0;
3944 }
3945 
3946 static ssize_t
3947 raid5_store_stripe_cache_size(mddev_t *mddev, const char *page, size_t len)
3948 {
3949 	raid5_conf_t *conf = mddev_to_conf(mddev);
3950 	char *end;
3951 	int new;
3952 	if (len >= PAGE_SIZE)
3953 		return -EINVAL;
3954 	if (!conf)
3955 		return -ENODEV;
3956 
3957 	new = simple_strtoul(page, &end, 10);
3958 	if (!*page || (*end && *end != '\n') )
3959 		return -EINVAL;
3960 	if (new <= 16 || new > 32768)
3961 		return -EINVAL;
3962 	while (new < conf->max_nr_stripes) {
3963 		if (drop_one_stripe(conf))
3964 			conf->max_nr_stripes--;
3965 		else
3966 			break;
3967 	}
3968 	md_allow_write(mddev);
3969 	while (new > conf->max_nr_stripes) {
3970 		if (grow_one_stripe(conf))
3971 			conf->max_nr_stripes++;
3972 		else break;
3973 	}
3974 	return len;
3975 }
3976 
3977 static struct md_sysfs_entry
3978 raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
3979 				raid5_show_stripe_cache_size,
3980 				raid5_store_stripe_cache_size);
3981 
3982 static ssize_t
3983 stripe_cache_active_show(mddev_t *mddev, char *page)
3984 {
3985 	raid5_conf_t *conf = mddev_to_conf(mddev);
3986 	if (conf)
3987 		return sprintf(page, "%d\n", atomic_read(&conf->active_stripes));
3988 	else
3989 		return 0;
3990 }
3991 
3992 static struct md_sysfs_entry
3993 raid5_stripecache_active = __ATTR_RO(stripe_cache_active);
3994 
3995 static struct attribute *raid5_attrs[] =  {
3996 	&raid5_stripecache_size.attr,
3997 	&raid5_stripecache_active.attr,
3998 	NULL,
3999 };
4000 static struct attribute_group raid5_attrs_group = {
4001 	.name = NULL,
4002 	.attrs = raid5_attrs,
4003 };
4004 
4005 static int run(mddev_t *mddev)
4006 {
4007 	raid5_conf_t *conf;
4008 	int raid_disk, memory;
4009 	mdk_rdev_t *rdev;
4010 	struct disk_info *disk;
4011 	struct list_head *tmp;
4012 	int working_disks = 0;
4013 
4014 	if (mddev->level != 5 && mddev->level != 4 && mddev->level != 6) {
4015 		printk(KERN_ERR "raid5: %s: raid level not set to 4/5/6 (%d)\n",
4016 		       mdname(mddev), mddev->level);
4017 		return -EIO;
4018 	}
4019 
4020 	if (mddev->reshape_position != MaxSector) {
4021 		/* Check that we can continue the reshape.
4022 		 * Currently only disks can change, it must
4023 		 * increase, and we must be past the point where
4024 		 * a stripe over-writes itself
4025 		 */
4026 		sector_t here_new, here_old;
4027 		int old_disks;
4028 		int max_degraded = (mddev->level == 5 ? 1 : 2);
4029 
4030 		if (mddev->new_level != mddev->level ||
4031 		    mddev->new_layout != mddev->layout ||
4032 		    mddev->new_chunk != mddev->chunk_size) {
4033 			printk(KERN_ERR "raid5: %s: unsupported reshape "
4034 			       "required - aborting.\n",
4035 			       mdname(mddev));
4036 			return -EINVAL;
4037 		}
4038 		if (mddev->delta_disks <= 0) {
4039 			printk(KERN_ERR "raid5: %s: unsupported reshape "
4040 			       "(reduce disks) required - aborting.\n",
4041 			       mdname(mddev));
4042 			return -EINVAL;
4043 		}
4044 		old_disks = mddev->raid_disks - mddev->delta_disks;
4045 		/* reshape_position must be on a new-stripe boundary, and one
4046 		 * further up in new geometry must map after here in old
4047 		 * geometry.
4048 		 */
4049 		here_new = mddev->reshape_position;
4050 		if (sector_div(here_new, (mddev->chunk_size>>9)*
4051 			       (mddev->raid_disks - max_degraded))) {
4052 			printk(KERN_ERR "raid5: reshape_position not "
4053 			       "on a stripe boundary\n");
4054 			return -EINVAL;
4055 		}
4056 		/* here_new is the stripe we will write to */
4057 		here_old = mddev->reshape_position;
4058 		sector_div(here_old, (mddev->chunk_size>>9)*
4059 			   (old_disks-max_degraded));
4060 		/* here_old is the first stripe that we might need to read
4061 		 * from */
4062 		if (here_new >= here_old) {
4063 			/* Reading from the same stripe as writing to - bad */
4064 			printk(KERN_ERR "raid5: reshape_position too early for "
4065 			       "auto-recovery - aborting.\n");
4066 			return -EINVAL;
4067 		}
4068 		printk(KERN_INFO "raid5: reshape will continue\n");
4069 		/* OK, we should be able to continue; */
4070 	}
4071 
4072 
4073 	mddev->private = kzalloc(sizeof (raid5_conf_t), GFP_KERNEL);
4074 	if ((conf = mddev->private) == NULL)
4075 		goto abort;
4076 	if (mddev->reshape_position == MaxSector) {
4077 		conf->previous_raid_disks = conf->raid_disks = mddev->raid_disks;
4078 	} else {
4079 		conf->raid_disks = mddev->raid_disks;
4080 		conf->previous_raid_disks = mddev->raid_disks - mddev->delta_disks;
4081 	}
4082 
4083 	conf->disks = kzalloc(conf->raid_disks * sizeof(struct disk_info),
4084 			      GFP_KERNEL);
4085 	if (!conf->disks)
4086 		goto abort;
4087 
4088 	conf->mddev = mddev;
4089 
4090 	if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
4091 		goto abort;
4092 
4093 	if (mddev->level == 6) {
4094 		conf->spare_page = alloc_page(GFP_KERNEL);
4095 		if (!conf->spare_page)
4096 			goto abort;
4097 	}
4098 	spin_lock_init(&conf->device_lock);
4099 	init_waitqueue_head(&conf->wait_for_stripe);
4100 	init_waitqueue_head(&conf->wait_for_overlap);
4101 	INIT_LIST_HEAD(&conf->handle_list);
4102 	INIT_LIST_HEAD(&conf->delayed_list);
4103 	INIT_LIST_HEAD(&conf->bitmap_list);
4104 	INIT_LIST_HEAD(&conf->inactive_list);
4105 	atomic_set(&conf->active_stripes, 0);
4106 	atomic_set(&conf->preread_active_stripes, 0);
4107 	atomic_set(&conf->active_aligned_reads, 0);
4108 
4109 	pr_debug("raid5: run(%s) called.\n", mdname(mddev));
4110 
4111 	ITERATE_RDEV(mddev,rdev,tmp) {
4112 		raid_disk = rdev->raid_disk;
4113 		if (raid_disk >= conf->raid_disks
4114 		    || raid_disk < 0)
4115 			continue;
4116 		disk = conf->disks + raid_disk;
4117 
4118 		disk->rdev = rdev;
4119 
4120 		if (test_bit(In_sync, &rdev->flags)) {
4121 			char b[BDEVNAME_SIZE];
4122 			printk(KERN_INFO "raid5: device %s operational as raid"
4123 				" disk %d\n", bdevname(rdev->bdev,b),
4124 				raid_disk);
4125 			working_disks++;
4126 		}
4127 	}
4128 
4129 	/*
4130 	 * 0 for a fully functional array, 1 or 2 for a degraded array.
4131 	 */
4132 	mddev->degraded = conf->raid_disks - working_disks;
4133 	conf->mddev = mddev;
4134 	conf->chunk_size = mddev->chunk_size;
4135 	conf->level = mddev->level;
4136 	if (conf->level == 6)
4137 		conf->max_degraded = 2;
4138 	else
4139 		conf->max_degraded = 1;
4140 	conf->algorithm = mddev->layout;
4141 	conf->max_nr_stripes = NR_STRIPES;
4142 	conf->expand_progress = mddev->reshape_position;
4143 
4144 	/* device size must be a multiple of chunk size */
4145 	mddev->size &= ~(mddev->chunk_size/1024 -1);
4146 	mddev->resync_max_sectors = mddev->size << 1;
4147 
4148 	if (conf->level == 6 && conf->raid_disks < 4) {
4149 		printk(KERN_ERR "raid6: not enough configured devices for %s (%d, minimum 4)\n",
4150 		       mdname(mddev), conf->raid_disks);
4151 		goto abort;
4152 	}
4153 	if (!conf->chunk_size || conf->chunk_size % 4) {
4154 		printk(KERN_ERR "raid5: invalid chunk size %d for %s\n",
4155 			conf->chunk_size, mdname(mddev));
4156 		goto abort;
4157 	}
4158 	if (conf->algorithm > ALGORITHM_RIGHT_SYMMETRIC) {
4159 		printk(KERN_ERR
4160 			"raid5: unsupported parity algorithm %d for %s\n",
4161 			conf->algorithm, mdname(mddev));
4162 		goto abort;
4163 	}
4164 	if (mddev->degraded > conf->max_degraded) {
4165 		printk(KERN_ERR "raid5: not enough operational devices for %s"
4166 			" (%d/%d failed)\n",
4167 			mdname(mddev), mddev->degraded, conf->raid_disks);
4168 		goto abort;
4169 	}
4170 
4171 	if (mddev->degraded > 0 &&
4172 	    mddev->recovery_cp != MaxSector) {
4173 		if (mddev->ok_start_degraded)
4174 			printk(KERN_WARNING
4175 			       "raid5: starting dirty degraded array: %s"
4176 			       "- data corruption possible.\n",
4177 			       mdname(mddev));
4178 		else {
4179 			printk(KERN_ERR
4180 			       "raid5: cannot start dirty degraded array for %s\n",
4181 			       mdname(mddev));
4182 			goto abort;
4183 		}
4184 	}
4185 
4186 	{
4187 		mddev->thread = md_register_thread(raid5d, mddev, "%s_raid5");
4188 		if (!mddev->thread) {
4189 			printk(KERN_ERR
4190 				"raid5: couldn't allocate thread for %s\n",
4191 				mdname(mddev));
4192 			goto abort;
4193 		}
4194 	}
4195 	memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
4196 		 conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
4197 	if (grow_stripes(conf, conf->max_nr_stripes)) {
4198 		printk(KERN_ERR
4199 			"raid5: couldn't allocate %dkB for buffers\n", memory);
4200 		shrink_stripes(conf);
4201 		md_unregister_thread(mddev->thread);
4202 		goto abort;
4203 	} else
4204 		printk(KERN_INFO "raid5: allocated %dkB for %s\n",
4205 			memory, mdname(mddev));
4206 
4207 	if (mddev->degraded == 0)
4208 		printk("raid5: raid level %d set %s active with %d out of %d"
4209 			" devices, algorithm %d\n", conf->level, mdname(mddev),
4210 			mddev->raid_disks-mddev->degraded, mddev->raid_disks,
4211 			conf->algorithm);
4212 	else
4213 		printk(KERN_ALERT "raid5: raid level %d set %s active with %d"
4214 			" out of %d devices, algorithm %d\n", conf->level,
4215 			mdname(mddev), mddev->raid_disks - mddev->degraded,
4216 			mddev->raid_disks, conf->algorithm);
4217 
4218 	print_raid5_conf(conf);
4219 
4220 	if (conf->expand_progress != MaxSector) {
4221 		printk("...ok start reshape thread\n");
4222 		conf->expand_lo = conf->expand_progress;
4223 		atomic_set(&conf->reshape_stripes, 0);
4224 		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
4225 		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
4226 		set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
4227 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
4228 		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
4229 							"%s_reshape");
4230 	}
4231 
4232 	/* read-ahead size must cover two whole stripes, which is
4233 	 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
4234 	 */
4235 	{
4236 		int data_disks = conf->previous_raid_disks - conf->max_degraded;
4237 		int stripe = data_disks *
4238 			(mddev->chunk_size / PAGE_SIZE);
4239 		if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
4240 			mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
4241 	}
4242 
4243 	/* Ok, everything is just fine now */
4244 	if (sysfs_create_group(&mddev->kobj, &raid5_attrs_group))
4245 		printk(KERN_WARNING
4246 		       "raid5: failed to create sysfs attributes for %s\n",
4247 		       mdname(mddev));
4248 
4249 	mddev->queue->unplug_fn = raid5_unplug_device;
4250 	mddev->queue->backing_dev_info.congested_data = mddev;
4251 	mddev->queue->backing_dev_info.congested_fn = raid5_congested;
4252 
4253 	mddev->array_size =  mddev->size * (conf->previous_raid_disks -
4254 					    conf->max_degraded);
4255 
4256 	blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);
4257 
4258 	return 0;
4259 abort:
4260 	if (conf) {
4261 		print_raid5_conf(conf);
4262 		safe_put_page(conf->spare_page);
4263 		kfree(conf->disks);
4264 		kfree(conf->stripe_hashtbl);
4265 		kfree(conf);
4266 	}
4267 	mddev->private = NULL;
4268 	printk(KERN_ALERT "raid5: failed to run raid set %s\n", mdname(mddev));
4269 	return -EIO;
4270 }
4271 
4272 
4273 
4274 static int stop(mddev_t *mddev)
4275 {
4276 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
4277 
4278 	md_unregister_thread(mddev->thread);
4279 	mddev->thread = NULL;
4280 	shrink_stripes(conf);
4281 	kfree(conf->stripe_hashtbl);
4282 	mddev->queue->backing_dev_info.congested_fn = NULL;
4283 	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
4284 	sysfs_remove_group(&mddev->kobj, &raid5_attrs_group);
4285 	kfree(conf->disks);
4286 	kfree(conf);
4287 	mddev->private = NULL;
4288 	return 0;
4289 }
4290 
4291 #ifdef DEBUG
4292 static void print_sh (struct seq_file *seq, struct stripe_head *sh)
4293 {
4294 	int i;
4295 
4296 	seq_printf(seq, "sh %llu, pd_idx %d, state %ld.\n",
4297 		   (unsigned long long)sh->sector, sh->pd_idx, sh->state);
4298 	seq_printf(seq, "sh %llu,  count %d.\n",
4299 		   (unsigned long long)sh->sector, atomic_read(&sh->count));
4300 	seq_printf(seq, "sh %llu, ", (unsigned long long)sh->sector);
4301 	for (i = 0; i < sh->disks; i++) {
4302 		seq_printf(seq, "(cache%d: %p %ld) ",
4303 			   i, sh->dev[i].page, sh->dev[i].flags);
4304 	}
4305 	seq_printf(seq, "\n");
4306 }
4307 
4308 static void printall (struct seq_file *seq, raid5_conf_t *conf)
4309 {
4310 	struct stripe_head *sh;
4311 	struct hlist_node *hn;
4312 	int i;
4313 
4314 	spin_lock_irq(&conf->device_lock);
4315 	for (i = 0; i < NR_HASH; i++) {
4316 		hlist_for_each_entry(sh, hn, &conf->stripe_hashtbl[i], hash) {
4317 			if (sh->raid_conf != conf)
4318 				continue;
4319 			print_sh(seq, sh);
4320 		}
4321 	}
4322 	spin_unlock_irq(&conf->device_lock);
4323 }
4324 #endif
4325 
4326 static void status (struct seq_file *seq, mddev_t *mddev)
4327 {
4328 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
4329 	int i;
4330 
4331 	seq_printf (seq, " level %d, %dk chunk, algorithm %d", mddev->level, mddev->chunk_size >> 10, mddev->layout);
4332 	seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->raid_disks - mddev->degraded);
4333 	for (i = 0; i < conf->raid_disks; i++)
4334 		seq_printf (seq, "%s",
4335 			       conf->disks[i].rdev &&
4336 			       test_bit(In_sync, &conf->disks[i].rdev->flags) ? "U" : "_");
4337 	seq_printf (seq, "]");
4338 #ifdef DEBUG
4339 	seq_printf (seq, "\n");
4340 	printall(seq, conf);
4341 #endif
4342 }
4343 
4344 static void print_raid5_conf (raid5_conf_t *conf)
4345 {
4346 	int i;
4347 	struct disk_info *tmp;
4348 
4349 	printk("RAID5 conf printout:\n");
4350 	if (!conf) {
4351 		printk("(conf==NULL)\n");
4352 		return;
4353 	}
4354 	printk(" --- rd:%d wd:%d\n", conf->raid_disks,
4355 		 conf->raid_disks - conf->mddev->degraded);
4356 
4357 	for (i = 0; i < conf->raid_disks; i++) {
4358 		char b[BDEVNAME_SIZE];
4359 		tmp = conf->disks + i;
4360 		if (tmp->rdev)
4361 		printk(" disk %d, o:%d, dev:%s\n",
4362 			i, !test_bit(Faulty, &tmp->rdev->flags),
4363 			bdevname(tmp->rdev->bdev,b));
4364 	}
4365 }
4366 
4367 static int raid5_spare_active(mddev_t *mddev)
4368 {
4369 	int i;
4370 	raid5_conf_t *conf = mddev->private;
4371 	struct disk_info *tmp;
4372 
4373 	for (i = 0; i < conf->raid_disks; i++) {
4374 		tmp = conf->disks + i;
4375 		if (tmp->rdev
4376 		    && !test_bit(Faulty, &tmp->rdev->flags)
4377 		    && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
4378 			unsigned long flags;
4379 			spin_lock_irqsave(&conf->device_lock, flags);
4380 			mddev->degraded--;
4381 			spin_unlock_irqrestore(&conf->device_lock, flags);
4382 		}
4383 	}
4384 	print_raid5_conf(conf);
4385 	return 0;
4386 }
4387 
4388 static int raid5_remove_disk(mddev_t *mddev, int number)
4389 {
4390 	raid5_conf_t *conf = mddev->private;
4391 	int err = 0;
4392 	mdk_rdev_t *rdev;
4393 	struct disk_info *p = conf->disks + number;
4394 
4395 	print_raid5_conf(conf);
4396 	rdev = p->rdev;
4397 	if (rdev) {
4398 		if (test_bit(In_sync, &rdev->flags) ||
4399 		    atomic_read(&rdev->nr_pending)) {
4400 			err = -EBUSY;
4401 			goto abort;
4402 		}
4403 		p->rdev = NULL;
4404 		synchronize_rcu();
4405 		if (atomic_read(&rdev->nr_pending)) {
4406 			/* lost the race, try later */
4407 			err = -EBUSY;
4408 			p->rdev = rdev;
4409 		}
4410 	}
4411 abort:
4412 
4413 	print_raid5_conf(conf);
4414 	return err;
4415 }
4416 
4417 static int raid5_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
4418 {
4419 	raid5_conf_t *conf = mddev->private;
4420 	int found = 0;
4421 	int disk;
4422 	struct disk_info *p;
4423 
4424 	if (mddev->degraded > conf->max_degraded)
4425 		/* no point adding a device */
4426 		return 0;
4427 
4428 	/*
4429 	 * find the disk ... but prefer rdev->saved_raid_disk
4430 	 * if possible.
4431 	 */
4432 	if (rdev->saved_raid_disk >= 0 &&
4433 	    conf->disks[rdev->saved_raid_disk].rdev == NULL)
4434 		disk = rdev->saved_raid_disk;
4435 	else
4436 		disk = 0;
4437 	for ( ; disk < conf->raid_disks; disk++)
4438 		if ((p=conf->disks + disk)->rdev == NULL) {
4439 			clear_bit(In_sync, &rdev->flags);
4440 			rdev->raid_disk = disk;
4441 			found = 1;
4442 			if (rdev->saved_raid_disk != disk)
4443 				conf->fullsync = 1;
4444 			rcu_assign_pointer(p->rdev, rdev);
4445 			break;
4446 		}
4447 	print_raid5_conf(conf);
4448 	return found;
4449 }
4450 
4451 static int raid5_resize(mddev_t *mddev, sector_t sectors)
4452 {
4453 	/* no resync is happening, and there is enough space
4454 	 * on all devices, so we can resize.
4455 	 * We need to make sure resync covers any new space.
4456 	 * If the array is shrinking we should possibly wait until
4457 	 * any io in the removed space completes, but it hardly seems
4458 	 * worth it.
4459 	 */
4460 	raid5_conf_t *conf = mddev_to_conf(mddev);
4461 
4462 	sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
4463 	mddev->array_size = (sectors * (mddev->raid_disks-conf->max_degraded))>>1;
4464 	set_capacity(mddev->gendisk, mddev->array_size << 1);
4465 	mddev->changed = 1;
4466 	if (sectors/2  > mddev->size && mddev->recovery_cp == MaxSector) {
4467 		mddev->recovery_cp = mddev->size << 1;
4468 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
4469 	}
4470 	mddev->size = sectors /2;
4471 	mddev->resync_max_sectors = sectors;
4472 	return 0;
4473 }
4474 
4475 #ifdef CONFIG_MD_RAID5_RESHAPE
4476 static int raid5_check_reshape(mddev_t *mddev)
4477 {
4478 	raid5_conf_t *conf = mddev_to_conf(mddev);
4479 	int err;
4480 
4481 	if (mddev->delta_disks < 0 ||
4482 	    mddev->new_level != mddev->level)
4483 		return -EINVAL; /* Cannot shrink array or change level yet */
4484 	if (mddev->delta_disks == 0)
4485 		return 0; /* nothing to do */
4486 
4487 	/* Can only proceed if there are plenty of stripe_heads.
4488 	 * We need a minimum of one full stripe,, and for sensible progress
4489 	 * it is best to have about 4 times that.
4490 	 * If we require 4 times, then the default 256 4K stripe_heads will
4491 	 * allow for chunk sizes up to 256K, which is probably OK.
4492 	 * If the chunk size is greater, user-space should request more
4493 	 * stripe_heads first.
4494 	 */
4495 	if ((mddev->chunk_size / STRIPE_SIZE) * 4 > conf->max_nr_stripes ||
4496 	    (mddev->new_chunk / STRIPE_SIZE) * 4 > conf->max_nr_stripes) {
4497 		printk(KERN_WARNING "raid5: reshape: not enough stripes.  Needed %lu\n",
4498 		       (mddev->chunk_size / STRIPE_SIZE)*4);
4499 		return -ENOSPC;
4500 	}
4501 
4502 	err = resize_stripes(conf, conf->raid_disks + mddev->delta_disks);
4503 	if (err)
4504 		return err;
4505 
4506 	if (mddev->degraded > conf->max_degraded)
4507 		return -EINVAL;
4508 	/* looks like we might be able to manage this */
4509 	return 0;
4510 }
4511 
4512 static int raid5_start_reshape(mddev_t *mddev)
4513 {
4514 	raid5_conf_t *conf = mddev_to_conf(mddev);
4515 	mdk_rdev_t *rdev;
4516 	struct list_head *rtmp;
4517 	int spares = 0;
4518 	int added_devices = 0;
4519 	unsigned long flags;
4520 
4521 	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
4522 		return -EBUSY;
4523 
4524 	ITERATE_RDEV(mddev, rdev, rtmp)
4525 		if (rdev->raid_disk < 0 &&
4526 		    !test_bit(Faulty, &rdev->flags))
4527 			spares++;
4528 
4529 	if (spares - mddev->degraded < mddev->delta_disks - conf->max_degraded)
4530 		/* Not enough devices even to make a degraded array
4531 		 * of that size
4532 		 */
4533 		return -EINVAL;
4534 
4535 	atomic_set(&conf->reshape_stripes, 0);
4536 	spin_lock_irq(&conf->device_lock);
4537 	conf->previous_raid_disks = conf->raid_disks;
4538 	conf->raid_disks += mddev->delta_disks;
4539 	conf->expand_progress = 0;
4540 	conf->expand_lo = 0;
4541 	spin_unlock_irq(&conf->device_lock);
4542 
4543 	/* Add some new drives, as many as will fit.
4544 	 * We know there are enough to make the newly sized array work.
4545 	 */
4546 	ITERATE_RDEV(mddev, rdev, rtmp)
4547 		if (rdev->raid_disk < 0 &&
4548 		    !test_bit(Faulty, &rdev->flags)) {
4549 			if (raid5_add_disk(mddev, rdev)) {
4550 				char nm[20];
4551 				set_bit(In_sync, &rdev->flags);
4552 				added_devices++;
4553 				rdev->recovery_offset = 0;
4554 				sprintf(nm, "rd%d", rdev->raid_disk);
4555 				if (sysfs_create_link(&mddev->kobj,
4556 						      &rdev->kobj, nm))
4557 					printk(KERN_WARNING
4558 					       "raid5: failed to create "
4559 					       " link %s for %s\n",
4560 					       nm, mdname(mddev));
4561 			} else
4562 				break;
4563 		}
4564 
4565 	spin_lock_irqsave(&conf->device_lock, flags);
4566 	mddev->degraded = (conf->raid_disks - conf->previous_raid_disks) - added_devices;
4567 	spin_unlock_irqrestore(&conf->device_lock, flags);
4568 	mddev->raid_disks = conf->raid_disks;
4569 	mddev->reshape_position = 0;
4570 	set_bit(MD_CHANGE_DEVS, &mddev->flags);
4571 
4572 	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
4573 	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
4574 	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
4575 	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
4576 	mddev->sync_thread = md_register_thread(md_do_sync, mddev,
4577 						"%s_reshape");
4578 	if (!mddev->sync_thread) {
4579 		mddev->recovery = 0;
4580 		spin_lock_irq(&conf->device_lock);
4581 		mddev->raid_disks = conf->raid_disks = conf->previous_raid_disks;
4582 		conf->expand_progress = MaxSector;
4583 		spin_unlock_irq(&conf->device_lock);
4584 		return -EAGAIN;
4585 	}
4586 	md_wakeup_thread(mddev->sync_thread);
4587 	md_new_event(mddev);
4588 	return 0;
4589 }
4590 #endif
4591 
4592 static void end_reshape(raid5_conf_t *conf)
4593 {
4594 	struct block_device *bdev;
4595 
4596 	if (!test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
4597 		conf->mddev->array_size = conf->mddev->size *
4598 			(conf->raid_disks - conf->max_degraded);
4599 		set_capacity(conf->mddev->gendisk, conf->mddev->array_size << 1);
4600 		conf->mddev->changed = 1;
4601 
4602 		bdev = bdget_disk(conf->mddev->gendisk, 0);
4603 		if (bdev) {
4604 			mutex_lock(&bdev->bd_inode->i_mutex);
4605 			i_size_write(bdev->bd_inode, (loff_t)conf->mddev->array_size << 10);
4606 			mutex_unlock(&bdev->bd_inode->i_mutex);
4607 			bdput(bdev);
4608 		}
4609 		spin_lock_irq(&conf->device_lock);
4610 		conf->expand_progress = MaxSector;
4611 		spin_unlock_irq(&conf->device_lock);
4612 		conf->mddev->reshape_position = MaxSector;
4613 
4614 		/* read-ahead size must cover two whole stripes, which is
4615 		 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
4616 		 */
4617 		{
4618 			int data_disks = conf->previous_raid_disks - conf->max_degraded;
4619 			int stripe = data_disks *
4620 				(conf->mddev->chunk_size / PAGE_SIZE);
4621 			if (conf->mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
4622 				conf->mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
4623 		}
4624 	}
4625 }
4626 
4627 static void raid5_quiesce(mddev_t *mddev, int state)
4628 {
4629 	raid5_conf_t *conf = mddev_to_conf(mddev);
4630 
4631 	switch(state) {
4632 	case 2: /* resume for a suspend */
4633 		wake_up(&conf->wait_for_overlap);
4634 		break;
4635 
4636 	case 1: /* stop all writes */
4637 		spin_lock_irq(&conf->device_lock);
4638 		conf->quiesce = 1;
4639 		wait_event_lock_irq(conf->wait_for_stripe,
4640 				    atomic_read(&conf->active_stripes) == 0 &&
4641 				    atomic_read(&conf->active_aligned_reads) == 0,
4642 				    conf->device_lock, /* nothing */);
4643 		spin_unlock_irq(&conf->device_lock);
4644 		break;
4645 
4646 	case 0: /* re-enable writes */
4647 		spin_lock_irq(&conf->device_lock);
4648 		conf->quiesce = 0;
4649 		wake_up(&conf->wait_for_stripe);
4650 		wake_up(&conf->wait_for_overlap);
4651 		spin_unlock_irq(&conf->device_lock);
4652 		break;
4653 	}
4654 }
4655 
4656 static struct mdk_personality raid6_personality =
4657 {
4658 	.name		= "raid6",
4659 	.level		= 6,
4660 	.owner		= THIS_MODULE,
4661 	.make_request	= make_request,
4662 	.run		= run,
4663 	.stop		= stop,
4664 	.status		= status,
4665 	.error_handler	= error,
4666 	.hot_add_disk	= raid5_add_disk,
4667 	.hot_remove_disk= raid5_remove_disk,
4668 	.spare_active	= raid5_spare_active,
4669 	.sync_request	= sync_request,
4670 	.resize		= raid5_resize,
4671 #ifdef CONFIG_MD_RAID5_RESHAPE
4672 	.check_reshape	= raid5_check_reshape,
4673 	.start_reshape  = raid5_start_reshape,
4674 #endif
4675 	.quiesce	= raid5_quiesce,
4676 };
4677 static struct mdk_personality raid5_personality =
4678 {
4679 	.name		= "raid5",
4680 	.level		= 5,
4681 	.owner		= THIS_MODULE,
4682 	.make_request	= make_request,
4683 	.run		= run,
4684 	.stop		= stop,
4685 	.status		= status,
4686 	.error_handler	= error,
4687 	.hot_add_disk	= raid5_add_disk,
4688 	.hot_remove_disk= raid5_remove_disk,
4689 	.spare_active	= raid5_spare_active,
4690 	.sync_request	= sync_request,
4691 	.resize		= raid5_resize,
4692 #ifdef CONFIG_MD_RAID5_RESHAPE
4693 	.check_reshape	= raid5_check_reshape,
4694 	.start_reshape  = raid5_start_reshape,
4695 #endif
4696 	.quiesce	= raid5_quiesce,
4697 };
4698 
4699 static struct mdk_personality raid4_personality =
4700 {
4701 	.name		= "raid4",
4702 	.level		= 4,
4703 	.owner		= THIS_MODULE,
4704 	.make_request	= make_request,
4705 	.run		= run,
4706 	.stop		= stop,
4707 	.status		= status,
4708 	.error_handler	= error,
4709 	.hot_add_disk	= raid5_add_disk,
4710 	.hot_remove_disk= raid5_remove_disk,
4711 	.spare_active	= raid5_spare_active,
4712 	.sync_request	= sync_request,
4713 	.resize		= raid5_resize,
4714 #ifdef CONFIG_MD_RAID5_RESHAPE
4715 	.check_reshape	= raid5_check_reshape,
4716 	.start_reshape  = raid5_start_reshape,
4717 #endif
4718 	.quiesce	= raid5_quiesce,
4719 };
4720 
4721 static int __init raid5_init(void)
4722 {
4723 	int e;
4724 
4725 	e = raid6_select_algo();
4726 	if ( e )
4727 		return e;
4728 	register_md_personality(&raid6_personality);
4729 	register_md_personality(&raid5_personality);
4730 	register_md_personality(&raid4_personality);
4731 	return 0;
4732 }
4733 
4734 static void raid5_exit(void)
4735 {
4736 	unregister_md_personality(&raid6_personality);
4737 	unregister_md_personality(&raid5_personality);
4738 	unregister_md_personality(&raid4_personality);
4739 }
4740 
4741 module_init(raid5_init);
4742 module_exit(raid5_exit);
4743 MODULE_LICENSE("GPL");
4744 MODULE_ALIAS("md-personality-4"); /* RAID5 */
4745 MODULE_ALIAS("md-raid5");
4746 MODULE_ALIAS("md-raid4");
4747 MODULE_ALIAS("md-level-5");
4748 MODULE_ALIAS("md-level-4");
4749 MODULE_ALIAS("md-personality-8"); /* RAID6 */
4750 MODULE_ALIAS("md-raid6");
4751 MODULE_ALIAS("md-level-6");
4752 
4753 /* This used to be two separate modules, they were: */
4754 MODULE_ALIAS("raid5");
4755 MODULE_ALIAS("raid6");
4756