xref: /openbmc/linux/drivers/md/raid5.c (revision 64c70b1c)
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 
56 /*
57  * Stripe cache
58  */
59 
60 #define NR_STRIPES		256
61 #define STRIPE_SIZE		PAGE_SIZE
62 #define STRIPE_SHIFT		(PAGE_SHIFT - 9)
63 #define STRIPE_SECTORS		(STRIPE_SIZE>>9)
64 #define	IO_THRESHOLD		1
65 #define NR_HASH			(PAGE_SIZE / sizeof(struct hlist_head))
66 #define HASH_MASK		(NR_HASH - 1)
67 
68 #define stripe_hash(conf, sect)	(&((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK]))
69 
70 /* bio's attached to a stripe+device for I/O are linked together in bi_sector
71  * order without overlap.  There may be several bio's per stripe+device, and
72  * a bio could span several devices.
73  * When walking this list for a particular stripe+device, we must never proceed
74  * beyond a bio that extends past this device, as the next bio might no longer
75  * be valid.
76  * This macro is used to determine the 'next' bio in the list, given the sector
77  * of the current stripe+device
78  */
79 #define r5_next_bio(bio, sect) ( ( (bio)->bi_sector + ((bio)->bi_size>>9) < sect + STRIPE_SECTORS) ? (bio)->bi_next : NULL)
80 /*
81  * The following can be used to debug the driver
82  */
83 #define RAID5_DEBUG	0
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 #define PRINTK(x...) ((void)(RAID5_DEBUG && printk(x)))
92 #if RAID5_DEBUG
93 #define inline
94 #define __inline__
95 #endif
96 
97 #if !RAID6_USE_EMPTY_ZERO_PAGE
98 /* In .bss so it's zeroed */
99 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
100 #endif
101 
102 static inline int raid6_next_disk(int disk, int raid_disks)
103 {
104 	disk++;
105 	return (disk < raid_disks) ? disk : 0;
106 }
107 static void print_raid5_conf (raid5_conf_t *conf);
108 
109 static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
110 {
111 	if (atomic_dec_and_test(&sh->count)) {
112 		BUG_ON(!list_empty(&sh->lru));
113 		BUG_ON(atomic_read(&conf->active_stripes)==0);
114 		if (test_bit(STRIPE_HANDLE, &sh->state)) {
115 			if (test_bit(STRIPE_DELAYED, &sh->state)) {
116 				list_add_tail(&sh->lru, &conf->delayed_list);
117 				blk_plug_device(conf->mddev->queue);
118 			} else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
119 				   sh->bm_seq - conf->seq_write > 0) {
120 				list_add_tail(&sh->lru, &conf->bitmap_list);
121 				blk_plug_device(conf->mddev->queue);
122 			} else {
123 				clear_bit(STRIPE_BIT_DELAY, &sh->state);
124 				list_add_tail(&sh->lru, &conf->handle_list);
125 			}
126 			md_wakeup_thread(conf->mddev->thread);
127 		} else {
128 			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
129 				atomic_dec(&conf->preread_active_stripes);
130 				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
131 					md_wakeup_thread(conf->mddev->thread);
132 			}
133 			atomic_dec(&conf->active_stripes);
134 			if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
135 				list_add_tail(&sh->lru, &conf->inactive_list);
136 				wake_up(&conf->wait_for_stripe);
137 				if (conf->retry_read_aligned)
138 					md_wakeup_thread(conf->mddev->thread);
139 			}
140 		}
141 	}
142 }
143 static void release_stripe(struct stripe_head *sh)
144 {
145 	raid5_conf_t *conf = sh->raid_conf;
146 	unsigned long flags;
147 
148 	spin_lock_irqsave(&conf->device_lock, flags);
149 	__release_stripe(conf, sh);
150 	spin_unlock_irqrestore(&conf->device_lock, flags);
151 }
152 
153 static inline void remove_hash(struct stripe_head *sh)
154 {
155 	PRINTK("remove_hash(), stripe %llu\n", (unsigned long long)sh->sector);
156 
157 	hlist_del_init(&sh->hash);
158 }
159 
160 static inline void insert_hash(raid5_conf_t *conf, struct stripe_head *sh)
161 {
162 	struct hlist_head *hp = stripe_hash(conf, sh->sector);
163 
164 	PRINTK("insert_hash(), stripe %llu\n", (unsigned long long)sh->sector);
165 
166 	CHECK_DEVLOCK();
167 	hlist_add_head(&sh->hash, hp);
168 }
169 
170 
171 /* find an idle stripe, make sure it is unhashed, and return it. */
172 static struct stripe_head *get_free_stripe(raid5_conf_t *conf)
173 {
174 	struct stripe_head *sh = NULL;
175 	struct list_head *first;
176 
177 	CHECK_DEVLOCK();
178 	if (list_empty(&conf->inactive_list))
179 		goto out;
180 	first = conf->inactive_list.next;
181 	sh = list_entry(first, struct stripe_head, lru);
182 	list_del_init(first);
183 	remove_hash(sh);
184 	atomic_inc(&conf->active_stripes);
185 out:
186 	return sh;
187 }
188 
189 static void shrink_buffers(struct stripe_head *sh, int num)
190 {
191 	struct page *p;
192 	int i;
193 
194 	for (i=0; i<num ; i++) {
195 		p = sh->dev[i].page;
196 		if (!p)
197 			continue;
198 		sh->dev[i].page = NULL;
199 		put_page(p);
200 	}
201 }
202 
203 static int grow_buffers(struct stripe_head *sh, int num)
204 {
205 	int i;
206 
207 	for (i=0; i<num; i++) {
208 		struct page *page;
209 
210 		if (!(page = alloc_page(GFP_KERNEL))) {
211 			return 1;
212 		}
213 		sh->dev[i].page = page;
214 	}
215 	return 0;
216 }
217 
218 static void raid5_build_block (struct stripe_head *sh, int i);
219 
220 static void init_stripe(struct stripe_head *sh, sector_t sector, int pd_idx, int disks)
221 {
222 	raid5_conf_t *conf = sh->raid_conf;
223 	int i;
224 
225 	BUG_ON(atomic_read(&sh->count) != 0);
226 	BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
227 
228 	CHECK_DEVLOCK();
229 	PRINTK("init_stripe called, stripe %llu\n",
230 		(unsigned long long)sh->sector);
231 
232 	remove_hash(sh);
233 
234 	sh->sector = sector;
235 	sh->pd_idx = pd_idx;
236 	sh->state = 0;
237 
238 	sh->disks = disks;
239 
240 	for (i = sh->disks; i--; ) {
241 		struct r5dev *dev = &sh->dev[i];
242 
243 		if (dev->toread || dev->towrite || dev->written ||
244 		    test_bit(R5_LOCKED, &dev->flags)) {
245 			printk("sector=%llx i=%d %p %p %p %d\n",
246 			       (unsigned long long)sh->sector, i, dev->toread,
247 			       dev->towrite, dev->written,
248 			       test_bit(R5_LOCKED, &dev->flags));
249 			BUG();
250 		}
251 		dev->flags = 0;
252 		raid5_build_block(sh, i);
253 	}
254 	insert_hash(conf, sh);
255 }
256 
257 static struct stripe_head *__find_stripe(raid5_conf_t *conf, sector_t sector, int disks)
258 {
259 	struct stripe_head *sh;
260 	struct hlist_node *hn;
261 
262 	CHECK_DEVLOCK();
263 	PRINTK("__find_stripe, sector %llu\n", (unsigned long long)sector);
264 	hlist_for_each_entry(sh, hn, stripe_hash(conf, sector), hash)
265 		if (sh->sector == sector && sh->disks == disks)
266 			return sh;
267 	PRINTK("__stripe %llu not in cache\n", (unsigned long long)sector);
268 	return NULL;
269 }
270 
271 static void unplug_slaves(mddev_t *mddev);
272 static void raid5_unplug_device(request_queue_t *q);
273 
274 static struct stripe_head *get_active_stripe(raid5_conf_t *conf, sector_t sector, int disks,
275 					     int pd_idx, int noblock)
276 {
277 	struct stripe_head *sh;
278 
279 	PRINTK("get_stripe, sector %llu\n", (unsigned long long)sector);
280 
281 	spin_lock_irq(&conf->device_lock);
282 
283 	do {
284 		wait_event_lock_irq(conf->wait_for_stripe,
285 				    conf->quiesce == 0,
286 				    conf->device_lock, /* nothing */);
287 		sh = __find_stripe(conf, sector, disks);
288 		if (!sh) {
289 			if (!conf->inactive_blocked)
290 				sh = get_free_stripe(conf);
291 			if (noblock && sh == NULL)
292 				break;
293 			if (!sh) {
294 				conf->inactive_blocked = 1;
295 				wait_event_lock_irq(conf->wait_for_stripe,
296 						    !list_empty(&conf->inactive_list) &&
297 						    (atomic_read(&conf->active_stripes)
298 						     < (conf->max_nr_stripes *3/4)
299 						     || !conf->inactive_blocked),
300 						    conf->device_lock,
301 						    raid5_unplug_device(conf->mddev->queue)
302 					);
303 				conf->inactive_blocked = 0;
304 			} else
305 				init_stripe(sh, sector, pd_idx, disks);
306 		} else {
307 			if (atomic_read(&sh->count)) {
308 			  BUG_ON(!list_empty(&sh->lru));
309 			} else {
310 				if (!test_bit(STRIPE_HANDLE, &sh->state))
311 					atomic_inc(&conf->active_stripes);
312 				if (list_empty(&sh->lru) &&
313 				    !test_bit(STRIPE_EXPANDING, &sh->state))
314 					BUG();
315 				list_del_init(&sh->lru);
316 			}
317 		}
318 	} while (sh == NULL);
319 
320 	if (sh)
321 		atomic_inc(&sh->count);
322 
323 	spin_unlock_irq(&conf->device_lock);
324 	return sh;
325 }
326 
327 static int grow_one_stripe(raid5_conf_t *conf)
328 {
329 	struct stripe_head *sh;
330 	sh = kmem_cache_alloc(conf->slab_cache, GFP_KERNEL);
331 	if (!sh)
332 		return 0;
333 	memset(sh, 0, sizeof(*sh) + (conf->raid_disks-1)*sizeof(struct r5dev));
334 	sh->raid_conf = conf;
335 	spin_lock_init(&sh->lock);
336 
337 	if (grow_buffers(sh, conf->raid_disks)) {
338 		shrink_buffers(sh, conf->raid_disks);
339 		kmem_cache_free(conf->slab_cache, sh);
340 		return 0;
341 	}
342 	sh->disks = conf->raid_disks;
343 	/* we just created an active stripe so... */
344 	atomic_set(&sh->count, 1);
345 	atomic_inc(&conf->active_stripes);
346 	INIT_LIST_HEAD(&sh->lru);
347 	release_stripe(sh);
348 	return 1;
349 }
350 
351 static int grow_stripes(raid5_conf_t *conf, int num)
352 {
353 	struct kmem_cache *sc;
354 	int devs = conf->raid_disks;
355 
356 	sprintf(conf->cache_name[0], "raid5-%s", mdname(conf->mddev));
357 	sprintf(conf->cache_name[1], "raid5-%s-alt", mdname(conf->mddev));
358 	conf->active_name = 0;
359 	sc = kmem_cache_create(conf->cache_name[conf->active_name],
360 			       sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
361 			       0, 0, NULL, NULL);
362 	if (!sc)
363 		return 1;
364 	conf->slab_cache = sc;
365 	conf->pool_size = devs;
366 	while (num--)
367 		if (!grow_one_stripe(conf))
368 			return 1;
369 	return 0;
370 }
371 
372 #ifdef CONFIG_MD_RAID5_RESHAPE
373 static int resize_stripes(raid5_conf_t *conf, int newsize)
374 {
375 	/* Make all the stripes able to hold 'newsize' devices.
376 	 * New slots in each stripe get 'page' set to a new page.
377 	 *
378 	 * This happens in stages:
379 	 * 1/ create a new kmem_cache and allocate the required number of
380 	 *    stripe_heads.
381 	 * 2/ gather all the old stripe_heads and tranfer the pages across
382 	 *    to the new stripe_heads.  This will have the side effect of
383 	 *    freezing the array as once all stripe_heads have been collected,
384 	 *    no IO will be possible.  Old stripe heads are freed once their
385 	 *    pages have been transferred over, and the old kmem_cache is
386 	 *    freed when all stripes are done.
387 	 * 3/ reallocate conf->disks to be suitable bigger.  If this fails,
388 	 *    we simple return a failre status - no need to clean anything up.
389 	 * 4/ allocate new pages for the new slots in the new stripe_heads.
390 	 *    If this fails, we don't bother trying the shrink the
391 	 *    stripe_heads down again, we just leave them as they are.
392 	 *    As each stripe_head is processed the new one is released into
393 	 *    active service.
394 	 *
395 	 * Once step2 is started, we cannot afford to wait for a write,
396 	 * so we use GFP_NOIO allocations.
397 	 */
398 	struct stripe_head *osh, *nsh;
399 	LIST_HEAD(newstripes);
400 	struct disk_info *ndisks;
401 	int err = 0;
402 	struct kmem_cache *sc;
403 	int i;
404 
405 	if (newsize <= conf->pool_size)
406 		return 0; /* never bother to shrink */
407 
408 	md_allow_write(conf->mddev);
409 
410 	/* Step 1 */
411 	sc = kmem_cache_create(conf->cache_name[1-conf->active_name],
412 			       sizeof(struct stripe_head)+(newsize-1)*sizeof(struct r5dev),
413 			       0, 0, NULL, NULL);
414 	if (!sc)
415 		return -ENOMEM;
416 
417 	for (i = conf->max_nr_stripes; i; i--) {
418 		nsh = kmem_cache_alloc(sc, GFP_KERNEL);
419 		if (!nsh)
420 			break;
421 
422 		memset(nsh, 0, sizeof(*nsh) + (newsize-1)*sizeof(struct r5dev));
423 
424 		nsh->raid_conf = conf;
425 		spin_lock_init(&nsh->lock);
426 
427 		list_add(&nsh->lru, &newstripes);
428 	}
429 	if (i) {
430 		/* didn't get enough, give up */
431 		while (!list_empty(&newstripes)) {
432 			nsh = list_entry(newstripes.next, struct stripe_head, lru);
433 			list_del(&nsh->lru);
434 			kmem_cache_free(sc, nsh);
435 		}
436 		kmem_cache_destroy(sc);
437 		return -ENOMEM;
438 	}
439 	/* Step 2 - Must use GFP_NOIO now.
440 	 * OK, we have enough stripes, start collecting inactive
441 	 * stripes and copying them over
442 	 */
443 	list_for_each_entry(nsh, &newstripes, lru) {
444 		spin_lock_irq(&conf->device_lock);
445 		wait_event_lock_irq(conf->wait_for_stripe,
446 				    !list_empty(&conf->inactive_list),
447 				    conf->device_lock,
448 				    unplug_slaves(conf->mddev)
449 			);
450 		osh = get_free_stripe(conf);
451 		spin_unlock_irq(&conf->device_lock);
452 		atomic_set(&nsh->count, 1);
453 		for(i=0; i<conf->pool_size; i++)
454 			nsh->dev[i].page = osh->dev[i].page;
455 		for( ; i<newsize; i++)
456 			nsh->dev[i].page = NULL;
457 		kmem_cache_free(conf->slab_cache, osh);
458 	}
459 	kmem_cache_destroy(conf->slab_cache);
460 
461 	/* Step 3.
462 	 * At this point, we are holding all the stripes so the array
463 	 * is completely stalled, so now is a good time to resize
464 	 * conf->disks.
465 	 */
466 	ndisks = kzalloc(newsize * sizeof(struct disk_info), GFP_NOIO);
467 	if (ndisks) {
468 		for (i=0; i<conf->raid_disks; i++)
469 			ndisks[i] = conf->disks[i];
470 		kfree(conf->disks);
471 		conf->disks = ndisks;
472 	} else
473 		err = -ENOMEM;
474 
475 	/* Step 4, return new stripes to service */
476 	while(!list_empty(&newstripes)) {
477 		nsh = list_entry(newstripes.next, struct stripe_head, lru);
478 		list_del_init(&nsh->lru);
479 		for (i=conf->raid_disks; i < newsize; i++)
480 			if (nsh->dev[i].page == NULL) {
481 				struct page *p = alloc_page(GFP_NOIO);
482 				nsh->dev[i].page = p;
483 				if (!p)
484 					err = -ENOMEM;
485 			}
486 		release_stripe(nsh);
487 	}
488 	/* critical section pass, GFP_NOIO no longer needed */
489 
490 	conf->slab_cache = sc;
491 	conf->active_name = 1-conf->active_name;
492 	conf->pool_size = newsize;
493 	return err;
494 }
495 #endif
496 
497 static int drop_one_stripe(raid5_conf_t *conf)
498 {
499 	struct stripe_head *sh;
500 
501 	spin_lock_irq(&conf->device_lock);
502 	sh = get_free_stripe(conf);
503 	spin_unlock_irq(&conf->device_lock);
504 	if (!sh)
505 		return 0;
506 	BUG_ON(atomic_read(&sh->count));
507 	shrink_buffers(sh, conf->pool_size);
508 	kmem_cache_free(conf->slab_cache, sh);
509 	atomic_dec(&conf->active_stripes);
510 	return 1;
511 }
512 
513 static void shrink_stripes(raid5_conf_t *conf)
514 {
515 	while (drop_one_stripe(conf))
516 		;
517 
518 	if (conf->slab_cache)
519 		kmem_cache_destroy(conf->slab_cache);
520 	conf->slab_cache = NULL;
521 }
522 
523 static int raid5_end_read_request(struct bio * bi, unsigned int bytes_done,
524 				   int error)
525 {
526  	struct stripe_head *sh = bi->bi_private;
527 	raid5_conf_t *conf = sh->raid_conf;
528 	int disks = sh->disks, i;
529 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
530 	char b[BDEVNAME_SIZE];
531 	mdk_rdev_t *rdev;
532 
533 	if (bi->bi_size)
534 		return 1;
535 
536 	for (i=0 ; i<disks; i++)
537 		if (bi == &sh->dev[i].req)
538 			break;
539 
540 	PRINTK("end_read_request %llu/%d, count: %d, uptodate %d.\n",
541 		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
542 		uptodate);
543 	if (i == disks) {
544 		BUG();
545 		return 0;
546 	}
547 
548 	if (uptodate) {
549 		set_bit(R5_UPTODATE, &sh->dev[i].flags);
550 		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
551 			rdev = conf->disks[i].rdev;
552 			printk(KERN_INFO "raid5:%s: read error corrected (%lu sectors at %llu on %s)\n",
553 			       mdname(conf->mddev), STRIPE_SECTORS,
554 			       (unsigned long long)sh->sector + rdev->data_offset,
555 			       bdevname(rdev->bdev, b));
556 			clear_bit(R5_ReadError, &sh->dev[i].flags);
557 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
558 		}
559 		if (atomic_read(&conf->disks[i].rdev->read_errors))
560 			atomic_set(&conf->disks[i].rdev->read_errors, 0);
561 	} else {
562 		const char *bdn = bdevname(conf->disks[i].rdev->bdev, b);
563 		int retry = 0;
564 		rdev = conf->disks[i].rdev;
565 
566 		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
567 		atomic_inc(&rdev->read_errors);
568 		if (conf->mddev->degraded)
569 			printk(KERN_WARNING "raid5:%s: read error not correctable (sector %llu on %s).\n",
570 			       mdname(conf->mddev),
571 			       (unsigned long long)sh->sector + rdev->data_offset,
572 			       bdn);
573 		else if (test_bit(R5_ReWrite, &sh->dev[i].flags))
574 			/* Oh, no!!! */
575 			printk(KERN_WARNING "raid5:%s: read error NOT corrected!! (sector %llu on %s).\n",
576 			       mdname(conf->mddev),
577 			       (unsigned long long)sh->sector + rdev->data_offset,
578 			       bdn);
579 		else if (atomic_read(&rdev->read_errors)
580 			 > conf->max_nr_stripes)
581 			printk(KERN_WARNING
582 			       "raid5:%s: Too many read errors, failing device %s.\n",
583 			       mdname(conf->mddev), bdn);
584 		else
585 			retry = 1;
586 		if (retry)
587 			set_bit(R5_ReadError, &sh->dev[i].flags);
588 		else {
589 			clear_bit(R5_ReadError, &sh->dev[i].flags);
590 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
591 			md_error(conf->mddev, rdev);
592 		}
593 	}
594 	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
595 	clear_bit(R5_LOCKED, &sh->dev[i].flags);
596 	set_bit(STRIPE_HANDLE, &sh->state);
597 	release_stripe(sh);
598 	return 0;
599 }
600 
601 static int raid5_end_write_request (struct bio *bi, unsigned int bytes_done,
602 				    int error)
603 {
604  	struct stripe_head *sh = bi->bi_private;
605 	raid5_conf_t *conf = sh->raid_conf;
606 	int disks = sh->disks, i;
607 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
608 
609 	if (bi->bi_size)
610 		return 1;
611 
612 	for (i=0 ; i<disks; i++)
613 		if (bi == &sh->dev[i].req)
614 			break;
615 
616 	PRINTK("end_write_request %llu/%d, count %d, uptodate: %d.\n",
617 		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
618 		uptodate);
619 	if (i == disks) {
620 		BUG();
621 		return 0;
622 	}
623 
624 	if (!uptodate)
625 		md_error(conf->mddev, conf->disks[i].rdev);
626 
627 	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
628 
629 	clear_bit(R5_LOCKED, &sh->dev[i].flags);
630 	set_bit(STRIPE_HANDLE, &sh->state);
631 	release_stripe(sh);
632 	return 0;
633 }
634 
635 
636 static sector_t compute_blocknr(struct stripe_head *sh, int i);
637 
638 static void raid5_build_block (struct stripe_head *sh, int i)
639 {
640 	struct r5dev *dev = &sh->dev[i];
641 
642 	bio_init(&dev->req);
643 	dev->req.bi_io_vec = &dev->vec;
644 	dev->req.bi_vcnt++;
645 	dev->req.bi_max_vecs++;
646 	dev->vec.bv_page = dev->page;
647 	dev->vec.bv_len = STRIPE_SIZE;
648 	dev->vec.bv_offset = 0;
649 
650 	dev->req.bi_sector = sh->sector;
651 	dev->req.bi_private = sh;
652 
653 	dev->flags = 0;
654 	dev->sector = compute_blocknr(sh, i);
655 }
656 
657 static void error(mddev_t *mddev, mdk_rdev_t *rdev)
658 {
659 	char b[BDEVNAME_SIZE];
660 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
661 	PRINTK("raid5: error called\n");
662 
663 	if (!test_bit(Faulty, &rdev->flags)) {
664 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
665 		if (test_and_clear_bit(In_sync, &rdev->flags)) {
666 			unsigned long flags;
667 			spin_lock_irqsave(&conf->device_lock, flags);
668 			mddev->degraded++;
669 			spin_unlock_irqrestore(&conf->device_lock, flags);
670 			/*
671 			 * if recovery was running, make sure it aborts.
672 			 */
673 			set_bit(MD_RECOVERY_ERR, &mddev->recovery);
674 		}
675 		set_bit(Faulty, &rdev->flags);
676 		printk (KERN_ALERT
677 			"raid5: Disk failure on %s, disabling device."
678 			" Operation continuing on %d devices\n",
679 			bdevname(rdev->bdev,b), conf->raid_disks - mddev->degraded);
680 	}
681 }
682 
683 /*
684  * Input: a 'big' sector number,
685  * Output: index of the data and parity disk, and the sector # in them.
686  */
687 static sector_t raid5_compute_sector(sector_t r_sector, unsigned int raid_disks,
688 			unsigned int data_disks, unsigned int * dd_idx,
689 			unsigned int * pd_idx, raid5_conf_t *conf)
690 {
691 	long stripe;
692 	unsigned long chunk_number;
693 	unsigned int chunk_offset;
694 	sector_t new_sector;
695 	int sectors_per_chunk = conf->chunk_size >> 9;
696 
697 	/* First compute the information on this sector */
698 
699 	/*
700 	 * Compute the chunk number and the sector offset inside the chunk
701 	 */
702 	chunk_offset = sector_div(r_sector, sectors_per_chunk);
703 	chunk_number = r_sector;
704 	BUG_ON(r_sector != chunk_number);
705 
706 	/*
707 	 * Compute the stripe number
708 	 */
709 	stripe = chunk_number / data_disks;
710 
711 	/*
712 	 * Compute the data disk and parity disk indexes inside the stripe
713 	 */
714 	*dd_idx = chunk_number % data_disks;
715 
716 	/*
717 	 * Select the parity disk based on the user selected algorithm.
718 	 */
719 	switch(conf->level) {
720 	case 4:
721 		*pd_idx = data_disks;
722 		break;
723 	case 5:
724 		switch (conf->algorithm) {
725 		case ALGORITHM_LEFT_ASYMMETRIC:
726 			*pd_idx = data_disks - stripe % raid_disks;
727 			if (*dd_idx >= *pd_idx)
728 				(*dd_idx)++;
729 			break;
730 		case ALGORITHM_RIGHT_ASYMMETRIC:
731 			*pd_idx = stripe % raid_disks;
732 			if (*dd_idx >= *pd_idx)
733 				(*dd_idx)++;
734 			break;
735 		case ALGORITHM_LEFT_SYMMETRIC:
736 			*pd_idx = data_disks - stripe % raid_disks;
737 			*dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;
738 			break;
739 		case ALGORITHM_RIGHT_SYMMETRIC:
740 			*pd_idx = stripe % raid_disks;
741 			*dd_idx = (*pd_idx + 1 + *dd_idx) % raid_disks;
742 			break;
743 		default:
744 			printk(KERN_ERR "raid5: unsupported algorithm %d\n",
745 				conf->algorithm);
746 		}
747 		break;
748 	case 6:
749 
750 		/**** FIX THIS ****/
751 		switch (conf->algorithm) {
752 		case ALGORITHM_LEFT_ASYMMETRIC:
753 			*pd_idx = raid_disks - 1 - (stripe % raid_disks);
754 			if (*pd_idx == raid_disks-1)
755 				(*dd_idx)++; 	/* Q D D D P */
756 			else if (*dd_idx >= *pd_idx)
757 				(*dd_idx) += 2; /* D D P Q D */
758 			break;
759 		case ALGORITHM_RIGHT_ASYMMETRIC:
760 			*pd_idx = stripe % raid_disks;
761 			if (*pd_idx == raid_disks-1)
762 				(*dd_idx)++; 	/* Q D D D P */
763 			else if (*dd_idx >= *pd_idx)
764 				(*dd_idx) += 2; /* D D P Q D */
765 			break;
766 		case ALGORITHM_LEFT_SYMMETRIC:
767 			*pd_idx = raid_disks - 1 - (stripe % raid_disks);
768 			*dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
769 			break;
770 		case ALGORITHM_RIGHT_SYMMETRIC:
771 			*pd_idx = stripe % raid_disks;
772 			*dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
773 			break;
774 		default:
775 			printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
776 				conf->algorithm);
777 		}
778 		break;
779 	}
780 
781 	/*
782 	 * Finally, compute the new sector number
783 	 */
784 	new_sector = (sector_t)stripe * sectors_per_chunk + chunk_offset;
785 	return new_sector;
786 }
787 
788 
789 static sector_t compute_blocknr(struct stripe_head *sh, int i)
790 {
791 	raid5_conf_t *conf = sh->raid_conf;
792 	int raid_disks = sh->disks;
793 	int data_disks = raid_disks - conf->max_degraded;
794 	sector_t new_sector = sh->sector, check;
795 	int sectors_per_chunk = conf->chunk_size >> 9;
796 	sector_t stripe;
797 	int chunk_offset;
798 	int chunk_number, dummy1, dummy2, dd_idx = i;
799 	sector_t r_sector;
800 
801 
802 	chunk_offset = sector_div(new_sector, sectors_per_chunk);
803 	stripe = new_sector;
804 	BUG_ON(new_sector != stripe);
805 
806 	if (i == sh->pd_idx)
807 		return 0;
808 	switch(conf->level) {
809 	case 4: break;
810 	case 5:
811 		switch (conf->algorithm) {
812 		case ALGORITHM_LEFT_ASYMMETRIC:
813 		case ALGORITHM_RIGHT_ASYMMETRIC:
814 			if (i > sh->pd_idx)
815 				i--;
816 			break;
817 		case ALGORITHM_LEFT_SYMMETRIC:
818 		case ALGORITHM_RIGHT_SYMMETRIC:
819 			if (i < sh->pd_idx)
820 				i += raid_disks;
821 			i -= (sh->pd_idx + 1);
822 			break;
823 		default:
824 			printk(KERN_ERR "raid5: unsupported algorithm %d\n",
825 			       conf->algorithm);
826 		}
827 		break;
828 	case 6:
829 		if (i == raid6_next_disk(sh->pd_idx, raid_disks))
830 			return 0; /* It is the Q disk */
831 		switch (conf->algorithm) {
832 		case ALGORITHM_LEFT_ASYMMETRIC:
833 		case ALGORITHM_RIGHT_ASYMMETRIC:
834 		  	if (sh->pd_idx == raid_disks-1)
835 				i--; 	/* Q D D D P */
836 			else if (i > sh->pd_idx)
837 				i -= 2; /* D D P Q D */
838 			break;
839 		case ALGORITHM_LEFT_SYMMETRIC:
840 		case ALGORITHM_RIGHT_SYMMETRIC:
841 			if (sh->pd_idx == raid_disks-1)
842 				i--; /* Q D D D P */
843 			else {
844 				/* D D P Q D */
845 				if (i < sh->pd_idx)
846 					i += raid_disks;
847 				i -= (sh->pd_idx + 2);
848 			}
849 			break;
850 		default:
851 			printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
852 				conf->algorithm);
853 		}
854 		break;
855 	}
856 
857 	chunk_number = stripe * data_disks + i;
858 	r_sector = (sector_t)chunk_number * sectors_per_chunk + chunk_offset;
859 
860 	check = raid5_compute_sector (r_sector, raid_disks, data_disks, &dummy1, &dummy2, conf);
861 	if (check != sh->sector || dummy1 != dd_idx || dummy2 != sh->pd_idx) {
862 		printk(KERN_ERR "compute_blocknr: map not correct\n");
863 		return 0;
864 	}
865 	return r_sector;
866 }
867 
868 
869 
870 /*
871  * Copy data between a page in the stripe cache, and one or more bion
872  * The page could align with the middle of the bio, or there could be
873  * several bion, each with several bio_vecs, which cover part of the page
874  * Multiple bion are linked together on bi_next.  There may be extras
875  * at the end of this list.  We ignore them.
876  */
877 static void copy_data(int frombio, struct bio *bio,
878 		     struct page *page,
879 		     sector_t sector)
880 {
881 	char *pa = page_address(page);
882 	struct bio_vec *bvl;
883 	int i;
884 	int page_offset;
885 
886 	if (bio->bi_sector >= sector)
887 		page_offset = (signed)(bio->bi_sector - sector) * 512;
888 	else
889 		page_offset = (signed)(sector - bio->bi_sector) * -512;
890 	bio_for_each_segment(bvl, bio, i) {
891 		int len = bio_iovec_idx(bio,i)->bv_len;
892 		int clen;
893 		int b_offset = 0;
894 
895 		if (page_offset < 0) {
896 			b_offset = -page_offset;
897 			page_offset += b_offset;
898 			len -= b_offset;
899 		}
900 
901 		if (len > 0 && page_offset + len > STRIPE_SIZE)
902 			clen = STRIPE_SIZE - page_offset;
903 		else clen = len;
904 
905 		if (clen > 0) {
906 			char *ba = __bio_kmap_atomic(bio, i, KM_USER0);
907 			if (frombio)
908 				memcpy(pa+page_offset, ba+b_offset, clen);
909 			else
910 				memcpy(ba+b_offset, pa+page_offset, clen);
911 			__bio_kunmap_atomic(ba, KM_USER0);
912 		}
913 		if (clen < len) /* hit end of page */
914 			break;
915 		page_offset +=  len;
916 	}
917 }
918 
919 #define check_xor() 	do { 						\
920 			   if (count == MAX_XOR_BLOCKS) {		\
921 				xor_block(count, STRIPE_SIZE, ptr);	\
922 				count = 1;				\
923 			   }						\
924 			} while(0)
925 
926 
927 static void compute_block(struct stripe_head *sh, int dd_idx)
928 {
929 	int i, count, disks = sh->disks;
930 	void *ptr[MAX_XOR_BLOCKS], *p;
931 
932 	PRINTK("compute_block, stripe %llu, idx %d\n",
933 		(unsigned long long)sh->sector, dd_idx);
934 
935 	ptr[0] = page_address(sh->dev[dd_idx].page);
936 	memset(ptr[0], 0, STRIPE_SIZE);
937 	count = 1;
938 	for (i = disks ; i--; ) {
939 		if (i == dd_idx)
940 			continue;
941 		p = page_address(sh->dev[i].page);
942 		if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
943 			ptr[count++] = p;
944 		else
945 			printk(KERN_ERR "compute_block() %d, stripe %llu, %d"
946 				" not present\n", dd_idx,
947 				(unsigned long long)sh->sector, i);
948 
949 		check_xor();
950 	}
951 	if (count != 1)
952 		xor_block(count, STRIPE_SIZE, ptr);
953 	set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
954 }
955 
956 static void compute_parity5(struct stripe_head *sh, int method)
957 {
958 	raid5_conf_t *conf = sh->raid_conf;
959 	int i, pd_idx = sh->pd_idx, disks = sh->disks, count;
960 	void *ptr[MAX_XOR_BLOCKS];
961 	struct bio *chosen;
962 
963 	PRINTK("compute_parity5, stripe %llu, method %d\n",
964 		(unsigned long long)sh->sector, method);
965 
966 	count = 1;
967 	ptr[0] = page_address(sh->dev[pd_idx].page);
968 	switch(method) {
969 	case READ_MODIFY_WRITE:
970 		BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags));
971 		for (i=disks ; i-- ;) {
972 			if (i==pd_idx)
973 				continue;
974 			if (sh->dev[i].towrite &&
975 			    test_bit(R5_UPTODATE, &sh->dev[i].flags)) {
976 				ptr[count++] = page_address(sh->dev[i].page);
977 				chosen = sh->dev[i].towrite;
978 				sh->dev[i].towrite = NULL;
979 
980 				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
981 					wake_up(&conf->wait_for_overlap);
982 
983 				BUG_ON(sh->dev[i].written);
984 				sh->dev[i].written = chosen;
985 				check_xor();
986 			}
987 		}
988 		break;
989 	case RECONSTRUCT_WRITE:
990 		memset(ptr[0], 0, STRIPE_SIZE);
991 		for (i= disks; i-- ;)
992 			if (i!=pd_idx && sh->dev[i].towrite) {
993 				chosen = sh->dev[i].towrite;
994 				sh->dev[i].towrite = NULL;
995 
996 				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
997 					wake_up(&conf->wait_for_overlap);
998 
999 				BUG_ON(sh->dev[i].written);
1000 				sh->dev[i].written = chosen;
1001 			}
1002 		break;
1003 	case CHECK_PARITY:
1004 		break;
1005 	}
1006 	if (count>1) {
1007 		xor_block(count, STRIPE_SIZE, ptr);
1008 		count = 1;
1009 	}
1010 
1011 	for (i = disks; i--;)
1012 		if (sh->dev[i].written) {
1013 			sector_t sector = sh->dev[i].sector;
1014 			struct bio *wbi = sh->dev[i].written;
1015 			while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
1016 				copy_data(1, wbi, sh->dev[i].page, sector);
1017 				wbi = r5_next_bio(wbi, sector);
1018 			}
1019 
1020 			set_bit(R5_LOCKED, &sh->dev[i].flags);
1021 			set_bit(R5_UPTODATE, &sh->dev[i].flags);
1022 		}
1023 
1024 	switch(method) {
1025 	case RECONSTRUCT_WRITE:
1026 	case CHECK_PARITY:
1027 		for (i=disks; i--;)
1028 			if (i != pd_idx) {
1029 				ptr[count++] = page_address(sh->dev[i].page);
1030 				check_xor();
1031 			}
1032 		break;
1033 	case READ_MODIFY_WRITE:
1034 		for (i = disks; i--;)
1035 			if (sh->dev[i].written) {
1036 				ptr[count++] = page_address(sh->dev[i].page);
1037 				check_xor();
1038 			}
1039 	}
1040 	if (count != 1)
1041 		xor_block(count, STRIPE_SIZE, ptr);
1042 
1043 	if (method != CHECK_PARITY) {
1044 		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1045 		set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
1046 	} else
1047 		clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1048 }
1049 
1050 static void compute_parity6(struct stripe_head *sh, int method)
1051 {
1052 	raid6_conf_t *conf = sh->raid_conf;
1053 	int i, pd_idx = sh->pd_idx, qd_idx, d0_idx, disks = sh->disks, count;
1054 	struct bio *chosen;
1055 	/**** FIX THIS: This could be very bad if disks is close to 256 ****/
1056 	void *ptrs[disks];
1057 
1058 	qd_idx = raid6_next_disk(pd_idx, disks);
1059 	d0_idx = raid6_next_disk(qd_idx, disks);
1060 
1061 	PRINTK("compute_parity, stripe %llu, method %d\n",
1062 		(unsigned long long)sh->sector, method);
1063 
1064 	switch(method) {
1065 	case READ_MODIFY_WRITE:
1066 		BUG();		/* READ_MODIFY_WRITE N/A for RAID-6 */
1067 	case RECONSTRUCT_WRITE:
1068 		for (i= disks; i-- ;)
1069 			if ( i != pd_idx && i != qd_idx && sh->dev[i].towrite ) {
1070 				chosen = sh->dev[i].towrite;
1071 				sh->dev[i].towrite = NULL;
1072 
1073 				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1074 					wake_up(&conf->wait_for_overlap);
1075 
1076 				BUG_ON(sh->dev[i].written);
1077 				sh->dev[i].written = chosen;
1078 			}
1079 		break;
1080 	case CHECK_PARITY:
1081 		BUG();		/* Not implemented yet */
1082 	}
1083 
1084 	for (i = disks; i--;)
1085 		if (sh->dev[i].written) {
1086 			sector_t sector = sh->dev[i].sector;
1087 			struct bio *wbi = sh->dev[i].written;
1088 			while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
1089 				copy_data(1, wbi, sh->dev[i].page, sector);
1090 				wbi = r5_next_bio(wbi, sector);
1091 			}
1092 
1093 			set_bit(R5_LOCKED, &sh->dev[i].flags);
1094 			set_bit(R5_UPTODATE, &sh->dev[i].flags);
1095 		}
1096 
1097 //	switch(method) {
1098 //	case RECONSTRUCT_WRITE:
1099 //	case CHECK_PARITY:
1100 //	case UPDATE_PARITY:
1101 		/* Note that unlike RAID-5, the ordering of the disks matters greatly. */
1102 		/* FIX: Is this ordering of drives even remotely optimal? */
1103 		count = 0;
1104 		i = d0_idx;
1105 		do {
1106 			ptrs[count++] = page_address(sh->dev[i].page);
1107 			if (count <= disks-2 && !test_bit(R5_UPTODATE, &sh->dev[i].flags))
1108 				printk("block %d/%d not uptodate on parity calc\n", i,count);
1109 			i = raid6_next_disk(i, disks);
1110 		} while ( i != d0_idx );
1111 //		break;
1112 //	}
1113 
1114 	raid6_call.gen_syndrome(disks, STRIPE_SIZE, ptrs);
1115 
1116 	switch(method) {
1117 	case RECONSTRUCT_WRITE:
1118 		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1119 		set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
1120 		set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
1121 		set_bit(R5_LOCKED,   &sh->dev[qd_idx].flags);
1122 		break;
1123 	case UPDATE_PARITY:
1124 		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
1125 		set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
1126 		break;
1127 	}
1128 }
1129 
1130 
1131 /* Compute one missing block */
1132 static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
1133 {
1134 	int i, count, disks = sh->disks;
1135 	void *ptr[MAX_XOR_BLOCKS], *p;
1136 	int pd_idx = sh->pd_idx;
1137 	int qd_idx = raid6_next_disk(pd_idx, disks);
1138 
1139 	PRINTK("compute_block_1, stripe %llu, idx %d\n",
1140 		(unsigned long long)sh->sector, dd_idx);
1141 
1142 	if ( dd_idx == qd_idx ) {
1143 		/* We're actually computing the Q drive */
1144 		compute_parity6(sh, UPDATE_PARITY);
1145 	} else {
1146 		ptr[0] = page_address(sh->dev[dd_idx].page);
1147 		if (!nozero) memset(ptr[0], 0, STRIPE_SIZE);
1148 		count = 1;
1149 		for (i = disks ; i--; ) {
1150 			if (i == dd_idx || i == qd_idx)
1151 				continue;
1152 			p = page_address(sh->dev[i].page);
1153 			if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
1154 				ptr[count++] = p;
1155 			else
1156 				printk("compute_block() %d, stripe %llu, %d"
1157 				       " not present\n", dd_idx,
1158 				       (unsigned long long)sh->sector, i);
1159 
1160 			check_xor();
1161 		}
1162 		if (count != 1)
1163 			xor_block(count, STRIPE_SIZE, ptr);
1164 		if (!nozero) set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
1165 		else clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
1166 	}
1167 }
1168 
1169 /* Compute two missing blocks */
1170 static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
1171 {
1172 	int i, count, disks = sh->disks;
1173 	int pd_idx = sh->pd_idx;
1174 	int qd_idx = raid6_next_disk(pd_idx, disks);
1175 	int d0_idx = raid6_next_disk(qd_idx, disks);
1176 	int faila, failb;
1177 
1178 	/* faila and failb are disk numbers relative to d0_idx */
1179 	/* pd_idx become disks-2 and qd_idx become disks-1 */
1180 	faila = (dd_idx1 < d0_idx) ? dd_idx1+(disks-d0_idx) : dd_idx1-d0_idx;
1181 	failb = (dd_idx2 < d0_idx) ? dd_idx2+(disks-d0_idx) : dd_idx2-d0_idx;
1182 
1183 	BUG_ON(faila == failb);
1184 	if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
1185 
1186 	PRINTK("compute_block_2, stripe %llu, idx %d,%d (%d,%d)\n",
1187 	       (unsigned long long)sh->sector, dd_idx1, dd_idx2, faila, failb);
1188 
1189 	if ( failb == disks-1 ) {
1190 		/* Q disk is one of the missing disks */
1191 		if ( faila == disks-2 ) {
1192 			/* Missing P+Q, just recompute */
1193 			compute_parity6(sh, UPDATE_PARITY);
1194 			return;
1195 		} else {
1196 			/* We're missing D+Q; recompute D from P */
1197 			compute_block_1(sh, (dd_idx1 == qd_idx) ? dd_idx2 : dd_idx1, 0);
1198 			compute_parity6(sh, UPDATE_PARITY); /* Is this necessary? */
1199 			return;
1200 		}
1201 	}
1202 
1203 	/* We're missing D+P or D+D; build pointer table */
1204 	{
1205 		/**** FIX THIS: This could be very bad if disks is close to 256 ****/
1206 		void *ptrs[disks];
1207 
1208 		count = 0;
1209 		i = d0_idx;
1210 		do {
1211 			ptrs[count++] = page_address(sh->dev[i].page);
1212 			i = raid6_next_disk(i, disks);
1213 			if (i != dd_idx1 && i != dd_idx2 &&
1214 			    !test_bit(R5_UPTODATE, &sh->dev[i].flags))
1215 				printk("compute_2 with missing block %d/%d\n", count, i);
1216 		} while ( i != d0_idx );
1217 
1218 		if ( failb == disks-2 ) {
1219 			/* We're missing D+P. */
1220 			raid6_datap_recov(disks, STRIPE_SIZE, faila, ptrs);
1221 		} else {
1222 			/* We're missing D+D. */
1223 			raid6_2data_recov(disks, STRIPE_SIZE, faila, failb, ptrs);
1224 		}
1225 
1226 		/* Both the above update both missing blocks */
1227 		set_bit(R5_UPTODATE, &sh->dev[dd_idx1].flags);
1228 		set_bit(R5_UPTODATE, &sh->dev[dd_idx2].flags);
1229 	}
1230 }
1231 
1232 
1233 
1234 /*
1235  * Each stripe/dev can have one or more bion attached.
1236  * toread/towrite point to the first in a chain.
1237  * The bi_next chain must be in order.
1238  */
1239 static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, int forwrite)
1240 {
1241 	struct bio **bip;
1242 	raid5_conf_t *conf = sh->raid_conf;
1243 	int firstwrite=0;
1244 
1245 	PRINTK("adding bh b#%llu to stripe s#%llu\n",
1246 		(unsigned long long)bi->bi_sector,
1247 		(unsigned long long)sh->sector);
1248 
1249 
1250 	spin_lock(&sh->lock);
1251 	spin_lock_irq(&conf->device_lock);
1252 	if (forwrite) {
1253 		bip = &sh->dev[dd_idx].towrite;
1254 		if (*bip == NULL && sh->dev[dd_idx].written == NULL)
1255 			firstwrite = 1;
1256 	} else
1257 		bip = &sh->dev[dd_idx].toread;
1258 	while (*bip && (*bip)->bi_sector < bi->bi_sector) {
1259 		if ((*bip)->bi_sector + ((*bip)->bi_size >> 9) > bi->bi_sector)
1260 			goto overlap;
1261 		bip = & (*bip)->bi_next;
1262 	}
1263 	if (*bip && (*bip)->bi_sector < bi->bi_sector + ((bi->bi_size)>>9))
1264 		goto overlap;
1265 
1266 	BUG_ON(*bip && bi->bi_next && (*bip) != bi->bi_next);
1267 	if (*bip)
1268 		bi->bi_next = *bip;
1269 	*bip = bi;
1270 	bi->bi_phys_segments ++;
1271 	spin_unlock_irq(&conf->device_lock);
1272 	spin_unlock(&sh->lock);
1273 
1274 	PRINTK("added bi b#%llu to stripe s#%llu, disk %d.\n",
1275 		(unsigned long long)bi->bi_sector,
1276 		(unsigned long long)sh->sector, dd_idx);
1277 
1278 	if (conf->mddev->bitmap && firstwrite) {
1279 		bitmap_startwrite(conf->mddev->bitmap, sh->sector,
1280 				  STRIPE_SECTORS, 0);
1281 		sh->bm_seq = conf->seq_flush+1;
1282 		set_bit(STRIPE_BIT_DELAY, &sh->state);
1283 	}
1284 
1285 	if (forwrite) {
1286 		/* check if page is covered */
1287 		sector_t sector = sh->dev[dd_idx].sector;
1288 		for (bi=sh->dev[dd_idx].towrite;
1289 		     sector < sh->dev[dd_idx].sector + STRIPE_SECTORS &&
1290 			     bi && bi->bi_sector <= sector;
1291 		     bi = r5_next_bio(bi, sh->dev[dd_idx].sector)) {
1292 			if (bi->bi_sector + (bi->bi_size>>9) >= sector)
1293 				sector = bi->bi_sector + (bi->bi_size>>9);
1294 		}
1295 		if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
1296 			set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
1297 	}
1298 	return 1;
1299 
1300  overlap:
1301 	set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
1302 	spin_unlock_irq(&conf->device_lock);
1303 	spin_unlock(&sh->lock);
1304 	return 0;
1305 }
1306 
1307 static void end_reshape(raid5_conf_t *conf);
1308 
1309 static int page_is_zero(struct page *p)
1310 {
1311 	char *a = page_address(p);
1312 	return ((*(u32*)a) == 0 &&
1313 		memcmp(a, a+4, STRIPE_SIZE-4)==0);
1314 }
1315 
1316 static int stripe_to_pdidx(sector_t stripe, raid5_conf_t *conf, int disks)
1317 {
1318 	int sectors_per_chunk = conf->chunk_size >> 9;
1319 	int pd_idx, dd_idx;
1320 	int chunk_offset = sector_div(stripe, sectors_per_chunk);
1321 
1322 	raid5_compute_sector(stripe * (disks - conf->max_degraded)
1323 			     *sectors_per_chunk + chunk_offset,
1324 			     disks, disks - conf->max_degraded,
1325 			     &dd_idx, &pd_idx, conf);
1326 	return pd_idx;
1327 }
1328 
1329 
1330 /*
1331  * handle_stripe - do things to a stripe.
1332  *
1333  * We lock the stripe and then examine the state of various bits
1334  * to see what needs to be done.
1335  * Possible results:
1336  *    return some read request which now have data
1337  *    return some write requests which are safely on disc
1338  *    schedule a read on some buffers
1339  *    schedule a write of some buffers
1340  *    return confirmation of parity correctness
1341  *
1342  * Parity calculations are done inside the stripe lock
1343  * buffers are taken off read_list or write_list, and bh_cache buffers
1344  * get BH_Lock set before the stripe lock is released.
1345  *
1346  */
1347 
1348 static void handle_stripe5(struct stripe_head *sh)
1349 {
1350 	raid5_conf_t *conf = sh->raid_conf;
1351 	int disks = sh->disks;
1352 	struct bio *return_bi= NULL;
1353 	struct bio *bi;
1354 	int i;
1355 	int syncing, expanding, expanded;
1356 	int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
1357 	int non_overwrite = 0;
1358 	int failed_num=0;
1359 	struct r5dev *dev;
1360 
1361 	PRINTK("handling stripe %llu, cnt=%d, pd_idx=%d\n",
1362 		(unsigned long long)sh->sector, atomic_read(&sh->count),
1363 		sh->pd_idx);
1364 
1365 	spin_lock(&sh->lock);
1366 	clear_bit(STRIPE_HANDLE, &sh->state);
1367 	clear_bit(STRIPE_DELAYED, &sh->state);
1368 
1369 	syncing = test_bit(STRIPE_SYNCING, &sh->state);
1370 	expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
1371 	expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
1372 	/* Now to look around and see what can be done */
1373 
1374 	rcu_read_lock();
1375 	for (i=disks; i--; ) {
1376 		mdk_rdev_t *rdev;
1377 		dev = &sh->dev[i];
1378 		clear_bit(R5_Insync, &dev->flags);
1379 
1380 		PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
1381 			i, dev->flags, dev->toread, dev->towrite, dev->written);
1382 		/* maybe we can reply to a read */
1383 		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
1384 			struct bio *rbi, *rbi2;
1385 			PRINTK("Return read for disc %d\n", i);
1386 			spin_lock_irq(&conf->device_lock);
1387 			rbi = dev->toread;
1388 			dev->toread = NULL;
1389 			if (test_and_clear_bit(R5_Overlap, &dev->flags))
1390 				wake_up(&conf->wait_for_overlap);
1391 			spin_unlock_irq(&conf->device_lock);
1392 			while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
1393 				copy_data(0, rbi, dev->page, dev->sector);
1394 				rbi2 = r5_next_bio(rbi, dev->sector);
1395 				spin_lock_irq(&conf->device_lock);
1396 				if (--rbi->bi_phys_segments == 0) {
1397 					rbi->bi_next = return_bi;
1398 					return_bi = rbi;
1399 				}
1400 				spin_unlock_irq(&conf->device_lock);
1401 				rbi = rbi2;
1402 			}
1403 		}
1404 
1405 		/* now count some things */
1406 		if (test_bit(R5_LOCKED, &dev->flags)) locked++;
1407 		if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
1408 
1409 
1410 		if (dev->toread) to_read++;
1411 		if (dev->towrite) {
1412 			to_write++;
1413 			if (!test_bit(R5_OVERWRITE, &dev->flags))
1414 				non_overwrite++;
1415 		}
1416 		if (dev->written) written++;
1417 		rdev = rcu_dereference(conf->disks[i].rdev);
1418 		if (!rdev || !test_bit(In_sync, &rdev->flags)) {
1419 			/* The ReadError flag will just be confusing now */
1420 			clear_bit(R5_ReadError, &dev->flags);
1421 			clear_bit(R5_ReWrite, &dev->flags);
1422 		}
1423 		if (!rdev || !test_bit(In_sync, &rdev->flags)
1424 		    || test_bit(R5_ReadError, &dev->flags)) {
1425 			failed++;
1426 			failed_num = i;
1427 		} else
1428 			set_bit(R5_Insync, &dev->flags);
1429 	}
1430 	rcu_read_unlock();
1431 	PRINTK("locked=%d uptodate=%d to_read=%d"
1432 		" to_write=%d failed=%d failed_num=%d\n",
1433 		locked, uptodate, to_read, to_write, failed, failed_num);
1434 	/* check if the array has lost two devices and, if so, some requests might
1435 	 * need to be failed
1436 	 */
1437 	if (failed > 1 && to_read+to_write+written) {
1438 		for (i=disks; i--; ) {
1439 			int bitmap_end = 0;
1440 
1441 			if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
1442 				mdk_rdev_t *rdev;
1443 				rcu_read_lock();
1444 				rdev = rcu_dereference(conf->disks[i].rdev);
1445 				if (rdev && test_bit(In_sync, &rdev->flags))
1446 					/* multiple read failures in one stripe */
1447 					md_error(conf->mddev, rdev);
1448 				rcu_read_unlock();
1449 			}
1450 
1451 			spin_lock_irq(&conf->device_lock);
1452 			/* fail all writes first */
1453 			bi = sh->dev[i].towrite;
1454 			sh->dev[i].towrite = NULL;
1455 			if (bi) { to_write--; bitmap_end = 1; }
1456 
1457 			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1458 				wake_up(&conf->wait_for_overlap);
1459 
1460 			while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
1461 				struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
1462 				clear_bit(BIO_UPTODATE, &bi->bi_flags);
1463 				if (--bi->bi_phys_segments == 0) {
1464 					md_write_end(conf->mddev);
1465 					bi->bi_next = return_bi;
1466 					return_bi = bi;
1467 				}
1468 				bi = nextbi;
1469 			}
1470 			/* and fail all 'written' */
1471 			bi = sh->dev[i].written;
1472 			sh->dev[i].written = NULL;
1473 			if (bi) bitmap_end = 1;
1474 			while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS) {
1475 				struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
1476 				clear_bit(BIO_UPTODATE, &bi->bi_flags);
1477 				if (--bi->bi_phys_segments == 0) {
1478 					md_write_end(conf->mddev);
1479 					bi->bi_next = return_bi;
1480 					return_bi = bi;
1481 				}
1482 				bi = bi2;
1483 			}
1484 
1485 			/* fail any reads if this device is non-operational */
1486 			if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
1487 			    test_bit(R5_ReadError, &sh->dev[i].flags)) {
1488 				bi = sh->dev[i].toread;
1489 				sh->dev[i].toread = NULL;
1490 				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1491 					wake_up(&conf->wait_for_overlap);
1492 				if (bi) to_read--;
1493 				while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
1494 					struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
1495 					clear_bit(BIO_UPTODATE, &bi->bi_flags);
1496 					if (--bi->bi_phys_segments == 0) {
1497 						bi->bi_next = return_bi;
1498 						return_bi = bi;
1499 					}
1500 					bi = nextbi;
1501 				}
1502 			}
1503 			spin_unlock_irq(&conf->device_lock);
1504 			if (bitmap_end)
1505 				bitmap_endwrite(conf->mddev->bitmap, sh->sector,
1506 						STRIPE_SECTORS, 0, 0);
1507 		}
1508 	}
1509 	if (failed > 1 && syncing) {
1510 		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
1511 		clear_bit(STRIPE_SYNCING, &sh->state);
1512 		syncing = 0;
1513 	}
1514 
1515 	/* might be able to return some write requests if the parity block
1516 	 * is safe, or on a failed drive
1517 	 */
1518 	dev = &sh->dev[sh->pd_idx];
1519 	if ( written &&
1520 	     ( (test_bit(R5_Insync, &dev->flags) && !test_bit(R5_LOCKED, &dev->flags) &&
1521 		test_bit(R5_UPTODATE, &dev->flags))
1522 	       || (failed == 1 && failed_num == sh->pd_idx))
1523 	    ) {
1524 	    /* any written block on an uptodate or failed drive can be returned.
1525 	     * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but
1526 	     * never LOCKED, so we don't need to test 'failed' directly.
1527 	     */
1528 	    for (i=disks; i--; )
1529 		if (sh->dev[i].written) {
1530 		    dev = &sh->dev[i];
1531 		    if (!test_bit(R5_LOCKED, &dev->flags) &&
1532 			 test_bit(R5_UPTODATE, &dev->flags) ) {
1533 			/* We can return any write requests */
1534 			    struct bio *wbi, *wbi2;
1535 			    int bitmap_end = 0;
1536 			    PRINTK("Return write for disc %d\n", i);
1537 			    spin_lock_irq(&conf->device_lock);
1538 			    wbi = dev->written;
1539 			    dev->written = NULL;
1540 			    while (wbi && wbi->bi_sector < dev->sector + STRIPE_SECTORS) {
1541 				    wbi2 = r5_next_bio(wbi, dev->sector);
1542 				    if (--wbi->bi_phys_segments == 0) {
1543 					    md_write_end(conf->mddev);
1544 					    wbi->bi_next = return_bi;
1545 					    return_bi = wbi;
1546 				    }
1547 				    wbi = wbi2;
1548 			    }
1549 			    if (dev->towrite == NULL)
1550 				    bitmap_end = 1;
1551 			    spin_unlock_irq(&conf->device_lock);
1552 			    if (bitmap_end)
1553 				    bitmap_endwrite(conf->mddev->bitmap, sh->sector,
1554 						    STRIPE_SECTORS,
1555 						    !test_bit(STRIPE_DEGRADED, &sh->state), 0);
1556 		    }
1557 		}
1558 	}
1559 
1560 	/* Now we might consider reading some blocks, either to check/generate
1561 	 * parity, or to satisfy requests
1562 	 * or to load a block that is being partially written.
1563 	 */
1564 	if (to_read || non_overwrite || (syncing && (uptodate < disks)) || expanding) {
1565 		for (i=disks; i--;) {
1566 			dev = &sh->dev[i];
1567 			if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
1568 			    (dev->toread ||
1569 			     (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
1570 			     syncing ||
1571 			     expanding ||
1572 			     (failed && (sh->dev[failed_num].toread ||
1573 					 (sh->dev[failed_num].towrite && !test_bit(R5_OVERWRITE, &sh->dev[failed_num].flags))))
1574 				    )
1575 				) {
1576 				/* we would like to get this block, possibly
1577 				 * by computing it, but we might not be able to
1578 				 */
1579 				if (uptodate == disks-1) {
1580 					PRINTK("Computing block %d\n", i);
1581 					compute_block(sh, i);
1582 					uptodate++;
1583 				} else if (test_bit(R5_Insync, &dev->flags)) {
1584 					set_bit(R5_LOCKED, &dev->flags);
1585 					set_bit(R5_Wantread, &dev->flags);
1586 					locked++;
1587 					PRINTK("Reading block %d (sync=%d)\n",
1588 						i, syncing);
1589 				}
1590 			}
1591 		}
1592 		set_bit(STRIPE_HANDLE, &sh->state);
1593 	}
1594 
1595 	/* now to consider writing and what else, if anything should be read */
1596 	if (to_write) {
1597 		int rmw=0, rcw=0;
1598 		for (i=disks ; i--;) {
1599 			/* would I have to read this buffer for read_modify_write */
1600 			dev = &sh->dev[i];
1601 			if ((dev->towrite || i == sh->pd_idx) &&
1602 			    (!test_bit(R5_LOCKED, &dev->flags)
1603 				    ) &&
1604 			    !test_bit(R5_UPTODATE, &dev->flags)) {
1605 				if (test_bit(R5_Insync, &dev->flags)
1606 /*				    && !(!mddev->insync && i == sh->pd_idx) */
1607 					)
1608 					rmw++;
1609 				else rmw += 2*disks;  /* cannot read it */
1610 			}
1611 			/* Would I have to read this buffer for reconstruct_write */
1612 			if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
1613 			    (!test_bit(R5_LOCKED, &dev->flags)
1614 				    ) &&
1615 			    !test_bit(R5_UPTODATE, &dev->flags)) {
1616 				if (test_bit(R5_Insync, &dev->flags)) rcw++;
1617 				else rcw += 2*disks;
1618 			}
1619 		}
1620 		PRINTK("for sector %llu, rmw=%d rcw=%d\n",
1621 			(unsigned long long)sh->sector, rmw, rcw);
1622 		set_bit(STRIPE_HANDLE, &sh->state);
1623 		if (rmw < rcw && rmw > 0)
1624 			/* prefer read-modify-write, but need to get some data */
1625 			for (i=disks; i--;) {
1626 				dev = &sh->dev[i];
1627 				if ((dev->towrite || i == sh->pd_idx) &&
1628 				    !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
1629 				    test_bit(R5_Insync, &dev->flags)) {
1630 					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
1631 					{
1632 						PRINTK("Read_old block %d for r-m-w\n", i);
1633 						set_bit(R5_LOCKED, &dev->flags);
1634 						set_bit(R5_Wantread, &dev->flags);
1635 						locked++;
1636 					} else {
1637 						set_bit(STRIPE_DELAYED, &sh->state);
1638 						set_bit(STRIPE_HANDLE, &sh->state);
1639 					}
1640 				}
1641 			}
1642 		if (rcw <= rmw && rcw > 0)
1643 			/* want reconstruct write, but need to get some data */
1644 			for (i=disks; i--;) {
1645 				dev = &sh->dev[i];
1646 				if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
1647 				    !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
1648 				    test_bit(R5_Insync, &dev->flags)) {
1649 					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
1650 					{
1651 						PRINTK("Read_old block %d for Reconstruct\n", i);
1652 						set_bit(R5_LOCKED, &dev->flags);
1653 						set_bit(R5_Wantread, &dev->flags);
1654 						locked++;
1655 					} else {
1656 						set_bit(STRIPE_DELAYED, &sh->state);
1657 						set_bit(STRIPE_HANDLE, &sh->state);
1658 					}
1659 				}
1660 			}
1661 		/* now if nothing is locked, and if we have enough data, we can start a write request */
1662 		if (locked == 0 && (rcw == 0 ||rmw == 0) &&
1663 		    !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
1664 			PRINTK("Computing parity...\n");
1665 			compute_parity5(sh, rcw==0 ? RECONSTRUCT_WRITE : READ_MODIFY_WRITE);
1666 			/* now every locked buffer is ready to be written */
1667 			for (i=disks; i--;)
1668 				if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
1669 					PRINTK("Writing block %d\n", i);
1670 					locked++;
1671 					set_bit(R5_Wantwrite, &sh->dev[i].flags);
1672 					if (!test_bit(R5_Insync, &sh->dev[i].flags)
1673 					    || (i==sh->pd_idx && failed == 0))
1674 						set_bit(STRIPE_INSYNC, &sh->state);
1675 				}
1676 			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
1677 				atomic_dec(&conf->preread_active_stripes);
1678 				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
1679 					md_wakeup_thread(conf->mddev->thread);
1680 			}
1681 		}
1682 	}
1683 
1684 	/* maybe we need to check and possibly fix the parity for this stripe
1685 	 * Any reads will already have been scheduled, so we just see if enough data
1686 	 * is available
1687 	 */
1688 	if (syncing && locked == 0 &&
1689 	    !test_bit(STRIPE_INSYNC, &sh->state)) {
1690 		set_bit(STRIPE_HANDLE, &sh->state);
1691 		if (failed == 0) {
1692 			BUG_ON(uptodate != disks);
1693 			compute_parity5(sh, CHECK_PARITY);
1694 			uptodate--;
1695 			if (page_is_zero(sh->dev[sh->pd_idx].page)) {
1696 				/* parity is correct (on disc, not in buffer any more) */
1697 				set_bit(STRIPE_INSYNC, &sh->state);
1698 			} else {
1699 				conf->mddev->resync_mismatches += STRIPE_SECTORS;
1700 				if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
1701 					/* don't try to repair!! */
1702 					set_bit(STRIPE_INSYNC, &sh->state);
1703 				else {
1704 					compute_block(sh, sh->pd_idx);
1705 					uptodate++;
1706 				}
1707 			}
1708 		}
1709 		if (!test_bit(STRIPE_INSYNC, &sh->state)) {
1710 			/* either failed parity check, or recovery is happening */
1711 			if (failed==0)
1712 				failed_num = sh->pd_idx;
1713 			dev = &sh->dev[failed_num];
1714 			BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
1715 			BUG_ON(uptodate != disks);
1716 
1717 			set_bit(R5_LOCKED, &dev->flags);
1718 			set_bit(R5_Wantwrite, &dev->flags);
1719 			clear_bit(STRIPE_DEGRADED, &sh->state);
1720 			locked++;
1721 			set_bit(STRIPE_INSYNC, &sh->state);
1722 		}
1723 	}
1724 	if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
1725 		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
1726 		clear_bit(STRIPE_SYNCING, &sh->state);
1727 	}
1728 
1729 	/* If the failed drive is just a ReadError, then we might need to progress
1730 	 * the repair/check process
1731 	 */
1732 	if (failed == 1 && ! conf->mddev->ro &&
1733 	    test_bit(R5_ReadError, &sh->dev[failed_num].flags)
1734 	    && !test_bit(R5_LOCKED, &sh->dev[failed_num].flags)
1735 	    && test_bit(R5_UPTODATE, &sh->dev[failed_num].flags)
1736 		) {
1737 		dev = &sh->dev[failed_num];
1738 		if (!test_bit(R5_ReWrite, &dev->flags)) {
1739 			set_bit(R5_Wantwrite, &dev->flags);
1740 			set_bit(R5_ReWrite, &dev->flags);
1741 			set_bit(R5_LOCKED, &dev->flags);
1742 			locked++;
1743 		} else {
1744 			/* let's read it back */
1745 			set_bit(R5_Wantread, &dev->flags);
1746 			set_bit(R5_LOCKED, &dev->flags);
1747 			locked++;
1748 		}
1749 	}
1750 
1751 	if (expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
1752 		/* Need to write out all blocks after computing parity */
1753 		sh->disks = conf->raid_disks;
1754 		sh->pd_idx = stripe_to_pdidx(sh->sector, conf, conf->raid_disks);
1755 		compute_parity5(sh, RECONSTRUCT_WRITE);
1756 		for (i= conf->raid_disks; i--;) {
1757 			set_bit(R5_LOCKED, &sh->dev[i].flags);
1758 			locked++;
1759 			set_bit(R5_Wantwrite, &sh->dev[i].flags);
1760 		}
1761 		clear_bit(STRIPE_EXPANDING, &sh->state);
1762 	} else if (expanded) {
1763 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
1764 		atomic_dec(&conf->reshape_stripes);
1765 		wake_up(&conf->wait_for_overlap);
1766 		md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
1767 	}
1768 
1769 	if (expanding && locked == 0) {
1770 		/* We have read all the blocks in this stripe and now we need to
1771 		 * copy some of them into a target stripe for expand.
1772 		 */
1773 		clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
1774 		for (i=0; i< sh->disks; i++)
1775 			if (i != sh->pd_idx) {
1776 				int dd_idx, pd_idx, j;
1777 				struct stripe_head *sh2;
1778 
1779 				sector_t bn = compute_blocknr(sh, i);
1780 				sector_t s = raid5_compute_sector(bn, conf->raid_disks,
1781 								  conf->raid_disks-1,
1782 								  &dd_idx, &pd_idx, conf);
1783 				sh2 = get_active_stripe(conf, s, conf->raid_disks, pd_idx, 1);
1784 				if (sh2 == NULL)
1785 					/* so far only the early blocks of this stripe
1786 					 * have been requested.  When later blocks
1787 					 * get requested, we will try again
1788 					 */
1789 					continue;
1790 				if(!test_bit(STRIPE_EXPANDING, &sh2->state) ||
1791 				   test_bit(R5_Expanded, &sh2->dev[dd_idx].flags)) {
1792 					/* must have already done this block */
1793 					release_stripe(sh2);
1794 					continue;
1795 				}
1796 				memcpy(page_address(sh2->dev[dd_idx].page),
1797 				       page_address(sh->dev[i].page),
1798 				       STRIPE_SIZE);
1799 				set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
1800 				set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
1801 				for (j=0; j<conf->raid_disks; j++)
1802 					if (j != sh2->pd_idx &&
1803 					    !test_bit(R5_Expanded, &sh2->dev[j].flags))
1804 						break;
1805 				if (j == conf->raid_disks) {
1806 					set_bit(STRIPE_EXPAND_READY, &sh2->state);
1807 					set_bit(STRIPE_HANDLE, &sh2->state);
1808 				}
1809 				release_stripe(sh2);
1810 			}
1811 	}
1812 
1813 	spin_unlock(&sh->lock);
1814 
1815 	while ((bi=return_bi)) {
1816 		int bytes = bi->bi_size;
1817 
1818 		return_bi = bi->bi_next;
1819 		bi->bi_next = NULL;
1820 		bi->bi_size = 0;
1821 		bi->bi_end_io(bi, bytes,
1822 			      test_bit(BIO_UPTODATE, &bi->bi_flags)
1823 			        ? 0 : -EIO);
1824 	}
1825 	for (i=disks; i-- ;) {
1826 		int rw;
1827 		struct bio *bi;
1828 		mdk_rdev_t *rdev;
1829 		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
1830 			rw = WRITE;
1831 		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
1832 			rw = READ;
1833 		else
1834 			continue;
1835 
1836 		bi = &sh->dev[i].req;
1837 
1838 		bi->bi_rw = rw;
1839 		if (rw == WRITE)
1840 			bi->bi_end_io = raid5_end_write_request;
1841 		else
1842 			bi->bi_end_io = raid5_end_read_request;
1843 
1844 		rcu_read_lock();
1845 		rdev = rcu_dereference(conf->disks[i].rdev);
1846 		if (rdev && test_bit(Faulty, &rdev->flags))
1847 			rdev = NULL;
1848 		if (rdev)
1849 			atomic_inc(&rdev->nr_pending);
1850 		rcu_read_unlock();
1851 
1852 		if (rdev) {
1853 			if (syncing || expanding || expanded)
1854 				md_sync_acct(rdev->bdev, STRIPE_SECTORS);
1855 
1856 			bi->bi_bdev = rdev->bdev;
1857 			PRINTK("for %llu schedule op %ld on disc %d\n",
1858 				(unsigned long long)sh->sector, bi->bi_rw, i);
1859 			atomic_inc(&sh->count);
1860 			bi->bi_sector = sh->sector + rdev->data_offset;
1861 			bi->bi_flags = 1 << BIO_UPTODATE;
1862 			bi->bi_vcnt = 1;
1863 			bi->bi_max_vecs = 1;
1864 			bi->bi_idx = 0;
1865 			bi->bi_io_vec = &sh->dev[i].vec;
1866 			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
1867 			bi->bi_io_vec[0].bv_offset = 0;
1868 			bi->bi_size = STRIPE_SIZE;
1869 			bi->bi_next = NULL;
1870 			if (rw == WRITE &&
1871 			    test_bit(R5_ReWrite, &sh->dev[i].flags))
1872 				atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
1873 			generic_make_request(bi);
1874 		} else {
1875 			if (rw == WRITE)
1876 				set_bit(STRIPE_DEGRADED, &sh->state);
1877 			PRINTK("skip op %ld on disc %d for sector %llu\n",
1878 				bi->bi_rw, i, (unsigned long long)sh->sector);
1879 			clear_bit(R5_LOCKED, &sh->dev[i].flags);
1880 			set_bit(STRIPE_HANDLE, &sh->state);
1881 		}
1882 	}
1883 }
1884 
1885 static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
1886 {
1887 	raid6_conf_t *conf = sh->raid_conf;
1888 	int disks = sh->disks;
1889 	struct bio *return_bi= NULL;
1890 	struct bio *bi;
1891 	int i;
1892 	int syncing, expanding, expanded;
1893 	int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
1894 	int non_overwrite = 0;
1895 	int failed_num[2] = {0, 0};
1896 	struct r5dev *dev, *pdev, *qdev;
1897 	int pd_idx = sh->pd_idx;
1898 	int qd_idx = raid6_next_disk(pd_idx, disks);
1899 	int p_failed, q_failed;
1900 
1901 	PRINTK("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d, qd_idx=%d\n",
1902 	       (unsigned long long)sh->sector, sh->state, atomic_read(&sh->count),
1903 	       pd_idx, qd_idx);
1904 
1905 	spin_lock(&sh->lock);
1906 	clear_bit(STRIPE_HANDLE, &sh->state);
1907 	clear_bit(STRIPE_DELAYED, &sh->state);
1908 
1909 	syncing = test_bit(STRIPE_SYNCING, &sh->state);
1910 	expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
1911 	expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
1912 	/* Now to look around and see what can be done */
1913 
1914 	rcu_read_lock();
1915 	for (i=disks; i--; ) {
1916 		mdk_rdev_t *rdev;
1917 		dev = &sh->dev[i];
1918 		clear_bit(R5_Insync, &dev->flags);
1919 
1920 		PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
1921 			i, dev->flags, dev->toread, dev->towrite, dev->written);
1922 		/* maybe we can reply to a read */
1923 		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
1924 			struct bio *rbi, *rbi2;
1925 			PRINTK("Return read for disc %d\n", i);
1926 			spin_lock_irq(&conf->device_lock);
1927 			rbi = dev->toread;
1928 			dev->toread = NULL;
1929 			if (test_and_clear_bit(R5_Overlap, &dev->flags))
1930 				wake_up(&conf->wait_for_overlap);
1931 			spin_unlock_irq(&conf->device_lock);
1932 			while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
1933 				copy_data(0, rbi, dev->page, dev->sector);
1934 				rbi2 = r5_next_bio(rbi, dev->sector);
1935 				spin_lock_irq(&conf->device_lock);
1936 				if (--rbi->bi_phys_segments == 0) {
1937 					rbi->bi_next = return_bi;
1938 					return_bi = rbi;
1939 				}
1940 				spin_unlock_irq(&conf->device_lock);
1941 				rbi = rbi2;
1942 			}
1943 		}
1944 
1945 		/* now count some things */
1946 		if (test_bit(R5_LOCKED, &dev->flags)) locked++;
1947 		if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
1948 
1949 
1950 		if (dev->toread) to_read++;
1951 		if (dev->towrite) {
1952 			to_write++;
1953 			if (!test_bit(R5_OVERWRITE, &dev->flags))
1954 				non_overwrite++;
1955 		}
1956 		if (dev->written) written++;
1957 		rdev = rcu_dereference(conf->disks[i].rdev);
1958 		if (!rdev || !test_bit(In_sync, &rdev->flags)) {
1959 			/* The ReadError flag will just be confusing now */
1960 			clear_bit(R5_ReadError, &dev->flags);
1961 			clear_bit(R5_ReWrite, &dev->flags);
1962 		}
1963 		if (!rdev || !test_bit(In_sync, &rdev->flags)
1964 		    || test_bit(R5_ReadError, &dev->flags)) {
1965 			if ( failed < 2 )
1966 				failed_num[failed] = i;
1967 			failed++;
1968 		} else
1969 			set_bit(R5_Insync, &dev->flags);
1970 	}
1971 	rcu_read_unlock();
1972 	PRINTK("locked=%d uptodate=%d to_read=%d"
1973 	       " to_write=%d failed=%d failed_num=%d,%d\n",
1974 	       locked, uptodate, to_read, to_write, failed,
1975 	       failed_num[0], failed_num[1]);
1976 	/* check if the array has lost >2 devices and, if so, some requests might
1977 	 * need to be failed
1978 	 */
1979 	if (failed > 2 && to_read+to_write+written) {
1980 		for (i=disks; i--; ) {
1981 			int bitmap_end = 0;
1982 
1983 			if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
1984 				mdk_rdev_t *rdev;
1985 				rcu_read_lock();
1986 				rdev = rcu_dereference(conf->disks[i].rdev);
1987 				if (rdev && test_bit(In_sync, &rdev->flags))
1988 					/* multiple read failures in one stripe */
1989 					md_error(conf->mddev, rdev);
1990 				rcu_read_unlock();
1991 			}
1992 
1993 			spin_lock_irq(&conf->device_lock);
1994 			/* fail all writes first */
1995 			bi = sh->dev[i].towrite;
1996 			sh->dev[i].towrite = NULL;
1997 			if (bi) { to_write--; bitmap_end = 1; }
1998 
1999 			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
2000 				wake_up(&conf->wait_for_overlap);
2001 
2002 			while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
2003 				struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
2004 				clear_bit(BIO_UPTODATE, &bi->bi_flags);
2005 				if (--bi->bi_phys_segments == 0) {
2006 					md_write_end(conf->mddev);
2007 					bi->bi_next = return_bi;
2008 					return_bi = bi;
2009 				}
2010 				bi = nextbi;
2011 			}
2012 			/* and fail all 'written' */
2013 			bi = sh->dev[i].written;
2014 			sh->dev[i].written = NULL;
2015 			if (bi) bitmap_end = 1;
2016 			while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS) {
2017 				struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
2018 				clear_bit(BIO_UPTODATE, &bi->bi_flags);
2019 				if (--bi->bi_phys_segments == 0) {
2020 					md_write_end(conf->mddev);
2021 					bi->bi_next = return_bi;
2022 					return_bi = bi;
2023 				}
2024 				bi = bi2;
2025 			}
2026 
2027 			/* fail any reads if this device is non-operational */
2028 			if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
2029 			    test_bit(R5_ReadError, &sh->dev[i].flags)) {
2030 				bi = sh->dev[i].toread;
2031 				sh->dev[i].toread = NULL;
2032 				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
2033 					wake_up(&conf->wait_for_overlap);
2034 				if (bi) to_read--;
2035 				while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
2036 					struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
2037 					clear_bit(BIO_UPTODATE, &bi->bi_flags);
2038 					if (--bi->bi_phys_segments == 0) {
2039 						bi->bi_next = return_bi;
2040 						return_bi = bi;
2041 					}
2042 					bi = nextbi;
2043 				}
2044 			}
2045 			spin_unlock_irq(&conf->device_lock);
2046 			if (bitmap_end)
2047 				bitmap_endwrite(conf->mddev->bitmap, sh->sector,
2048 						STRIPE_SECTORS, 0, 0);
2049 		}
2050 	}
2051 	if (failed > 2 && syncing) {
2052 		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
2053 		clear_bit(STRIPE_SYNCING, &sh->state);
2054 		syncing = 0;
2055 	}
2056 
2057 	/*
2058 	 * might be able to return some write requests if the parity blocks
2059 	 * are safe, or on a failed drive
2060 	 */
2061 	pdev = &sh->dev[pd_idx];
2062 	p_failed = (failed >= 1 && failed_num[0] == pd_idx)
2063 		|| (failed >= 2 && failed_num[1] == pd_idx);
2064 	qdev = &sh->dev[qd_idx];
2065 	q_failed = (failed >= 1 && failed_num[0] == qd_idx)
2066 		|| (failed >= 2 && failed_num[1] == qd_idx);
2067 
2068 	if ( written &&
2069 	     ( p_failed || ((test_bit(R5_Insync, &pdev->flags)
2070 			     && !test_bit(R5_LOCKED, &pdev->flags)
2071 			     && test_bit(R5_UPTODATE, &pdev->flags))) ) &&
2072 	     ( q_failed || ((test_bit(R5_Insync, &qdev->flags)
2073 			     && !test_bit(R5_LOCKED, &qdev->flags)
2074 			     && test_bit(R5_UPTODATE, &qdev->flags))) ) ) {
2075 		/* any written block on an uptodate or failed drive can be
2076 		 * returned.  Note that if we 'wrote' to a failed drive,
2077 		 * it will be UPTODATE, but never LOCKED, so we don't need
2078 		 * to test 'failed' directly.
2079 		 */
2080 		for (i=disks; i--; )
2081 			if (sh->dev[i].written) {
2082 				dev = &sh->dev[i];
2083 				if (!test_bit(R5_LOCKED, &dev->flags) &&
2084 				    test_bit(R5_UPTODATE, &dev->flags) ) {
2085 					/* We can return any write requests */
2086 					int bitmap_end = 0;
2087 					struct bio *wbi, *wbi2;
2088 					PRINTK("Return write for stripe %llu disc %d\n",
2089 					       (unsigned long long)sh->sector, i);
2090 					spin_lock_irq(&conf->device_lock);
2091 					wbi = dev->written;
2092 					dev->written = NULL;
2093 					while (wbi && wbi->bi_sector < dev->sector + STRIPE_SECTORS) {
2094 						wbi2 = r5_next_bio(wbi, dev->sector);
2095 						if (--wbi->bi_phys_segments == 0) {
2096 							md_write_end(conf->mddev);
2097 							wbi->bi_next = return_bi;
2098 							return_bi = wbi;
2099 						}
2100 						wbi = wbi2;
2101 					}
2102 					if (dev->towrite == NULL)
2103 						bitmap_end = 1;
2104 					spin_unlock_irq(&conf->device_lock);
2105 					if (bitmap_end)
2106 						bitmap_endwrite(conf->mddev->bitmap, sh->sector,
2107 								STRIPE_SECTORS,
2108 								!test_bit(STRIPE_DEGRADED, &sh->state), 0);
2109 				}
2110 			}
2111 	}
2112 
2113 	/* Now we might consider reading some blocks, either to check/generate
2114 	 * parity, or to satisfy requests
2115 	 * or to load a block that is being partially written.
2116 	 */
2117 	if (to_read || non_overwrite || (to_write && failed) ||
2118 	    (syncing && (uptodate < disks)) || expanding) {
2119 		for (i=disks; i--;) {
2120 			dev = &sh->dev[i];
2121 			if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
2122 			    (dev->toread ||
2123 			     (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
2124 			     syncing ||
2125 			     expanding ||
2126 			     (failed >= 1 && (sh->dev[failed_num[0]].toread || to_write)) ||
2127 			     (failed >= 2 && (sh->dev[failed_num[1]].toread || to_write))
2128 				    )
2129 				) {
2130 				/* we would like to get this block, possibly
2131 				 * by computing it, but we might not be able to
2132 				 */
2133 				if (uptodate == disks-1) {
2134 					PRINTK("Computing stripe %llu block %d\n",
2135 					       (unsigned long long)sh->sector, i);
2136 					compute_block_1(sh, i, 0);
2137 					uptodate++;
2138 				} else if ( uptodate == disks-2 && failed >= 2 ) {
2139 					/* Computing 2-failure is *very* expensive; only do it if failed >= 2 */
2140 					int other;
2141 					for (other=disks; other--;) {
2142 						if ( other == i )
2143 							continue;
2144 						if ( !test_bit(R5_UPTODATE, &sh->dev[other].flags) )
2145 							break;
2146 					}
2147 					BUG_ON(other < 0);
2148 					PRINTK("Computing stripe %llu blocks %d,%d\n",
2149 					       (unsigned long long)sh->sector, i, other);
2150 					compute_block_2(sh, i, other);
2151 					uptodate += 2;
2152 				} else if (test_bit(R5_Insync, &dev->flags)) {
2153 					set_bit(R5_LOCKED, &dev->flags);
2154 					set_bit(R5_Wantread, &dev->flags);
2155 					locked++;
2156 					PRINTK("Reading block %d (sync=%d)\n",
2157 						i, syncing);
2158 				}
2159 			}
2160 		}
2161 		set_bit(STRIPE_HANDLE, &sh->state);
2162 	}
2163 
2164 	/* now to consider writing and what else, if anything should be read */
2165 	if (to_write) {
2166 		int rcw=0, must_compute=0;
2167 		for (i=disks ; i--;) {
2168 			dev = &sh->dev[i];
2169 			/* Would I have to read this buffer for reconstruct_write */
2170 			if (!test_bit(R5_OVERWRITE, &dev->flags)
2171 			    && i != pd_idx && i != qd_idx
2172 			    && (!test_bit(R5_LOCKED, &dev->flags)
2173 				    ) &&
2174 			    !test_bit(R5_UPTODATE, &dev->flags)) {
2175 				if (test_bit(R5_Insync, &dev->flags)) rcw++;
2176 				else {
2177 					PRINTK("raid6: must_compute: disk %d flags=%#lx\n", i, dev->flags);
2178 					must_compute++;
2179 				}
2180 			}
2181 		}
2182 		PRINTK("for sector %llu, rcw=%d, must_compute=%d\n",
2183 		       (unsigned long long)sh->sector, rcw, must_compute);
2184 		set_bit(STRIPE_HANDLE, &sh->state);
2185 
2186 		if (rcw > 0)
2187 			/* want reconstruct write, but need to get some data */
2188 			for (i=disks; i--;) {
2189 				dev = &sh->dev[i];
2190 				if (!test_bit(R5_OVERWRITE, &dev->flags)
2191 				    && !(failed == 0 && (i == pd_idx || i == qd_idx))
2192 				    && !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
2193 				    test_bit(R5_Insync, &dev->flags)) {
2194 					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
2195 					{
2196 						PRINTK("Read_old stripe %llu block %d for Reconstruct\n",
2197 						       (unsigned long long)sh->sector, i);
2198 						set_bit(R5_LOCKED, &dev->flags);
2199 						set_bit(R5_Wantread, &dev->flags);
2200 						locked++;
2201 					} else {
2202 						PRINTK("Request delayed stripe %llu block %d for Reconstruct\n",
2203 						       (unsigned long long)sh->sector, i);
2204 						set_bit(STRIPE_DELAYED, &sh->state);
2205 						set_bit(STRIPE_HANDLE, &sh->state);
2206 					}
2207 				}
2208 			}
2209 		/* now if nothing is locked, and if we have enough data, we can start a write request */
2210 		if (locked == 0 && rcw == 0 &&
2211 		    !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
2212 			if ( must_compute > 0 ) {
2213 				/* We have failed blocks and need to compute them */
2214 				switch ( failed ) {
2215 				case 0:	BUG();
2216 				case 1: compute_block_1(sh, failed_num[0], 0); break;
2217 				case 2: compute_block_2(sh, failed_num[0], failed_num[1]); break;
2218 				default: BUG();	/* This request should have been failed? */
2219 				}
2220 			}
2221 
2222 			PRINTK("Computing parity for stripe %llu\n", (unsigned long long)sh->sector);
2223 			compute_parity6(sh, RECONSTRUCT_WRITE);
2224 			/* now every locked buffer is ready to be written */
2225 			for (i=disks; i--;)
2226 				if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
2227 					PRINTK("Writing stripe %llu block %d\n",
2228 					       (unsigned long long)sh->sector, i);
2229 					locked++;
2230 					set_bit(R5_Wantwrite, &sh->dev[i].flags);
2231 				}
2232 			/* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */
2233 			set_bit(STRIPE_INSYNC, &sh->state);
2234 
2235 			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
2236 				atomic_dec(&conf->preread_active_stripes);
2237 				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
2238 					md_wakeup_thread(conf->mddev->thread);
2239 			}
2240 		}
2241 	}
2242 
2243 	/* maybe we need to check and possibly fix the parity for this stripe
2244 	 * Any reads will already have been scheduled, so we just see if enough data
2245 	 * is available
2246 	 */
2247 	if (syncing && locked == 0 && !test_bit(STRIPE_INSYNC, &sh->state)) {
2248 		int update_p = 0, update_q = 0;
2249 		struct r5dev *dev;
2250 
2251 		set_bit(STRIPE_HANDLE, &sh->state);
2252 
2253 		BUG_ON(failed>2);
2254 		BUG_ON(uptodate < disks);
2255 		/* Want to check and possibly repair P and Q.
2256 		 * However there could be one 'failed' device, in which
2257 		 * case we can only check one of them, possibly using the
2258 		 * other to generate missing data
2259 		 */
2260 
2261 		/* If !tmp_page, we cannot do the calculations,
2262 		 * but as we have set STRIPE_HANDLE, we will soon be called
2263 		 * by stripe_handle with a tmp_page - just wait until then.
2264 		 */
2265 		if (tmp_page) {
2266 			if (failed == q_failed) {
2267 				/* The only possible failed device holds 'Q', so it makes
2268 				 * sense to check P (If anything else were failed, we would
2269 				 * have used P to recreate it).
2270 				 */
2271 				compute_block_1(sh, pd_idx, 1);
2272 				if (!page_is_zero(sh->dev[pd_idx].page)) {
2273 					compute_block_1(sh,pd_idx,0);
2274 					update_p = 1;
2275 				}
2276 			}
2277 			if (!q_failed && failed < 2) {
2278 				/* q is not failed, and we didn't use it to generate
2279 				 * anything, so it makes sense to check it
2280 				 */
2281 				memcpy(page_address(tmp_page),
2282 				       page_address(sh->dev[qd_idx].page),
2283 				       STRIPE_SIZE);
2284 				compute_parity6(sh, UPDATE_PARITY);
2285 				if (memcmp(page_address(tmp_page),
2286 					   page_address(sh->dev[qd_idx].page),
2287 					   STRIPE_SIZE)!= 0) {
2288 					clear_bit(STRIPE_INSYNC, &sh->state);
2289 					update_q = 1;
2290 				}
2291 			}
2292 			if (update_p || update_q) {
2293 				conf->mddev->resync_mismatches += STRIPE_SECTORS;
2294 				if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
2295 					/* don't try to repair!! */
2296 					update_p = update_q = 0;
2297 			}
2298 
2299 			/* now write out any block on a failed drive,
2300 			 * or P or Q if they need it
2301 			 */
2302 
2303 			if (failed == 2) {
2304 				dev = &sh->dev[failed_num[1]];
2305 				locked++;
2306 				set_bit(R5_LOCKED, &dev->flags);
2307 				set_bit(R5_Wantwrite, &dev->flags);
2308 			}
2309 			if (failed >= 1) {
2310 				dev = &sh->dev[failed_num[0]];
2311 				locked++;
2312 				set_bit(R5_LOCKED, &dev->flags);
2313 				set_bit(R5_Wantwrite, &dev->flags);
2314 			}
2315 
2316 			if (update_p) {
2317 				dev = &sh->dev[pd_idx];
2318 				locked ++;
2319 				set_bit(R5_LOCKED, &dev->flags);
2320 				set_bit(R5_Wantwrite, &dev->flags);
2321 			}
2322 			if (update_q) {
2323 				dev = &sh->dev[qd_idx];
2324 				locked++;
2325 				set_bit(R5_LOCKED, &dev->flags);
2326 				set_bit(R5_Wantwrite, &dev->flags);
2327 			}
2328 			clear_bit(STRIPE_DEGRADED, &sh->state);
2329 
2330 			set_bit(STRIPE_INSYNC, &sh->state);
2331 		}
2332 	}
2333 
2334 	if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
2335 		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
2336 		clear_bit(STRIPE_SYNCING, &sh->state);
2337 	}
2338 
2339 	/* If the failed drives are just a ReadError, then we might need
2340 	 * to progress the repair/check process
2341 	 */
2342 	if (failed <= 2 && ! conf->mddev->ro)
2343 		for (i=0; i<failed;i++) {
2344 			dev = &sh->dev[failed_num[i]];
2345 			if (test_bit(R5_ReadError, &dev->flags)
2346 			    && !test_bit(R5_LOCKED, &dev->flags)
2347 			    && test_bit(R5_UPTODATE, &dev->flags)
2348 				) {
2349 				if (!test_bit(R5_ReWrite, &dev->flags)) {
2350 					set_bit(R5_Wantwrite, &dev->flags);
2351 					set_bit(R5_ReWrite, &dev->flags);
2352 					set_bit(R5_LOCKED, &dev->flags);
2353 				} else {
2354 					/* let's read it back */
2355 					set_bit(R5_Wantread, &dev->flags);
2356 					set_bit(R5_LOCKED, &dev->flags);
2357 				}
2358 			}
2359 		}
2360 
2361 	if (expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
2362 		/* Need to write out all blocks after computing P&Q */
2363 		sh->disks = conf->raid_disks;
2364 		sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
2365 					     conf->raid_disks);
2366 		compute_parity6(sh, RECONSTRUCT_WRITE);
2367 		for (i = conf->raid_disks ; i-- ;  ) {
2368 			set_bit(R5_LOCKED, &sh->dev[i].flags);
2369 			locked++;
2370 			set_bit(R5_Wantwrite, &sh->dev[i].flags);
2371 		}
2372 		clear_bit(STRIPE_EXPANDING, &sh->state);
2373 	} else if (expanded) {
2374 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
2375 		atomic_dec(&conf->reshape_stripes);
2376 		wake_up(&conf->wait_for_overlap);
2377 		md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
2378 	}
2379 
2380 	if (expanding && locked == 0) {
2381 		/* We have read all the blocks in this stripe and now we need to
2382 		 * copy some of them into a target stripe for expand.
2383 		 */
2384 		clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
2385 		for (i = 0; i < sh->disks ; i++)
2386 			if (i != pd_idx && i != qd_idx) {
2387 				int dd_idx2, pd_idx2, j;
2388 				struct stripe_head *sh2;
2389 
2390 				sector_t bn = compute_blocknr(sh, i);
2391 				sector_t s = raid5_compute_sector(
2392 					bn, conf->raid_disks,
2393 					conf->raid_disks - conf->max_degraded,
2394 					&dd_idx2, &pd_idx2, conf);
2395 				sh2 = get_active_stripe(conf, s,
2396 							conf->raid_disks,
2397 						       pd_idx2, 1);
2398 				if (sh2 == NULL)
2399 					/* so for only the early blocks of
2400 					 * this stripe have been requests.
2401 					 * When later blocks get requests, we
2402 					 * will try again
2403 					 */
2404 					continue;
2405 				if (!test_bit(STRIPE_EXPANDING, &sh2->state) ||
2406 				    test_bit(R5_Expanded,
2407 					     &sh2->dev[dd_idx2].flags)) {
2408 					/* must have already done this block */
2409 					release_stripe(sh2);
2410 					continue;
2411 				}
2412 				memcpy(page_address(sh2->dev[dd_idx2].page),
2413 				       page_address(sh->dev[i].page),
2414 				       STRIPE_SIZE);
2415 				set_bit(R5_Expanded, &sh2->dev[dd_idx2].flags);
2416 				set_bit(R5_UPTODATE, &sh2->dev[dd_idx2].flags);
2417 				for (j = 0 ; j < conf->raid_disks ; j++)
2418 					if (j != sh2->pd_idx &&
2419 					    j != raid6_next_disk(sh2->pd_idx,
2420 							   sh2->disks) &&
2421 					    !test_bit(R5_Expanded,
2422 						      &sh2->dev[j].flags))
2423 						break;
2424 				if (j == conf->raid_disks) {
2425 					set_bit(STRIPE_EXPAND_READY,
2426 						&sh2->state);
2427 					set_bit(STRIPE_HANDLE, &sh2->state);
2428 				}
2429 				release_stripe(sh2);
2430 			}
2431 	}
2432 
2433 	spin_unlock(&sh->lock);
2434 
2435 	while ((bi=return_bi)) {
2436 		int bytes = bi->bi_size;
2437 
2438 		return_bi = bi->bi_next;
2439 		bi->bi_next = NULL;
2440 		bi->bi_size = 0;
2441 		bi->bi_end_io(bi, bytes,
2442 			      test_bit(BIO_UPTODATE, &bi->bi_flags)
2443 			        ? 0 : -EIO);
2444 	}
2445 	for (i=disks; i-- ;) {
2446 		int rw;
2447 		struct bio *bi;
2448 		mdk_rdev_t *rdev;
2449 		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
2450 			rw = WRITE;
2451 		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
2452 			rw = READ;
2453 		else
2454 			continue;
2455 
2456 		bi = &sh->dev[i].req;
2457 
2458 		bi->bi_rw = rw;
2459 		if (rw == WRITE)
2460 			bi->bi_end_io = raid5_end_write_request;
2461 		else
2462 			bi->bi_end_io = raid5_end_read_request;
2463 
2464 		rcu_read_lock();
2465 		rdev = rcu_dereference(conf->disks[i].rdev);
2466 		if (rdev && test_bit(Faulty, &rdev->flags))
2467 			rdev = NULL;
2468 		if (rdev)
2469 			atomic_inc(&rdev->nr_pending);
2470 		rcu_read_unlock();
2471 
2472 		if (rdev) {
2473 			if (syncing || expanding || expanded)
2474 				md_sync_acct(rdev->bdev, STRIPE_SECTORS);
2475 
2476 			bi->bi_bdev = rdev->bdev;
2477 			PRINTK("for %llu schedule op %ld on disc %d\n",
2478 				(unsigned long long)sh->sector, bi->bi_rw, i);
2479 			atomic_inc(&sh->count);
2480 			bi->bi_sector = sh->sector + rdev->data_offset;
2481 			bi->bi_flags = 1 << BIO_UPTODATE;
2482 			bi->bi_vcnt = 1;
2483 			bi->bi_max_vecs = 1;
2484 			bi->bi_idx = 0;
2485 			bi->bi_io_vec = &sh->dev[i].vec;
2486 			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
2487 			bi->bi_io_vec[0].bv_offset = 0;
2488 			bi->bi_size = STRIPE_SIZE;
2489 			bi->bi_next = NULL;
2490 			if (rw == WRITE &&
2491 			    test_bit(R5_ReWrite, &sh->dev[i].flags))
2492 				atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
2493 			generic_make_request(bi);
2494 		} else {
2495 			if (rw == WRITE)
2496 				set_bit(STRIPE_DEGRADED, &sh->state);
2497 			PRINTK("skip op %ld on disc %d for sector %llu\n",
2498 				bi->bi_rw, i, (unsigned long long)sh->sector);
2499 			clear_bit(R5_LOCKED, &sh->dev[i].flags);
2500 			set_bit(STRIPE_HANDLE, &sh->state);
2501 		}
2502 	}
2503 }
2504 
2505 static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
2506 {
2507 	if (sh->raid_conf->level == 6)
2508 		handle_stripe6(sh, tmp_page);
2509 	else
2510 		handle_stripe5(sh);
2511 }
2512 
2513 
2514 
2515 static void raid5_activate_delayed(raid5_conf_t *conf)
2516 {
2517 	if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
2518 		while (!list_empty(&conf->delayed_list)) {
2519 			struct list_head *l = conf->delayed_list.next;
2520 			struct stripe_head *sh;
2521 			sh = list_entry(l, struct stripe_head, lru);
2522 			list_del_init(l);
2523 			clear_bit(STRIPE_DELAYED, &sh->state);
2524 			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
2525 				atomic_inc(&conf->preread_active_stripes);
2526 			list_add_tail(&sh->lru, &conf->handle_list);
2527 		}
2528 	}
2529 }
2530 
2531 static void activate_bit_delay(raid5_conf_t *conf)
2532 {
2533 	/* device_lock is held */
2534 	struct list_head head;
2535 	list_add(&head, &conf->bitmap_list);
2536 	list_del_init(&conf->bitmap_list);
2537 	while (!list_empty(&head)) {
2538 		struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
2539 		list_del_init(&sh->lru);
2540 		atomic_inc(&sh->count);
2541 		__release_stripe(conf, sh);
2542 	}
2543 }
2544 
2545 static void unplug_slaves(mddev_t *mddev)
2546 {
2547 	raid5_conf_t *conf = mddev_to_conf(mddev);
2548 	int i;
2549 
2550 	rcu_read_lock();
2551 	for (i=0; i<mddev->raid_disks; i++) {
2552 		mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
2553 		if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
2554 			request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
2555 
2556 			atomic_inc(&rdev->nr_pending);
2557 			rcu_read_unlock();
2558 
2559 			if (r_queue->unplug_fn)
2560 				r_queue->unplug_fn(r_queue);
2561 
2562 			rdev_dec_pending(rdev, mddev);
2563 			rcu_read_lock();
2564 		}
2565 	}
2566 	rcu_read_unlock();
2567 }
2568 
2569 static void raid5_unplug_device(request_queue_t *q)
2570 {
2571 	mddev_t *mddev = q->queuedata;
2572 	raid5_conf_t *conf = mddev_to_conf(mddev);
2573 	unsigned long flags;
2574 
2575 	spin_lock_irqsave(&conf->device_lock, flags);
2576 
2577 	if (blk_remove_plug(q)) {
2578 		conf->seq_flush++;
2579 		raid5_activate_delayed(conf);
2580 	}
2581 	md_wakeup_thread(mddev->thread);
2582 
2583 	spin_unlock_irqrestore(&conf->device_lock, flags);
2584 
2585 	unplug_slaves(mddev);
2586 }
2587 
2588 static int raid5_issue_flush(request_queue_t *q, struct gendisk *disk,
2589 			     sector_t *error_sector)
2590 {
2591 	mddev_t *mddev = q->queuedata;
2592 	raid5_conf_t *conf = mddev_to_conf(mddev);
2593 	int i, ret = 0;
2594 
2595 	rcu_read_lock();
2596 	for (i=0; i<mddev->raid_disks && ret == 0; i++) {
2597 		mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
2598 		if (rdev && !test_bit(Faulty, &rdev->flags)) {
2599 			struct block_device *bdev = rdev->bdev;
2600 			request_queue_t *r_queue = bdev_get_queue(bdev);
2601 
2602 			if (!r_queue->issue_flush_fn)
2603 				ret = -EOPNOTSUPP;
2604 			else {
2605 				atomic_inc(&rdev->nr_pending);
2606 				rcu_read_unlock();
2607 				ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
2608 							      error_sector);
2609 				rdev_dec_pending(rdev, mddev);
2610 				rcu_read_lock();
2611 			}
2612 		}
2613 	}
2614 	rcu_read_unlock();
2615 	return ret;
2616 }
2617 
2618 static int raid5_congested(void *data, int bits)
2619 {
2620 	mddev_t *mddev = data;
2621 	raid5_conf_t *conf = mddev_to_conf(mddev);
2622 
2623 	/* No difference between reads and writes.  Just check
2624 	 * how busy the stripe_cache is
2625 	 */
2626 	if (conf->inactive_blocked)
2627 		return 1;
2628 	if (conf->quiesce)
2629 		return 1;
2630 	if (list_empty_careful(&conf->inactive_list))
2631 		return 1;
2632 
2633 	return 0;
2634 }
2635 
2636 /* We want read requests to align with chunks where possible,
2637  * but write requests don't need to.
2638  */
2639 static int raid5_mergeable_bvec(request_queue_t *q, struct bio *bio, struct bio_vec *biovec)
2640 {
2641 	mddev_t *mddev = q->queuedata;
2642 	sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
2643 	int max;
2644 	unsigned int chunk_sectors = mddev->chunk_size >> 9;
2645 	unsigned int bio_sectors = bio->bi_size >> 9;
2646 
2647 	if (bio_data_dir(bio) == WRITE)
2648 		return biovec->bv_len; /* always allow writes to be mergeable */
2649 
2650 	max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
2651 	if (max < 0) max = 0;
2652 	if (max <= biovec->bv_len && bio_sectors == 0)
2653 		return biovec->bv_len;
2654 	else
2655 		return max;
2656 }
2657 
2658 
2659 static int in_chunk_boundary(mddev_t *mddev, struct bio *bio)
2660 {
2661 	sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
2662 	unsigned int chunk_sectors = mddev->chunk_size >> 9;
2663 	unsigned int bio_sectors = bio->bi_size >> 9;
2664 
2665 	return  chunk_sectors >=
2666 		((sector & (chunk_sectors - 1)) + bio_sectors);
2667 }
2668 
2669 /*
2670  *  add bio to the retry LIFO  ( in O(1) ... we are in interrupt )
2671  *  later sampled by raid5d.
2672  */
2673 static void add_bio_to_retry(struct bio *bi,raid5_conf_t *conf)
2674 {
2675 	unsigned long flags;
2676 
2677 	spin_lock_irqsave(&conf->device_lock, flags);
2678 
2679 	bi->bi_next = conf->retry_read_aligned_list;
2680 	conf->retry_read_aligned_list = bi;
2681 
2682 	spin_unlock_irqrestore(&conf->device_lock, flags);
2683 	md_wakeup_thread(conf->mddev->thread);
2684 }
2685 
2686 
2687 static struct bio *remove_bio_from_retry(raid5_conf_t *conf)
2688 {
2689 	struct bio *bi;
2690 
2691 	bi = conf->retry_read_aligned;
2692 	if (bi) {
2693 		conf->retry_read_aligned = NULL;
2694 		return bi;
2695 	}
2696 	bi = conf->retry_read_aligned_list;
2697 	if(bi) {
2698 		conf->retry_read_aligned_list = bi->bi_next;
2699 		bi->bi_next = NULL;
2700 		bi->bi_phys_segments = 1; /* biased count of active stripes */
2701 		bi->bi_hw_segments = 0; /* count of processed stripes */
2702 	}
2703 
2704 	return bi;
2705 }
2706 
2707 
2708 /*
2709  *  The "raid5_align_endio" should check if the read succeeded and if it
2710  *  did, call bio_endio on the original bio (having bio_put the new bio
2711  *  first).
2712  *  If the read failed..
2713  */
2714 static int raid5_align_endio(struct bio *bi, unsigned int bytes, int error)
2715 {
2716 	struct bio* raid_bi  = bi->bi_private;
2717 	mddev_t *mddev;
2718 	raid5_conf_t *conf;
2719 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
2720 	mdk_rdev_t *rdev;
2721 
2722 	if (bi->bi_size)
2723 		return 1;
2724 	bio_put(bi);
2725 
2726 	mddev = raid_bi->bi_bdev->bd_disk->queue->queuedata;
2727 	conf = mddev_to_conf(mddev);
2728 	rdev = (void*)raid_bi->bi_next;
2729 	raid_bi->bi_next = NULL;
2730 
2731 	rdev_dec_pending(rdev, conf->mddev);
2732 
2733 	if (!error && uptodate) {
2734 		bio_endio(raid_bi, bytes, 0);
2735 		if (atomic_dec_and_test(&conf->active_aligned_reads))
2736 			wake_up(&conf->wait_for_stripe);
2737 		return 0;
2738 	}
2739 
2740 
2741 	PRINTK("raid5_align_endio : io error...handing IO for a retry\n");
2742 
2743 	add_bio_to_retry(raid_bi, conf);
2744 	return 0;
2745 }
2746 
2747 static int bio_fits_rdev(struct bio *bi)
2748 {
2749 	request_queue_t *q = bdev_get_queue(bi->bi_bdev);
2750 
2751 	if ((bi->bi_size>>9) > q->max_sectors)
2752 		return 0;
2753 	blk_recount_segments(q, bi);
2754 	if (bi->bi_phys_segments > q->max_phys_segments ||
2755 	    bi->bi_hw_segments > q->max_hw_segments)
2756 		return 0;
2757 
2758 	if (q->merge_bvec_fn)
2759 		/* it's too hard to apply the merge_bvec_fn at this stage,
2760 		 * just just give up
2761 		 */
2762 		return 0;
2763 
2764 	return 1;
2765 }
2766 
2767 
2768 static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
2769 {
2770 	mddev_t *mddev = q->queuedata;
2771 	raid5_conf_t *conf = mddev_to_conf(mddev);
2772 	const unsigned int raid_disks = conf->raid_disks;
2773 	const unsigned int data_disks = raid_disks - conf->max_degraded;
2774 	unsigned int dd_idx, pd_idx;
2775 	struct bio* align_bi;
2776 	mdk_rdev_t *rdev;
2777 
2778 	if (!in_chunk_boundary(mddev, raid_bio)) {
2779 		PRINTK("chunk_aligned_read : non aligned\n");
2780 		return 0;
2781 	}
2782 	/*
2783  	 * use bio_clone to make a copy of the bio
2784 	 */
2785 	align_bi = bio_clone(raid_bio, GFP_NOIO);
2786 	if (!align_bi)
2787 		return 0;
2788 	/*
2789 	 *   set bi_end_io to a new function, and set bi_private to the
2790 	 *     original bio.
2791 	 */
2792 	align_bi->bi_end_io  = raid5_align_endio;
2793 	align_bi->bi_private = raid_bio;
2794 	/*
2795 	 *	compute position
2796 	 */
2797 	align_bi->bi_sector =  raid5_compute_sector(raid_bio->bi_sector,
2798 					raid_disks,
2799 					data_disks,
2800 					&dd_idx,
2801 					&pd_idx,
2802 					conf);
2803 
2804 	rcu_read_lock();
2805 	rdev = rcu_dereference(conf->disks[dd_idx].rdev);
2806 	if (rdev && test_bit(In_sync, &rdev->flags)) {
2807 		atomic_inc(&rdev->nr_pending);
2808 		rcu_read_unlock();
2809 		raid_bio->bi_next = (void*)rdev;
2810 		align_bi->bi_bdev =  rdev->bdev;
2811 		align_bi->bi_flags &= ~(1 << BIO_SEG_VALID);
2812 		align_bi->bi_sector += rdev->data_offset;
2813 
2814 		if (!bio_fits_rdev(align_bi)) {
2815 			/* too big in some way */
2816 			bio_put(align_bi);
2817 			rdev_dec_pending(rdev, mddev);
2818 			return 0;
2819 		}
2820 
2821 		spin_lock_irq(&conf->device_lock);
2822 		wait_event_lock_irq(conf->wait_for_stripe,
2823 				    conf->quiesce == 0,
2824 				    conf->device_lock, /* nothing */);
2825 		atomic_inc(&conf->active_aligned_reads);
2826 		spin_unlock_irq(&conf->device_lock);
2827 
2828 		generic_make_request(align_bi);
2829 		return 1;
2830 	} else {
2831 		rcu_read_unlock();
2832 		bio_put(align_bi);
2833 		return 0;
2834 	}
2835 }
2836 
2837 
2838 static int make_request(request_queue_t *q, struct bio * bi)
2839 {
2840 	mddev_t *mddev = q->queuedata;
2841 	raid5_conf_t *conf = mddev_to_conf(mddev);
2842 	unsigned int dd_idx, pd_idx;
2843 	sector_t new_sector;
2844 	sector_t logical_sector, last_sector;
2845 	struct stripe_head *sh;
2846 	const int rw = bio_data_dir(bi);
2847 	int remaining;
2848 
2849 	if (unlikely(bio_barrier(bi))) {
2850 		bio_endio(bi, bi->bi_size, -EOPNOTSUPP);
2851 		return 0;
2852 	}
2853 
2854 	md_write_start(mddev, bi);
2855 
2856 	disk_stat_inc(mddev->gendisk, ios[rw]);
2857 	disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bi));
2858 
2859 	if (rw == READ &&
2860 	     mddev->reshape_position == MaxSector &&
2861 	     chunk_aligned_read(q,bi))
2862             	return 0;
2863 
2864 	logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
2865 	last_sector = bi->bi_sector + (bi->bi_size>>9);
2866 	bi->bi_next = NULL;
2867 	bi->bi_phys_segments = 1;	/* over-loaded to count active stripes */
2868 
2869 	for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
2870 		DEFINE_WAIT(w);
2871 		int disks, data_disks;
2872 
2873 	retry:
2874 		prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
2875 		if (likely(conf->expand_progress == MaxSector))
2876 			disks = conf->raid_disks;
2877 		else {
2878 			/* spinlock is needed as expand_progress may be
2879 			 * 64bit on a 32bit platform, and so it might be
2880 			 * possible to see a half-updated value
2881 			 * Ofcourse expand_progress could change after
2882 			 * the lock is dropped, so once we get a reference
2883 			 * to the stripe that we think it is, we will have
2884 			 * to check again.
2885 			 */
2886 			spin_lock_irq(&conf->device_lock);
2887 			disks = conf->raid_disks;
2888 			if (logical_sector >= conf->expand_progress)
2889 				disks = conf->previous_raid_disks;
2890 			else {
2891 				if (logical_sector >= conf->expand_lo) {
2892 					spin_unlock_irq(&conf->device_lock);
2893 					schedule();
2894 					goto retry;
2895 				}
2896 			}
2897 			spin_unlock_irq(&conf->device_lock);
2898 		}
2899 		data_disks = disks - conf->max_degraded;
2900 
2901  		new_sector = raid5_compute_sector(logical_sector, disks, data_disks,
2902 						  &dd_idx, &pd_idx, conf);
2903 		PRINTK("raid5: make_request, sector %llu logical %llu\n",
2904 			(unsigned long long)new_sector,
2905 			(unsigned long long)logical_sector);
2906 
2907 		sh = get_active_stripe(conf, new_sector, disks, pd_idx, (bi->bi_rw&RWA_MASK));
2908 		if (sh) {
2909 			if (unlikely(conf->expand_progress != MaxSector)) {
2910 				/* expansion might have moved on while waiting for a
2911 				 * stripe, so we must do the range check again.
2912 				 * Expansion could still move past after this
2913 				 * test, but as we are holding a reference to
2914 				 * 'sh', we know that if that happens,
2915 				 *  STRIPE_EXPANDING will get set and the expansion
2916 				 * won't proceed until we finish with the stripe.
2917 				 */
2918 				int must_retry = 0;
2919 				spin_lock_irq(&conf->device_lock);
2920 				if (logical_sector <  conf->expand_progress &&
2921 				    disks == conf->previous_raid_disks)
2922 					/* mismatch, need to try again */
2923 					must_retry = 1;
2924 				spin_unlock_irq(&conf->device_lock);
2925 				if (must_retry) {
2926 					release_stripe(sh);
2927 					goto retry;
2928 				}
2929 			}
2930 			/* FIXME what if we get a false positive because these
2931 			 * are being updated.
2932 			 */
2933 			if (logical_sector >= mddev->suspend_lo &&
2934 			    logical_sector < mddev->suspend_hi) {
2935 				release_stripe(sh);
2936 				schedule();
2937 				goto retry;
2938 			}
2939 
2940 			if (test_bit(STRIPE_EXPANDING, &sh->state) ||
2941 			    !add_stripe_bio(sh, bi, dd_idx, (bi->bi_rw&RW_MASK))) {
2942 				/* Stripe is busy expanding or
2943 				 * add failed due to overlap.  Flush everything
2944 				 * and wait a while
2945 				 */
2946 				raid5_unplug_device(mddev->queue);
2947 				release_stripe(sh);
2948 				schedule();
2949 				goto retry;
2950 			}
2951 			finish_wait(&conf->wait_for_overlap, &w);
2952 			handle_stripe(sh, NULL);
2953 			release_stripe(sh);
2954 		} else {
2955 			/* cannot get stripe for read-ahead, just give-up */
2956 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
2957 			finish_wait(&conf->wait_for_overlap, &w);
2958 			break;
2959 		}
2960 
2961 	}
2962 	spin_lock_irq(&conf->device_lock);
2963 	remaining = --bi->bi_phys_segments;
2964 	spin_unlock_irq(&conf->device_lock);
2965 	if (remaining == 0) {
2966 		int bytes = bi->bi_size;
2967 
2968 		if ( rw == WRITE )
2969 			md_write_end(mddev);
2970 		bi->bi_size = 0;
2971 		bi->bi_end_io(bi, bytes,
2972 			      test_bit(BIO_UPTODATE, &bi->bi_flags)
2973 			        ? 0 : -EIO);
2974 	}
2975 	return 0;
2976 }
2977 
2978 static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped)
2979 {
2980 	/* reshaping is quite different to recovery/resync so it is
2981 	 * handled quite separately ... here.
2982 	 *
2983 	 * On each call to sync_request, we gather one chunk worth of
2984 	 * destination stripes and flag them as expanding.
2985 	 * Then we find all the source stripes and request reads.
2986 	 * As the reads complete, handle_stripe will copy the data
2987 	 * into the destination stripe and release that stripe.
2988 	 */
2989 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
2990 	struct stripe_head *sh;
2991 	int pd_idx;
2992 	sector_t first_sector, last_sector;
2993 	int raid_disks = conf->previous_raid_disks;
2994 	int data_disks = raid_disks - conf->max_degraded;
2995 	int new_data_disks = conf->raid_disks - conf->max_degraded;
2996 	int i;
2997 	int dd_idx;
2998 	sector_t writepos, safepos, gap;
2999 
3000 	if (sector_nr == 0 &&
3001 	    conf->expand_progress != 0) {
3002 		/* restarting in the middle, skip the initial sectors */
3003 		sector_nr = conf->expand_progress;
3004 		sector_div(sector_nr, new_data_disks);
3005 		*skipped = 1;
3006 		return sector_nr;
3007 	}
3008 
3009 	/* we update the metadata when there is more than 3Meg
3010 	 * in the block range (that is rather arbitrary, should
3011 	 * probably be time based) or when the data about to be
3012 	 * copied would over-write the source of the data at
3013 	 * the front of the range.
3014 	 * i.e. one new_stripe forward from expand_progress new_maps
3015 	 * to after where expand_lo old_maps to
3016 	 */
3017 	writepos = conf->expand_progress +
3018 		conf->chunk_size/512*(new_data_disks);
3019 	sector_div(writepos, new_data_disks);
3020 	safepos = conf->expand_lo;
3021 	sector_div(safepos, data_disks);
3022 	gap = conf->expand_progress - conf->expand_lo;
3023 
3024 	if (writepos >= safepos ||
3025 	    gap > (new_data_disks)*3000*2 /*3Meg*/) {
3026 		/* Cannot proceed until we've updated the superblock... */
3027 		wait_event(conf->wait_for_overlap,
3028 			   atomic_read(&conf->reshape_stripes)==0);
3029 		mddev->reshape_position = conf->expand_progress;
3030 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
3031 		md_wakeup_thread(mddev->thread);
3032 		wait_event(mddev->sb_wait, mddev->flags == 0 ||
3033 			   kthread_should_stop());
3034 		spin_lock_irq(&conf->device_lock);
3035 		conf->expand_lo = mddev->reshape_position;
3036 		spin_unlock_irq(&conf->device_lock);
3037 		wake_up(&conf->wait_for_overlap);
3038 	}
3039 
3040 	for (i=0; i < conf->chunk_size/512; i+= STRIPE_SECTORS) {
3041 		int j;
3042 		int skipped = 0;
3043 		pd_idx = stripe_to_pdidx(sector_nr+i, conf, conf->raid_disks);
3044 		sh = get_active_stripe(conf, sector_nr+i,
3045 				       conf->raid_disks, pd_idx, 0);
3046 		set_bit(STRIPE_EXPANDING, &sh->state);
3047 		atomic_inc(&conf->reshape_stripes);
3048 		/* If any of this stripe is beyond the end of the old
3049 		 * array, then we need to zero those blocks
3050 		 */
3051 		for (j=sh->disks; j--;) {
3052 			sector_t s;
3053 			if (j == sh->pd_idx)
3054 				continue;
3055 			if (conf->level == 6 &&
3056 			    j == raid6_next_disk(sh->pd_idx, sh->disks))
3057 				continue;
3058 			s = compute_blocknr(sh, j);
3059 			if (s < (mddev->array_size<<1)) {
3060 				skipped = 1;
3061 				continue;
3062 			}
3063 			memset(page_address(sh->dev[j].page), 0, STRIPE_SIZE);
3064 			set_bit(R5_Expanded, &sh->dev[j].flags);
3065 			set_bit(R5_UPTODATE, &sh->dev[j].flags);
3066 		}
3067 		if (!skipped) {
3068 			set_bit(STRIPE_EXPAND_READY, &sh->state);
3069 			set_bit(STRIPE_HANDLE, &sh->state);
3070 		}
3071 		release_stripe(sh);
3072 	}
3073 	spin_lock_irq(&conf->device_lock);
3074 	conf->expand_progress = (sector_nr + i) * new_data_disks;
3075 	spin_unlock_irq(&conf->device_lock);
3076 	/* Ok, those stripe are ready. We can start scheduling
3077 	 * reads on the source stripes.
3078 	 * The source stripes are determined by mapping the first and last
3079 	 * block on the destination stripes.
3080 	 */
3081 	first_sector =
3082 		raid5_compute_sector(sector_nr*(new_data_disks),
3083 				     raid_disks, data_disks,
3084 				     &dd_idx, &pd_idx, conf);
3085 	last_sector =
3086 		raid5_compute_sector((sector_nr+conf->chunk_size/512)
3087 				     *(new_data_disks) -1,
3088 				     raid_disks, data_disks,
3089 				     &dd_idx, &pd_idx, conf);
3090 	if (last_sector >= (mddev->size<<1))
3091 		last_sector = (mddev->size<<1)-1;
3092 	while (first_sector <= last_sector) {
3093 		pd_idx = stripe_to_pdidx(first_sector, conf,
3094 					 conf->previous_raid_disks);
3095 		sh = get_active_stripe(conf, first_sector,
3096 				       conf->previous_raid_disks, pd_idx, 0);
3097 		set_bit(STRIPE_EXPAND_SOURCE, &sh->state);
3098 		set_bit(STRIPE_HANDLE, &sh->state);
3099 		release_stripe(sh);
3100 		first_sector += STRIPE_SECTORS;
3101 	}
3102 	return conf->chunk_size>>9;
3103 }
3104 
3105 /* FIXME go_faster isn't used */
3106 static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster)
3107 {
3108 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
3109 	struct stripe_head *sh;
3110 	int pd_idx;
3111 	int raid_disks = conf->raid_disks;
3112 	sector_t max_sector = mddev->size << 1;
3113 	int sync_blocks;
3114 	int still_degraded = 0;
3115 	int i;
3116 
3117 	if (sector_nr >= max_sector) {
3118 		/* just being told to finish up .. nothing much to do */
3119 		unplug_slaves(mddev);
3120 		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) {
3121 			end_reshape(conf);
3122 			return 0;
3123 		}
3124 
3125 		if (mddev->curr_resync < max_sector) /* aborted */
3126 			bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
3127 					&sync_blocks, 1);
3128 		else /* completed sync */
3129 			conf->fullsync = 0;
3130 		bitmap_close_sync(mddev->bitmap);
3131 
3132 		return 0;
3133 	}
3134 
3135 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
3136 		return reshape_request(mddev, sector_nr, skipped);
3137 
3138 	/* if there is too many failed drives and we are trying
3139 	 * to resync, then assert that we are finished, because there is
3140 	 * nothing we can do.
3141 	 */
3142 	if (mddev->degraded >= conf->max_degraded &&
3143 	    test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
3144 		sector_t rv = (mddev->size << 1) - sector_nr;
3145 		*skipped = 1;
3146 		return rv;
3147 	}
3148 	if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
3149 	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
3150 	    !conf->fullsync && sync_blocks >= STRIPE_SECTORS) {
3151 		/* we can skip this block, and probably more */
3152 		sync_blocks /= STRIPE_SECTORS;
3153 		*skipped = 1;
3154 		return sync_blocks * STRIPE_SECTORS; /* keep things rounded to whole stripes */
3155 	}
3156 
3157 	pd_idx = stripe_to_pdidx(sector_nr, conf, raid_disks);
3158 	sh = get_active_stripe(conf, sector_nr, raid_disks, pd_idx, 1);
3159 	if (sh == NULL) {
3160 		sh = get_active_stripe(conf, sector_nr, raid_disks, pd_idx, 0);
3161 		/* make sure we don't swamp the stripe cache if someone else
3162 		 * is trying to get access
3163 		 */
3164 		schedule_timeout_uninterruptible(1);
3165 	}
3166 	/* Need to check if array will still be degraded after recovery/resync
3167 	 * We don't need to check the 'failed' flag as when that gets set,
3168 	 * recovery aborts.
3169 	 */
3170 	for (i=0; i<mddev->raid_disks; i++)
3171 		if (conf->disks[i].rdev == NULL)
3172 			still_degraded = 1;
3173 
3174 	bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);
3175 
3176 	spin_lock(&sh->lock);
3177 	set_bit(STRIPE_SYNCING, &sh->state);
3178 	clear_bit(STRIPE_INSYNC, &sh->state);
3179 	spin_unlock(&sh->lock);
3180 
3181 	handle_stripe(sh, NULL);
3182 	release_stripe(sh);
3183 
3184 	return STRIPE_SECTORS;
3185 }
3186 
3187 static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
3188 {
3189 	/* We may not be able to submit a whole bio at once as there
3190 	 * may not be enough stripe_heads available.
3191 	 * We cannot pre-allocate enough stripe_heads as we may need
3192 	 * more than exist in the cache (if we allow ever large chunks).
3193 	 * So we do one stripe head at a time and record in
3194 	 * ->bi_hw_segments how many have been done.
3195 	 *
3196 	 * We *know* that this entire raid_bio is in one chunk, so
3197 	 * it will be only one 'dd_idx' and only need one call to raid5_compute_sector.
3198 	 */
3199 	struct stripe_head *sh;
3200 	int dd_idx, pd_idx;
3201 	sector_t sector, logical_sector, last_sector;
3202 	int scnt = 0;
3203 	int remaining;
3204 	int handled = 0;
3205 
3206 	logical_sector = raid_bio->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
3207 	sector = raid5_compute_sector(	logical_sector,
3208 					conf->raid_disks,
3209 					conf->raid_disks - conf->max_degraded,
3210 					&dd_idx,
3211 					&pd_idx,
3212 					conf);
3213 	last_sector = raid_bio->bi_sector + (raid_bio->bi_size>>9);
3214 
3215 	for (; logical_sector < last_sector;
3216 	     logical_sector += STRIPE_SECTORS,
3217 		     sector += STRIPE_SECTORS,
3218 		     scnt++) {
3219 
3220 		if (scnt < raid_bio->bi_hw_segments)
3221 			/* already done this stripe */
3222 			continue;
3223 
3224 		sh = get_active_stripe(conf, sector, conf->raid_disks, pd_idx, 1);
3225 
3226 		if (!sh) {
3227 			/* failed to get a stripe - must wait */
3228 			raid_bio->bi_hw_segments = scnt;
3229 			conf->retry_read_aligned = raid_bio;
3230 			return handled;
3231 		}
3232 
3233 		set_bit(R5_ReadError, &sh->dev[dd_idx].flags);
3234 		if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
3235 			release_stripe(sh);
3236 			raid_bio->bi_hw_segments = scnt;
3237 			conf->retry_read_aligned = raid_bio;
3238 			return handled;
3239 		}
3240 
3241 		handle_stripe(sh, NULL);
3242 		release_stripe(sh);
3243 		handled++;
3244 	}
3245 	spin_lock_irq(&conf->device_lock);
3246 	remaining = --raid_bio->bi_phys_segments;
3247 	spin_unlock_irq(&conf->device_lock);
3248 	if (remaining == 0) {
3249 		int bytes = raid_bio->bi_size;
3250 
3251 		raid_bio->bi_size = 0;
3252 		raid_bio->bi_end_io(raid_bio, bytes,
3253 			      test_bit(BIO_UPTODATE, &raid_bio->bi_flags)
3254 			        ? 0 : -EIO);
3255 	}
3256 	if (atomic_dec_and_test(&conf->active_aligned_reads))
3257 		wake_up(&conf->wait_for_stripe);
3258 	return handled;
3259 }
3260 
3261 
3262 
3263 /*
3264  * This is our raid5 kernel thread.
3265  *
3266  * We scan the hash table for stripes which can be handled now.
3267  * During the scan, completed stripes are saved for us by the interrupt
3268  * handler, so that they will not have to wait for our next wakeup.
3269  */
3270 static void raid5d (mddev_t *mddev)
3271 {
3272 	struct stripe_head *sh;
3273 	raid5_conf_t *conf = mddev_to_conf(mddev);
3274 	int handled;
3275 
3276 	PRINTK("+++ raid5d active\n");
3277 
3278 	md_check_recovery(mddev);
3279 
3280 	handled = 0;
3281 	spin_lock_irq(&conf->device_lock);
3282 	while (1) {
3283 		struct list_head *first;
3284 		struct bio *bio;
3285 
3286 		if (conf->seq_flush != conf->seq_write) {
3287 			int seq = conf->seq_flush;
3288 			spin_unlock_irq(&conf->device_lock);
3289 			bitmap_unplug(mddev->bitmap);
3290 			spin_lock_irq(&conf->device_lock);
3291 			conf->seq_write = seq;
3292 			activate_bit_delay(conf);
3293 		}
3294 
3295 		if (list_empty(&conf->handle_list) &&
3296 		    atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD &&
3297 		    !blk_queue_plugged(mddev->queue) &&
3298 		    !list_empty(&conf->delayed_list))
3299 			raid5_activate_delayed(conf);
3300 
3301 		while ((bio = remove_bio_from_retry(conf))) {
3302 			int ok;
3303 			spin_unlock_irq(&conf->device_lock);
3304 			ok = retry_aligned_read(conf, bio);
3305 			spin_lock_irq(&conf->device_lock);
3306 			if (!ok)
3307 				break;
3308 			handled++;
3309 		}
3310 
3311 		if (list_empty(&conf->handle_list))
3312 			break;
3313 
3314 		first = conf->handle_list.next;
3315 		sh = list_entry(first, struct stripe_head, lru);
3316 
3317 		list_del_init(first);
3318 		atomic_inc(&sh->count);
3319 		BUG_ON(atomic_read(&sh->count)!= 1);
3320 		spin_unlock_irq(&conf->device_lock);
3321 
3322 		handled++;
3323 		handle_stripe(sh, conf->spare_page);
3324 		release_stripe(sh);
3325 
3326 		spin_lock_irq(&conf->device_lock);
3327 	}
3328 	PRINTK("%d stripes handled\n", handled);
3329 
3330 	spin_unlock_irq(&conf->device_lock);
3331 
3332 	unplug_slaves(mddev);
3333 
3334 	PRINTK("--- raid5d inactive\n");
3335 }
3336 
3337 static ssize_t
3338 raid5_show_stripe_cache_size(mddev_t *mddev, char *page)
3339 {
3340 	raid5_conf_t *conf = mddev_to_conf(mddev);
3341 	if (conf)
3342 		return sprintf(page, "%d\n", conf->max_nr_stripes);
3343 	else
3344 		return 0;
3345 }
3346 
3347 static ssize_t
3348 raid5_store_stripe_cache_size(mddev_t *mddev, const char *page, size_t len)
3349 {
3350 	raid5_conf_t *conf = mddev_to_conf(mddev);
3351 	char *end;
3352 	int new;
3353 	if (len >= PAGE_SIZE)
3354 		return -EINVAL;
3355 	if (!conf)
3356 		return -ENODEV;
3357 
3358 	new = simple_strtoul(page, &end, 10);
3359 	if (!*page || (*end && *end != '\n') )
3360 		return -EINVAL;
3361 	if (new <= 16 || new > 32768)
3362 		return -EINVAL;
3363 	while (new < conf->max_nr_stripes) {
3364 		if (drop_one_stripe(conf))
3365 			conf->max_nr_stripes--;
3366 		else
3367 			break;
3368 	}
3369 	md_allow_write(mddev);
3370 	while (new > conf->max_nr_stripes) {
3371 		if (grow_one_stripe(conf))
3372 			conf->max_nr_stripes++;
3373 		else break;
3374 	}
3375 	return len;
3376 }
3377 
3378 static struct md_sysfs_entry
3379 raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
3380 				raid5_show_stripe_cache_size,
3381 				raid5_store_stripe_cache_size);
3382 
3383 static ssize_t
3384 stripe_cache_active_show(mddev_t *mddev, char *page)
3385 {
3386 	raid5_conf_t *conf = mddev_to_conf(mddev);
3387 	if (conf)
3388 		return sprintf(page, "%d\n", atomic_read(&conf->active_stripes));
3389 	else
3390 		return 0;
3391 }
3392 
3393 static struct md_sysfs_entry
3394 raid5_stripecache_active = __ATTR_RO(stripe_cache_active);
3395 
3396 static struct attribute *raid5_attrs[] =  {
3397 	&raid5_stripecache_size.attr,
3398 	&raid5_stripecache_active.attr,
3399 	NULL,
3400 };
3401 static struct attribute_group raid5_attrs_group = {
3402 	.name = NULL,
3403 	.attrs = raid5_attrs,
3404 };
3405 
3406 static int run(mddev_t *mddev)
3407 {
3408 	raid5_conf_t *conf;
3409 	int raid_disk, memory;
3410 	mdk_rdev_t *rdev;
3411 	struct disk_info *disk;
3412 	struct list_head *tmp;
3413 	int working_disks = 0;
3414 
3415 	if (mddev->level != 5 && mddev->level != 4 && mddev->level != 6) {
3416 		printk(KERN_ERR "raid5: %s: raid level not set to 4/5/6 (%d)\n",
3417 		       mdname(mddev), mddev->level);
3418 		return -EIO;
3419 	}
3420 
3421 	if (mddev->reshape_position != MaxSector) {
3422 		/* Check that we can continue the reshape.
3423 		 * Currently only disks can change, it must
3424 		 * increase, and we must be past the point where
3425 		 * a stripe over-writes itself
3426 		 */
3427 		sector_t here_new, here_old;
3428 		int old_disks;
3429 		int max_degraded = (mddev->level == 5 ? 1 : 2);
3430 
3431 		if (mddev->new_level != mddev->level ||
3432 		    mddev->new_layout != mddev->layout ||
3433 		    mddev->new_chunk != mddev->chunk_size) {
3434 			printk(KERN_ERR "raid5: %s: unsupported reshape "
3435 			       "required - aborting.\n",
3436 			       mdname(mddev));
3437 			return -EINVAL;
3438 		}
3439 		if (mddev->delta_disks <= 0) {
3440 			printk(KERN_ERR "raid5: %s: unsupported reshape "
3441 			       "(reduce disks) required - aborting.\n",
3442 			       mdname(mddev));
3443 			return -EINVAL;
3444 		}
3445 		old_disks = mddev->raid_disks - mddev->delta_disks;
3446 		/* reshape_position must be on a new-stripe boundary, and one
3447 		 * further up in new geometry must map after here in old
3448 		 * geometry.
3449 		 */
3450 		here_new = mddev->reshape_position;
3451 		if (sector_div(here_new, (mddev->chunk_size>>9)*
3452 			       (mddev->raid_disks - max_degraded))) {
3453 			printk(KERN_ERR "raid5: reshape_position not "
3454 			       "on a stripe boundary\n");
3455 			return -EINVAL;
3456 		}
3457 		/* here_new is the stripe we will write to */
3458 		here_old = mddev->reshape_position;
3459 		sector_div(here_old, (mddev->chunk_size>>9)*
3460 			   (old_disks-max_degraded));
3461 		/* here_old is the first stripe that we might need to read
3462 		 * from */
3463 		if (here_new >= here_old) {
3464 			/* Reading from the same stripe as writing to - bad */
3465 			printk(KERN_ERR "raid5: reshape_position too early for "
3466 			       "auto-recovery - aborting.\n");
3467 			return -EINVAL;
3468 		}
3469 		printk(KERN_INFO "raid5: reshape will continue\n");
3470 		/* OK, we should be able to continue; */
3471 	}
3472 
3473 
3474 	mddev->private = kzalloc(sizeof (raid5_conf_t), GFP_KERNEL);
3475 	if ((conf = mddev->private) == NULL)
3476 		goto abort;
3477 	if (mddev->reshape_position == MaxSector) {
3478 		conf->previous_raid_disks = conf->raid_disks = mddev->raid_disks;
3479 	} else {
3480 		conf->raid_disks = mddev->raid_disks;
3481 		conf->previous_raid_disks = mddev->raid_disks - mddev->delta_disks;
3482 	}
3483 
3484 	conf->disks = kzalloc(conf->raid_disks * sizeof(struct disk_info),
3485 			      GFP_KERNEL);
3486 	if (!conf->disks)
3487 		goto abort;
3488 
3489 	conf->mddev = mddev;
3490 
3491 	if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
3492 		goto abort;
3493 
3494 	if (mddev->level == 6) {
3495 		conf->spare_page = alloc_page(GFP_KERNEL);
3496 		if (!conf->spare_page)
3497 			goto abort;
3498 	}
3499 	spin_lock_init(&conf->device_lock);
3500 	init_waitqueue_head(&conf->wait_for_stripe);
3501 	init_waitqueue_head(&conf->wait_for_overlap);
3502 	INIT_LIST_HEAD(&conf->handle_list);
3503 	INIT_LIST_HEAD(&conf->delayed_list);
3504 	INIT_LIST_HEAD(&conf->bitmap_list);
3505 	INIT_LIST_HEAD(&conf->inactive_list);
3506 	atomic_set(&conf->active_stripes, 0);
3507 	atomic_set(&conf->preread_active_stripes, 0);
3508 	atomic_set(&conf->active_aligned_reads, 0);
3509 
3510 	PRINTK("raid5: run(%s) called.\n", mdname(mddev));
3511 
3512 	ITERATE_RDEV(mddev,rdev,tmp) {
3513 		raid_disk = rdev->raid_disk;
3514 		if (raid_disk >= conf->raid_disks
3515 		    || raid_disk < 0)
3516 			continue;
3517 		disk = conf->disks + raid_disk;
3518 
3519 		disk->rdev = rdev;
3520 
3521 		if (test_bit(In_sync, &rdev->flags)) {
3522 			char b[BDEVNAME_SIZE];
3523 			printk(KERN_INFO "raid5: device %s operational as raid"
3524 				" disk %d\n", bdevname(rdev->bdev,b),
3525 				raid_disk);
3526 			working_disks++;
3527 		}
3528 	}
3529 
3530 	/*
3531 	 * 0 for a fully functional array, 1 or 2 for a degraded array.
3532 	 */
3533 	mddev->degraded = conf->raid_disks - working_disks;
3534 	conf->mddev = mddev;
3535 	conf->chunk_size = mddev->chunk_size;
3536 	conf->level = mddev->level;
3537 	if (conf->level == 6)
3538 		conf->max_degraded = 2;
3539 	else
3540 		conf->max_degraded = 1;
3541 	conf->algorithm = mddev->layout;
3542 	conf->max_nr_stripes = NR_STRIPES;
3543 	conf->expand_progress = mddev->reshape_position;
3544 
3545 	/* device size must be a multiple of chunk size */
3546 	mddev->size &= ~(mddev->chunk_size/1024 -1);
3547 	mddev->resync_max_sectors = mddev->size << 1;
3548 
3549 	if (conf->level == 6 && conf->raid_disks < 4) {
3550 		printk(KERN_ERR "raid6: not enough configured devices for %s (%d, minimum 4)\n",
3551 		       mdname(mddev), conf->raid_disks);
3552 		goto abort;
3553 	}
3554 	if (!conf->chunk_size || conf->chunk_size % 4) {
3555 		printk(KERN_ERR "raid5: invalid chunk size %d for %s\n",
3556 			conf->chunk_size, mdname(mddev));
3557 		goto abort;
3558 	}
3559 	if (conf->algorithm > ALGORITHM_RIGHT_SYMMETRIC) {
3560 		printk(KERN_ERR
3561 			"raid5: unsupported parity algorithm %d for %s\n",
3562 			conf->algorithm, mdname(mddev));
3563 		goto abort;
3564 	}
3565 	if (mddev->degraded > conf->max_degraded) {
3566 		printk(KERN_ERR "raid5: not enough operational devices for %s"
3567 			" (%d/%d failed)\n",
3568 			mdname(mddev), mddev->degraded, conf->raid_disks);
3569 		goto abort;
3570 	}
3571 
3572 	if (mddev->degraded > 0 &&
3573 	    mddev->recovery_cp != MaxSector) {
3574 		if (mddev->ok_start_degraded)
3575 			printk(KERN_WARNING
3576 			       "raid5: starting dirty degraded array: %s"
3577 			       "- data corruption possible.\n",
3578 			       mdname(mddev));
3579 		else {
3580 			printk(KERN_ERR
3581 			       "raid5: cannot start dirty degraded array for %s\n",
3582 			       mdname(mddev));
3583 			goto abort;
3584 		}
3585 	}
3586 
3587 	{
3588 		mddev->thread = md_register_thread(raid5d, mddev, "%s_raid5");
3589 		if (!mddev->thread) {
3590 			printk(KERN_ERR
3591 				"raid5: couldn't allocate thread for %s\n",
3592 				mdname(mddev));
3593 			goto abort;
3594 		}
3595 	}
3596 	memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
3597 		 conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
3598 	if (grow_stripes(conf, conf->max_nr_stripes)) {
3599 		printk(KERN_ERR
3600 			"raid5: couldn't allocate %dkB for buffers\n", memory);
3601 		shrink_stripes(conf);
3602 		md_unregister_thread(mddev->thread);
3603 		goto abort;
3604 	} else
3605 		printk(KERN_INFO "raid5: allocated %dkB for %s\n",
3606 			memory, mdname(mddev));
3607 
3608 	if (mddev->degraded == 0)
3609 		printk("raid5: raid level %d set %s active with %d out of %d"
3610 			" devices, algorithm %d\n", conf->level, mdname(mddev),
3611 			mddev->raid_disks-mddev->degraded, mddev->raid_disks,
3612 			conf->algorithm);
3613 	else
3614 		printk(KERN_ALERT "raid5: raid level %d set %s active with %d"
3615 			" out of %d devices, algorithm %d\n", conf->level,
3616 			mdname(mddev), mddev->raid_disks - mddev->degraded,
3617 			mddev->raid_disks, conf->algorithm);
3618 
3619 	print_raid5_conf(conf);
3620 
3621 	if (conf->expand_progress != MaxSector) {
3622 		printk("...ok start reshape thread\n");
3623 		conf->expand_lo = conf->expand_progress;
3624 		atomic_set(&conf->reshape_stripes, 0);
3625 		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
3626 		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
3627 		set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
3628 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
3629 		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
3630 							"%s_reshape");
3631 	}
3632 
3633 	/* read-ahead size must cover two whole stripes, which is
3634 	 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
3635 	 */
3636 	{
3637 		int data_disks = conf->previous_raid_disks - conf->max_degraded;
3638 		int stripe = data_disks *
3639 			(mddev->chunk_size / PAGE_SIZE);
3640 		if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
3641 			mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
3642 	}
3643 
3644 	/* Ok, everything is just fine now */
3645 	if (sysfs_create_group(&mddev->kobj, &raid5_attrs_group))
3646 		printk(KERN_WARNING
3647 		       "raid5: failed to create sysfs attributes for %s\n",
3648 		       mdname(mddev));
3649 
3650 	mddev->queue->unplug_fn = raid5_unplug_device;
3651 	mddev->queue->issue_flush_fn = raid5_issue_flush;
3652 	mddev->queue->backing_dev_info.congested_data = mddev;
3653 	mddev->queue->backing_dev_info.congested_fn = raid5_congested;
3654 
3655 	mddev->array_size =  mddev->size * (conf->previous_raid_disks -
3656 					    conf->max_degraded);
3657 
3658 	blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);
3659 
3660 	return 0;
3661 abort:
3662 	if (conf) {
3663 		print_raid5_conf(conf);
3664 		safe_put_page(conf->spare_page);
3665 		kfree(conf->disks);
3666 		kfree(conf->stripe_hashtbl);
3667 		kfree(conf);
3668 	}
3669 	mddev->private = NULL;
3670 	printk(KERN_ALERT "raid5: failed to run raid set %s\n", mdname(mddev));
3671 	return -EIO;
3672 }
3673 
3674 
3675 
3676 static int stop(mddev_t *mddev)
3677 {
3678 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
3679 
3680 	md_unregister_thread(mddev->thread);
3681 	mddev->thread = NULL;
3682 	shrink_stripes(conf);
3683 	kfree(conf->stripe_hashtbl);
3684 	mddev->queue->backing_dev_info.congested_fn = NULL;
3685 	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
3686 	sysfs_remove_group(&mddev->kobj, &raid5_attrs_group);
3687 	kfree(conf->disks);
3688 	kfree(conf);
3689 	mddev->private = NULL;
3690 	return 0;
3691 }
3692 
3693 #if RAID5_DEBUG
3694 static void print_sh (struct seq_file *seq, struct stripe_head *sh)
3695 {
3696 	int i;
3697 
3698 	seq_printf(seq, "sh %llu, pd_idx %d, state %ld.\n",
3699 		   (unsigned long long)sh->sector, sh->pd_idx, sh->state);
3700 	seq_printf(seq, "sh %llu,  count %d.\n",
3701 		   (unsigned long long)sh->sector, atomic_read(&sh->count));
3702 	seq_printf(seq, "sh %llu, ", (unsigned long long)sh->sector);
3703 	for (i = 0; i < sh->disks; i++) {
3704 		seq_printf(seq, "(cache%d: %p %ld) ",
3705 			   i, sh->dev[i].page, sh->dev[i].flags);
3706 	}
3707 	seq_printf(seq, "\n");
3708 }
3709 
3710 static void printall (struct seq_file *seq, raid5_conf_t *conf)
3711 {
3712 	struct stripe_head *sh;
3713 	struct hlist_node *hn;
3714 	int i;
3715 
3716 	spin_lock_irq(&conf->device_lock);
3717 	for (i = 0; i < NR_HASH; i++) {
3718 		hlist_for_each_entry(sh, hn, &conf->stripe_hashtbl[i], hash) {
3719 			if (sh->raid_conf != conf)
3720 				continue;
3721 			print_sh(seq, sh);
3722 		}
3723 	}
3724 	spin_unlock_irq(&conf->device_lock);
3725 }
3726 #endif
3727 
3728 static void status (struct seq_file *seq, mddev_t *mddev)
3729 {
3730 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
3731 	int i;
3732 
3733 	seq_printf (seq, " level %d, %dk chunk, algorithm %d", mddev->level, mddev->chunk_size >> 10, mddev->layout);
3734 	seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->raid_disks - mddev->degraded);
3735 	for (i = 0; i < conf->raid_disks; i++)
3736 		seq_printf (seq, "%s",
3737 			       conf->disks[i].rdev &&
3738 			       test_bit(In_sync, &conf->disks[i].rdev->flags) ? "U" : "_");
3739 	seq_printf (seq, "]");
3740 #if RAID5_DEBUG
3741 	seq_printf (seq, "\n");
3742 	printall(seq, conf);
3743 #endif
3744 }
3745 
3746 static void print_raid5_conf (raid5_conf_t *conf)
3747 {
3748 	int i;
3749 	struct disk_info *tmp;
3750 
3751 	printk("RAID5 conf printout:\n");
3752 	if (!conf) {
3753 		printk("(conf==NULL)\n");
3754 		return;
3755 	}
3756 	printk(" --- rd:%d wd:%d\n", conf->raid_disks,
3757 		 conf->raid_disks - conf->mddev->degraded);
3758 
3759 	for (i = 0; i < conf->raid_disks; i++) {
3760 		char b[BDEVNAME_SIZE];
3761 		tmp = conf->disks + i;
3762 		if (tmp->rdev)
3763 		printk(" disk %d, o:%d, dev:%s\n",
3764 			i, !test_bit(Faulty, &tmp->rdev->flags),
3765 			bdevname(tmp->rdev->bdev,b));
3766 	}
3767 }
3768 
3769 static int raid5_spare_active(mddev_t *mddev)
3770 {
3771 	int i;
3772 	raid5_conf_t *conf = mddev->private;
3773 	struct disk_info *tmp;
3774 
3775 	for (i = 0; i < conf->raid_disks; i++) {
3776 		tmp = conf->disks + i;
3777 		if (tmp->rdev
3778 		    && !test_bit(Faulty, &tmp->rdev->flags)
3779 		    && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
3780 			unsigned long flags;
3781 			spin_lock_irqsave(&conf->device_lock, flags);
3782 			mddev->degraded--;
3783 			spin_unlock_irqrestore(&conf->device_lock, flags);
3784 		}
3785 	}
3786 	print_raid5_conf(conf);
3787 	return 0;
3788 }
3789 
3790 static int raid5_remove_disk(mddev_t *mddev, int number)
3791 {
3792 	raid5_conf_t *conf = mddev->private;
3793 	int err = 0;
3794 	mdk_rdev_t *rdev;
3795 	struct disk_info *p = conf->disks + number;
3796 
3797 	print_raid5_conf(conf);
3798 	rdev = p->rdev;
3799 	if (rdev) {
3800 		if (test_bit(In_sync, &rdev->flags) ||
3801 		    atomic_read(&rdev->nr_pending)) {
3802 			err = -EBUSY;
3803 			goto abort;
3804 		}
3805 		p->rdev = NULL;
3806 		synchronize_rcu();
3807 		if (atomic_read(&rdev->nr_pending)) {
3808 			/* lost the race, try later */
3809 			err = -EBUSY;
3810 			p->rdev = rdev;
3811 		}
3812 	}
3813 abort:
3814 
3815 	print_raid5_conf(conf);
3816 	return err;
3817 }
3818 
3819 static int raid5_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
3820 {
3821 	raid5_conf_t *conf = mddev->private;
3822 	int found = 0;
3823 	int disk;
3824 	struct disk_info *p;
3825 
3826 	if (mddev->degraded > conf->max_degraded)
3827 		/* no point adding a device */
3828 		return 0;
3829 
3830 	/*
3831 	 * find the disk ... but prefer rdev->saved_raid_disk
3832 	 * if possible.
3833 	 */
3834 	if (rdev->saved_raid_disk >= 0 &&
3835 	    conf->disks[rdev->saved_raid_disk].rdev == NULL)
3836 		disk = rdev->saved_raid_disk;
3837 	else
3838 		disk = 0;
3839 	for ( ; disk < conf->raid_disks; disk++)
3840 		if ((p=conf->disks + disk)->rdev == NULL) {
3841 			clear_bit(In_sync, &rdev->flags);
3842 			rdev->raid_disk = disk;
3843 			found = 1;
3844 			if (rdev->saved_raid_disk != disk)
3845 				conf->fullsync = 1;
3846 			rcu_assign_pointer(p->rdev, rdev);
3847 			break;
3848 		}
3849 	print_raid5_conf(conf);
3850 	return found;
3851 }
3852 
3853 static int raid5_resize(mddev_t *mddev, sector_t sectors)
3854 {
3855 	/* no resync is happening, and there is enough space
3856 	 * on all devices, so we can resize.
3857 	 * We need to make sure resync covers any new space.
3858 	 * If the array is shrinking we should possibly wait until
3859 	 * any io in the removed space completes, but it hardly seems
3860 	 * worth it.
3861 	 */
3862 	raid5_conf_t *conf = mddev_to_conf(mddev);
3863 
3864 	sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
3865 	mddev->array_size = (sectors * (mddev->raid_disks-conf->max_degraded))>>1;
3866 	set_capacity(mddev->gendisk, mddev->array_size << 1);
3867 	mddev->changed = 1;
3868 	if (sectors/2  > mddev->size && mddev->recovery_cp == MaxSector) {
3869 		mddev->recovery_cp = mddev->size << 1;
3870 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
3871 	}
3872 	mddev->size = sectors /2;
3873 	mddev->resync_max_sectors = sectors;
3874 	return 0;
3875 }
3876 
3877 #ifdef CONFIG_MD_RAID5_RESHAPE
3878 static int raid5_check_reshape(mddev_t *mddev)
3879 {
3880 	raid5_conf_t *conf = mddev_to_conf(mddev);
3881 	int err;
3882 
3883 	if (mddev->delta_disks < 0 ||
3884 	    mddev->new_level != mddev->level)
3885 		return -EINVAL; /* Cannot shrink array or change level yet */
3886 	if (mddev->delta_disks == 0)
3887 		return 0; /* nothing to do */
3888 
3889 	/* Can only proceed if there are plenty of stripe_heads.
3890 	 * We need a minimum of one full stripe,, and for sensible progress
3891 	 * it is best to have about 4 times that.
3892 	 * If we require 4 times, then the default 256 4K stripe_heads will
3893 	 * allow for chunk sizes up to 256K, which is probably OK.
3894 	 * If the chunk size is greater, user-space should request more
3895 	 * stripe_heads first.
3896 	 */
3897 	if ((mddev->chunk_size / STRIPE_SIZE) * 4 > conf->max_nr_stripes ||
3898 	    (mddev->new_chunk / STRIPE_SIZE) * 4 > conf->max_nr_stripes) {
3899 		printk(KERN_WARNING "raid5: reshape: not enough stripes.  Needed %lu\n",
3900 		       (mddev->chunk_size / STRIPE_SIZE)*4);
3901 		return -ENOSPC;
3902 	}
3903 
3904 	err = resize_stripes(conf, conf->raid_disks + mddev->delta_disks);
3905 	if (err)
3906 		return err;
3907 
3908 	if (mddev->degraded > conf->max_degraded)
3909 		return -EINVAL;
3910 	/* looks like we might be able to manage this */
3911 	return 0;
3912 }
3913 
3914 static int raid5_start_reshape(mddev_t *mddev)
3915 {
3916 	raid5_conf_t *conf = mddev_to_conf(mddev);
3917 	mdk_rdev_t *rdev;
3918 	struct list_head *rtmp;
3919 	int spares = 0;
3920 	int added_devices = 0;
3921 	unsigned long flags;
3922 
3923 	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
3924 		return -EBUSY;
3925 
3926 	ITERATE_RDEV(mddev, rdev, rtmp)
3927 		if (rdev->raid_disk < 0 &&
3928 		    !test_bit(Faulty, &rdev->flags))
3929 			spares++;
3930 
3931 	if (spares - mddev->degraded < mddev->delta_disks - conf->max_degraded)
3932 		/* Not enough devices even to make a degraded array
3933 		 * of that size
3934 		 */
3935 		return -EINVAL;
3936 
3937 	atomic_set(&conf->reshape_stripes, 0);
3938 	spin_lock_irq(&conf->device_lock);
3939 	conf->previous_raid_disks = conf->raid_disks;
3940 	conf->raid_disks += mddev->delta_disks;
3941 	conf->expand_progress = 0;
3942 	conf->expand_lo = 0;
3943 	spin_unlock_irq(&conf->device_lock);
3944 
3945 	/* Add some new drives, as many as will fit.
3946 	 * We know there are enough to make the newly sized array work.
3947 	 */
3948 	ITERATE_RDEV(mddev, rdev, rtmp)
3949 		if (rdev->raid_disk < 0 &&
3950 		    !test_bit(Faulty, &rdev->flags)) {
3951 			if (raid5_add_disk(mddev, rdev)) {
3952 				char nm[20];
3953 				set_bit(In_sync, &rdev->flags);
3954 				added_devices++;
3955 				rdev->recovery_offset = 0;
3956 				sprintf(nm, "rd%d", rdev->raid_disk);
3957 				if (sysfs_create_link(&mddev->kobj,
3958 						      &rdev->kobj, nm))
3959 					printk(KERN_WARNING
3960 					       "raid5: failed to create "
3961 					       " link %s for %s\n",
3962 					       nm, mdname(mddev));
3963 			} else
3964 				break;
3965 		}
3966 
3967 	spin_lock_irqsave(&conf->device_lock, flags);
3968 	mddev->degraded = (conf->raid_disks - conf->previous_raid_disks) - added_devices;
3969 	spin_unlock_irqrestore(&conf->device_lock, flags);
3970 	mddev->raid_disks = conf->raid_disks;
3971 	mddev->reshape_position = 0;
3972 	set_bit(MD_CHANGE_DEVS, &mddev->flags);
3973 
3974 	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
3975 	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
3976 	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
3977 	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
3978 	mddev->sync_thread = md_register_thread(md_do_sync, mddev,
3979 						"%s_reshape");
3980 	if (!mddev->sync_thread) {
3981 		mddev->recovery = 0;
3982 		spin_lock_irq(&conf->device_lock);
3983 		mddev->raid_disks = conf->raid_disks = conf->previous_raid_disks;
3984 		conf->expand_progress = MaxSector;
3985 		spin_unlock_irq(&conf->device_lock);
3986 		return -EAGAIN;
3987 	}
3988 	md_wakeup_thread(mddev->sync_thread);
3989 	md_new_event(mddev);
3990 	return 0;
3991 }
3992 #endif
3993 
3994 static void end_reshape(raid5_conf_t *conf)
3995 {
3996 	struct block_device *bdev;
3997 
3998 	if (!test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
3999 		conf->mddev->array_size = conf->mddev->size *
4000 			(conf->raid_disks - conf->max_degraded);
4001 		set_capacity(conf->mddev->gendisk, conf->mddev->array_size << 1);
4002 		conf->mddev->changed = 1;
4003 
4004 		bdev = bdget_disk(conf->mddev->gendisk, 0);
4005 		if (bdev) {
4006 			mutex_lock(&bdev->bd_inode->i_mutex);
4007 			i_size_write(bdev->bd_inode, (loff_t)conf->mddev->array_size << 10);
4008 			mutex_unlock(&bdev->bd_inode->i_mutex);
4009 			bdput(bdev);
4010 		}
4011 		spin_lock_irq(&conf->device_lock);
4012 		conf->expand_progress = MaxSector;
4013 		spin_unlock_irq(&conf->device_lock);
4014 		conf->mddev->reshape_position = MaxSector;
4015 
4016 		/* read-ahead size must cover two whole stripes, which is
4017 		 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
4018 		 */
4019 		{
4020 			int data_disks = conf->previous_raid_disks - conf->max_degraded;
4021 			int stripe = data_disks *
4022 				(conf->mddev->chunk_size / PAGE_SIZE);
4023 			if (conf->mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
4024 				conf->mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
4025 		}
4026 	}
4027 }
4028 
4029 static void raid5_quiesce(mddev_t *mddev, int state)
4030 {
4031 	raid5_conf_t *conf = mddev_to_conf(mddev);
4032 
4033 	switch(state) {
4034 	case 2: /* resume for a suspend */
4035 		wake_up(&conf->wait_for_overlap);
4036 		break;
4037 
4038 	case 1: /* stop all writes */
4039 		spin_lock_irq(&conf->device_lock);
4040 		conf->quiesce = 1;
4041 		wait_event_lock_irq(conf->wait_for_stripe,
4042 				    atomic_read(&conf->active_stripes) == 0 &&
4043 				    atomic_read(&conf->active_aligned_reads) == 0,
4044 				    conf->device_lock, /* nothing */);
4045 		spin_unlock_irq(&conf->device_lock);
4046 		break;
4047 
4048 	case 0: /* re-enable writes */
4049 		spin_lock_irq(&conf->device_lock);
4050 		conf->quiesce = 0;
4051 		wake_up(&conf->wait_for_stripe);
4052 		wake_up(&conf->wait_for_overlap);
4053 		spin_unlock_irq(&conf->device_lock);
4054 		break;
4055 	}
4056 }
4057 
4058 static struct mdk_personality raid6_personality =
4059 {
4060 	.name		= "raid6",
4061 	.level		= 6,
4062 	.owner		= THIS_MODULE,
4063 	.make_request	= make_request,
4064 	.run		= run,
4065 	.stop		= stop,
4066 	.status		= status,
4067 	.error_handler	= error,
4068 	.hot_add_disk	= raid5_add_disk,
4069 	.hot_remove_disk= raid5_remove_disk,
4070 	.spare_active	= raid5_spare_active,
4071 	.sync_request	= sync_request,
4072 	.resize		= raid5_resize,
4073 #ifdef CONFIG_MD_RAID5_RESHAPE
4074 	.check_reshape	= raid5_check_reshape,
4075 	.start_reshape  = raid5_start_reshape,
4076 #endif
4077 	.quiesce	= raid5_quiesce,
4078 };
4079 static struct mdk_personality raid5_personality =
4080 {
4081 	.name		= "raid5",
4082 	.level		= 5,
4083 	.owner		= THIS_MODULE,
4084 	.make_request	= make_request,
4085 	.run		= run,
4086 	.stop		= stop,
4087 	.status		= status,
4088 	.error_handler	= error,
4089 	.hot_add_disk	= raid5_add_disk,
4090 	.hot_remove_disk= raid5_remove_disk,
4091 	.spare_active	= raid5_spare_active,
4092 	.sync_request	= sync_request,
4093 	.resize		= raid5_resize,
4094 #ifdef CONFIG_MD_RAID5_RESHAPE
4095 	.check_reshape	= raid5_check_reshape,
4096 	.start_reshape  = raid5_start_reshape,
4097 #endif
4098 	.quiesce	= raid5_quiesce,
4099 };
4100 
4101 static struct mdk_personality raid4_personality =
4102 {
4103 	.name		= "raid4",
4104 	.level		= 4,
4105 	.owner		= THIS_MODULE,
4106 	.make_request	= make_request,
4107 	.run		= run,
4108 	.stop		= stop,
4109 	.status		= status,
4110 	.error_handler	= error,
4111 	.hot_add_disk	= raid5_add_disk,
4112 	.hot_remove_disk= raid5_remove_disk,
4113 	.spare_active	= raid5_spare_active,
4114 	.sync_request	= sync_request,
4115 	.resize		= raid5_resize,
4116 #ifdef CONFIG_MD_RAID5_RESHAPE
4117 	.check_reshape	= raid5_check_reshape,
4118 	.start_reshape  = raid5_start_reshape,
4119 #endif
4120 	.quiesce	= raid5_quiesce,
4121 };
4122 
4123 static int __init raid5_init(void)
4124 {
4125 	int e;
4126 
4127 	e = raid6_select_algo();
4128 	if ( e )
4129 		return e;
4130 	register_md_personality(&raid6_personality);
4131 	register_md_personality(&raid5_personality);
4132 	register_md_personality(&raid4_personality);
4133 	return 0;
4134 }
4135 
4136 static void raid5_exit(void)
4137 {
4138 	unregister_md_personality(&raid6_personality);
4139 	unregister_md_personality(&raid5_personality);
4140 	unregister_md_personality(&raid4_personality);
4141 }
4142 
4143 module_init(raid5_init);
4144 module_exit(raid5_exit);
4145 MODULE_LICENSE("GPL");
4146 MODULE_ALIAS("md-personality-4"); /* RAID5 */
4147 MODULE_ALIAS("md-raid5");
4148 MODULE_ALIAS("md-raid4");
4149 MODULE_ALIAS("md-level-5");
4150 MODULE_ALIAS("md-level-4");
4151 MODULE_ALIAS("md-personality-8"); /* RAID6 */
4152 MODULE_ALIAS("md-raid6");
4153 MODULE_ALIAS("md-level-6");
4154 
4155 /* This used to be two separate modules, they were: */
4156 MODULE_ALIAS("raid5");
4157 MODULE_ALIAS("raid6");
4158