xref: /openbmc/linux/drivers/md/raid10.c (revision ee7da21a)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * raid10.c : Multiple Devices driver for Linux
4  *
5  * Copyright (C) 2000-2004 Neil Brown
6  *
7  * RAID-10 support for md.
8  *
9  * Base on code in raid1.c.  See raid1.c for further copyright information.
10  */
11 
12 #include <linux/slab.h>
13 #include <linux/delay.h>
14 #include <linux/blkdev.h>
15 #include <linux/module.h>
16 #include <linux/seq_file.h>
17 #include <linux/ratelimit.h>
18 #include <linux/kthread.h>
19 #include <linux/raid/md_p.h>
20 #include <trace/events/block.h>
21 #include "md.h"
22 #include "raid10.h"
23 #include "raid0.h"
24 #include "md-bitmap.h"
25 
26 /*
27  * RAID10 provides a combination of RAID0 and RAID1 functionality.
28  * The layout of data is defined by
29  *    chunk_size
30  *    raid_disks
31  *    near_copies (stored in low byte of layout)
32  *    far_copies (stored in second byte of layout)
33  *    far_offset (stored in bit 16 of layout )
34  *    use_far_sets (stored in bit 17 of layout )
35  *    use_far_sets_bugfixed (stored in bit 18 of layout )
36  *
37  * The data to be stored is divided into chunks using chunksize.  Each device
38  * is divided into far_copies sections.   In each section, chunks are laid out
39  * in a style similar to raid0, but near_copies copies of each chunk is stored
40  * (each on a different drive).  The starting device for each section is offset
41  * near_copies from the starting device of the previous section.  Thus there
42  * are (near_copies * far_copies) of each chunk, and each is on a different
43  * drive.  near_copies and far_copies must be at least one, and their product
44  * is at most raid_disks.
45  *
46  * If far_offset is true, then the far_copies are handled a bit differently.
47  * The copies are still in different stripes, but instead of being very far
48  * apart on disk, there are adjacent stripes.
49  *
50  * The far and offset algorithms are handled slightly differently if
51  * 'use_far_sets' is true.  In this case, the array's devices are grouped into
52  * sets that are (near_copies * far_copies) in size.  The far copied stripes
53  * are still shifted by 'near_copies' devices, but this shifting stays confined
54  * to the set rather than the entire array.  This is done to improve the number
55  * of device combinations that can fail without causing the array to fail.
56  * Example 'far' algorithm w/o 'use_far_sets' (each letter represents a chunk
57  * on a device):
58  *    A B C D    A B C D E
59  *      ...         ...
60  *    D A B C    E A B C D
61  * Example 'far' algorithm w/ 'use_far_sets' enabled (sets illustrated w/ []'s):
62  *    [A B] [C D]    [A B] [C D E]
63  *    |...| |...|    |...| | ... |
64  *    [B A] [D C]    [B A] [E C D]
65  */
66 
67 static void allow_barrier(struct r10conf *conf);
68 static void lower_barrier(struct r10conf *conf);
69 static int _enough(struct r10conf *conf, int previous, int ignore);
70 static int enough(struct r10conf *conf, int ignore);
71 static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
72 				int *skipped);
73 static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio);
74 static void end_reshape_write(struct bio *bio);
75 static void end_reshape(struct r10conf *conf);
76 
77 #define raid10_log(md, fmt, args...)				\
78 	do { if ((md)->queue) blk_add_trace_msg((md)->queue, "raid10 " fmt, ##args); } while (0)
79 
80 #include "raid1-10.c"
81 
82 /*
83  * for resync bio, r10bio pointer can be retrieved from the per-bio
84  * 'struct resync_pages'.
85  */
86 static inline struct r10bio *get_resync_r10bio(struct bio *bio)
87 {
88 	return get_resync_pages(bio)->raid_bio;
89 }
90 
91 static void * r10bio_pool_alloc(gfp_t gfp_flags, void *data)
92 {
93 	struct r10conf *conf = data;
94 	int size = offsetof(struct r10bio, devs[conf->geo.raid_disks]);
95 
96 	/* allocate a r10bio with room for raid_disks entries in the
97 	 * bios array */
98 	return kzalloc(size, gfp_flags);
99 }
100 
101 #define RESYNC_SECTORS (RESYNC_BLOCK_SIZE >> 9)
102 /* amount of memory to reserve for resync requests */
103 #define RESYNC_WINDOW (1024*1024)
104 /* maximum number of concurrent requests, memory permitting */
105 #define RESYNC_DEPTH (32*1024*1024/RESYNC_BLOCK_SIZE)
106 #define CLUSTER_RESYNC_WINDOW (32 * RESYNC_WINDOW)
107 #define CLUSTER_RESYNC_WINDOW_SECTORS (CLUSTER_RESYNC_WINDOW >> 9)
108 
109 /*
110  * When performing a resync, we need to read and compare, so
111  * we need as many pages are there are copies.
112  * When performing a recovery, we need 2 bios, one for read,
113  * one for write (we recover only one drive per r10buf)
114  *
115  */
116 static void * r10buf_pool_alloc(gfp_t gfp_flags, void *data)
117 {
118 	struct r10conf *conf = data;
119 	struct r10bio *r10_bio;
120 	struct bio *bio;
121 	int j;
122 	int nalloc, nalloc_rp;
123 	struct resync_pages *rps;
124 
125 	r10_bio = r10bio_pool_alloc(gfp_flags, conf);
126 	if (!r10_bio)
127 		return NULL;
128 
129 	if (test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery) ||
130 	    test_bit(MD_RECOVERY_RESHAPE, &conf->mddev->recovery))
131 		nalloc = conf->copies; /* resync */
132 	else
133 		nalloc = 2; /* recovery */
134 
135 	/* allocate once for all bios */
136 	if (!conf->have_replacement)
137 		nalloc_rp = nalloc;
138 	else
139 		nalloc_rp = nalloc * 2;
140 	rps = kmalloc_array(nalloc_rp, sizeof(struct resync_pages), gfp_flags);
141 	if (!rps)
142 		goto out_free_r10bio;
143 
144 	/*
145 	 * Allocate bios.
146 	 */
147 	for (j = nalloc ; j-- ; ) {
148 		bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
149 		if (!bio)
150 			goto out_free_bio;
151 		r10_bio->devs[j].bio = bio;
152 		if (!conf->have_replacement)
153 			continue;
154 		bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
155 		if (!bio)
156 			goto out_free_bio;
157 		r10_bio->devs[j].repl_bio = bio;
158 	}
159 	/*
160 	 * Allocate RESYNC_PAGES data pages and attach them
161 	 * where needed.
162 	 */
163 	for (j = 0; j < nalloc; j++) {
164 		struct bio *rbio = r10_bio->devs[j].repl_bio;
165 		struct resync_pages *rp, *rp_repl;
166 
167 		rp = &rps[j];
168 		if (rbio)
169 			rp_repl = &rps[nalloc + j];
170 
171 		bio = r10_bio->devs[j].bio;
172 
173 		if (!j || test_bit(MD_RECOVERY_SYNC,
174 				   &conf->mddev->recovery)) {
175 			if (resync_alloc_pages(rp, gfp_flags))
176 				goto out_free_pages;
177 		} else {
178 			memcpy(rp, &rps[0], sizeof(*rp));
179 			resync_get_all_pages(rp);
180 		}
181 
182 		rp->raid_bio = r10_bio;
183 		bio->bi_private = rp;
184 		if (rbio) {
185 			memcpy(rp_repl, rp, sizeof(*rp));
186 			rbio->bi_private = rp_repl;
187 		}
188 	}
189 
190 	return r10_bio;
191 
192 out_free_pages:
193 	while (--j >= 0)
194 		resync_free_pages(&rps[j]);
195 
196 	j = 0;
197 out_free_bio:
198 	for ( ; j < nalloc; j++) {
199 		if (r10_bio->devs[j].bio)
200 			bio_put(r10_bio->devs[j].bio);
201 		if (r10_bio->devs[j].repl_bio)
202 			bio_put(r10_bio->devs[j].repl_bio);
203 	}
204 	kfree(rps);
205 out_free_r10bio:
206 	rbio_pool_free(r10_bio, conf);
207 	return NULL;
208 }
209 
210 static void r10buf_pool_free(void *__r10_bio, void *data)
211 {
212 	struct r10conf *conf = data;
213 	struct r10bio *r10bio = __r10_bio;
214 	int j;
215 	struct resync_pages *rp = NULL;
216 
217 	for (j = conf->copies; j--; ) {
218 		struct bio *bio = r10bio->devs[j].bio;
219 
220 		if (bio) {
221 			rp = get_resync_pages(bio);
222 			resync_free_pages(rp);
223 			bio_put(bio);
224 		}
225 
226 		bio = r10bio->devs[j].repl_bio;
227 		if (bio)
228 			bio_put(bio);
229 	}
230 
231 	/* resync pages array stored in the 1st bio's .bi_private */
232 	kfree(rp);
233 
234 	rbio_pool_free(r10bio, conf);
235 }
236 
237 static void put_all_bios(struct r10conf *conf, struct r10bio *r10_bio)
238 {
239 	int i;
240 
241 	for (i = 0; i < conf->geo.raid_disks; i++) {
242 		struct bio **bio = & r10_bio->devs[i].bio;
243 		if (!BIO_SPECIAL(*bio))
244 			bio_put(*bio);
245 		*bio = NULL;
246 		bio = &r10_bio->devs[i].repl_bio;
247 		if (r10_bio->read_slot < 0 && !BIO_SPECIAL(*bio))
248 			bio_put(*bio);
249 		*bio = NULL;
250 	}
251 }
252 
253 static void free_r10bio(struct r10bio *r10_bio)
254 {
255 	struct r10conf *conf = r10_bio->mddev->private;
256 
257 	put_all_bios(conf, r10_bio);
258 	mempool_free(r10_bio, &conf->r10bio_pool);
259 }
260 
261 static void put_buf(struct r10bio *r10_bio)
262 {
263 	struct r10conf *conf = r10_bio->mddev->private;
264 
265 	mempool_free(r10_bio, &conf->r10buf_pool);
266 
267 	lower_barrier(conf);
268 }
269 
270 static void reschedule_retry(struct r10bio *r10_bio)
271 {
272 	unsigned long flags;
273 	struct mddev *mddev = r10_bio->mddev;
274 	struct r10conf *conf = mddev->private;
275 
276 	spin_lock_irqsave(&conf->device_lock, flags);
277 	list_add(&r10_bio->retry_list, &conf->retry_list);
278 	conf->nr_queued ++;
279 	spin_unlock_irqrestore(&conf->device_lock, flags);
280 
281 	/* wake up frozen array... */
282 	wake_up(&conf->wait_barrier);
283 
284 	md_wakeup_thread(mddev->thread);
285 }
286 
287 /*
288  * raid_end_bio_io() is called when we have finished servicing a mirrored
289  * operation and are ready to return a success/failure code to the buffer
290  * cache layer.
291  */
292 static void raid_end_bio_io(struct r10bio *r10_bio)
293 {
294 	struct bio *bio = r10_bio->master_bio;
295 	struct r10conf *conf = r10_bio->mddev->private;
296 
297 	if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
298 		bio->bi_status = BLK_STS_IOERR;
299 
300 	if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
301 		bio_end_io_acct(bio, r10_bio->start_time);
302 	bio_endio(bio);
303 	/*
304 	 * Wake up any possible resync thread that waits for the device
305 	 * to go idle.
306 	 */
307 	allow_barrier(conf);
308 
309 	free_r10bio(r10_bio);
310 }
311 
312 /*
313  * Update disk head position estimator based on IRQ completion info.
314  */
315 static inline void update_head_pos(int slot, struct r10bio *r10_bio)
316 {
317 	struct r10conf *conf = r10_bio->mddev->private;
318 
319 	conf->mirrors[r10_bio->devs[slot].devnum].head_position =
320 		r10_bio->devs[slot].addr + (r10_bio->sectors);
321 }
322 
323 /*
324  * Find the disk number which triggered given bio
325  */
326 static int find_bio_disk(struct r10conf *conf, struct r10bio *r10_bio,
327 			 struct bio *bio, int *slotp, int *replp)
328 {
329 	int slot;
330 	int repl = 0;
331 
332 	for (slot = 0; slot < conf->geo.raid_disks; slot++) {
333 		if (r10_bio->devs[slot].bio == bio)
334 			break;
335 		if (r10_bio->devs[slot].repl_bio == bio) {
336 			repl = 1;
337 			break;
338 		}
339 	}
340 
341 	update_head_pos(slot, r10_bio);
342 
343 	if (slotp)
344 		*slotp = slot;
345 	if (replp)
346 		*replp = repl;
347 	return r10_bio->devs[slot].devnum;
348 }
349 
350 static void raid10_end_read_request(struct bio *bio)
351 {
352 	int uptodate = !bio->bi_status;
353 	struct r10bio *r10_bio = bio->bi_private;
354 	int slot;
355 	struct md_rdev *rdev;
356 	struct r10conf *conf = r10_bio->mddev->private;
357 
358 	slot = r10_bio->read_slot;
359 	rdev = r10_bio->devs[slot].rdev;
360 	/*
361 	 * this branch is our 'one mirror IO has finished' event handler:
362 	 */
363 	update_head_pos(slot, r10_bio);
364 
365 	if (uptodate) {
366 		/*
367 		 * Set R10BIO_Uptodate in our master bio, so that
368 		 * we will return a good error code to the higher
369 		 * levels even if IO on some other mirrored buffer fails.
370 		 *
371 		 * The 'master' represents the composite IO operation to
372 		 * user-side. So if something waits for IO, then it will
373 		 * wait for the 'master' bio.
374 		 */
375 		set_bit(R10BIO_Uptodate, &r10_bio->state);
376 	} else {
377 		/* If all other devices that store this block have
378 		 * failed, we want to return the error upwards rather
379 		 * than fail the last device.  Here we redefine
380 		 * "uptodate" to mean "Don't want to retry"
381 		 */
382 		if (!_enough(conf, test_bit(R10BIO_Previous, &r10_bio->state),
383 			     rdev->raid_disk))
384 			uptodate = 1;
385 	}
386 	if (uptodate) {
387 		raid_end_bio_io(r10_bio);
388 		rdev_dec_pending(rdev, conf->mddev);
389 	} else {
390 		/*
391 		 * oops, read error - keep the refcount on the rdev
392 		 */
393 		char b[BDEVNAME_SIZE];
394 		pr_err_ratelimited("md/raid10:%s: %s: rescheduling sector %llu\n",
395 				   mdname(conf->mddev),
396 				   bdevname(rdev->bdev, b),
397 				   (unsigned long long)r10_bio->sector);
398 		set_bit(R10BIO_ReadError, &r10_bio->state);
399 		reschedule_retry(r10_bio);
400 	}
401 }
402 
403 static void close_write(struct r10bio *r10_bio)
404 {
405 	/* clear the bitmap if all writes complete successfully */
406 	md_bitmap_endwrite(r10_bio->mddev->bitmap, r10_bio->sector,
407 			   r10_bio->sectors,
408 			   !test_bit(R10BIO_Degraded, &r10_bio->state),
409 			   0);
410 	md_write_end(r10_bio->mddev);
411 }
412 
413 static void one_write_done(struct r10bio *r10_bio)
414 {
415 	if (atomic_dec_and_test(&r10_bio->remaining)) {
416 		if (test_bit(R10BIO_WriteError, &r10_bio->state))
417 			reschedule_retry(r10_bio);
418 		else {
419 			close_write(r10_bio);
420 			if (test_bit(R10BIO_MadeGood, &r10_bio->state))
421 				reschedule_retry(r10_bio);
422 			else
423 				raid_end_bio_io(r10_bio);
424 		}
425 	}
426 }
427 
428 static void raid10_end_write_request(struct bio *bio)
429 {
430 	struct r10bio *r10_bio = bio->bi_private;
431 	int dev;
432 	int dec_rdev = 1;
433 	struct r10conf *conf = r10_bio->mddev->private;
434 	int slot, repl;
435 	struct md_rdev *rdev = NULL;
436 	struct bio *to_put = NULL;
437 	bool discard_error;
438 
439 	discard_error = bio->bi_status && bio_op(bio) == REQ_OP_DISCARD;
440 
441 	dev = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
442 
443 	if (repl)
444 		rdev = conf->mirrors[dev].replacement;
445 	if (!rdev) {
446 		smp_rmb();
447 		repl = 0;
448 		rdev = conf->mirrors[dev].rdev;
449 	}
450 	/*
451 	 * this branch is our 'one mirror IO has finished' event handler:
452 	 */
453 	if (bio->bi_status && !discard_error) {
454 		if (repl)
455 			/* Never record new bad blocks to replacement,
456 			 * just fail it.
457 			 */
458 			md_error(rdev->mddev, rdev);
459 		else {
460 			set_bit(WriteErrorSeen,	&rdev->flags);
461 			if (!test_and_set_bit(WantReplacement, &rdev->flags))
462 				set_bit(MD_RECOVERY_NEEDED,
463 					&rdev->mddev->recovery);
464 
465 			dec_rdev = 0;
466 			if (test_bit(FailFast, &rdev->flags) &&
467 			    (bio->bi_opf & MD_FAILFAST)) {
468 				md_error(rdev->mddev, rdev);
469 			}
470 
471 			/*
472 			 * When the device is faulty, it is not necessary to
473 			 * handle write error.
474 			 */
475 			if (!test_bit(Faulty, &rdev->flags))
476 				set_bit(R10BIO_WriteError, &r10_bio->state);
477 			else {
478 				/* Fail the request */
479 				set_bit(R10BIO_Degraded, &r10_bio->state);
480 				r10_bio->devs[slot].bio = NULL;
481 				to_put = bio;
482 				dec_rdev = 1;
483 			}
484 		}
485 	} else {
486 		/*
487 		 * Set R10BIO_Uptodate in our master bio, so that
488 		 * we will return a good error code for to the higher
489 		 * levels even if IO on some other mirrored buffer fails.
490 		 *
491 		 * The 'master' represents the composite IO operation to
492 		 * user-side. So if something waits for IO, then it will
493 		 * wait for the 'master' bio.
494 		 */
495 		sector_t first_bad;
496 		int bad_sectors;
497 
498 		/*
499 		 * Do not set R10BIO_Uptodate if the current device is
500 		 * rebuilding or Faulty. This is because we cannot use
501 		 * such device for properly reading the data back (we could
502 		 * potentially use it, if the current write would have felt
503 		 * before rdev->recovery_offset, but for simplicity we don't
504 		 * check this here.
505 		 */
506 		if (test_bit(In_sync, &rdev->flags) &&
507 		    !test_bit(Faulty, &rdev->flags))
508 			set_bit(R10BIO_Uptodate, &r10_bio->state);
509 
510 		/* Maybe we can clear some bad blocks. */
511 		if (is_badblock(rdev,
512 				r10_bio->devs[slot].addr,
513 				r10_bio->sectors,
514 				&first_bad, &bad_sectors) && !discard_error) {
515 			bio_put(bio);
516 			if (repl)
517 				r10_bio->devs[slot].repl_bio = IO_MADE_GOOD;
518 			else
519 				r10_bio->devs[slot].bio = IO_MADE_GOOD;
520 			dec_rdev = 0;
521 			set_bit(R10BIO_MadeGood, &r10_bio->state);
522 		}
523 	}
524 
525 	/*
526 	 *
527 	 * Let's see if all mirrored write operations have finished
528 	 * already.
529 	 */
530 	one_write_done(r10_bio);
531 	if (dec_rdev)
532 		rdev_dec_pending(rdev, conf->mddev);
533 	if (to_put)
534 		bio_put(to_put);
535 }
536 
537 /*
538  * RAID10 layout manager
539  * As well as the chunksize and raid_disks count, there are two
540  * parameters: near_copies and far_copies.
541  * near_copies * far_copies must be <= raid_disks.
542  * Normally one of these will be 1.
543  * If both are 1, we get raid0.
544  * If near_copies == raid_disks, we get raid1.
545  *
546  * Chunks are laid out in raid0 style with near_copies copies of the
547  * first chunk, followed by near_copies copies of the next chunk and
548  * so on.
549  * If far_copies > 1, then after 1/far_copies of the array has been assigned
550  * as described above, we start again with a device offset of near_copies.
551  * So we effectively have another copy of the whole array further down all
552  * the drives, but with blocks on different drives.
553  * With this layout, and block is never stored twice on the one device.
554  *
555  * raid10_find_phys finds the sector offset of a given virtual sector
556  * on each device that it is on.
557  *
558  * raid10_find_virt does the reverse mapping, from a device and a
559  * sector offset to a virtual address
560  */
561 
562 static void __raid10_find_phys(struct geom *geo, struct r10bio *r10bio)
563 {
564 	int n,f;
565 	sector_t sector;
566 	sector_t chunk;
567 	sector_t stripe;
568 	int dev;
569 	int slot = 0;
570 	int last_far_set_start, last_far_set_size;
571 
572 	last_far_set_start = (geo->raid_disks / geo->far_set_size) - 1;
573 	last_far_set_start *= geo->far_set_size;
574 
575 	last_far_set_size = geo->far_set_size;
576 	last_far_set_size += (geo->raid_disks % geo->far_set_size);
577 
578 	/* now calculate first sector/dev */
579 	chunk = r10bio->sector >> geo->chunk_shift;
580 	sector = r10bio->sector & geo->chunk_mask;
581 
582 	chunk *= geo->near_copies;
583 	stripe = chunk;
584 	dev = sector_div(stripe, geo->raid_disks);
585 	if (geo->far_offset)
586 		stripe *= geo->far_copies;
587 
588 	sector += stripe << geo->chunk_shift;
589 
590 	/* and calculate all the others */
591 	for (n = 0; n < geo->near_copies; n++) {
592 		int d = dev;
593 		int set;
594 		sector_t s = sector;
595 		r10bio->devs[slot].devnum = d;
596 		r10bio->devs[slot].addr = s;
597 		slot++;
598 
599 		for (f = 1; f < geo->far_copies; f++) {
600 			set = d / geo->far_set_size;
601 			d += geo->near_copies;
602 
603 			if ((geo->raid_disks % geo->far_set_size) &&
604 			    (d > last_far_set_start)) {
605 				d -= last_far_set_start;
606 				d %= last_far_set_size;
607 				d += last_far_set_start;
608 			} else {
609 				d %= geo->far_set_size;
610 				d += geo->far_set_size * set;
611 			}
612 			s += geo->stride;
613 			r10bio->devs[slot].devnum = d;
614 			r10bio->devs[slot].addr = s;
615 			slot++;
616 		}
617 		dev++;
618 		if (dev >= geo->raid_disks) {
619 			dev = 0;
620 			sector += (geo->chunk_mask + 1);
621 		}
622 	}
623 }
624 
625 static void raid10_find_phys(struct r10conf *conf, struct r10bio *r10bio)
626 {
627 	struct geom *geo = &conf->geo;
628 
629 	if (conf->reshape_progress != MaxSector &&
630 	    ((r10bio->sector >= conf->reshape_progress) !=
631 	     conf->mddev->reshape_backwards)) {
632 		set_bit(R10BIO_Previous, &r10bio->state);
633 		geo = &conf->prev;
634 	} else
635 		clear_bit(R10BIO_Previous, &r10bio->state);
636 
637 	__raid10_find_phys(geo, r10bio);
638 }
639 
640 static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)
641 {
642 	sector_t offset, chunk, vchunk;
643 	/* Never use conf->prev as this is only called during resync
644 	 * or recovery, so reshape isn't happening
645 	 */
646 	struct geom *geo = &conf->geo;
647 	int far_set_start = (dev / geo->far_set_size) * geo->far_set_size;
648 	int far_set_size = geo->far_set_size;
649 	int last_far_set_start;
650 
651 	if (geo->raid_disks % geo->far_set_size) {
652 		last_far_set_start = (geo->raid_disks / geo->far_set_size) - 1;
653 		last_far_set_start *= geo->far_set_size;
654 
655 		if (dev >= last_far_set_start) {
656 			far_set_size = geo->far_set_size;
657 			far_set_size += (geo->raid_disks % geo->far_set_size);
658 			far_set_start = last_far_set_start;
659 		}
660 	}
661 
662 	offset = sector & geo->chunk_mask;
663 	if (geo->far_offset) {
664 		int fc;
665 		chunk = sector >> geo->chunk_shift;
666 		fc = sector_div(chunk, geo->far_copies);
667 		dev -= fc * geo->near_copies;
668 		if (dev < far_set_start)
669 			dev += far_set_size;
670 	} else {
671 		while (sector >= geo->stride) {
672 			sector -= geo->stride;
673 			if (dev < (geo->near_copies + far_set_start))
674 				dev += far_set_size - geo->near_copies;
675 			else
676 				dev -= geo->near_copies;
677 		}
678 		chunk = sector >> geo->chunk_shift;
679 	}
680 	vchunk = chunk * geo->raid_disks + dev;
681 	sector_div(vchunk, geo->near_copies);
682 	return (vchunk << geo->chunk_shift) + offset;
683 }
684 
685 /*
686  * This routine returns the disk from which the requested read should
687  * be done. There is a per-array 'next expected sequential IO' sector
688  * number - if this matches on the next IO then we use the last disk.
689  * There is also a per-disk 'last know head position' sector that is
690  * maintained from IRQ contexts, both the normal and the resync IO
691  * completion handlers update this position correctly. If there is no
692  * perfect sequential match then we pick the disk whose head is closest.
693  *
694  * If there are 2 mirrors in the same 2 devices, performance degrades
695  * because position is mirror, not device based.
696  *
697  * The rdev for the device selected will have nr_pending incremented.
698  */
699 
700 /*
701  * FIXME: possibly should rethink readbalancing and do it differently
702  * depending on near_copies / far_copies geometry.
703  */
704 static struct md_rdev *read_balance(struct r10conf *conf,
705 				    struct r10bio *r10_bio,
706 				    int *max_sectors)
707 {
708 	const sector_t this_sector = r10_bio->sector;
709 	int disk, slot;
710 	int sectors = r10_bio->sectors;
711 	int best_good_sectors;
712 	sector_t new_distance, best_dist;
713 	struct md_rdev *best_dist_rdev, *best_pending_rdev, *rdev = NULL;
714 	int do_balance;
715 	int best_dist_slot, best_pending_slot;
716 	bool has_nonrot_disk = false;
717 	unsigned int min_pending;
718 	struct geom *geo = &conf->geo;
719 
720 	raid10_find_phys(conf, r10_bio);
721 	rcu_read_lock();
722 	best_dist_slot = -1;
723 	min_pending = UINT_MAX;
724 	best_dist_rdev = NULL;
725 	best_pending_rdev = NULL;
726 	best_dist = MaxSector;
727 	best_good_sectors = 0;
728 	do_balance = 1;
729 	clear_bit(R10BIO_FailFast, &r10_bio->state);
730 	/*
731 	 * Check if we can balance. We can balance on the whole
732 	 * device if no resync is going on (recovery is ok), or below
733 	 * the resync window. We take the first readable disk when
734 	 * above the resync window.
735 	 */
736 	if ((conf->mddev->recovery_cp < MaxSector
737 	     && (this_sector + sectors >= conf->next_resync)) ||
738 	    (mddev_is_clustered(conf->mddev) &&
739 	     md_cluster_ops->area_resyncing(conf->mddev, READ, this_sector,
740 					    this_sector + sectors)))
741 		do_balance = 0;
742 
743 	for (slot = 0; slot < conf->copies ; slot++) {
744 		sector_t first_bad;
745 		int bad_sectors;
746 		sector_t dev_sector;
747 		unsigned int pending;
748 		bool nonrot;
749 
750 		if (r10_bio->devs[slot].bio == IO_BLOCKED)
751 			continue;
752 		disk = r10_bio->devs[slot].devnum;
753 		rdev = rcu_dereference(conf->mirrors[disk].replacement);
754 		if (rdev == NULL || test_bit(Faulty, &rdev->flags) ||
755 		    r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
756 			rdev = rcu_dereference(conf->mirrors[disk].rdev);
757 		if (rdev == NULL ||
758 		    test_bit(Faulty, &rdev->flags))
759 			continue;
760 		if (!test_bit(In_sync, &rdev->flags) &&
761 		    r10_bio->devs[slot].addr + sectors > rdev->recovery_offset)
762 			continue;
763 
764 		dev_sector = r10_bio->devs[slot].addr;
765 		if (is_badblock(rdev, dev_sector, sectors,
766 				&first_bad, &bad_sectors)) {
767 			if (best_dist < MaxSector)
768 				/* Already have a better slot */
769 				continue;
770 			if (first_bad <= dev_sector) {
771 				/* Cannot read here.  If this is the
772 				 * 'primary' device, then we must not read
773 				 * beyond 'bad_sectors' from another device.
774 				 */
775 				bad_sectors -= (dev_sector - first_bad);
776 				if (!do_balance && sectors > bad_sectors)
777 					sectors = bad_sectors;
778 				if (best_good_sectors > sectors)
779 					best_good_sectors = sectors;
780 			} else {
781 				sector_t good_sectors =
782 					first_bad - dev_sector;
783 				if (good_sectors > best_good_sectors) {
784 					best_good_sectors = good_sectors;
785 					best_dist_slot = slot;
786 					best_dist_rdev = rdev;
787 				}
788 				if (!do_balance)
789 					/* Must read from here */
790 					break;
791 			}
792 			continue;
793 		} else
794 			best_good_sectors = sectors;
795 
796 		if (!do_balance)
797 			break;
798 
799 		nonrot = blk_queue_nonrot(bdev_get_queue(rdev->bdev));
800 		has_nonrot_disk |= nonrot;
801 		pending = atomic_read(&rdev->nr_pending);
802 		if (min_pending > pending && nonrot) {
803 			min_pending = pending;
804 			best_pending_slot = slot;
805 			best_pending_rdev = rdev;
806 		}
807 
808 		if (best_dist_slot >= 0)
809 			/* At least 2 disks to choose from so failfast is OK */
810 			set_bit(R10BIO_FailFast, &r10_bio->state);
811 		/* This optimisation is debatable, and completely destroys
812 		 * sequential read speed for 'far copies' arrays.  So only
813 		 * keep it for 'near' arrays, and review those later.
814 		 */
815 		if (geo->near_copies > 1 && !pending)
816 			new_distance = 0;
817 
818 		/* for far > 1 always use the lowest address */
819 		else if (geo->far_copies > 1)
820 			new_distance = r10_bio->devs[slot].addr;
821 		else
822 			new_distance = abs(r10_bio->devs[slot].addr -
823 					   conf->mirrors[disk].head_position);
824 
825 		if (new_distance < best_dist) {
826 			best_dist = new_distance;
827 			best_dist_slot = slot;
828 			best_dist_rdev = rdev;
829 		}
830 	}
831 	if (slot >= conf->copies) {
832 		if (has_nonrot_disk) {
833 			slot = best_pending_slot;
834 			rdev = best_pending_rdev;
835 		} else {
836 			slot = best_dist_slot;
837 			rdev = best_dist_rdev;
838 		}
839 	}
840 
841 	if (slot >= 0) {
842 		atomic_inc(&rdev->nr_pending);
843 		r10_bio->read_slot = slot;
844 	} else
845 		rdev = NULL;
846 	rcu_read_unlock();
847 	*max_sectors = best_good_sectors;
848 
849 	return rdev;
850 }
851 
852 static void flush_pending_writes(struct r10conf *conf)
853 {
854 	/* Any writes that have been queued but are awaiting
855 	 * bitmap updates get flushed here.
856 	 */
857 	spin_lock_irq(&conf->device_lock);
858 
859 	if (conf->pending_bio_list.head) {
860 		struct blk_plug plug;
861 		struct bio *bio;
862 
863 		bio = bio_list_get(&conf->pending_bio_list);
864 		conf->pending_count = 0;
865 		spin_unlock_irq(&conf->device_lock);
866 
867 		/*
868 		 * As this is called in a wait_event() loop (see freeze_array),
869 		 * current->state might be TASK_UNINTERRUPTIBLE which will
870 		 * cause a warning when we prepare to wait again.  As it is
871 		 * rare that this path is taken, it is perfectly safe to force
872 		 * us to go around the wait_event() loop again, so the warning
873 		 * is a false-positive. Silence the warning by resetting
874 		 * thread state
875 		 */
876 		__set_current_state(TASK_RUNNING);
877 
878 		blk_start_plug(&plug);
879 		/* flush any pending bitmap writes to disk
880 		 * before proceeding w/ I/O */
881 		md_bitmap_unplug(conf->mddev->bitmap);
882 		wake_up(&conf->wait_barrier);
883 
884 		while (bio) { /* submit pending writes */
885 			struct bio *next = bio->bi_next;
886 			struct md_rdev *rdev = (void*)bio->bi_bdev;
887 			bio->bi_next = NULL;
888 			bio_set_dev(bio, rdev->bdev);
889 			if (test_bit(Faulty, &rdev->flags)) {
890 				bio_io_error(bio);
891 			} else if (unlikely((bio_op(bio) ==  REQ_OP_DISCARD) &&
892 					    !blk_queue_discard(bio->bi_bdev->bd_disk->queue)))
893 				/* Just ignore it */
894 				bio_endio(bio);
895 			else
896 				submit_bio_noacct(bio);
897 			bio = next;
898 		}
899 		blk_finish_plug(&plug);
900 	} else
901 		spin_unlock_irq(&conf->device_lock);
902 }
903 
904 /* Barriers....
905  * Sometimes we need to suspend IO while we do something else,
906  * either some resync/recovery, or reconfigure the array.
907  * To do this we raise a 'barrier'.
908  * The 'barrier' is a counter that can be raised multiple times
909  * to count how many activities are happening which preclude
910  * normal IO.
911  * We can only raise the barrier if there is no pending IO.
912  * i.e. if nr_pending == 0.
913  * We choose only to raise the barrier if no-one is waiting for the
914  * barrier to go down.  This means that as soon as an IO request
915  * is ready, no other operations which require a barrier will start
916  * until the IO request has had a chance.
917  *
918  * So: regular IO calls 'wait_barrier'.  When that returns there
919  *    is no backgroup IO happening,  It must arrange to call
920  *    allow_barrier when it has finished its IO.
921  * backgroup IO calls must call raise_barrier.  Once that returns
922  *    there is no normal IO happeing.  It must arrange to call
923  *    lower_barrier when the particular background IO completes.
924  */
925 
926 static void raise_barrier(struct r10conf *conf, int force)
927 {
928 	BUG_ON(force && !conf->barrier);
929 	spin_lock_irq(&conf->resync_lock);
930 
931 	/* Wait until no block IO is waiting (unless 'force') */
932 	wait_event_lock_irq(conf->wait_barrier, force || !conf->nr_waiting,
933 			    conf->resync_lock);
934 
935 	/* block any new IO from starting */
936 	conf->barrier++;
937 
938 	/* Now wait for all pending IO to complete */
939 	wait_event_lock_irq(conf->wait_barrier,
940 			    !atomic_read(&conf->nr_pending) && conf->barrier < RESYNC_DEPTH,
941 			    conf->resync_lock);
942 
943 	spin_unlock_irq(&conf->resync_lock);
944 }
945 
946 static void lower_barrier(struct r10conf *conf)
947 {
948 	unsigned long flags;
949 	spin_lock_irqsave(&conf->resync_lock, flags);
950 	conf->barrier--;
951 	spin_unlock_irqrestore(&conf->resync_lock, flags);
952 	wake_up(&conf->wait_barrier);
953 }
954 
955 static void wait_barrier(struct r10conf *conf)
956 {
957 	spin_lock_irq(&conf->resync_lock);
958 	if (conf->barrier) {
959 		struct bio_list *bio_list = current->bio_list;
960 		conf->nr_waiting++;
961 		/* Wait for the barrier to drop.
962 		 * However if there are already pending
963 		 * requests (preventing the barrier from
964 		 * rising completely), and the
965 		 * pre-process bio queue isn't empty,
966 		 * then don't wait, as we need to empty
967 		 * that queue to get the nr_pending
968 		 * count down.
969 		 */
970 		raid10_log(conf->mddev, "wait barrier");
971 		wait_event_lock_irq(conf->wait_barrier,
972 				    !conf->barrier ||
973 				    (atomic_read(&conf->nr_pending) &&
974 				     bio_list &&
975 				     (!bio_list_empty(&bio_list[0]) ||
976 				      !bio_list_empty(&bio_list[1]))) ||
977 				     /* move on if recovery thread is
978 				      * blocked by us
979 				      */
980 				     (conf->mddev->thread->tsk == current &&
981 				      test_bit(MD_RECOVERY_RUNNING,
982 					       &conf->mddev->recovery) &&
983 				      conf->nr_queued > 0),
984 				    conf->resync_lock);
985 		conf->nr_waiting--;
986 		if (!conf->nr_waiting)
987 			wake_up(&conf->wait_barrier);
988 	}
989 	atomic_inc(&conf->nr_pending);
990 	spin_unlock_irq(&conf->resync_lock);
991 }
992 
993 static void allow_barrier(struct r10conf *conf)
994 {
995 	if ((atomic_dec_and_test(&conf->nr_pending)) ||
996 			(conf->array_freeze_pending))
997 		wake_up(&conf->wait_barrier);
998 }
999 
1000 static void freeze_array(struct r10conf *conf, int extra)
1001 {
1002 	/* stop syncio and normal IO and wait for everything to
1003 	 * go quiet.
1004 	 * We increment barrier and nr_waiting, and then
1005 	 * wait until nr_pending match nr_queued+extra
1006 	 * This is called in the context of one normal IO request
1007 	 * that has failed. Thus any sync request that might be pending
1008 	 * will be blocked by nr_pending, and we need to wait for
1009 	 * pending IO requests to complete or be queued for re-try.
1010 	 * Thus the number queued (nr_queued) plus this request (extra)
1011 	 * must match the number of pending IOs (nr_pending) before
1012 	 * we continue.
1013 	 */
1014 	spin_lock_irq(&conf->resync_lock);
1015 	conf->array_freeze_pending++;
1016 	conf->barrier++;
1017 	conf->nr_waiting++;
1018 	wait_event_lock_irq_cmd(conf->wait_barrier,
1019 				atomic_read(&conf->nr_pending) == conf->nr_queued+extra,
1020 				conf->resync_lock,
1021 				flush_pending_writes(conf));
1022 
1023 	conf->array_freeze_pending--;
1024 	spin_unlock_irq(&conf->resync_lock);
1025 }
1026 
1027 static void unfreeze_array(struct r10conf *conf)
1028 {
1029 	/* reverse the effect of the freeze */
1030 	spin_lock_irq(&conf->resync_lock);
1031 	conf->barrier--;
1032 	conf->nr_waiting--;
1033 	wake_up(&conf->wait_barrier);
1034 	spin_unlock_irq(&conf->resync_lock);
1035 }
1036 
1037 static sector_t choose_data_offset(struct r10bio *r10_bio,
1038 				   struct md_rdev *rdev)
1039 {
1040 	if (!test_bit(MD_RECOVERY_RESHAPE, &rdev->mddev->recovery) ||
1041 	    test_bit(R10BIO_Previous, &r10_bio->state))
1042 		return rdev->data_offset;
1043 	else
1044 		return rdev->new_data_offset;
1045 }
1046 
1047 struct raid10_plug_cb {
1048 	struct blk_plug_cb	cb;
1049 	struct bio_list		pending;
1050 	int			pending_cnt;
1051 };
1052 
1053 static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
1054 {
1055 	struct raid10_plug_cb *plug = container_of(cb, struct raid10_plug_cb,
1056 						   cb);
1057 	struct mddev *mddev = plug->cb.data;
1058 	struct r10conf *conf = mddev->private;
1059 	struct bio *bio;
1060 
1061 	if (from_schedule || current->bio_list) {
1062 		spin_lock_irq(&conf->device_lock);
1063 		bio_list_merge(&conf->pending_bio_list, &plug->pending);
1064 		conf->pending_count += plug->pending_cnt;
1065 		spin_unlock_irq(&conf->device_lock);
1066 		wake_up(&conf->wait_barrier);
1067 		md_wakeup_thread(mddev->thread);
1068 		kfree(plug);
1069 		return;
1070 	}
1071 
1072 	/* we aren't scheduling, so we can do the write-out directly. */
1073 	bio = bio_list_get(&plug->pending);
1074 	md_bitmap_unplug(mddev->bitmap);
1075 	wake_up(&conf->wait_barrier);
1076 
1077 	while (bio) { /* submit pending writes */
1078 		struct bio *next = bio->bi_next;
1079 		struct md_rdev *rdev = (void*)bio->bi_bdev;
1080 		bio->bi_next = NULL;
1081 		bio_set_dev(bio, rdev->bdev);
1082 		if (test_bit(Faulty, &rdev->flags)) {
1083 			bio_io_error(bio);
1084 		} else if (unlikely((bio_op(bio) ==  REQ_OP_DISCARD) &&
1085 				    !blk_queue_discard(bio->bi_bdev->bd_disk->queue)))
1086 			/* Just ignore it */
1087 			bio_endio(bio);
1088 		else
1089 			submit_bio_noacct(bio);
1090 		bio = next;
1091 	}
1092 	kfree(plug);
1093 }
1094 
1095 /*
1096  * 1. Register the new request and wait if the reconstruction thread has put
1097  * up a bar for new requests. Continue immediately if no resync is active
1098  * currently.
1099  * 2. If IO spans the reshape position.  Need to wait for reshape to pass.
1100  */
1101 static void regular_request_wait(struct mddev *mddev, struct r10conf *conf,
1102 				 struct bio *bio, sector_t sectors)
1103 {
1104 	wait_barrier(conf);
1105 	while (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
1106 	    bio->bi_iter.bi_sector < conf->reshape_progress &&
1107 	    bio->bi_iter.bi_sector + sectors > conf->reshape_progress) {
1108 		raid10_log(conf->mddev, "wait reshape");
1109 		allow_barrier(conf);
1110 		wait_event(conf->wait_barrier,
1111 			   conf->reshape_progress <= bio->bi_iter.bi_sector ||
1112 			   conf->reshape_progress >= bio->bi_iter.bi_sector +
1113 			   sectors);
1114 		wait_barrier(conf);
1115 	}
1116 }
1117 
1118 static void raid10_read_request(struct mddev *mddev, struct bio *bio,
1119 				struct r10bio *r10_bio)
1120 {
1121 	struct r10conf *conf = mddev->private;
1122 	struct bio *read_bio;
1123 	const int op = bio_op(bio);
1124 	const unsigned long do_sync = (bio->bi_opf & REQ_SYNC);
1125 	int max_sectors;
1126 	struct md_rdev *rdev;
1127 	char b[BDEVNAME_SIZE];
1128 	int slot = r10_bio->read_slot;
1129 	struct md_rdev *err_rdev = NULL;
1130 	gfp_t gfp = GFP_NOIO;
1131 
1132 	if (slot >= 0 && r10_bio->devs[slot].rdev) {
1133 		/*
1134 		 * This is an error retry, but we cannot
1135 		 * safely dereference the rdev in the r10_bio,
1136 		 * we must use the one in conf.
1137 		 * If it has already been disconnected (unlikely)
1138 		 * we lose the device name in error messages.
1139 		 */
1140 		int disk;
1141 		/*
1142 		 * As we are blocking raid10, it is a little safer to
1143 		 * use __GFP_HIGH.
1144 		 */
1145 		gfp = GFP_NOIO | __GFP_HIGH;
1146 
1147 		rcu_read_lock();
1148 		disk = r10_bio->devs[slot].devnum;
1149 		err_rdev = rcu_dereference(conf->mirrors[disk].rdev);
1150 		if (err_rdev)
1151 			bdevname(err_rdev->bdev, b);
1152 		else {
1153 			strcpy(b, "???");
1154 			/* This never gets dereferenced */
1155 			err_rdev = r10_bio->devs[slot].rdev;
1156 		}
1157 		rcu_read_unlock();
1158 	}
1159 
1160 	regular_request_wait(mddev, conf, bio, r10_bio->sectors);
1161 	rdev = read_balance(conf, r10_bio, &max_sectors);
1162 	if (!rdev) {
1163 		if (err_rdev) {
1164 			pr_crit_ratelimited("md/raid10:%s: %s: unrecoverable I/O read error for block %llu\n",
1165 					    mdname(mddev), b,
1166 					    (unsigned long long)r10_bio->sector);
1167 		}
1168 		raid_end_bio_io(r10_bio);
1169 		return;
1170 	}
1171 	if (err_rdev)
1172 		pr_err_ratelimited("md/raid10:%s: %s: redirecting sector %llu to another mirror\n",
1173 				   mdname(mddev),
1174 				   bdevname(rdev->bdev, b),
1175 				   (unsigned long long)r10_bio->sector);
1176 	if (max_sectors < bio_sectors(bio)) {
1177 		struct bio *split = bio_split(bio, max_sectors,
1178 					      gfp, &conf->bio_split);
1179 		bio_chain(split, bio);
1180 		allow_barrier(conf);
1181 		submit_bio_noacct(bio);
1182 		wait_barrier(conf);
1183 		bio = split;
1184 		r10_bio->master_bio = bio;
1185 		r10_bio->sectors = max_sectors;
1186 	}
1187 	slot = r10_bio->read_slot;
1188 
1189 	if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
1190 		r10_bio->start_time = bio_start_io_acct(bio);
1191 	read_bio = bio_clone_fast(bio, gfp, &mddev->bio_set);
1192 
1193 	r10_bio->devs[slot].bio = read_bio;
1194 	r10_bio->devs[slot].rdev = rdev;
1195 
1196 	read_bio->bi_iter.bi_sector = r10_bio->devs[slot].addr +
1197 		choose_data_offset(r10_bio, rdev);
1198 	bio_set_dev(read_bio, rdev->bdev);
1199 	read_bio->bi_end_io = raid10_end_read_request;
1200 	bio_set_op_attrs(read_bio, op, do_sync);
1201 	if (test_bit(FailFast, &rdev->flags) &&
1202 	    test_bit(R10BIO_FailFast, &r10_bio->state))
1203 	        read_bio->bi_opf |= MD_FAILFAST;
1204 	read_bio->bi_private = r10_bio;
1205 
1206 	if (mddev->gendisk)
1207 	        trace_block_bio_remap(read_bio, disk_devt(mddev->gendisk),
1208 	                              r10_bio->sector);
1209 	submit_bio_noacct(read_bio);
1210 	return;
1211 }
1212 
1213 static void raid10_write_one_disk(struct mddev *mddev, struct r10bio *r10_bio,
1214 				  struct bio *bio, bool replacement,
1215 				  int n_copy)
1216 {
1217 	const int op = bio_op(bio);
1218 	const unsigned long do_sync = (bio->bi_opf & REQ_SYNC);
1219 	const unsigned long do_fua = (bio->bi_opf & REQ_FUA);
1220 	unsigned long flags;
1221 	struct blk_plug_cb *cb;
1222 	struct raid10_plug_cb *plug = NULL;
1223 	struct r10conf *conf = mddev->private;
1224 	struct md_rdev *rdev;
1225 	int devnum = r10_bio->devs[n_copy].devnum;
1226 	struct bio *mbio;
1227 
1228 	if (replacement) {
1229 		rdev = conf->mirrors[devnum].replacement;
1230 		if (rdev == NULL) {
1231 			/* Replacement just got moved to main 'rdev' */
1232 			smp_mb();
1233 			rdev = conf->mirrors[devnum].rdev;
1234 		}
1235 	} else
1236 		rdev = conf->mirrors[devnum].rdev;
1237 
1238 	mbio = bio_clone_fast(bio, GFP_NOIO, &mddev->bio_set);
1239 	if (replacement)
1240 		r10_bio->devs[n_copy].repl_bio = mbio;
1241 	else
1242 		r10_bio->devs[n_copy].bio = mbio;
1243 
1244 	mbio->bi_iter.bi_sector	= (r10_bio->devs[n_copy].addr +
1245 				   choose_data_offset(r10_bio, rdev));
1246 	bio_set_dev(mbio, rdev->bdev);
1247 	mbio->bi_end_io	= raid10_end_write_request;
1248 	bio_set_op_attrs(mbio, op, do_sync | do_fua);
1249 	if (!replacement && test_bit(FailFast,
1250 				     &conf->mirrors[devnum].rdev->flags)
1251 			 && enough(conf, devnum))
1252 		mbio->bi_opf |= MD_FAILFAST;
1253 	mbio->bi_private = r10_bio;
1254 
1255 	if (conf->mddev->gendisk)
1256 		trace_block_bio_remap(mbio, disk_devt(conf->mddev->gendisk),
1257 				      r10_bio->sector);
1258 	/* flush_pending_writes() needs access to the rdev so...*/
1259 	mbio->bi_bdev = (void *)rdev;
1260 
1261 	atomic_inc(&r10_bio->remaining);
1262 
1263 	cb = blk_check_plugged(raid10_unplug, mddev, sizeof(*plug));
1264 	if (cb)
1265 		plug = container_of(cb, struct raid10_plug_cb, cb);
1266 	else
1267 		plug = NULL;
1268 	if (plug) {
1269 		bio_list_add(&plug->pending, mbio);
1270 		plug->pending_cnt++;
1271 	} else {
1272 		spin_lock_irqsave(&conf->device_lock, flags);
1273 		bio_list_add(&conf->pending_bio_list, mbio);
1274 		conf->pending_count++;
1275 		spin_unlock_irqrestore(&conf->device_lock, flags);
1276 		md_wakeup_thread(mddev->thread);
1277 	}
1278 }
1279 
1280 static void wait_blocked_dev(struct mddev *mddev, struct r10bio *r10_bio)
1281 {
1282 	int i;
1283 	struct r10conf *conf = mddev->private;
1284 	struct md_rdev *blocked_rdev;
1285 
1286 retry_wait:
1287 	blocked_rdev = NULL;
1288 	rcu_read_lock();
1289 	for (i = 0; i < conf->copies; i++) {
1290 		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
1291 		struct md_rdev *rrdev = rcu_dereference(
1292 			conf->mirrors[i].replacement);
1293 		if (rdev == rrdev)
1294 			rrdev = NULL;
1295 		if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
1296 			atomic_inc(&rdev->nr_pending);
1297 			blocked_rdev = rdev;
1298 			break;
1299 		}
1300 		if (rrdev && unlikely(test_bit(Blocked, &rrdev->flags))) {
1301 			atomic_inc(&rrdev->nr_pending);
1302 			blocked_rdev = rrdev;
1303 			break;
1304 		}
1305 
1306 		if (rdev && test_bit(WriteErrorSeen, &rdev->flags)) {
1307 			sector_t first_bad;
1308 			sector_t dev_sector = r10_bio->devs[i].addr;
1309 			int bad_sectors;
1310 			int is_bad;
1311 
1312 			/*
1313 			 * Discard request doesn't care the write result
1314 			 * so it doesn't need to wait blocked disk here.
1315 			 */
1316 			if (!r10_bio->sectors)
1317 				continue;
1318 
1319 			is_bad = is_badblock(rdev, dev_sector, r10_bio->sectors,
1320 					     &first_bad, &bad_sectors);
1321 			if (is_bad < 0) {
1322 				/*
1323 				 * Mustn't write here until the bad block
1324 				 * is acknowledged
1325 				 */
1326 				atomic_inc(&rdev->nr_pending);
1327 				set_bit(BlockedBadBlocks, &rdev->flags);
1328 				blocked_rdev = rdev;
1329 				break;
1330 			}
1331 		}
1332 	}
1333 	rcu_read_unlock();
1334 
1335 	if (unlikely(blocked_rdev)) {
1336 		/* Have to wait for this device to get unblocked, then retry */
1337 		allow_barrier(conf);
1338 		raid10_log(conf->mddev, "%s wait rdev %d blocked",
1339 				__func__, blocked_rdev->raid_disk);
1340 		md_wait_for_blocked_rdev(blocked_rdev, mddev);
1341 		wait_barrier(conf);
1342 		goto retry_wait;
1343 	}
1344 }
1345 
1346 static void raid10_write_request(struct mddev *mddev, struct bio *bio,
1347 				 struct r10bio *r10_bio)
1348 {
1349 	struct r10conf *conf = mddev->private;
1350 	int i;
1351 	sector_t sectors;
1352 	int max_sectors;
1353 
1354 	if ((mddev_is_clustered(mddev) &&
1355 	     md_cluster_ops->area_resyncing(mddev, WRITE,
1356 					    bio->bi_iter.bi_sector,
1357 					    bio_end_sector(bio)))) {
1358 		DEFINE_WAIT(w);
1359 		for (;;) {
1360 			prepare_to_wait(&conf->wait_barrier,
1361 					&w, TASK_IDLE);
1362 			if (!md_cluster_ops->area_resyncing(mddev, WRITE,
1363 				 bio->bi_iter.bi_sector, bio_end_sector(bio)))
1364 				break;
1365 			schedule();
1366 		}
1367 		finish_wait(&conf->wait_barrier, &w);
1368 	}
1369 
1370 	sectors = r10_bio->sectors;
1371 	regular_request_wait(mddev, conf, bio, sectors);
1372 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
1373 	    (mddev->reshape_backwards
1374 	     ? (bio->bi_iter.bi_sector < conf->reshape_safe &&
1375 		bio->bi_iter.bi_sector + sectors > conf->reshape_progress)
1376 	     : (bio->bi_iter.bi_sector + sectors > conf->reshape_safe &&
1377 		bio->bi_iter.bi_sector < conf->reshape_progress))) {
1378 		/* Need to update reshape_position in metadata */
1379 		mddev->reshape_position = conf->reshape_progress;
1380 		set_mask_bits(&mddev->sb_flags, 0,
1381 			      BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_PENDING));
1382 		md_wakeup_thread(mddev->thread);
1383 		raid10_log(conf->mddev, "wait reshape metadata");
1384 		wait_event(mddev->sb_wait,
1385 			   !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));
1386 
1387 		conf->reshape_safe = mddev->reshape_position;
1388 	}
1389 
1390 	if (conf->pending_count >= max_queued_requests) {
1391 		md_wakeup_thread(mddev->thread);
1392 		raid10_log(mddev, "wait queued");
1393 		wait_event(conf->wait_barrier,
1394 			   conf->pending_count < max_queued_requests);
1395 	}
1396 	/* first select target devices under rcu_lock and
1397 	 * inc refcount on their rdev.  Record them by setting
1398 	 * bios[x] to bio
1399 	 * If there are known/acknowledged bad blocks on any device
1400 	 * on which we have seen a write error, we want to avoid
1401 	 * writing to those blocks.  This potentially requires several
1402 	 * writes to write around the bad blocks.  Each set of writes
1403 	 * gets its own r10_bio with a set of bios attached.
1404 	 */
1405 
1406 	r10_bio->read_slot = -1; /* make sure repl_bio gets freed */
1407 	raid10_find_phys(conf, r10_bio);
1408 
1409 	wait_blocked_dev(mddev, r10_bio);
1410 
1411 	rcu_read_lock();
1412 	max_sectors = r10_bio->sectors;
1413 
1414 	for (i = 0;  i < conf->copies; i++) {
1415 		int d = r10_bio->devs[i].devnum;
1416 		struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev);
1417 		struct md_rdev *rrdev = rcu_dereference(
1418 			conf->mirrors[d].replacement);
1419 		if (rdev == rrdev)
1420 			rrdev = NULL;
1421 		if (rdev && (test_bit(Faulty, &rdev->flags)))
1422 			rdev = NULL;
1423 		if (rrdev && (test_bit(Faulty, &rrdev->flags)))
1424 			rrdev = NULL;
1425 
1426 		r10_bio->devs[i].bio = NULL;
1427 		r10_bio->devs[i].repl_bio = NULL;
1428 
1429 		if (!rdev && !rrdev) {
1430 			set_bit(R10BIO_Degraded, &r10_bio->state);
1431 			continue;
1432 		}
1433 		if (rdev && test_bit(WriteErrorSeen, &rdev->flags)) {
1434 			sector_t first_bad;
1435 			sector_t dev_sector = r10_bio->devs[i].addr;
1436 			int bad_sectors;
1437 			int is_bad;
1438 
1439 			is_bad = is_badblock(rdev, dev_sector, max_sectors,
1440 					     &first_bad, &bad_sectors);
1441 			if (is_bad && first_bad <= dev_sector) {
1442 				/* Cannot write here at all */
1443 				bad_sectors -= (dev_sector - first_bad);
1444 				if (bad_sectors < max_sectors)
1445 					/* Mustn't write more than bad_sectors
1446 					 * to other devices yet
1447 					 */
1448 					max_sectors = bad_sectors;
1449 				/* We don't set R10BIO_Degraded as that
1450 				 * only applies if the disk is missing,
1451 				 * so it might be re-added, and we want to
1452 				 * know to recover this chunk.
1453 				 * In this case the device is here, and the
1454 				 * fact that this chunk is not in-sync is
1455 				 * recorded in the bad block log.
1456 				 */
1457 				continue;
1458 			}
1459 			if (is_bad) {
1460 				int good_sectors = first_bad - dev_sector;
1461 				if (good_sectors < max_sectors)
1462 					max_sectors = good_sectors;
1463 			}
1464 		}
1465 		if (rdev) {
1466 			r10_bio->devs[i].bio = bio;
1467 			atomic_inc(&rdev->nr_pending);
1468 		}
1469 		if (rrdev) {
1470 			r10_bio->devs[i].repl_bio = bio;
1471 			atomic_inc(&rrdev->nr_pending);
1472 		}
1473 	}
1474 	rcu_read_unlock();
1475 
1476 	if (max_sectors < r10_bio->sectors)
1477 		r10_bio->sectors = max_sectors;
1478 
1479 	if (r10_bio->sectors < bio_sectors(bio)) {
1480 		struct bio *split = bio_split(bio, r10_bio->sectors,
1481 					      GFP_NOIO, &conf->bio_split);
1482 		bio_chain(split, bio);
1483 		allow_barrier(conf);
1484 		submit_bio_noacct(bio);
1485 		wait_barrier(conf);
1486 		bio = split;
1487 		r10_bio->master_bio = bio;
1488 	}
1489 
1490 	if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
1491 		r10_bio->start_time = bio_start_io_acct(bio);
1492 	atomic_set(&r10_bio->remaining, 1);
1493 	md_bitmap_startwrite(mddev->bitmap, r10_bio->sector, r10_bio->sectors, 0);
1494 
1495 	for (i = 0; i < conf->copies; i++) {
1496 		if (r10_bio->devs[i].bio)
1497 			raid10_write_one_disk(mddev, r10_bio, bio, false, i);
1498 		if (r10_bio->devs[i].repl_bio)
1499 			raid10_write_one_disk(mddev, r10_bio, bio, true, i);
1500 	}
1501 	one_write_done(r10_bio);
1502 }
1503 
1504 static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
1505 {
1506 	struct r10conf *conf = mddev->private;
1507 	struct r10bio *r10_bio;
1508 
1509 	r10_bio = mempool_alloc(&conf->r10bio_pool, GFP_NOIO);
1510 
1511 	r10_bio->master_bio = bio;
1512 	r10_bio->sectors = sectors;
1513 
1514 	r10_bio->mddev = mddev;
1515 	r10_bio->sector = bio->bi_iter.bi_sector;
1516 	r10_bio->state = 0;
1517 	r10_bio->read_slot = -1;
1518 	memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) *
1519 			conf->geo.raid_disks);
1520 
1521 	if (bio_data_dir(bio) == READ)
1522 		raid10_read_request(mddev, bio, r10_bio);
1523 	else
1524 		raid10_write_request(mddev, bio, r10_bio);
1525 }
1526 
1527 static void raid_end_discard_bio(struct r10bio *r10bio)
1528 {
1529 	struct r10conf *conf = r10bio->mddev->private;
1530 	struct r10bio *first_r10bio;
1531 
1532 	while (atomic_dec_and_test(&r10bio->remaining)) {
1533 
1534 		allow_barrier(conf);
1535 
1536 		if (!test_bit(R10BIO_Discard, &r10bio->state)) {
1537 			first_r10bio = (struct r10bio *)r10bio->master_bio;
1538 			free_r10bio(r10bio);
1539 			r10bio = first_r10bio;
1540 		} else {
1541 			md_write_end(r10bio->mddev);
1542 			bio_endio(r10bio->master_bio);
1543 			free_r10bio(r10bio);
1544 			break;
1545 		}
1546 	}
1547 }
1548 
1549 static void raid10_end_discard_request(struct bio *bio)
1550 {
1551 	struct r10bio *r10_bio = bio->bi_private;
1552 	struct r10conf *conf = r10_bio->mddev->private;
1553 	struct md_rdev *rdev = NULL;
1554 	int dev;
1555 	int slot, repl;
1556 
1557 	/*
1558 	 * We don't care the return value of discard bio
1559 	 */
1560 	if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
1561 		set_bit(R10BIO_Uptodate, &r10_bio->state);
1562 
1563 	dev = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
1564 	if (repl)
1565 		rdev = conf->mirrors[dev].replacement;
1566 	if (!rdev) {
1567 		/*
1568 		 * raid10_remove_disk uses smp_mb to make sure rdev is set to
1569 		 * replacement before setting replacement to NULL. It can read
1570 		 * rdev first without barrier protect even replacment is NULL
1571 		 */
1572 		smp_rmb();
1573 		rdev = conf->mirrors[dev].rdev;
1574 	}
1575 
1576 	raid_end_discard_bio(r10_bio);
1577 	rdev_dec_pending(rdev, conf->mddev);
1578 }
1579 
1580 /*
1581  * There are some limitations to handle discard bio
1582  * 1st, the discard size is bigger than stripe_size*2.
1583  * 2st, if the discard bio spans reshape progress, we use the old way to
1584  * handle discard bio
1585  */
1586 static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
1587 {
1588 	struct r10conf *conf = mddev->private;
1589 	struct geom *geo = &conf->geo;
1590 	int far_copies = geo->far_copies;
1591 	bool first_copy = true;
1592 	struct r10bio *r10_bio, *first_r10bio;
1593 	struct bio *split;
1594 	int disk;
1595 	sector_t chunk;
1596 	unsigned int stripe_size;
1597 	unsigned int stripe_data_disks;
1598 	sector_t split_size;
1599 	sector_t bio_start, bio_end;
1600 	sector_t first_stripe_index, last_stripe_index;
1601 	sector_t start_disk_offset;
1602 	unsigned int start_disk_index;
1603 	sector_t end_disk_offset;
1604 	unsigned int end_disk_index;
1605 	unsigned int remainder;
1606 
1607 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
1608 		return -EAGAIN;
1609 
1610 	wait_barrier(conf);
1611 
1612 	/*
1613 	 * Check reshape again to avoid reshape happens after checking
1614 	 * MD_RECOVERY_RESHAPE and before wait_barrier
1615 	 */
1616 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
1617 		goto out;
1618 
1619 	if (geo->near_copies)
1620 		stripe_data_disks = geo->raid_disks / geo->near_copies +
1621 					geo->raid_disks % geo->near_copies;
1622 	else
1623 		stripe_data_disks = geo->raid_disks;
1624 
1625 	stripe_size = stripe_data_disks << geo->chunk_shift;
1626 
1627 	bio_start = bio->bi_iter.bi_sector;
1628 	bio_end = bio_end_sector(bio);
1629 
1630 	/*
1631 	 * Maybe one discard bio is smaller than strip size or across one
1632 	 * stripe and discard region is larger than one stripe size. For far
1633 	 * offset layout, if the discard region is not aligned with stripe
1634 	 * size, there is hole when we submit discard bio to member disk.
1635 	 * For simplicity, we only handle discard bio which discard region
1636 	 * is bigger than stripe_size * 2
1637 	 */
1638 	if (bio_sectors(bio) < stripe_size*2)
1639 		goto out;
1640 
1641 	/*
1642 	 * Keep bio aligned with strip size.
1643 	 */
1644 	div_u64_rem(bio_start, stripe_size, &remainder);
1645 	if (remainder) {
1646 		split_size = stripe_size - remainder;
1647 		split = bio_split(bio, split_size, GFP_NOIO, &conf->bio_split);
1648 		bio_chain(split, bio);
1649 		allow_barrier(conf);
1650 		/* Resend the fist split part */
1651 		submit_bio_noacct(split);
1652 		wait_barrier(conf);
1653 	}
1654 	div_u64_rem(bio_end, stripe_size, &remainder);
1655 	if (remainder) {
1656 		split_size = bio_sectors(bio) - remainder;
1657 		split = bio_split(bio, split_size, GFP_NOIO, &conf->bio_split);
1658 		bio_chain(split, bio);
1659 		allow_barrier(conf);
1660 		/* Resend the second split part */
1661 		submit_bio_noacct(bio);
1662 		bio = split;
1663 		wait_barrier(conf);
1664 	}
1665 
1666 	bio_start = bio->bi_iter.bi_sector;
1667 	bio_end = bio_end_sector(bio);
1668 
1669 	/*
1670 	 * Raid10 uses chunk as the unit to store data. It's similar like raid0.
1671 	 * One stripe contains the chunks from all member disk (one chunk from
1672 	 * one disk at the same HBA address). For layout detail, see 'man md 4'
1673 	 */
1674 	chunk = bio_start >> geo->chunk_shift;
1675 	chunk *= geo->near_copies;
1676 	first_stripe_index = chunk;
1677 	start_disk_index = sector_div(first_stripe_index, geo->raid_disks);
1678 	if (geo->far_offset)
1679 		first_stripe_index *= geo->far_copies;
1680 	start_disk_offset = (bio_start & geo->chunk_mask) +
1681 				(first_stripe_index << geo->chunk_shift);
1682 
1683 	chunk = bio_end >> geo->chunk_shift;
1684 	chunk *= geo->near_copies;
1685 	last_stripe_index = chunk;
1686 	end_disk_index = sector_div(last_stripe_index, geo->raid_disks);
1687 	if (geo->far_offset)
1688 		last_stripe_index *= geo->far_copies;
1689 	end_disk_offset = (bio_end & geo->chunk_mask) +
1690 				(last_stripe_index << geo->chunk_shift);
1691 
1692 retry_discard:
1693 	r10_bio = mempool_alloc(&conf->r10bio_pool, GFP_NOIO);
1694 	r10_bio->mddev = mddev;
1695 	r10_bio->state = 0;
1696 	r10_bio->sectors = 0;
1697 	memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) * geo->raid_disks);
1698 	wait_blocked_dev(mddev, r10_bio);
1699 
1700 	/*
1701 	 * For far layout it needs more than one r10bio to cover all regions.
1702 	 * Inspired by raid10_sync_request, we can use the first r10bio->master_bio
1703 	 * to record the discard bio. Other r10bio->master_bio record the first
1704 	 * r10bio. The first r10bio only release after all other r10bios finish.
1705 	 * The discard bio returns only first r10bio finishes
1706 	 */
1707 	if (first_copy) {
1708 		r10_bio->master_bio = bio;
1709 		set_bit(R10BIO_Discard, &r10_bio->state);
1710 		first_copy = false;
1711 		first_r10bio = r10_bio;
1712 	} else
1713 		r10_bio->master_bio = (struct bio *)first_r10bio;
1714 
1715 	rcu_read_lock();
1716 	for (disk = 0; disk < geo->raid_disks; disk++) {
1717 		struct md_rdev *rdev = rcu_dereference(conf->mirrors[disk].rdev);
1718 		struct md_rdev *rrdev = rcu_dereference(
1719 			conf->mirrors[disk].replacement);
1720 
1721 		r10_bio->devs[disk].bio = NULL;
1722 		r10_bio->devs[disk].repl_bio = NULL;
1723 
1724 		if (rdev && (test_bit(Faulty, &rdev->flags)))
1725 			rdev = NULL;
1726 		if (rrdev && (test_bit(Faulty, &rrdev->flags)))
1727 			rrdev = NULL;
1728 		if (!rdev && !rrdev)
1729 			continue;
1730 
1731 		if (rdev) {
1732 			r10_bio->devs[disk].bio = bio;
1733 			atomic_inc(&rdev->nr_pending);
1734 		}
1735 		if (rrdev) {
1736 			r10_bio->devs[disk].repl_bio = bio;
1737 			atomic_inc(&rrdev->nr_pending);
1738 		}
1739 	}
1740 	rcu_read_unlock();
1741 
1742 	atomic_set(&r10_bio->remaining, 1);
1743 	for (disk = 0; disk < geo->raid_disks; disk++) {
1744 		sector_t dev_start, dev_end;
1745 		struct bio *mbio, *rbio = NULL;
1746 		struct md_rdev *rdev = rcu_dereference(conf->mirrors[disk].rdev);
1747 		struct md_rdev *rrdev = rcu_dereference(
1748 			conf->mirrors[disk].replacement);
1749 
1750 		/*
1751 		 * Now start to calculate the start and end address for each disk.
1752 		 * The space between dev_start and dev_end is the discard region.
1753 		 *
1754 		 * For dev_start, it needs to consider three conditions:
1755 		 * 1st, the disk is before start_disk, you can imagine the disk in
1756 		 * the next stripe. So the dev_start is the start address of next
1757 		 * stripe.
1758 		 * 2st, the disk is after start_disk, it means the disk is at the
1759 		 * same stripe of first disk
1760 		 * 3st, the first disk itself, we can use start_disk_offset directly
1761 		 */
1762 		if (disk < start_disk_index)
1763 			dev_start = (first_stripe_index + 1) * mddev->chunk_sectors;
1764 		else if (disk > start_disk_index)
1765 			dev_start = first_stripe_index * mddev->chunk_sectors;
1766 		else
1767 			dev_start = start_disk_offset;
1768 
1769 		if (disk < end_disk_index)
1770 			dev_end = (last_stripe_index + 1) * mddev->chunk_sectors;
1771 		else if (disk > end_disk_index)
1772 			dev_end = last_stripe_index * mddev->chunk_sectors;
1773 		else
1774 			dev_end = end_disk_offset;
1775 
1776 		/*
1777 		 * It only handles discard bio which size is >= stripe size, so
1778 		 * dev_end > dev_start all the time
1779 		 */
1780 		if (r10_bio->devs[disk].bio) {
1781 			mbio = bio_clone_fast(bio, GFP_NOIO, &mddev->bio_set);
1782 			mbio->bi_end_io = raid10_end_discard_request;
1783 			mbio->bi_private = r10_bio;
1784 			r10_bio->devs[disk].bio = mbio;
1785 			r10_bio->devs[disk].devnum = disk;
1786 			atomic_inc(&r10_bio->remaining);
1787 			md_submit_discard_bio(mddev, rdev, mbio,
1788 					dev_start + choose_data_offset(r10_bio, rdev),
1789 					dev_end - dev_start);
1790 			bio_endio(mbio);
1791 		}
1792 		if (r10_bio->devs[disk].repl_bio) {
1793 			rbio = bio_clone_fast(bio, GFP_NOIO, &mddev->bio_set);
1794 			rbio->bi_end_io = raid10_end_discard_request;
1795 			rbio->bi_private = r10_bio;
1796 			r10_bio->devs[disk].repl_bio = rbio;
1797 			r10_bio->devs[disk].devnum = disk;
1798 			atomic_inc(&r10_bio->remaining);
1799 			md_submit_discard_bio(mddev, rrdev, rbio,
1800 					dev_start + choose_data_offset(r10_bio, rrdev),
1801 					dev_end - dev_start);
1802 			bio_endio(rbio);
1803 		}
1804 	}
1805 
1806 	if (!geo->far_offset && --far_copies) {
1807 		first_stripe_index += geo->stride >> geo->chunk_shift;
1808 		start_disk_offset += geo->stride;
1809 		last_stripe_index += geo->stride >> geo->chunk_shift;
1810 		end_disk_offset += geo->stride;
1811 		atomic_inc(&first_r10bio->remaining);
1812 		raid_end_discard_bio(r10_bio);
1813 		wait_barrier(conf);
1814 		goto retry_discard;
1815 	}
1816 
1817 	raid_end_discard_bio(r10_bio);
1818 
1819 	return 0;
1820 out:
1821 	allow_barrier(conf);
1822 	return -EAGAIN;
1823 }
1824 
1825 static bool raid10_make_request(struct mddev *mddev, struct bio *bio)
1826 {
1827 	struct r10conf *conf = mddev->private;
1828 	sector_t chunk_mask = (conf->geo.chunk_mask & conf->prev.chunk_mask);
1829 	int chunk_sects = chunk_mask + 1;
1830 	int sectors = bio_sectors(bio);
1831 
1832 	if (unlikely(bio->bi_opf & REQ_PREFLUSH)
1833 	    && md_flush_request(mddev, bio))
1834 		return true;
1835 
1836 	if (!md_write_start(mddev, bio))
1837 		return false;
1838 
1839 	if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
1840 		if (!raid10_handle_discard(mddev, bio))
1841 			return true;
1842 
1843 	/*
1844 	 * If this request crosses a chunk boundary, we need to split
1845 	 * it.
1846 	 */
1847 	if (unlikely((bio->bi_iter.bi_sector & chunk_mask) +
1848 		     sectors > chunk_sects
1849 		     && (conf->geo.near_copies < conf->geo.raid_disks
1850 			 || conf->prev.near_copies <
1851 			 conf->prev.raid_disks)))
1852 		sectors = chunk_sects -
1853 			(bio->bi_iter.bi_sector &
1854 			 (chunk_sects - 1));
1855 	__make_request(mddev, bio, sectors);
1856 
1857 	/* In case raid10d snuck in to freeze_array */
1858 	wake_up(&conf->wait_barrier);
1859 	return true;
1860 }
1861 
1862 static void raid10_status(struct seq_file *seq, struct mddev *mddev)
1863 {
1864 	struct r10conf *conf = mddev->private;
1865 	int i;
1866 
1867 	if (conf->geo.near_copies < conf->geo.raid_disks)
1868 		seq_printf(seq, " %dK chunks", mddev->chunk_sectors / 2);
1869 	if (conf->geo.near_copies > 1)
1870 		seq_printf(seq, " %d near-copies", conf->geo.near_copies);
1871 	if (conf->geo.far_copies > 1) {
1872 		if (conf->geo.far_offset)
1873 			seq_printf(seq, " %d offset-copies", conf->geo.far_copies);
1874 		else
1875 			seq_printf(seq, " %d far-copies", conf->geo.far_copies);
1876 		if (conf->geo.far_set_size != conf->geo.raid_disks)
1877 			seq_printf(seq, " %d devices per set", conf->geo.far_set_size);
1878 	}
1879 	seq_printf(seq, " [%d/%d] [", conf->geo.raid_disks,
1880 					conf->geo.raid_disks - mddev->degraded);
1881 	rcu_read_lock();
1882 	for (i = 0; i < conf->geo.raid_disks; i++) {
1883 		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
1884 		seq_printf(seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
1885 	}
1886 	rcu_read_unlock();
1887 	seq_printf(seq, "]");
1888 }
1889 
1890 /* check if there are enough drives for
1891  * every block to appear on atleast one.
1892  * Don't consider the device numbered 'ignore'
1893  * as we might be about to remove it.
1894  */
1895 static int _enough(struct r10conf *conf, int previous, int ignore)
1896 {
1897 	int first = 0;
1898 	int has_enough = 0;
1899 	int disks, ncopies;
1900 	if (previous) {
1901 		disks = conf->prev.raid_disks;
1902 		ncopies = conf->prev.near_copies;
1903 	} else {
1904 		disks = conf->geo.raid_disks;
1905 		ncopies = conf->geo.near_copies;
1906 	}
1907 
1908 	rcu_read_lock();
1909 	do {
1910 		int n = conf->copies;
1911 		int cnt = 0;
1912 		int this = first;
1913 		while (n--) {
1914 			struct md_rdev *rdev;
1915 			if (this != ignore &&
1916 			    (rdev = rcu_dereference(conf->mirrors[this].rdev)) &&
1917 			    test_bit(In_sync, &rdev->flags))
1918 				cnt++;
1919 			this = (this+1) % disks;
1920 		}
1921 		if (cnt == 0)
1922 			goto out;
1923 		first = (first + ncopies) % disks;
1924 	} while (first != 0);
1925 	has_enough = 1;
1926 out:
1927 	rcu_read_unlock();
1928 	return has_enough;
1929 }
1930 
1931 static int enough(struct r10conf *conf, int ignore)
1932 {
1933 	/* when calling 'enough', both 'prev' and 'geo' must
1934 	 * be stable.
1935 	 * This is ensured if ->reconfig_mutex or ->device_lock
1936 	 * is held.
1937 	 */
1938 	return _enough(conf, 0, ignore) &&
1939 		_enough(conf, 1, ignore);
1940 }
1941 
1942 static void raid10_error(struct mddev *mddev, struct md_rdev *rdev)
1943 {
1944 	char b[BDEVNAME_SIZE];
1945 	struct r10conf *conf = mddev->private;
1946 	unsigned long flags;
1947 
1948 	/*
1949 	 * If it is not operational, then we have already marked it as dead
1950 	 * else if it is the last working disks with "fail_last_dev == false",
1951 	 * ignore the error, let the next level up know.
1952 	 * else mark the drive as failed
1953 	 */
1954 	spin_lock_irqsave(&conf->device_lock, flags);
1955 	if (test_bit(In_sync, &rdev->flags) && !mddev->fail_last_dev
1956 	    && !enough(conf, rdev->raid_disk)) {
1957 		/*
1958 		 * Don't fail the drive, just return an IO error.
1959 		 */
1960 		spin_unlock_irqrestore(&conf->device_lock, flags);
1961 		return;
1962 	}
1963 	if (test_and_clear_bit(In_sync, &rdev->flags))
1964 		mddev->degraded++;
1965 	/*
1966 	 * If recovery is running, make sure it aborts.
1967 	 */
1968 	set_bit(MD_RECOVERY_INTR, &mddev->recovery);
1969 	set_bit(Blocked, &rdev->flags);
1970 	set_bit(Faulty, &rdev->flags);
1971 	set_mask_bits(&mddev->sb_flags, 0,
1972 		      BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_PENDING));
1973 	spin_unlock_irqrestore(&conf->device_lock, flags);
1974 	pr_crit("md/raid10:%s: Disk failure on %s, disabling device.\n"
1975 		"md/raid10:%s: Operation continuing on %d devices.\n",
1976 		mdname(mddev), bdevname(rdev->bdev, b),
1977 		mdname(mddev), conf->geo.raid_disks - mddev->degraded);
1978 }
1979 
1980 static void print_conf(struct r10conf *conf)
1981 {
1982 	int i;
1983 	struct md_rdev *rdev;
1984 
1985 	pr_debug("RAID10 conf printout:\n");
1986 	if (!conf) {
1987 		pr_debug("(!conf)\n");
1988 		return;
1989 	}
1990 	pr_debug(" --- wd:%d rd:%d\n", conf->geo.raid_disks - conf->mddev->degraded,
1991 		 conf->geo.raid_disks);
1992 
1993 	/* This is only called with ->reconfix_mutex held, so
1994 	 * rcu protection of rdev is not needed */
1995 	for (i = 0; i < conf->geo.raid_disks; i++) {
1996 		char b[BDEVNAME_SIZE];
1997 		rdev = conf->mirrors[i].rdev;
1998 		if (rdev)
1999 			pr_debug(" disk %d, wo:%d, o:%d, dev:%s\n",
2000 				 i, !test_bit(In_sync, &rdev->flags),
2001 				 !test_bit(Faulty, &rdev->flags),
2002 				 bdevname(rdev->bdev,b));
2003 	}
2004 }
2005 
2006 static void close_sync(struct r10conf *conf)
2007 {
2008 	wait_barrier(conf);
2009 	allow_barrier(conf);
2010 
2011 	mempool_exit(&conf->r10buf_pool);
2012 }
2013 
2014 static int raid10_spare_active(struct mddev *mddev)
2015 {
2016 	int i;
2017 	struct r10conf *conf = mddev->private;
2018 	struct raid10_info *tmp;
2019 	int count = 0;
2020 	unsigned long flags;
2021 
2022 	/*
2023 	 * Find all non-in_sync disks within the RAID10 configuration
2024 	 * and mark them in_sync
2025 	 */
2026 	for (i = 0; i < conf->geo.raid_disks; i++) {
2027 		tmp = conf->mirrors + i;
2028 		if (tmp->replacement
2029 		    && tmp->replacement->recovery_offset == MaxSector
2030 		    && !test_bit(Faulty, &tmp->replacement->flags)
2031 		    && !test_and_set_bit(In_sync, &tmp->replacement->flags)) {
2032 			/* Replacement has just become active */
2033 			if (!tmp->rdev
2034 			    || !test_and_clear_bit(In_sync, &tmp->rdev->flags))
2035 				count++;
2036 			if (tmp->rdev) {
2037 				/* Replaced device not technically faulty,
2038 				 * but we need to be sure it gets removed
2039 				 * and never re-added.
2040 				 */
2041 				set_bit(Faulty, &tmp->rdev->flags);
2042 				sysfs_notify_dirent_safe(
2043 					tmp->rdev->sysfs_state);
2044 			}
2045 			sysfs_notify_dirent_safe(tmp->replacement->sysfs_state);
2046 		} else if (tmp->rdev
2047 			   && tmp->rdev->recovery_offset == MaxSector
2048 			   && !test_bit(Faulty, &tmp->rdev->flags)
2049 			   && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
2050 			count++;
2051 			sysfs_notify_dirent_safe(tmp->rdev->sysfs_state);
2052 		}
2053 	}
2054 	spin_lock_irqsave(&conf->device_lock, flags);
2055 	mddev->degraded -= count;
2056 	spin_unlock_irqrestore(&conf->device_lock, flags);
2057 
2058 	print_conf(conf);
2059 	return count;
2060 }
2061 
2062 static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
2063 {
2064 	struct r10conf *conf = mddev->private;
2065 	int err = -EEXIST;
2066 	int mirror;
2067 	int first = 0;
2068 	int last = conf->geo.raid_disks - 1;
2069 
2070 	if (mddev->recovery_cp < MaxSector)
2071 		/* only hot-add to in-sync arrays, as recovery is
2072 		 * very different from resync
2073 		 */
2074 		return -EBUSY;
2075 	if (rdev->saved_raid_disk < 0 && !_enough(conf, 1, -1))
2076 		return -EINVAL;
2077 
2078 	if (md_integrity_add_rdev(rdev, mddev))
2079 		return -ENXIO;
2080 
2081 	if (rdev->raid_disk >= 0)
2082 		first = last = rdev->raid_disk;
2083 
2084 	if (rdev->saved_raid_disk >= first &&
2085 	    rdev->saved_raid_disk < conf->geo.raid_disks &&
2086 	    conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
2087 		mirror = rdev->saved_raid_disk;
2088 	else
2089 		mirror = first;
2090 	for ( ; mirror <= last ; mirror++) {
2091 		struct raid10_info *p = &conf->mirrors[mirror];
2092 		if (p->recovery_disabled == mddev->recovery_disabled)
2093 			continue;
2094 		if (p->rdev) {
2095 			if (!test_bit(WantReplacement, &p->rdev->flags) ||
2096 			    p->replacement != NULL)
2097 				continue;
2098 			clear_bit(In_sync, &rdev->flags);
2099 			set_bit(Replacement, &rdev->flags);
2100 			rdev->raid_disk = mirror;
2101 			err = 0;
2102 			if (mddev->gendisk)
2103 				disk_stack_limits(mddev->gendisk, rdev->bdev,
2104 						  rdev->data_offset << 9);
2105 			conf->fullsync = 1;
2106 			rcu_assign_pointer(p->replacement, rdev);
2107 			break;
2108 		}
2109 
2110 		if (mddev->gendisk)
2111 			disk_stack_limits(mddev->gendisk, rdev->bdev,
2112 					  rdev->data_offset << 9);
2113 
2114 		p->head_position = 0;
2115 		p->recovery_disabled = mddev->recovery_disabled - 1;
2116 		rdev->raid_disk = mirror;
2117 		err = 0;
2118 		if (rdev->saved_raid_disk != mirror)
2119 			conf->fullsync = 1;
2120 		rcu_assign_pointer(p->rdev, rdev);
2121 		break;
2122 	}
2123 	if (mddev->queue && blk_queue_discard(bdev_get_queue(rdev->bdev)))
2124 		blk_queue_flag_set(QUEUE_FLAG_DISCARD, mddev->queue);
2125 
2126 	print_conf(conf);
2127 	return err;
2128 }
2129 
2130 static int raid10_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
2131 {
2132 	struct r10conf *conf = mddev->private;
2133 	int err = 0;
2134 	int number = rdev->raid_disk;
2135 	struct md_rdev **rdevp;
2136 	struct raid10_info *p = conf->mirrors + number;
2137 
2138 	print_conf(conf);
2139 	if (rdev == p->rdev)
2140 		rdevp = &p->rdev;
2141 	else if (rdev == p->replacement)
2142 		rdevp = &p->replacement;
2143 	else
2144 		return 0;
2145 
2146 	if (test_bit(In_sync, &rdev->flags) ||
2147 	    atomic_read(&rdev->nr_pending)) {
2148 		err = -EBUSY;
2149 		goto abort;
2150 	}
2151 	/* Only remove non-faulty devices if recovery
2152 	 * is not possible.
2153 	 */
2154 	if (!test_bit(Faulty, &rdev->flags) &&
2155 	    mddev->recovery_disabled != p->recovery_disabled &&
2156 	    (!p->replacement || p->replacement == rdev) &&
2157 	    number < conf->geo.raid_disks &&
2158 	    enough(conf, -1)) {
2159 		err = -EBUSY;
2160 		goto abort;
2161 	}
2162 	*rdevp = NULL;
2163 	if (!test_bit(RemoveSynchronized, &rdev->flags)) {
2164 		synchronize_rcu();
2165 		if (atomic_read(&rdev->nr_pending)) {
2166 			/* lost the race, try later */
2167 			err = -EBUSY;
2168 			*rdevp = rdev;
2169 			goto abort;
2170 		}
2171 	}
2172 	if (p->replacement) {
2173 		/* We must have just cleared 'rdev' */
2174 		p->rdev = p->replacement;
2175 		clear_bit(Replacement, &p->replacement->flags);
2176 		smp_mb(); /* Make sure other CPUs may see both as identical
2177 			   * but will never see neither -- if they are careful.
2178 			   */
2179 		p->replacement = NULL;
2180 	}
2181 
2182 	clear_bit(WantReplacement, &rdev->flags);
2183 	err = md_integrity_register(mddev);
2184 
2185 abort:
2186 
2187 	print_conf(conf);
2188 	return err;
2189 }
2190 
2191 static void __end_sync_read(struct r10bio *r10_bio, struct bio *bio, int d)
2192 {
2193 	struct r10conf *conf = r10_bio->mddev->private;
2194 
2195 	if (!bio->bi_status)
2196 		set_bit(R10BIO_Uptodate, &r10_bio->state);
2197 	else
2198 		/* The write handler will notice the lack of
2199 		 * R10BIO_Uptodate and record any errors etc
2200 		 */
2201 		atomic_add(r10_bio->sectors,
2202 			   &conf->mirrors[d].rdev->corrected_errors);
2203 
2204 	/* for reconstruct, we always reschedule after a read.
2205 	 * for resync, only after all reads
2206 	 */
2207 	rdev_dec_pending(conf->mirrors[d].rdev, conf->mddev);
2208 	if (test_bit(R10BIO_IsRecover, &r10_bio->state) ||
2209 	    atomic_dec_and_test(&r10_bio->remaining)) {
2210 		/* we have read all the blocks,
2211 		 * do the comparison in process context in raid10d
2212 		 */
2213 		reschedule_retry(r10_bio);
2214 	}
2215 }
2216 
2217 static void end_sync_read(struct bio *bio)
2218 {
2219 	struct r10bio *r10_bio = get_resync_r10bio(bio);
2220 	struct r10conf *conf = r10_bio->mddev->private;
2221 	int d = find_bio_disk(conf, r10_bio, bio, NULL, NULL);
2222 
2223 	__end_sync_read(r10_bio, bio, d);
2224 }
2225 
2226 static void end_reshape_read(struct bio *bio)
2227 {
2228 	/* reshape read bio isn't allocated from r10buf_pool */
2229 	struct r10bio *r10_bio = bio->bi_private;
2230 
2231 	__end_sync_read(r10_bio, bio, r10_bio->read_slot);
2232 }
2233 
2234 static void end_sync_request(struct r10bio *r10_bio)
2235 {
2236 	struct mddev *mddev = r10_bio->mddev;
2237 
2238 	while (atomic_dec_and_test(&r10_bio->remaining)) {
2239 		if (r10_bio->master_bio == NULL) {
2240 			/* the primary of several recovery bios */
2241 			sector_t s = r10_bio->sectors;
2242 			if (test_bit(R10BIO_MadeGood, &r10_bio->state) ||
2243 			    test_bit(R10BIO_WriteError, &r10_bio->state))
2244 				reschedule_retry(r10_bio);
2245 			else
2246 				put_buf(r10_bio);
2247 			md_done_sync(mddev, s, 1);
2248 			break;
2249 		} else {
2250 			struct r10bio *r10_bio2 = (struct r10bio *)r10_bio->master_bio;
2251 			if (test_bit(R10BIO_MadeGood, &r10_bio->state) ||
2252 			    test_bit(R10BIO_WriteError, &r10_bio->state))
2253 				reschedule_retry(r10_bio);
2254 			else
2255 				put_buf(r10_bio);
2256 			r10_bio = r10_bio2;
2257 		}
2258 	}
2259 }
2260 
2261 static void end_sync_write(struct bio *bio)
2262 {
2263 	struct r10bio *r10_bio = get_resync_r10bio(bio);
2264 	struct mddev *mddev = r10_bio->mddev;
2265 	struct r10conf *conf = mddev->private;
2266 	int d;
2267 	sector_t first_bad;
2268 	int bad_sectors;
2269 	int slot;
2270 	int repl;
2271 	struct md_rdev *rdev = NULL;
2272 
2273 	d = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
2274 	if (repl)
2275 		rdev = conf->mirrors[d].replacement;
2276 	else
2277 		rdev = conf->mirrors[d].rdev;
2278 
2279 	if (bio->bi_status) {
2280 		if (repl)
2281 			md_error(mddev, rdev);
2282 		else {
2283 			set_bit(WriteErrorSeen, &rdev->flags);
2284 			if (!test_and_set_bit(WantReplacement, &rdev->flags))
2285 				set_bit(MD_RECOVERY_NEEDED,
2286 					&rdev->mddev->recovery);
2287 			set_bit(R10BIO_WriteError, &r10_bio->state);
2288 		}
2289 	} else if (is_badblock(rdev,
2290 			     r10_bio->devs[slot].addr,
2291 			     r10_bio->sectors,
2292 			     &first_bad, &bad_sectors))
2293 		set_bit(R10BIO_MadeGood, &r10_bio->state);
2294 
2295 	rdev_dec_pending(rdev, mddev);
2296 
2297 	end_sync_request(r10_bio);
2298 }
2299 
2300 /*
2301  * Note: sync and recover and handled very differently for raid10
2302  * This code is for resync.
2303  * For resync, we read through virtual addresses and read all blocks.
2304  * If there is any error, we schedule a write.  The lowest numbered
2305  * drive is authoritative.
2306  * However requests come for physical address, so we need to map.
2307  * For every physical address there are raid_disks/copies virtual addresses,
2308  * which is always are least one, but is not necessarly an integer.
2309  * This means that a physical address can span multiple chunks, so we may
2310  * have to submit multiple io requests for a single sync request.
2311  */
2312 /*
2313  * We check if all blocks are in-sync and only write to blocks that
2314  * aren't in sync
2315  */
2316 static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
2317 {
2318 	struct r10conf *conf = mddev->private;
2319 	int i, first;
2320 	struct bio *tbio, *fbio;
2321 	int vcnt;
2322 	struct page **tpages, **fpages;
2323 
2324 	atomic_set(&r10_bio->remaining, 1);
2325 
2326 	/* find the first device with a block */
2327 	for (i=0; i<conf->copies; i++)
2328 		if (!r10_bio->devs[i].bio->bi_status)
2329 			break;
2330 
2331 	if (i == conf->copies)
2332 		goto done;
2333 
2334 	first = i;
2335 	fbio = r10_bio->devs[i].bio;
2336 	fbio->bi_iter.bi_size = r10_bio->sectors << 9;
2337 	fbio->bi_iter.bi_idx = 0;
2338 	fpages = get_resync_pages(fbio)->pages;
2339 
2340 	vcnt = (r10_bio->sectors + (PAGE_SIZE >> 9) - 1) >> (PAGE_SHIFT - 9);
2341 	/* now find blocks with errors */
2342 	for (i=0 ; i < conf->copies ; i++) {
2343 		int  j, d;
2344 		struct md_rdev *rdev;
2345 		struct resync_pages *rp;
2346 
2347 		tbio = r10_bio->devs[i].bio;
2348 
2349 		if (tbio->bi_end_io != end_sync_read)
2350 			continue;
2351 		if (i == first)
2352 			continue;
2353 
2354 		tpages = get_resync_pages(tbio)->pages;
2355 		d = r10_bio->devs[i].devnum;
2356 		rdev = conf->mirrors[d].rdev;
2357 		if (!r10_bio->devs[i].bio->bi_status) {
2358 			/* We know that the bi_io_vec layout is the same for
2359 			 * both 'first' and 'i', so we just compare them.
2360 			 * All vec entries are PAGE_SIZE;
2361 			 */
2362 			int sectors = r10_bio->sectors;
2363 			for (j = 0; j < vcnt; j++) {
2364 				int len = PAGE_SIZE;
2365 				if (sectors < (len / 512))
2366 					len = sectors * 512;
2367 				if (memcmp(page_address(fpages[j]),
2368 					   page_address(tpages[j]),
2369 					   len))
2370 					break;
2371 				sectors -= len/512;
2372 			}
2373 			if (j == vcnt)
2374 				continue;
2375 			atomic64_add(r10_bio->sectors, &mddev->resync_mismatches);
2376 			if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
2377 				/* Don't fix anything. */
2378 				continue;
2379 		} else if (test_bit(FailFast, &rdev->flags)) {
2380 			/* Just give up on this device */
2381 			md_error(rdev->mddev, rdev);
2382 			continue;
2383 		}
2384 		/* Ok, we need to write this bio, either to correct an
2385 		 * inconsistency or to correct an unreadable block.
2386 		 * First we need to fixup bv_offset, bv_len and
2387 		 * bi_vecs, as the read request might have corrupted these
2388 		 */
2389 		rp = get_resync_pages(tbio);
2390 		bio_reset(tbio);
2391 
2392 		md_bio_reset_resync_pages(tbio, rp, fbio->bi_iter.bi_size);
2393 
2394 		rp->raid_bio = r10_bio;
2395 		tbio->bi_private = rp;
2396 		tbio->bi_iter.bi_sector = r10_bio->devs[i].addr;
2397 		tbio->bi_end_io = end_sync_write;
2398 		bio_set_op_attrs(tbio, REQ_OP_WRITE, 0);
2399 
2400 		bio_copy_data(tbio, fbio);
2401 
2402 		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
2403 		atomic_inc(&r10_bio->remaining);
2404 		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(tbio));
2405 
2406 		if (test_bit(FailFast, &conf->mirrors[d].rdev->flags))
2407 			tbio->bi_opf |= MD_FAILFAST;
2408 		tbio->bi_iter.bi_sector += conf->mirrors[d].rdev->data_offset;
2409 		bio_set_dev(tbio, conf->mirrors[d].rdev->bdev);
2410 		submit_bio_noacct(tbio);
2411 	}
2412 
2413 	/* Now write out to any replacement devices
2414 	 * that are active
2415 	 */
2416 	for (i = 0; i < conf->copies; i++) {
2417 		int d;
2418 
2419 		tbio = r10_bio->devs[i].repl_bio;
2420 		if (!tbio || !tbio->bi_end_io)
2421 			continue;
2422 		if (r10_bio->devs[i].bio->bi_end_io != end_sync_write
2423 		    && r10_bio->devs[i].bio != fbio)
2424 			bio_copy_data(tbio, fbio);
2425 		d = r10_bio->devs[i].devnum;
2426 		atomic_inc(&r10_bio->remaining);
2427 		md_sync_acct(conf->mirrors[d].replacement->bdev,
2428 			     bio_sectors(tbio));
2429 		submit_bio_noacct(tbio);
2430 	}
2431 
2432 done:
2433 	if (atomic_dec_and_test(&r10_bio->remaining)) {
2434 		md_done_sync(mddev, r10_bio->sectors, 1);
2435 		put_buf(r10_bio);
2436 	}
2437 }
2438 
2439 /*
2440  * Now for the recovery code.
2441  * Recovery happens across physical sectors.
2442  * We recover all non-is_sync drives by finding the virtual address of
2443  * each, and then choose a working drive that also has that virt address.
2444  * There is a separate r10_bio for each non-in_sync drive.
2445  * Only the first two slots are in use. The first for reading,
2446  * The second for writing.
2447  *
2448  */
2449 static void fix_recovery_read_error(struct r10bio *r10_bio)
2450 {
2451 	/* We got a read error during recovery.
2452 	 * We repeat the read in smaller page-sized sections.
2453 	 * If a read succeeds, write it to the new device or record
2454 	 * a bad block if we cannot.
2455 	 * If a read fails, record a bad block on both old and
2456 	 * new devices.
2457 	 */
2458 	struct mddev *mddev = r10_bio->mddev;
2459 	struct r10conf *conf = mddev->private;
2460 	struct bio *bio = r10_bio->devs[0].bio;
2461 	sector_t sect = 0;
2462 	int sectors = r10_bio->sectors;
2463 	int idx = 0;
2464 	int dr = r10_bio->devs[0].devnum;
2465 	int dw = r10_bio->devs[1].devnum;
2466 	struct page **pages = get_resync_pages(bio)->pages;
2467 
2468 	while (sectors) {
2469 		int s = sectors;
2470 		struct md_rdev *rdev;
2471 		sector_t addr;
2472 		int ok;
2473 
2474 		if (s > (PAGE_SIZE>>9))
2475 			s = PAGE_SIZE >> 9;
2476 
2477 		rdev = conf->mirrors[dr].rdev;
2478 		addr = r10_bio->devs[0].addr + sect,
2479 		ok = sync_page_io(rdev,
2480 				  addr,
2481 				  s << 9,
2482 				  pages[idx],
2483 				  REQ_OP_READ, 0, false);
2484 		if (ok) {
2485 			rdev = conf->mirrors[dw].rdev;
2486 			addr = r10_bio->devs[1].addr + sect;
2487 			ok = sync_page_io(rdev,
2488 					  addr,
2489 					  s << 9,
2490 					  pages[idx],
2491 					  REQ_OP_WRITE, 0, false);
2492 			if (!ok) {
2493 				set_bit(WriteErrorSeen, &rdev->flags);
2494 				if (!test_and_set_bit(WantReplacement,
2495 						      &rdev->flags))
2496 					set_bit(MD_RECOVERY_NEEDED,
2497 						&rdev->mddev->recovery);
2498 			}
2499 		}
2500 		if (!ok) {
2501 			/* We don't worry if we cannot set a bad block -
2502 			 * it really is bad so there is no loss in not
2503 			 * recording it yet
2504 			 */
2505 			rdev_set_badblocks(rdev, addr, s, 0);
2506 
2507 			if (rdev != conf->mirrors[dw].rdev) {
2508 				/* need bad block on destination too */
2509 				struct md_rdev *rdev2 = conf->mirrors[dw].rdev;
2510 				addr = r10_bio->devs[1].addr + sect;
2511 				ok = rdev_set_badblocks(rdev2, addr, s, 0);
2512 				if (!ok) {
2513 					/* just abort the recovery */
2514 					pr_notice("md/raid10:%s: recovery aborted due to read error\n",
2515 						  mdname(mddev));
2516 
2517 					conf->mirrors[dw].recovery_disabled
2518 						= mddev->recovery_disabled;
2519 					set_bit(MD_RECOVERY_INTR,
2520 						&mddev->recovery);
2521 					break;
2522 				}
2523 			}
2524 		}
2525 
2526 		sectors -= s;
2527 		sect += s;
2528 		idx++;
2529 	}
2530 }
2531 
2532 static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
2533 {
2534 	struct r10conf *conf = mddev->private;
2535 	int d;
2536 	struct bio *wbio, *wbio2;
2537 
2538 	if (!test_bit(R10BIO_Uptodate, &r10_bio->state)) {
2539 		fix_recovery_read_error(r10_bio);
2540 		end_sync_request(r10_bio);
2541 		return;
2542 	}
2543 
2544 	/*
2545 	 * share the pages with the first bio
2546 	 * and submit the write request
2547 	 */
2548 	d = r10_bio->devs[1].devnum;
2549 	wbio = r10_bio->devs[1].bio;
2550 	wbio2 = r10_bio->devs[1].repl_bio;
2551 	/* Need to test wbio2->bi_end_io before we call
2552 	 * submit_bio_noacct as if the former is NULL,
2553 	 * the latter is free to free wbio2.
2554 	 */
2555 	if (wbio2 && !wbio2->bi_end_io)
2556 		wbio2 = NULL;
2557 	if (wbio->bi_end_io) {
2558 		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
2559 		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));
2560 		submit_bio_noacct(wbio);
2561 	}
2562 	if (wbio2) {
2563 		atomic_inc(&conf->mirrors[d].replacement->nr_pending);
2564 		md_sync_acct(conf->mirrors[d].replacement->bdev,
2565 			     bio_sectors(wbio2));
2566 		submit_bio_noacct(wbio2);
2567 	}
2568 }
2569 
2570 /*
2571  * Used by fix_read_error() to decay the per rdev read_errors.
2572  * We halve the read error count for every hour that has elapsed
2573  * since the last recorded read error.
2574  *
2575  */
2576 static void check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev)
2577 {
2578 	long cur_time_mon;
2579 	unsigned long hours_since_last;
2580 	unsigned int read_errors = atomic_read(&rdev->read_errors);
2581 
2582 	cur_time_mon = ktime_get_seconds();
2583 
2584 	if (rdev->last_read_error == 0) {
2585 		/* first time we've seen a read error */
2586 		rdev->last_read_error = cur_time_mon;
2587 		return;
2588 	}
2589 
2590 	hours_since_last = (long)(cur_time_mon -
2591 			    rdev->last_read_error) / 3600;
2592 
2593 	rdev->last_read_error = cur_time_mon;
2594 
2595 	/*
2596 	 * if hours_since_last is > the number of bits in read_errors
2597 	 * just set read errors to 0. We do this to avoid
2598 	 * overflowing the shift of read_errors by hours_since_last.
2599 	 */
2600 	if (hours_since_last >= 8 * sizeof(read_errors))
2601 		atomic_set(&rdev->read_errors, 0);
2602 	else
2603 		atomic_set(&rdev->read_errors, read_errors >> hours_since_last);
2604 }
2605 
2606 static int r10_sync_page_io(struct md_rdev *rdev, sector_t sector,
2607 			    int sectors, struct page *page, int rw)
2608 {
2609 	sector_t first_bad;
2610 	int bad_sectors;
2611 
2612 	if (is_badblock(rdev, sector, sectors, &first_bad, &bad_sectors)
2613 	    && (rw == READ || test_bit(WriteErrorSeen, &rdev->flags)))
2614 		return -1;
2615 	if (sync_page_io(rdev, sector, sectors << 9, page, rw, 0, false))
2616 		/* success */
2617 		return 1;
2618 	if (rw == WRITE) {
2619 		set_bit(WriteErrorSeen, &rdev->flags);
2620 		if (!test_and_set_bit(WantReplacement, &rdev->flags))
2621 			set_bit(MD_RECOVERY_NEEDED,
2622 				&rdev->mddev->recovery);
2623 	}
2624 	/* need to record an error - either for the block or the device */
2625 	if (!rdev_set_badblocks(rdev, sector, sectors, 0))
2626 		md_error(rdev->mddev, rdev);
2627 	return 0;
2628 }
2629 
2630 /*
2631  * This is a kernel thread which:
2632  *
2633  *	1.	Retries failed read operations on working mirrors.
2634  *	2.	Updates the raid superblock when problems encounter.
2635  *	3.	Performs writes following reads for array synchronising.
2636  */
2637 
2638 static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10bio *r10_bio)
2639 {
2640 	int sect = 0; /* Offset from r10_bio->sector */
2641 	int sectors = r10_bio->sectors;
2642 	struct md_rdev *rdev;
2643 	int max_read_errors = atomic_read(&mddev->max_corr_read_errors);
2644 	int d = r10_bio->devs[r10_bio->read_slot].devnum;
2645 
2646 	/* still own a reference to this rdev, so it cannot
2647 	 * have been cleared recently.
2648 	 */
2649 	rdev = conf->mirrors[d].rdev;
2650 
2651 	if (test_bit(Faulty, &rdev->flags))
2652 		/* drive has already been failed, just ignore any
2653 		   more fix_read_error() attempts */
2654 		return;
2655 
2656 	check_decay_read_errors(mddev, rdev);
2657 	atomic_inc(&rdev->read_errors);
2658 	if (atomic_read(&rdev->read_errors) > max_read_errors) {
2659 		char b[BDEVNAME_SIZE];
2660 		bdevname(rdev->bdev, b);
2661 
2662 		pr_notice("md/raid10:%s: %s: Raid device exceeded read_error threshold [cur %d:max %d]\n",
2663 			  mdname(mddev), b,
2664 			  atomic_read(&rdev->read_errors), max_read_errors);
2665 		pr_notice("md/raid10:%s: %s: Failing raid device\n",
2666 			  mdname(mddev), b);
2667 		md_error(mddev, rdev);
2668 		r10_bio->devs[r10_bio->read_slot].bio = IO_BLOCKED;
2669 		return;
2670 	}
2671 
2672 	while(sectors) {
2673 		int s = sectors;
2674 		int sl = r10_bio->read_slot;
2675 		int success = 0;
2676 		int start;
2677 
2678 		if (s > (PAGE_SIZE>>9))
2679 			s = PAGE_SIZE >> 9;
2680 
2681 		rcu_read_lock();
2682 		do {
2683 			sector_t first_bad;
2684 			int bad_sectors;
2685 
2686 			d = r10_bio->devs[sl].devnum;
2687 			rdev = rcu_dereference(conf->mirrors[d].rdev);
2688 			if (rdev &&
2689 			    test_bit(In_sync, &rdev->flags) &&
2690 			    !test_bit(Faulty, &rdev->flags) &&
2691 			    is_badblock(rdev, r10_bio->devs[sl].addr + sect, s,
2692 					&first_bad, &bad_sectors) == 0) {
2693 				atomic_inc(&rdev->nr_pending);
2694 				rcu_read_unlock();
2695 				success = sync_page_io(rdev,
2696 						       r10_bio->devs[sl].addr +
2697 						       sect,
2698 						       s<<9,
2699 						       conf->tmppage,
2700 						       REQ_OP_READ, 0, false);
2701 				rdev_dec_pending(rdev, mddev);
2702 				rcu_read_lock();
2703 				if (success)
2704 					break;
2705 			}
2706 			sl++;
2707 			if (sl == conf->copies)
2708 				sl = 0;
2709 		} while (!success && sl != r10_bio->read_slot);
2710 		rcu_read_unlock();
2711 
2712 		if (!success) {
2713 			/* Cannot read from anywhere, just mark the block
2714 			 * as bad on the first device to discourage future
2715 			 * reads.
2716 			 */
2717 			int dn = r10_bio->devs[r10_bio->read_slot].devnum;
2718 			rdev = conf->mirrors[dn].rdev;
2719 
2720 			if (!rdev_set_badblocks(
2721 				    rdev,
2722 				    r10_bio->devs[r10_bio->read_slot].addr
2723 				    + sect,
2724 				    s, 0)) {
2725 				md_error(mddev, rdev);
2726 				r10_bio->devs[r10_bio->read_slot].bio
2727 					= IO_BLOCKED;
2728 			}
2729 			break;
2730 		}
2731 
2732 		start = sl;
2733 		/* write it back and re-read */
2734 		rcu_read_lock();
2735 		while (sl != r10_bio->read_slot) {
2736 			char b[BDEVNAME_SIZE];
2737 
2738 			if (sl==0)
2739 				sl = conf->copies;
2740 			sl--;
2741 			d = r10_bio->devs[sl].devnum;
2742 			rdev = rcu_dereference(conf->mirrors[d].rdev);
2743 			if (!rdev ||
2744 			    test_bit(Faulty, &rdev->flags) ||
2745 			    !test_bit(In_sync, &rdev->flags))
2746 				continue;
2747 
2748 			atomic_inc(&rdev->nr_pending);
2749 			rcu_read_unlock();
2750 			if (r10_sync_page_io(rdev,
2751 					     r10_bio->devs[sl].addr +
2752 					     sect,
2753 					     s, conf->tmppage, WRITE)
2754 			    == 0) {
2755 				/* Well, this device is dead */
2756 				pr_notice("md/raid10:%s: read correction write failed (%d sectors at %llu on %s)\n",
2757 					  mdname(mddev), s,
2758 					  (unsigned long long)(
2759 						  sect +
2760 						  choose_data_offset(r10_bio,
2761 								     rdev)),
2762 					  bdevname(rdev->bdev, b));
2763 				pr_notice("md/raid10:%s: %s: failing drive\n",
2764 					  mdname(mddev),
2765 					  bdevname(rdev->bdev, b));
2766 			}
2767 			rdev_dec_pending(rdev, mddev);
2768 			rcu_read_lock();
2769 		}
2770 		sl = start;
2771 		while (sl != r10_bio->read_slot) {
2772 			char b[BDEVNAME_SIZE];
2773 
2774 			if (sl==0)
2775 				sl = conf->copies;
2776 			sl--;
2777 			d = r10_bio->devs[sl].devnum;
2778 			rdev = rcu_dereference(conf->mirrors[d].rdev);
2779 			if (!rdev ||
2780 			    test_bit(Faulty, &rdev->flags) ||
2781 			    !test_bit(In_sync, &rdev->flags))
2782 				continue;
2783 
2784 			atomic_inc(&rdev->nr_pending);
2785 			rcu_read_unlock();
2786 			switch (r10_sync_page_io(rdev,
2787 					     r10_bio->devs[sl].addr +
2788 					     sect,
2789 					     s, conf->tmppage,
2790 						 READ)) {
2791 			case 0:
2792 				/* Well, this device is dead */
2793 				pr_notice("md/raid10:%s: unable to read back corrected sectors (%d sectors at %llu on %s)\n",
2794 				       mdname(mddev), s,
2795 				       (unsigned long long)(
2796 					       sect +
2797 					       choose_data_offset(r10_bio, rdev)),
2798 				       bdevname(rdev->bdev, b));
2799 				pr_notice("md/raid10:%s: %s: failing drive\n",
2800 				       mdname(mddev),
2801 				       bdevname(rdev->bdev, b));
2802 				break;
2803 			case 1:
2804 				pr_info("md/raid10:%s: read error corrected (%d sectors at %llu on %s)\n",
2805 				       mdname(mddev), s,
2806 				       (unsigned long long)(
2807 					       sect +
2808 					       choose_data_offset(r10_bio, rdev)),
2809 				       bdevname(rdev->bdev, b));
2810 				atomic_add(s, &rdev->corrected_errors);
2811 			}
2812 
2813 			rdev_dec_pending(rdev, mddev);
2814 			rcu_read_lock();
2815 		}
2816 		rcu_read_unlock();
2817 
2818 		sectors -= s;
2819 		sect += s;
2820 	}
2821 }
2822 
2823 static int narrow_write_error(struct r10bio *r10_bio, int i)
2824 {
2825 	struct bio *bio = r10_bio->master_bio;
2826 	struct mddev *mddev = r10_bio->mddev;
2827 	struct r10conf *conf = mddev->private;
2828 	struct md_rdev *rdev = conf->mirrors[r10_bio->devs[i].devnum].rdev;
2829 	/* bio has the data to be written to slot 'i' where
2830 	 * we just recently had a write error.
2831 	 * We repeatedly clone the bio and trim down to one block,
2832 	 * then try the write.  Where the write fails we record
2833 	 * a bad block.
2834 	 * It is conceivable that the bio doesn't exactly align with
2835 	 * blocks.  We must handle this.
2836 	 *
2837 	 * We currently own a reference to the rdev.
2838 	 */
2839 
2840 	int block_sectors;
2841 	sector_t sector;
2842 	int sectors;
2843 	int sect_to_write = r10_bio->sectors;
2844 	int ok = 1;
2845 
2846 	if (rdev->badblocks.shift < 0)
2847 		return 0;
2848 
2849 	block_sectors = roundup(1 << rdev->badblocks.shift,
2850 				bdev_logical_block_size(rdev->bdev) >> 9);
2851 	sector = r10_bio->sector;
2852 	sectors = ((r10_bio->sector + block_sectors)
2853 		   & ~(sector_t)(block_sectors - 1))
2854 		- sector;
2855 
2856 	while (sect_to_write) {
2857 		struct bio *wbio;
2858 		sector_t wsector;
2859 		if (sectors > sect_to_write)
2860 			sectors = sect_to_write;
2861 		/* Write at 'sector' for 'sectors' */
2862 		wbio = bio_clone_fast(bio, GFP_NOIO, &mddev->bio_set);
2863 		bio_trim(wbio, sector - bio->bi_iter.bi_sector, sectors);
2864 		wsector = r10_bio->devs[i].addr + (sector - r10_bio->sector);
2865 		wbio->bi_iter.bi_sector = wsector +
2866 				   choose_data_offset(r10_bio, rdev);
2867 		bio_set_dev(wbio, rdev->bdev);
2868 		bio_set_op_attrs(wbio, REQ_OP_WRITE, 0);
2869 
2870 		if (submit_bio_wait(wbio) < 0)
2871 			/* Failure! */
2872 			ok = rdev_set_badblocks(rdev, wsector,
2873 						sectors, 0)
2874 				&& ok;
2875 
2876 		bio_put(wbio);
2877 		sect_to_write -= sectors;
2878 		sector += sectors;
2879 		sectors = block_sectors;
2880 	}
2881 	return ok;
2882 }
2883 
2884 static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
2885 {
2886 	int slot = r10_bio->read_slot;
2887 	struct bio *bio;
2888 	struct r10conf *conf = mddev->private;
2889 	struct md_rdev *rdev = r10_bio->devs[slot].rdev;
2890 
2891 	/* we got a read error. Maybe the drive is bad.  Maybe just
2892 	 * the block and we can fix it.
2893 	 * We freeze all other IO, and try reading the block from
2894 	 * other devices.  When we find one, we re-write
2895 	 * and check it that fixes the read error.
2896 	 * This is all done synchronously while the array is
2897 	 * frozen.
2898 	 */
2899 	bio = r10_bio->devs[slot].bio;
2900 	bio_put(bio);
2901 	r10_bio->devs[slot].bio = NULL;
2902 
2903 	if (mddev->ro)
2904 		r10_bio->devs[slot].bio = IO_BLOCKED;
2905 	else if (!test_bit(FailFast, &rdev->flags)) {
2906 		freeze_array(conf, 1);
2907 		fix_read_error(conf, mddev, r10_bio);
2908 		unfreeze_array(conf);
2909 	} else
2910 		md_error(mddev, rdev);
2911 
2912 	rdev_dec_pending(rdev, mddev);
2913 	allow_barrier(conf);
2914 	r10_bio->state = 0;
2915 	raid10_read_request(mddev, r10_bio->master_bio, r10_bio);
2916 }
2917 
2918 static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)
2919 {
2920 	/* Some sort of write request has finished and it
2921 	 * succeeded in writing where we thought there was a
2922 	 * bad block.  So forget the bad block.
2923 	 * Or possibly if failed and we need to record
2924 	 * a bad block.
2925 	 */
2926 	int m;
2927 	struct md_rdev *rdev;
2928 
2929 	if (test_bit(R10BIO_IsSync, &r10_bio->state) ||
2930 	    test_bit(R10BIO_IsRecover, &r10_bio->state)) {
2931 		for (m = 0; m < conf->copies; m++) {
2932 			int dev = r10_bio->devs[m].devnum;
2933 			rdev = conf->mirrors[dev].rdev;
2934 			if (r10_bio->devs[m].bio == NULL ||
2935 				r10_bio->devs[m].bio->bi_end_io == NULL)
2936 				continue;
2937 			if (!r10_bio->devs[m].bio->bi_status) {
2938 				rdev_clear_badblocks(
2939 					rdev,
2940 					r10_bio->devs[m].addr,
2941 					r10_bio->sectors, 0);
2942 			} else {
2943 				if (!rdev_set_badblocks(
2944 					    rdev,
2945 					    r10_bio->devs[m].addr,
2946 					    r10_bio->sectors, 0))
2947 					md_error(conf->mddev, rdev);
2948 			}
2949 			rdev = conf->mirrors[dev].replacement;
2950 			if (r10_bio->devs[m].repl_bio == NULL ||
2951 				r10_bio->devs[m].repl_bio->bi_end_io == NULL)
2952 				continue;
2953 
2954 			if (!r10_bio->devs[m].repl_bio->bi_status) {
2955 				rdev_clear_badblocks(
2956 					rdev,
2957 					r10_bio->devs[m].addr,
2958 					r10_bio->sectors, 0);
2959 			} else {
2960 				if (!rdev_set_badblocks(
2961 					    rdev,
2962 					    r10_bio->devs[m].addr,
2963 					    r10_bio->sectors, 0))
2964 					md_error(conf->mddev, rdev);
2965 			}
2966 		}
2967 		put_buf(r10_bio);
2968 	} else {
2969 		bool fail = false;
2970 		for (m = 0; m < conf->copies; m++) {
2971 			int dev = r10_bio->devs[m].devnum;
2972 			struct bio *bio = r10_bio->devs[m].bio;
2973 			rdev = conf->mirrors[dev].rdev;
2974 			if (bio == IO_MADE_GOOD) {
2975 				rdev_clear_badblocks(
2976 					rdev,
2977 					r10_bio->devs[m].addr,
2978 					r10_bio->sectors, 0);
2979 				rdev_dec_pending(rdev, conf->mddev);
2980 			} else if (bio != NULL && bio->bi_status) {
2981 				fail = true;
2982 				if (!narrow_write_error(r10_bio, m)) {
2983 					md_error(conf->mddev, rdev);
2984 					set_bit(R10BIO_Degraded,
2985 						&r10_bio->state);
2986 				}
2987 				rdev_dec_pending(rdev, conf->mddev);
2988 			}
2989 			bio = r10_bio->devs[m].repl_bio;
2990 			rdev = conf->mirrors[dev].replacement;
2991 			if (rdev && bio == IO_MADE_GOOD) {
2992 				rdev_clear_badblocks(
2993 					rdev,
2994 					r10_bio->devs[m].addr,
2995 					r10_bio->sectors, 0);
2996 				rdev_dec_pending(rdev, conf->mddev);
2997 			}
2998 		}
2999 		if (fail) {
3000 			spin_lock_irq(&conf->device_lock);
3001 			list_add(&r10_bio->retry_list, &conf->bio_end_io_list);
3002 			conf->nr_queued++;
3003 			spin_unlock_irq(&conf->device_lock);
3004 			/*
3005 			 * In case freeze_array() is waiting for condition
3006 			 * nr_pending == nr_queued + extra to be true.
3007 			 */
3008 			wake_up(&conf->wait_barrier);
3009 			md_wakeup_thread(conf->mddev->thread);
3010 		} else {
3011 			if (test_bit(R10BIO_WriteError,
3012 				     &r10_bio->state))
3013 				close_write(r10_bio);
3014 			raid_end_bio_io(r10_bio);
3015 		}
3016 	}
3017 }
3018 
3019 static void raid10d(struct md_thread *thread)
3020 {
3021 	struct mddev *mddev = thread->mddev;
3022 	struct r10bio *r10_bio;
3023 	unsigned long flags;
3024 	struct r10conf *conf = mddev->private;
3025 	struct list_head *head = &conf->retry_list;
3026 	struct blk_plug plug;
3027 
3028 	md_check_recovery(mddev);
3029 
3030 	if (!list_empty_careful(&conf->bio_end_io_list) &&
3031 	    !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) {
3032 		LIST_HEAD(tmp);
3033 		spin_lock_irqsave(&conf->device_lock, flags);
3034 		if (!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) {
3035 			while (!list_empty(&conf->bio_end_io_list)) {
3036 				list_move(conf->bio_end_io_list.prev, &tmp);
3037 				conf->nr_queued--;
3038 			}
3039 		}
3040 		spin_unlock_irqrestore(&conf->device_lock, flags);
3041 		while (!list_empty(&tmp)) {
3042 			r10_bio = list_first_entry(&tmp, struct r10bio,
3043 						   retry_list);
3044 			list_del(&r10_bio->retry_list);
3045 			if (mddev->degraded)
3046 				set_bit(R10BIO_Degraded, &r10_bio->state);
3047 
3048 			if (test_bit(R10BIO_WriteError,
3049 				     &r10_bio->state))
3050 				close_write(r10_bio);
3051 			raid_end_bio_io(r10_bio);
3052 		}
3053 	}
3054 
3055 	blk_start_plug(&plug);
3056 	for (;;) {
3057 
3058 		flush_pending_writes(conf);
3059 
3060 		spin_lock_irqsave(&conf->device_lock, flags);
3061 		if (list_empty(head)) {
3062 			spin_unlock_irqrestore(&conf->device_lock, flags);
3063 			break;
3064 		}
3065 		r10_bio = list_entry(head->prev, struct r10bio, retry_list);
3066 		list_del(head->prev);
3067 		conf->nr_queued--;
3068 		spin_unlock_irqrestore(&conf->device_lock, flags);
3069 
3070 		mddev = r10_bio->mddev;
3071 		conf = mddev->private;
3072 		if (test_bit(R10BIO_MadeGood, &r10_bio->state) ||
3073 		    test_bit(R10BIO_WriteError, &r10_bio->state))
3074 			handle_write_completed(conf, r10_bio);
3075 		else if (test_bit(R10BIO_IsReshape, &r10_bio->state))
3076 			reshape_request_write(mddev, r10_bio);
3077 		else if (test_bit(R10BIO_IsSync, &r10_bio->state))
3078 			sync_request_write(mddev, r10_bio);
3079 		else if (test_bit(R10BIO_IsRecover, &r10_bio->state))
3080 			recovery_request_write(mddev, r10_bio);
3081 		else if (test_bit(R10BIO_ReadError, &r10_bio->state))
3082 			handle_read_error(mddev, r10_bio);
3083 		else
3084 			WARN_ON_ONCE(1);
3085 
3086 		cond_resched();
3087 		if (mddev->sb_flags & ~(1<<MD_SB_CHANGE_PENDING))
3088 			md_check_recovery(mddev);
3089 	}
3090 	blk_finish_plug(&plug);
3091 }
3092 
3093 static int init_resync(struct r10conf *conf)
3094 {
3095 	int ret, buffs, i;
3096 
3097 	buffs = RESYNC_WINDOW / RESYNC_BLOCK_SIZE;
3098 	BUG_ON(mempool_initialized(&conf->r10buf_pool));
3099 	conf->have_replacement = 0;
3100 	for (i = 0; i < conf->geo.raid_disks; i++)
3101 		if (conf->mirrors[i].replacement)
3102 			conf->have_replacement = 1;
3103 	ret = mempool_init(&conf->r10buf_pool, buffs,
3104 			   r10buf_pool_alloc, r10buf_pool_free, conf);
3105 	if (ret)
3106 		return ret;
3107 	conf->next_resync = 0;
3108 	return 0;
3109 }
3110 
3111 static struct r10bio *raid10_alloc_init_r10buf(struct r10conf *conf)
3112 {
3113 	struct r10bio *r10bio = mempool_alloc(&conf->r10buf_pool, GFP_NOIO);
3114 	struct rsync_pages *rp;
3115 	struct bio *bio;
3116 	int nalloc;
3117 	int i;
3118 
3119 	if (test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery) ||
3120 	    test_bit(MD_RECOVERY_RESHAPE, &conf->mddev->recovery))
3121 		nalloc = conf->copies; /* resync */
3122 	else
3123 		nalloc = 2; /* recovery */
3124 
3125 	for (i = 0; i < nalloc; i++) {
3126 		bio = r10bio->devs[i].bio;
3127 		rp = bio->bi_private;
3128 		bio_reset(bio);
3129 		bio->bi_private = rp;
3130 		bio = r10bio->devs[i].repl_bio;
3131 		if (bio) {
3132 			rp = bio->bi_private;
3133 			bio_reset(bio);
3134 			bio->bi_private = rp;
3135 		}
3136 	}
3137 	return r10bio;
3138 }
3139 
3140 /*
3141  * Set cluster_sync_high since we need other nodes to add the
3142  * range [cluster_sync_low, cluster_sync_high] to suspend list.
3143  */
3144 static void raid10_set_cluster_sync_high(struct r10conf *conf)
3145 {
3146 	sector_t window_size;
3147 	int extra_chunk, chunks;
3148 
3149 	/*
3150 	 * First, here we define "stripe" as a unit which across
3151 	 * all member devices one time, so we get chunks by use
3152 	 * raid_disks / near_copies. Otherwise, if near_copies is
3153 	 * close to raid_disks, then resync window could increases
3154 	 * linearly with the increase of raid_disks, which means
3155 	 * we will suspend a really large IO window while it is not
3156 	 * necessary. If raid_disks is not divisible by near_copies,
3157 	 * an extra chunk is needed to ensure the whole "stripe" is
3158 	 * covered.
3159 	 */
3160 
3161 	chunks = conf->geo.raid_disks / conf->geo.near_copies;
3162 	if (conf->geo.raid_disks % conf->geo.near_copies == 0)
3163 		extra_chunk = 0;
3164 	else
3165 		extra_chunk = 1;
3166 	window_size = (chunks + extra_chunk) * conf->mddev->chunk_sectors;
3167 
3168 	/*
3169 	 * At least use a 32M window to align with raid1's resync window
3170 	 */
3171 	window_size = (CLUSTER_RESYNC_WINDOW_SECTORS > window_size) ?
3172 			CLUSTER_RESYNC_WINDOW_SECTORS : window_size;
3173 
3174 	conf->cluster_sync_high = conf->cluster_sync_low + window_size;
3175 }
3176 
3177 /*
3178  * perform a "sync" on one "block"
3179  *
3180  * We need to make sure that no normal I/O request - particularly write
3181  * requests - conflict with active sync requests.
3182  *
3183  * This is achieved by tracking pending requests and a 'barrier' concept
3184  * that can be installed to exclude normal IO requests.
3185  *
3186  * Resync and recovery are handled very differently.
3187  * We differentiate by looking at MD_RECOVERY_SYNC in mddev->recovery.
3188  *
3189  * For resync, we iterate over virtual addresses, read all copies,
3190  * and update if there are differences.  If only one copy is live,
3191  * skip it.
3192  * For recovery, we iterate over physical addresses, read a good
3193  * value for each non-in_sync drive, and over-write.
3194  *
3195  * So, for recovery we may have several outstanding complex requests for a
3196  * given address, one for each out-of-sync device.  We model this by allocating
3197  * a number of r10_bio structures, one for each out-of-sync device.
3198  * As we setup these structures, we collect all bio's together into a list
3199  * which we then process collectively to add pages, and then process again
3200  * to pass to submit_bio_noacct.
3201  *
3202  * The r10_bio structures are linked using a borrowed master_bio pointer.
3203  * This link is counted in ->remaining.  When the r10_bio that points to NULL
3204  * has its remaining count decremented to 0, the whole complex operation
3205  * is complete.
3206  *
3207  */
3208 
3209 static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
3210 			     int *skipped)
3211 {
3212 	struct r10conf *conf = mddev->private;
3213 	struct r10bio *r10_bio;
3214 	struct bio *biolist = NULL, *bio;
3215 	sector_t max_sector, nr_sectors;
3216 	int i;
3217 	int max_sync;
3218 	sector_t sync_blocks;
3219 	sector_t sectors_skipped = 0;
3220 	int chunks_skipped = 0;
3221 	sector_t chunk_mask = conf->geo.chunk_mask;
3222 	int page_idx = 0;
3223 
3224 	if (!mempool_initialized(&conf->r10buf_pool))
3225 		if (init_resync(conf))
3226 			return 0;
3227 
3228 	/*
3229 	 * Allow skipping a full rebuild for incremental assembly
3230 	 * of a clean array, like RAID1 does.
3231 	 */
3232 	if (mddev->bitmap == NULL &&
3233 	    mddev->recovery_cp == MaxSector &&
3234 	    mddev->reshape_position == MaxSector &&
3235 	    !test_bit(MD_RECOVERY_SYNC, &mddev->recovery) &&
3236 	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
3237 	    !test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
3238 	    conf->fullsync == 0) {
3239 		*skipped = 1;
3240 		return mddev->dev_sectors - sector_nr;
3241 	}
3242 
3243  skipped:
3244 	max_sector = mddev->dev_sectors;
3245 	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
3246 	    test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
3247 		max_sector = mddev->resync_max_sectors;
3248 	if (sector_nr >= max_sector) {
3249 		conf->cluster_sync_low = 0;
3250 		conf->cluster_sync_high = 0;
3251 
3252 		/* If we aborted, we need to abort the
3253 		 * sync on the 'current' bitmap chucks (there can
3254 		 * be several when recovering multiple devices).
3255 		 * as we may have started syncing it but not finished.
3256 		 * We can find the current address in
3257 		 * mddev->curr_resync, but for recovery,
3258 		 * we need to convert that to several
3259 		 * virtual addresses.
3260 		 */
3261 		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) {
3262 			end_reshape(conf);
3263 			close_sync(conf);
3264 			return 0;
3265 		}
3266 
3267 		if (mddev->curr_resync < max_sector) { /* aborted */
3268 			if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
3269 				md_bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
3270 						   &sync_blocks, 1);
3271 			else for (i = 0; i < conf->geo.raid_disks; i++) {
3272 				sector_t sect =
3273 					raid10_find_virt(conf, mddev->curr_resync, i);
3274 				md_bitmap_end_sync(mddev->bitmap, sect,
3275 						   &sync_blocks, 1);
3276 			}
3277 		} else {
3278 			/* completed sync */
3279 			if ((!mddev->bitmap || conf->fullsync)
3280 			    && conf->have_replacement
3281 			    && test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
3282 				/* Completed a full sync so the replacements
3283 				 * are now fully recovered.
3284 				 */
3285 				rcu_read_lock();
3286 				for (i = 0; i < conf->geo.raid_disks; i++) {
3287 					struct md_rdev *rdev =
3288 						rcu_dereference(conf->mirrors[i].replacement);
3289 					if (rdev)
3290 						rdev->recovery_offset = MaxSector;
3291 				}
3292 				rcu_read_unlock();
3293 			}
3294 			conf->fullsync = 0;
3295 		}
3296 		md_bitmap_close_sync(mddev->bitmap);
3297 		close_sync(conf);
3298 		*skipped = 1;
3299 		return sectors_skipped;
3300 	}
3301 
3302 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
3303 		return reshape_request(mddev, sector_nr, skipped);
3304 
3305 	if (chunks_skipped >= conf->geo.raid_disks) {
3306 		/* if there has been nothing to do on any drive,
3307 		 * then there is nothing to do at all..
3308 		 */
3309 		*skipped = 1;
3310 		return (max_sector - sector_nr) + sectors_skipped;
3311 	}
3312 
3313 	if (max_sector > mddev->resync_max)
3314 		max_sector = mddev->resync_max; /* Don't do IO beyond here */
3315 
3316 	/* make sure whole request will fit in a chunk - if chunks
3317 	 * are meaningful
3318 	 */
3319 	if (conf->geo.near_copies < conf->geo.raid_disks &&
3320 	    max_sector > (sector_nr | chunk_mask))
3321 		max_sector = (sector_nr | chunk_mask) + 1;
3322 
3323 	/*
3324 	 * If there is non-resync activity waiting for a turn, then let it
3325 	 * though before starting on this new sync request.
3326 	 */
3327 	if (conf->nr_waiting)
3328 		schedule_timeout_uninterruptible(1);
3329 
3330 	/* Again, very different code for resync and recovery.
3331 	 * Both must result in an r10bio with a list of bios that
3332 	 * have bi_end_io, bi_sector, bi_bdev set,
3333 	 * and bi_private set to the r10bio.
3334 	 * For recovery, we may actually create several r10bios
3335 	 * with 2 bios in each, that correspond to the bios in the main one.
3336 	 * In this case, the subordinate r10bios link back through a
3337 	 * borrowed master_bio pointer, and the counter in the master
3338 	 * includes a ref from each subordinate.
3339 	 */
3340 	/* First, we decide what to do and set ->bi_end_io
3341 	 * To end_sync_read if we want to read, and
3342 	 * end_sync_write if we will want to write.
3343 	 */
3344 
3345 	max_sync = RESYNC_PAGES << (PAGE_SHIFT-9);
3346 	if (!test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
3347 		/* recovery... the complicated one */
3348 		int j;
3349 		r10_bio = NULL;
3350 
3351 		for (i = 0 ; i < conf->geo.raid_disks; i++) {
3352 			int still_degraded;
3353 			struct r10bio *rb2;
3354 			sector_t sect;
3355 			int must_sync;
3356 			int any_working;
3357 			int need_recover = 0;
3358 			int need_replace = 0;
3359 			struct raid10_info *mirror = &conf->mirrors[i];
3360 			struct md_rdev *mrdev, *mreplace;
3361 
3362 			rcu_read_lock();
3363 			mrdev = rcu_dereference(mirror->rdev);
3364 			mreplace = rcu_dereference(mirror->replacement);
3365 
3366 			if (mrdev != NULL &&
3367 			    !test_bit(Faulty, &mrdev->flags) &&
3368 			    !test_bit(In_sync, &mrdev->flags))
3369 				need_recover = 1;
3370 			if (mreplace != NULL &&
3371 			    !test_bit(Faulty, &mreplace->flags))
3372 				need_replace = 1;
3373 
3374 			if (!need_recover && !need_replace) {
3375 				rcu_read_unlock();
3376 				continue;
3377 			}
3378 
3379 			still_degraded = 0;
3380 			/* want to reconstruct this device */
3381 			rb2 = r10_bio;
3382 			sect = raid10_find_virt(conf, sector_nr, i);
3383 			if (sect >= mddev->resync_max_sectors) {
3384 				/* last stripe is not complete - don't
3385 				 * try to recover this sector.
3386 				 */
3387 				rcu_read_unlock();
3388 				continue;
3389 			}
3390 			if (mreplace && test_bit(Faulty, &mreplace->flags))
3391 				mreplace = NULL;
3392 			/* Unless we are doing a full sync, or a replacement
3393 			 * we only need to recover the block if it is set in
3394 			 * the bitmap
3395 			 */
3396 			must_sync = md_bitmap_start_sync(mddev->bitmap, sect,
3397 							 &sync_blocks, 1);
3398 			if (sync_blocks < max_sync)
3399 				max_sync = sync_blocks;
3400 			if (!must_sync &&
3401 			    mreplace == NULL &&
3402 			    !conf->fullsync) {
3403 				/* yep, skip the sync_blocks here, but don't assume
3404 				 * that there will never be anything to do here
3405 				 */
3406 				chunks_skipped = -1;
3407 				rcu_read_unlock();
3408 				continue;
3409 			}
3410 			atomic_inc(&mrdev->nr_pending);
3411 			if (mreplace)
3412 				atomic_inc(&mreplace->nr_pending);
3413 			rcu_read_unlock();
3414 
3415 			r10_bio = raid10_alloc_init_r10buf(conf);
3416 			r10_bio->state = 0;
3417 			raise_barrier(conf, rb2 != NULL);
3418 			atomic_set(&r10_bio->remaining, 0);
3419 
3420 			r10_bio->master_bio = (struct bio*)rb2;
3421 			if (rb2)
3422 				atomic_inc(&rb2->remaining);
3423 			r10_bio->mddev = mddev;
3424 			set_bit(R10BIO_IsRecover, &r10_bio->state);
3425 			r10_bio->sector = sect;
3426 
3427 			raid10_find_phys(conf, r10_bio);
3428 
3429 			/* Need to check if the array will still be
3430 			 * degraded
3431 			 */
3432 			rcu_read_lock();
3433 			for (j = 0; j < conf->geo.raid_disks; j++) {
3434 				struct md_rdev *rdev = rcu_dereference(
3435 					conf->mirrors[j].rdev);
3436 				if (rdev == NULL || test_bit(Faulty, &rdev->flags)) {
3437 					still_degraded = 1;
3438 					break;
3439 				}
3440 			}
3441 
3442 			must_sync = md_bitmap_start_sync(mddev->bitmap, sect,
3443 							 &sync_blocks, still_degraded);
3444 
3445 			any_working = 0;
3446 			for (j=0; j<conf->copies;j++) {
3447 				int k;
3448 				int d = r10_bio->devs[j].devnum;
3449 				sector_t from_addr, to_addr;
3450 				struct md_rdev *rdev =
3451 					rcu_dereference(conf->mirrors[d].rdev);
3452 				sector_t sector, first_bad;
3453 				int bad_sectors;
3454 				if (!rdev ||
3455 				    !test_bit(In_sync, &rdev->flags))
3456 					continue;
3457 				/* This is where we read from */
3458 				any_working = 1;
3459 				sector = r10_bio->devs[j].addr;
3460 
3461 				if (is_badblock(rdev, sector, max_sync,
3462 						&first_bad, &bad_sectors)) {
3463 					if (first_bad > sector)
3464 						max_sync = first_bad - sector;
3465 					else {
3466 						bad_sectors -= (sector
3467 								- first_bad);
3468 						if (max_sync > bad_sectors)
3469 							max_sync = bad_sectors;
3470 						continue;
3471 					}
3472 				}
3473 				bio = r10_bio->devs[0].bio;
3474 				bio->bi_next = biolist;
3475 				biolist = bio;
3476 				bio->bi_end_io = end_sync_read;
3477 				bio_set_op_attrs(bio, REQ_OP_READ, 0);
3478 				if (test_bit(FailFast, &rdev->flags))
3479 					bio->bi_opf |= MD_FAILFAST;
3480 				from_addr = r10_bio->devs[j].addr;
3481 				bio->bi_iter.bi_sector = from_addr +
3482 					rdev->data_offset;
3483 				bio_set_dev(bio, rdev->bdev);
3484 				atomic_inc(&rdev->nr_pending);
3485 				/* and we write to 'i' (if not in_sync) */
3486 
3487 				for (k=0; k<conf->copies; k++)
3488 					if (r10_bio->devs[k].devnum == i)
3489 						break;
3490 				BUG_ON(k == conf->copies);
3491 				to_addr = r10_bio->devs[k].addr;
3492 				r10_bio->devs[0].devnum = d;
3493 				r10_bio->devs[0].addr = from_addr;
3494 				r10_bio->devs[1].devnum = i;
3495 				r10_bio->devs[1].addr = to_addr;
3496 
3497 				if (need_recover) {
3498 					bio = r10_bio->devs[1].bio;
3499 					bio->bi_next = biolist;
3500 					biolist = bio;
3501 					bio->bi_end_io = end_sync_write;
3502 					bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
3503 					bio->bi_iter.bi_sector = to_addr
3504 						+ mrdev->data_offset;
3505 					bio_set_dev(bio, mrdev->bdev);
3506 					atomic_inc(&r10_bio->remaining);
3507 				} else
3508 					r10_bio->devs[1].bio->bi_end_io = NULL;
3509 
3510 				/* and maybe write to replacement */
3511 				bio = r10_bio->devs[1].repl_bio;
3512 				if (bio)
3513 					bio->bi_end_io = NULL;
3514 				/* Note: if need_replace, then bio
3515 				 * cannot be NULL as r10buf_pool_alloc will
3516 				 * have allocated it.
3517 				 */
3518 				if (!need_replace)
3519 					break;
3520 				bio->bi_next = biolist;
3521 				biolist = bio;
3522 				bio->bi_end_io = end_sync_write;
3523 				bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
3524 				bio->bi_iter.bi_sector = to_addr +
3525 					mreplace->data_offset;
3526 				bio_set_dev(bio, mreplace->bdev);
3527 				atomic_inc(&r10_bio->remaining);
3528 				break;
3529 			}
3530 			rcu_read_unlock();
3531 			if (j == conf->copies) {
3532 				/* Cannot recover, so abort the recovery or
3533 				 * record a bad block */
3534 				if (any_working) {
3535 					/* problem is that there are bad blocks
3536 					 * on other device(s)
3537 					 */
3538 					int k;
3539 					for (k = 0; k < conf->copies; k++)
3540 						if (r10_bio->devs[k].devnum == i)
3541 							break;
3542 					if (!test_bit(In_sync,
3543 						      &mrdev->flags)
3544 					    && !rdev_set_badblocks(
3545 						    mrdev,
3546 						    r10_bio->devs[k].addr,
3547 						    max_sync, 0))
3548 						any_working = 0;
3549 					if (mreplace &&
3550 					    !rdev_set_badblocks(
3551 						    mreplace,
3552 						    r10_bio->devs[k].addr,
3553 						    max_sync, 0))
3554 						any_working = 0;
3555 				}
3556 				if (!any_working)  {
3557 					if (!test_and_set_bit(MD_RECOVERY_INTR,
3558 							      &mddev->recovery))
3559 						pr_warn("md/raid10:%s: insufficient working devices for recovery.\n",
3560 						       mdname(mddev));
3561 					mirror->recovery_disabled
3562 						= mddev->recovery_disabled;
3563 				}
3564 				put_buf(r10_bio);
3565 				if (rb2)
3566 					atomic_dec(&rb2->remaining);
3567 				r10_bio = rb2;
3568 				rdev_dec_pending(mrdev, mddev);
3569 				if (mreplace)
3570 					rdev_dec_pending(mreplace, mddev);
3571 				break;
3572 			}
3573 			rdev_dec_pending(mrdev, mddev);
3574 			if (mreplace)
3575 				rdev_dec_pending(mreplace, mddev);
3576 			if (r10_bio->devs[0].bio->bi_opf & MD_FAILFAST) {
3577 				/* Only want this if there is elsewhere to
3578 				 * read from. 'j' is currently the first
3579 				 * readable copy.
3580 				 */
3581 				int targets = 1;
3582 				for (; j < conf->copies; j++) {
3583 					int d = r10_bio->devs[j].devnum;
3584 					if (conf->mirrors[d].rdev &&
3585 					    test_bit(In_sync,
3586 						      &conf->mirrors[d].rdev->flags))
3587 						targets++;
3588 				}
3589 				if (targets == 1)
3590 					r10_bio->devs[0].bio->bi_opf
3591 						&= ~MD_FAILFAST;
3592 			}
3593 		}
3594 		if (biolist == NULL) {
3595 			while (r10_bio) {
3596 				struct r10bio *rb2 = r10_bio;
3597 				r10_bio = (struct r10bio*) rb2->master_bio;
3598 				rb2->master_bio = NULL;
3599 				put_buf(rb2);
3600 			}
3601 			goto giveup;
3602 		}
3603 	} else {
3604 		/* resync. Schedule a read for every block at this virt offset */
3605 		int count = 0;
3606 
3607 		/*
3608 		 * Since curr_resync_completed could probably not update in
3609 		 * time, and we will set cluster_sync_low based on it.
3610 		 * Let's check against "sector_nr + 2 * RESYNC_SECTORS" for
3611 		 * safety reason, which ensures curr_resync_completed is
3612 		 * updated in bitmap_cond_end_sync.
3613 		 */
3614 		md_bitmap_cond_end_sync(mddev->bitmap, sector_nr,
3615 					mddev_is_clustered(mddev) &&
3616 					(sector_nr + 2 * RESYNC_SECTORS > conf->cluster_sync_high));
3617 
3618 		if (!md_bitmap_start_sync(mddev->bitmap, sector_nr,
3619 					  &sync_blocks, mddev->degraded) &&
3620 		    !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED,
3621 						 &mddev->recovery)) {
3622 			/* We can skip this block */
3623 			*skipped = 1;
3624 			return sync_blocks + sectors_skipped;
3625 		}
3626 		if (sync_blocks < max_sync)
3627 			max_sync = sync_blocks;
3628 		r10_bio = raid10_alloc_init_r10buf(conf);
3629 		r10_bio->state = 0;
3630 
3631 		r10_bio->mddev = mddev;
3632 		atomic_set(&r10_bio->remaining, 0);
3633 		raise_barrier(conf, 0);
3634 		conf->next_resync = sector_nr;
3635 
3636 		r10_bio->master_bio = NULL;
3637 		r10_bio->sector = sector_nr;
3638 		set_bit(R10BIO_IsSync, &r10_bio->state);
3639 		raid10_find_phys(conf, r10_bio);
3640 		r10_bio->sectors = (sector_nr | chunk_mask) - sector_nr + 1;
3641 
3642 		for (i = 0; i < conf->copies; i++) {
3643 			int d = r10_bio->devs[i].devnum;
3644 			sector_t first_bad, sector;
3645 			int bad_sectors;
3646 			struct md_rdev *rdev;
3647 
3648 			if (r10_bio->devs[i].repl_bio)
3649 				r10_bio->devs[i].repl_bio->bi_end_io = NULL;
3650 
3651 			bio = r10_bio->devs[i].bio;
3652 			bio->bi_status = BLK_STS_IOERR;
3653 			rcu_read_lock();
3654 			rdev = rcu_dereference(conf->mirrors[d].rdev);
3655 			if (rdev == NULL || test_bit(Faulty, &rdev->flags)) {
3656 				rcu_read_unlock();
3657 				continue;
3658 			}
3659 			sector = r10_bio->devs[i].addr;
3660 			if (is_badblock(rdev, sector, max_sync,
3661 					&first_bad, &bad_sectors)) {
3662 				if (first_bad > sector)
3663 					max_sync = first_bad - sector;
3664 				else {
3665 					bad_sectors -= (sector - first_bad);
3666 					if (max_sync > bad_sectors)
3667 						max_sync = bad_sectors;
3668 					rcu_read_unlock();
3669 					continue;
3670 				}
3671 			}
3672 			atomic_inc(&rdev->nr_pending);
3673 			atomic_inc(&r10_bio->remaining);
3674 			bio->bi_next = biolist;
3675 			biolist = bio;
3676 			bio->bi_end_io = end_sync_read;
3677 			bio_set_op_attrs(bio, REQ_OP_READ, 0);
3678 			if (test_bit(FailFast, &rdev->flags))
3679 				bio->bi_opf |= MD_FAILFAST;
3680 			bio->bi_iter.bi_sector = sector + rdev->data_offset;
3681 			bio_set_dev(bio, rdev->bdev);
3682 			count++;
3683 
3684 			rdev = rcu_dereference(conf->mirrors[d].replacement);
3685 			if (rdev == NULL || test_bit(Faulty, &rdev->flags)) {
3686 				rcu_read_unlock();
3687 				continue;
3688 			}
3689 			atomic_inc(&rdev->nr_pending);
3690 
3691 			/* Need to set up for writing to the replacement */
3692 			bio = r10_bio->devs[i].repl_bio;
3693 			bio->bi_status = BLK_STS_IOERR;
3694 
3695 			sector = r10_bio->devs[i].addr;
3696 			bio->bi_next = biolist;
3697 			biolist = bio;
3698 			bio->bi_end_io = end_sync_write;
3699 			bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
3700 			if (test_bit(FailFast, &rdev->flags))
3701 				bio->bi_opf |= MD_FAILFAST;
3702 			bio->bi_iter.bi_sector = sector + rdev->data_offset;
3703 			bio_set_dev(bio, rdev->bdev);
3704 			count++;
3705 			rcu_read_unlock();
3706 		}
3707 
3708 		if (count < 2) {
3709 			for (i=0; i<conf->copies; i++) {
3710 				int d = r10_bio->devs[i].devnum;
3711 				if (r10_bio->devs[i].bio->bi_end_io)
3712 					rdev_dec_pending(conf->mirrors[d].rdev,
3713 							 mddev);
3714 				if (r10_bio->devs[i].repl_bio &&
3715 				    r10_bio->devs[i].repl_bio->bi_end_io)
3716 					rdev_dec_pending(
3717 						conf->mirrors[d].replacement,
3718 						mddev);
3719 			}
3720 			put_buf(r10_bio);
3721 			biolist = NULL;
3722 			goto giveup;
3723 		}
3724 	}
3725 
3726 	nr_sectors = 0;
3727 	if (sector_nr + max_sync < max_sector)
3728 		max_sector = sector_nr + max_sync;
3729 	do {
3730 		struct page *page;
3731 		int len = PAGE_SIZE;
3732 		if (sector_nr + (len>>9) > max_sector)
3733 			len = (max_sector - sector_nr) << 9;
3734 		if (len == 0)
3735 			break;
3736 		for (bio= biolist ; bio ; bio=bio->bi_next) {
3737 			struct resync_pages *rp = get_resync_pages(bio);
3738 			page = resync_fetch_page(rp, page_idx);
3739 			/*
3740 			 * won't fail because the vec table is big enough
3741 			 * to hold all these pages
3742 			 */
3743 			bio_add_page(bio, page, len, 0);
3744 		}
3745 		nr_sectors += len>>9;
3746 		sector_nr += len>>9;
3747 	} while (++page_idx < RESYNC_PAGES);
3748 	r10_bio->sectors = nr_sectors;
3749 
3750 	if (mddev_is_clustered(mddev) &&
3751 	    test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
3752 		/* It is resync not recovery */
3753 		if (conf->cluster_sync_high < sector_nr + nr_sectors) {
3754 			conf->cluster_sync_low = mddev->curr_resync_completed;
3755 			raid10_set_cluster_sync_high(conf);
3756 			/* Send resync message */
3757 			md_cluster_ops->resync_info_update(mddev,
3758 						conf->cluster_sync_low,
3759 						conf->cluster_sync_high);
3760 		}
3761 	} else if (mddev_is_clustered(mddev)) {
3762 		/* This is recovery not resync */
3763 		sector_t sect_va1, sect_va2;
3764 		bool broadcast_msg = false;
3765 
3766 		for (i = 0; i < conf->geo.raid_disks; i++) {
3767 			/*
3768 			 * sector_nr is a device address for recovery, so we
3769 			 * need translate it to array address before compare
3770 			 * with cluster_sync_high.
3771 			 */
3772 			sect_va1 = raid10_find_virt(conf, sector_nr, i);
3773 
3774 			if (conf->cluster_sync_high < sect_va1 + nr_sectors) {
3775 				broadcast_msg = true;
3776 				/*
3777 				 * curr_resync_completed is similar as
3778 				 * sector_nr, so make the translation too.
3779 				 */
3780 				sect_va2 = raid10_find_virt(conf,
3781 					mddev->curr_resync_completed, i);
3782 
3783 				if (conf->cluster_sync_low == 0 ||
3784 				    conf->cluster_sync_low > sect_va2)
3785 					conf->cluster_sync_low = sect_va2;
3786 			}
3787 		}
3788 		if (broadcast_msg) {
3789 			raid10_set_cluster_sync_high(conf);
3790 			md_cluster_ops->resync_info_update(mddev,
3791 						conf->cluster_sync_low,
3792 						conf->cluster_sync_high);
3793 		}
3794 	}
3795 
3796 	while (biolist) {
3797 		bio = biolist;
3798 		biolist = biolist->bi_next;
3799 
3800 		bio->bi_next = NULL;
3801 		r10_bio = get_resync_r10bio(bio);
3802 		r10_bio->sectors = nr_sectors;
3803 
3804 		if (bio->bi_end_io == end_sync_read) {
3805 			md_sync_acct_bio(bio, nr_sectors);
3806 			bio->bi_status = 0;
3807 			submit_bio_noacct(bio);
3808 		}
3809 	}
3810 
3811 	if (sectors_skipped)
3812 		/* pretend they weren't skipped, it makes
3813 		 * no important difference in this case
3814 		 */
3815 		md_done_sync(mddev, sectors_skipped, 1);
3816 
3817 	return sectors_skipped + nr_sectors;
3818  giveup:
3819 	/* There is nowhere to write, so all non-sync
3820 	 * drives must be failed or in resync, all drives
3821 	 * have a bad block, so try the next chunk...
3822 	 */
3823 	if (sector_nr + max_sync < max_sector)
3824 		max_sector = sector_nr + max_sync;
3825 
3826 	sectors_skipped += (max_sector - sector_nr);
3827 	chunks_skipped ++;
3828 	sector_nr = max_sector;
3829 	goto skipped;
3830 }
3831 
3832 static sector_t
3833 raid10_size(struct mddev *mddev, sector_t sectors, int raid_disks)
3834 {
3835 	sector_t size;
3836 	struct r10conf *conf = mddev->private;
3837 
3838 	if (!raid_disks)
3839 		raid_disks = min(conf->geo.raid_disks,
3840 				 conf->prev.raid_disks);
3841 	if (!sectors)
3842 		sectors = conf->dev_sectors;
3843 
3844 	size = sectors >> conf->geo.chunk_shift;
3845 	sector_div(size, conf->geo.far_copies);
3846 	size = size * raid_disks;
3847 	sector_div(size, conf->geo.near_copies);
3848 
3849 	return size << conf->geo.chunk_shift;
3850 }
3851 
3852 static void calc_sectors(struct r10conf *conf, sector_t size)
3853 {
3854 	/* Calculate the number of sectors-per-device that will
3855 	 * actually be used, and set conf->dev_sectors and
3856 	 * conf->stride
3857 	 */
3858 
3859 	size = size >> conf->geo.chunk_shift;
3860 	sector_div(size, conf->geo.far_copies);
3861 	size = size * conf->geo.raid_disks;
3862 	sector_div(size, conf->geo.near_copies);
3863 	/* 'size' is now the number of chunks in the array */
3864 	/* calculate "used chunks per device" */
3865 	size = size * conf->copies;
3866 
3867 	/* We need to round up when dividing by raid_disks to
3868 	 * get the stride size.
3869 	 */
3870 	size = DIV_ROUND_UP_SECTOR_T(size, conf->geo.raid_disks);
3871 
3872 	conf->dev_sectors = size << conf->geo.chunk_shift;
3873 
3874 	if (conf->geo.far_offset)
3875 		conf->geo.stride = 1 << conf->geo.chunk_shift;
3876 	else {
3877 		sector_div(size, conf->geo.far_copies);
3878 		conf->geo.stride = size << conf->geo.chunk_shift;
3879 	}
3880 }
3881 
3882 enum geo_type {geo_new, geo_old, geo_start};
3883 static int setup_geo(struct geom *geo, struct mddev *mddev, enum geo_type new)
3884 {
3885 	int nc, fc, fo;
3886 	int layout, chunk, disks;
3887 	switch (new) {
3888 	case geo_old:
3889 		layout = mddev->layout;
3890 		chunk = mddev->chunk_sectors;
3891 		disks = mddev->raid_disks - mddev->delta_disks;
3892 		break;
3893 	case geo_new:
3894 		layout = mddev->new_layout;
3895 		chunk = mddev->new_chunk_sectors;
3896 		disks = mddev->raid_disks;
3897 		break;
3898 	default: /* avoid 'may be unused' warnings */
3899 	case geo_start: /* new when starting reshape - raid_disks not
3900 			 * updated yet. */
3901 		layout = mddev->new_layout;
3902 		chunk = mddev->new_chunk_sectors;
3903 		disks = mddev->raid_disks + mddev->delta_disks;
3904 		break;
3905 	}
3906 	if (layout >> 19)
3907 		return -1;
3908 	if (chunk < (PAGE_SIZE >> 9) ||
3909 	    !is_power_of_2(chunk))
3910 		return -2;
3911 	nc = layout & 255;
3912 	fc = (layout >> 8) & 255;
3913 	fo = layout & (1<<16);
3914 	geo->raid_disks = disks;
3915 	geo->near_copies = nc;
3916 	geo->far_copies = fc;
3917 	geo->far_offset = fo;
3918 	switch (layout >> 17) {
3919 	case 0:	/* original layout.  simple but not always optimal */
3920 		geo->far_set_size = disks;
3921 		break;
3922 	case 1: /* "improved" layout which was buggy.  Hopefully no-one is
3923 		 * actually using this, but leave code here just in case.*/
3924 		geo->far_set_size = disks/fc;
3925 		WARN(geo->far_set_size < fc,
3926 		     "This RAID10 layout does not provide data safety - please backup and create new array\n");
3927 		break;
3928 	case 2: /* "improved" layout fixed to match documentation */
3929 		geo->far_set_size = fc * nc;
3930 		break;
3931 	default: /* Not a valid layout */
3932 		return -1;
3933 	}
3934 	geo->chunk_mask = chunk - 1;
3935 	geo->chunk_shift = ffz(~chunk);
3936 	return nc*fc;
3937 }
3938 
3939 static struct r10conf *setup_conf(struct mddev *mddev)
3940 {
3941 	struct r10conf *conf = NULL;
3942 	int err = -EINVAL;
3943 	struct geom geo;
3944 	int copies;
3945 
3946 	copies = setup_geo(&geo, mddev, geo_new);
3947 
3948 	if (copies == -2) {
3949 		pr_warn("md/raid10:%s: chunk size must be at least PAGE_SIZE(%ld) and be a power of 2.\n",
3950 			mdname(mddev), PAGE_SIZE);
3951 		goto out;
3952 	}
3953 
3954 	if (copies < 2 || copies > mddev->raid_disks) {
3955 		pr_warn("md/raid10:%s: unsupported raid10 layout: 0x%8x\n",
3956 			mdname(mddev), mddev->new_layout);
3957 		goto out;
3958 	}
3959 
3960 	err = -ENOMEM;
3961 	conf = kzalloc(sizeof(struct r10conf), GFP_KERNEL);
3962 	if (!conf)
3963 		goto out;
3964 
3965 	/* FIXME calc properly */
3966 	conf->mirrors = kcalloc(mddev->raid_disks + max(0, -mddev->delta_disks),
3967 				sizeof(struct raid10_info),
3968 				GFP_KERNEL);
3969 	if (!conf->mirrors)
3970 		goto out;
3971 
3972 	conf->tmppage = alloc_page(GFP_KERNEL);
3973 	if (!conf->tmppage)
3974 		goto out;
3975 
3976 	conf->geo = geo;
3977 	conf->copies = copies;
3978 	err = mempool_init(&conf->r10bio_pool, NR_RAID_BIOS, r10bio_pool_alloc,
3979 			   rbio_pool_free, conf);
3980 	if (err)
3981 		goto out;
3982 
3983 	err = bioset_init(&conf->bio_split, BIO_POOL_SIZE, 0, 0);
3984 	if (err)
3985 		goto out;
3986 
3987 	calc_sectors(conf, mddev->dev_sectors);
3988 	if (mddev->reshape_position == MaxSector) {
3989 		conf->prev = conf->geo;
3990 		conf->reshape_progress = MaxSector;
3991 	} else {
3992 		if (setup_geo(&conf->prev, mddev, geo_old) != conf->copies) {
3993 			err = -EINVAL;
3994 			goto out;
3995 		}
3996 		conf->reshape_progress = mddev->reshape_position;
3997 		if (conf->prev.far_offset)
3998 			conf->prev.stride = 1 << conf->prev.chunk_shift;
3999 		else
4000 			/* far_copies must be 1 */
4001 			conf->prev.stride = conf->dev_sectors;
4002 	}
4003 	conf->reshape_safe = conf->reshape_progress;
4004 	spin_lock_init(&conf->device_lock);
4005 	INIT_LIST_HEAD(&conf->retry_list);
4006 	INIT_LIST_HEAD(&conf->bio_end_io_list);
4007 
4008 	spin_lock_init(&conf->resync_lock);
4009 	init_waitqueue_head(&conf->wait_barrier);
4010 	atomic_set(&conf->nr_pending, 0);
4011 
4012 	err = -ENOMEM;
4013 	conf->thread = md_register_thread(raid10d, mddev, "raid10");
4014 	if (!conf->thread)
4015 		goto out;
4016 
4017 	conf->mddev = mddev;
4018 	return conf;
4019 
4020  out:
4021 	if (conf) {
4022 		mempool_exit(&conf->r10bio_pool);
4023 		kfree(conf->mirrors);
4024 		safe_put_page(conf->tmppage);
4025 		bioset_exit(&conf->bio_split);
4026 		kfree(conf);
4027 	}
4028 	return ERR_PTR(err);
4029 }
4030 
4031 static void raid10_set_io_opt(struct r10conf *conf)
4032 {
4033 	int raid_disks = conf->geo.raid_disks;
4034 
4035 	if (!(conf->geo.raid_disks % conf->geo.near_copies))
4036 		raid_disks /= conf->geo.near_copies;
4037 	blk_queue_io_opt(conf->mddev->queue, (conf->mddev->chunk_sectors << 9) *
4038 			 raid_disks);
4039 }
4040 
4041 static int raid10_run(struct mddev *mddev)
4042 {
4043 	struct r10conf *conf;
4044 	int i, disk_idx;
4045 	struct raid10_info *disk;
4046 	struct md_rdev *rdev;
4047 	sector_t size;
4048 	sector_t min_offset_diff = 0;
4049 	int first = 1;
4050 	bool discard_supported = false;
4051 
4052 	if (mddev_init_writes_pending(mddev) < 0)
4053 		return -ENOMEM;
4054 
4055 	if (mddev->private == NULL) {
4056 		conf = setup_conf(mddev);
4057 		if (IS_ERR(conf))
4058 			return PTR_ERR(conf);
4059 		mddev->private = conf;
4060 	}
4061 	conf = mddev->private;
4062 	if (!conf)
4063 		goto out;
4064 
4065 	if (mddev_is_clustered(conf->mddev)) {
4066 		int fc, fo;
4067 
4068 		fc = (mddev->layout >> 8) & 255;
4069 		fo = mddev->layout & (1<<16);
4070 		if (fc > 1 || fo > 0) {
4071 			pr_err("only near layout is supported by clustered"
4072 				" raid10\n");
4073 			goto out_free_conf;
4074 		}
4075 	}
4076 
4077 	mddev->thread = conf->thread;
4078 	conf->thread = NULL;
4079 
4080 	if (mddev->queue) {
4081 		blk_queue_max_discard_sectors(mddev->queue,
4082 					      UINT_MAX);
4083 		blk_queue_max_write_same_sectors(mddev->queue, 0);
4084 		blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
4085 		blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
4086 		raid10_set_io_opt(conf);
4087 	}
4088 
4089 	rdev_for_each(rdev, mddev) {
4090 		long long diff;
4091 
4092 		disk_idx = rdev->raid_disk;
4093 		if (disk_idx < 0)
4094 			continue;
4095 		if (disk_idx >= conf->geo.raid_disks &&
4096 		    disk_idx >= conf->prev.raid_disks)
4097 			continue;
4098 		disk = conf->mirrors + disk_idx;
4099 
4100 		if (test_bit(Replacement, &rdev->flags)) {
4101 			if (disk->replacement)
4102 				goto out_free_conf;
4103 			disk->replacement = rdev;
4104 		} else {
4105 			if (disk->rdev)
4106 				goto out_free_conf;
4107 			disk->rdev = rdev;
4108 		}
4109 		diff = (rdev->new_data_offset - rdev->data_offset);
4110 		if (!mddev->reshape_backwards)
4111 			diff = -diff;
4112 		if (diff < 0)
4113 			diff = 0;
4114 		if (first || diff < min_offset_diff)
4115 			min_offset_diff = diff;
4116 
4117 		if (mddev->gendisk)
4118 			disk_stack_limits(mddev->gendisk, rdev->bdev,
4119 					  rdev->data_offset << 9);
4120 
4121 		disk->head_position = 0;
4122 
4123 		if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
4124 			discard_supported = true;
4125 		first = 0;
4126 	}
4127 
4128 	if (mddev->queue) {
4129 		if (discard_supported)
4130 			blk_queue_flag_set(QUEUE_FLAG_DISCARD,
4131 						mddev->queue);
4132 		else
4133 			blk_queue_flag_clear(QUEUE_FLAG_DISCARD,
4134 						  mddev->queue);
4135 	}
4136 	/* need to check that every block has at least one working mirror */
4137 	if (!enough(conf, -1)) {
4138 		pr_err("md/raid10:%s: not enough operational mirrors.\n",
4139 		       mdname(mddev));
4140 		goto out_free_conf;
4141 	}
4142 
4143 	if (conf->reshape_progress != MaxSector) {
4144 		/* must ensure that shape change is supported */
4145 		if (conf->geo.far_copies != 1 &&
4146 		    conf->geo.far_offset == 0)
4147 			goto out_free_conf;
4148 		if (conf->prev.far_copies != 1 &&
4149 		    conf->prev.far_offset == 0)
4150 			goto out_free_conf;
4151 	}
4152 
4153 	mddev->degraded = 0;
4154 	for (i = 0;
4155 	     i < conf->geo.raid_disks
4156 		     || i < conf->prev.raid_disks;
4157 	     i++) {
4158 
4159 		disk = conf->mirrors + i;
4160 
4161 		if (!disk->rdev && disk->replacement) {
4162 			/* The replacement is all we have - use it */
4163 			disk->rdev = disk->replacement;
4164 			disk->replacement = NULL;
4165 			clear_bit(Replacement, &disk->rdev->flags);
4166 		}
4167 
4168 		if (!disk->rdev ||
4169 		    !test_bit(In_sync, &disk->rdev->flags)) {
4170 			disk->head_position = 0;
4171 			mddev->degraded++;
4172 			if (disk->rdev &&
4173 			    disk->rdev->saved_raid_disk < 0)
4174 				conf->fullsync = 1;
4175 		}
4176 
4177 		if (disk->replacement &&
4178 		    !test_bit(In_sync, &disk->replacement->flags) &&
4179 		    disk->replacement->saved_raid_disk < 0) {
4180 			conf->fullsync = 1;
4181 		}
4182 
4183 		disk->recovery_disabled = mddev->recovery_disabled - 1;
4184 	}
4185 
4186 	if (mddev->recovery_cp != MaxSector)
4187 		pr_notice("md/raid10:%s: not clean -- starting background reconstruction\n",
4188 			  mdname(mddev));
4189 	pr_info("md/raid10:%s: active with %d out of %d devices\n",
4190 		mdname(mddev), conf->geo.raid_disks - mddev->degraded,
4191 		conf->geo.raid_disks);
4192 	/*
4193 	 * Ok, everything is just fine now
4194 	 */
4195 	mddev->dev_sectors = conf->dev_sectors;
4196 	size = raid10_size(mddev, 0, 0);
4197 	md_set_array_sectors(mddev, size);
4198 	mddev->resync_max_sectors = size;
4199 	set_bit(MD_FAILFAST_SUPPORTED, &mddev->flags);
4200 
4201 	if (md_integrity_register(mddev))
4202 		goto out_free_conf;
4203 
4204 	if (conf->reshape_progress != MaxSector) {
4205 		unsigned long before_length, after_length;
4206 
4207 		before_length = ((1 << conf->prev.chunk_shift) *
4208 				 conf->prev.far_copies);
4209 		after_length = ((1 << conf->geo.chunk_shift) *
4210 				conf->geo.far_copies);
4211 
4212 		if (max(before_length, after_length) > min_offset_diff) {
4213 			/* This cannot work */
4214 			pr_warn("md/raid10: offset difference not enough to continue reshape\n");
4215 			goto out_free_conf;
4216 		}
4217 		conf->offset_diff = min_offset_diff;
4218 
4219 		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
4220 		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
4221 		set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
4222 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
4223 		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
4224 							"reshape");
4225 		if (!mddev->sync_thread)
4226 			goto out_free_conf;
4227 	}
4228 
4229 	return 0;
4230 
4231 out_free_conf:
4232 	md_unregister_thread(&mddev->thread);
4233 	mempool_exit(&conf->r10bio_pool);
4234 	safe_put_page(conf->tmppage);
4235 	kfree(conf->mirrors);
4236 	kfree(conf);
4237 	mddev->private = NULL;
4238 out:
4239 	return -EIO;
4240 }
4241 
4242 static void raid10_free(struct mddev *mddev, void *priv)
4243 {
4244 	struct r10conf *conf = priv;
4245 
4246 	mempool_exit(&conf->r10bio_pool);
4247 	safe_put_page(conf->tmppage);
4248 	kfree(conf->mirrors);
4249 	kfree(conf->mirrors_old);
4250 	kfree(conf->mirrors_new);
4251 	bioset_exit(&conf->bio_split);
4252 	kfree(conf);
4253 }
4254 
4255 static void raid10_quiesce(struct mddev *mddev, int quiesce)
4256 {
4257 	struct r10conf *conf = mddev->private;
4258 
4259 	if (quiesce)
4260 		raise_barrier(conf, 0);
4261 	else
4262 		lower_barrier(conf);
4263 }
4264 
4265 static int raid10_resize(struct mddev *mddev, sector_t sectors)
4266 {
4267 	/* Resize of 'far' arrays is not supported.
4268 	 * For 'near' and 'offset' arrays we can set the
4269 	 * number of sectors used to be an appropriate multiple
4270 	 * of the chunk size.
4271 	 * For 'offset', this is far_copies*chunksize.
4272 	 * For 'near' the multiplier is the LCM of
4273 	 * near_copies and raid_disks.
4274 	 * So if far_copies > 1 && !far_offset, fail.
4275 	 * Else find LCM(raid_disks, near_copy)*far_copies and
4276 	 * multiply by chunk_size.  Then round to this number.
4277 	 * This is mostly done by raid10_size()
4278 	 */
4279 	struct r10conf *conf = mddev->private;
4280 	sector_t oldsize, size;
4281 
4282 	if (mddev->reshape_position != MaxSector)
4283 		return -EBUSY;
4284 
4285 	if (conf->geo.far_copies > 1 && !conf->geo.far_offset)
4286 		return -EINVAL;
4287 
4288 	oldsize = raid10_size(mddev, 0, 0);
4289 	size = raid10_size(mddev, sectors, 0);
4290 	if (mddev->external_size &&
4291 	    mddev->array_sectors > size)
4292 		return -EINVAL;
4293 	if (mddev->bitmap) {
4294 		int ret = md_bitmap_resize(mddev->bitmap, size, 0, 0);
4295 		if (ret)
4296 			return ret;
4297 	}
4298 	md_set_array_sectors(mddev, size);
4299 	if (sectors > mddev->dev_sectors &&
4300 	    mddev->recovery_cp > oldsize) {
4301 		mddev->recovery_cp = oldsize;
4302 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
4303 	}
4304 	calc_sectors(conf, sectors);
4305 	mddev->dev_sectors = conf->dev_sectors;
4306 	mddev->resync_max_sectors = size;
4307 	return 0;
4308 }
4309 
4310 static void *raid10_takeover_raid0(struct mddev *mddev, sector_t size, int devs)
4311 {
4312 	struct md_rdev *rdev;
4313 	struct r10conf *conf;
4314 
4315 	if (mddev->degraded > 0) {
4316 		pr_warn("md/raid10:%s: Error: degraded raid0!\n",
4317 			mdname(mddev));
4318 		return ERR_PTR(-EINVAL);
4319 	}
4320 	sector_div(size, devs);
4321 
4322 	/* Set new parameters */
4323 	mddev->new_level = 10;
4324 	/* new layout: far_copies = 1, near_copies = 2 */
4325 	mddev->new_layout = (1<<8) + 2;
4326 	mddev->new_chunk_sectors = mddev->chunk_sectors;
4327 	mddev->delta_disks = mddev->raid_disks;
4328 	mddev->raid_disks *= 2;
4329 	/* make sure it will be not marked as dirty */
4330 	mddev->recovery_cp = MaxSector;
4331 	mddev->dev_sectors = size;
4332 
4333 	conf = setup_conf(mddev);
4334 	if (!IS_ERR(conf)) {
4335 		rdev_for_each(rdev, mddev)
4336 			if (rdev->raid_disk >= 0) {
4337 				rdev->new_raid_disk = rdev->raid_disk * 2;
4338 				rdev->sectors = size;
4339 			}
4340 		conf->barrier = 1;
4341 	}
4342 
4343 	return conf;
4344 }
4345 
4346 static void *raid10_takeover(struct mddev *mddev)
4347 {
4348 	struct r0conf *raid0_conf;
4349 
4350 	/* raid10 can take over:
4351 	 *  raid0 - providing it has only two drives
4352 	 */
4353 	if (mddev->level == 0) {
4354 		/* for raid0 takeover only one zone is supported */
4355 		raid0_conf = mddev->private;
4356 		if (raid0_conf->nr_strip_zones > 1) {
4357 			pr_warn("md/raid10:%s: cannot takeover raid 0 with more than one zone.\n",
4358 				mdname(mddev));
4359 			return ERR_PTR(-EINVAL);
4360 		}
4361 		return raid10_takeover_raid0(mddev,
4362 			raid0_conf->strip_zone->zone_end,
4363 			raid0_conf->strip_zone->nb_dev);
4364 	}
4365 	return ERR_PTR(-EINVAL);
4366 }
4367 
4368 static int raid10_check_reshape(struct mddev *mddev)
4369 {
4370 	/* Called when there is a request to change
4371 	 * - layout (to ->new_layout)
4372 	 * - chunk size (to ->new_chunk_sectors)
4373 	 * - raid_disks (by delta_disks)
4374 	 * or when trying to restart a reshape that was ongoing.
4375 	 *
4376 	 * We need to validate the request and possibly allocate
4377 	 * space if that might be an issue later.
4378 	 *
4379 	 * Currently we reject any reshape of a 'far' mode array,
4380 	 * allow chunk size to change if new is generally acceptable,
4381 	 * allow raid_disks to increase, and allow
4382 	 * a switch between 'near' mode and 'offset' mode.
4383 	 */
4384 	struct r10conf *conf = mddev->private;
4385 	struct geom geo;
4386 
4387 	if (conf->geo.far_copies != 1 && !conf->geo.far_offset)
4388 		return -EINVAL;
4389 
4390 	if (setup_geo(&geo, mddev, geo_start) != conf->copies)
4391 		/* mustn't change number of copies */
4392 		return -EINVAL;
4393 	if (geo.far_copies > 1 && !geo.far_offset)
4394 		/* Cannot switch to 'far' mode */
4395 		return -EINVAL;
4396 
4397 	if (mddev->array_sectors & geo.chunk_mask)
4398 			/* not factor of array size */
4399 			return -EINVAL;
4400 
4401 	if (!enough(conf, -1))
4402 		return -EINVAL;
4403 
4404 	kfree(conf->mirrors_new);
4405 	conf->mirrors_new = NULL;
4406 	if (mddev->delta_disks > 0) {
4407 		/* allocate new 'mirrors' list */
4408 		conf->mirrors_new =
4409 			kcalloc(mddev->raid_disks + mddev->delta_disks,
4410 				sizeof(struct raid10_info),
4411 				GFP_KERNEL);
4412 		if (!conf->mirrors_new)
4413 			return -ENOMEM;
4414 	}
4415 	return 0;
4416 }
4417 
4418 /*
4419  * Need to check if array has failed when deciding whether to:
4420  *  - start an array
4421  *  - remove non-faulty devices
4422  *  - add a spare
4423  *  - allow a reshape
4424  * This determination is simple when no reshape is happening.
4425  * However if there is a reshape, we need to carefully check
4426  * both the before and after sections.
4427  * This is because some failed devices may only affect one
4428  * of the two sections, and some non-in_sync devices may
4429  * be insync in the section most affected by failed devices.
4430  */
4431 static int calc_degraded(struct r10conf *conf)
4432 {
4433 	int degraded, degraded2;
4434 	int i;
4435 
4436 	rcu_read_lock();
4437 	degraded = 0;
4438 	/* 'prev' section first */
4439 	for (i = 0; i < conf->prev.raid_disks; i++) {
4440 		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
4441 		if (!rdev || test_bit(Faulty, &rdev->flags))
4442 			degraded++;
4443 		else if (!test_bit(In_sync, &rdev->flags))
4444 			/* When we can reduce the number of devices in
4445 			 * an array, this might not contribute to
4446 			 * 'degraded'.  It does now.
4447 			 */
4448 			degraded++;
4449 	}
4450 	rcu_read_unlock();
4451 	if (conf->geo.raid_disks == conf->prev.raid_disks)
4452 		return degraded;
4453 	rcu_read_lock();
4454 	degraded2 = 0;
4455 	for (i = 0; i < conf->geo.raid_disks; i++) {
4456 		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
4457 		if (!rdev || test_bit(Faulty, &rdev->flags))
4458 			degraded2++;
4459 		else if (!test_bit(In_sync, &rdev->flags)) {
4460 			/* If reshape is increasing the number of devices,
4461 			 * this section has already been recovered, so
4462 			 * it doesn't contribute to degraded.
4463 			 * else it does.
4464 			 */
4465 			if (conf->geo.raid_disks <= conf->prev.raid_disks)
4466 				degraded2++;
4467 		}
4468 	}
4469 	rcu_read_unlock();
4470 	if (degraded2 > degraded)
4471 		return degraded2;
4472 	return degraded;
4473 }
4474 
4475 static int raid10_start_reshape(struct mddev *mddev)
4476 {
4477 	/* A 'reshape' has been requested. This commits
4478 	 * the various 'new' fields and sets MD_RECOVER_RESHAPE
4479 	 * This also checks if there are enough spares and adds them
4480 	 * to the array.
4481 	 * We currently require enough spares to make the final
4482 	 * array non-degraded.  We also require that the difference
4483 	 * between old and new data_offset - on each device - is
4484 	 * enough that we never risk over-writing.
4485 	 */
4486 
4487 	unsigned long before_length, after_length;
4488 	sector_t min_offset_diff = 0;
4489 	int first = 1;
4490 	struct geom new;
4491 	struct r10conf *conf = mddev->private;
4492 	struct md_rdev *rdev;
4493 	int spares = 0;
4494 	int ret;
4495 
4496 	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
4497 		return -EBUSY;
4498 
4499 	if (setup_geo(&new, mddev, geo_start) != conf->copies)
4500 		return -EINVAL;
4501 
4502 	before_length = ((1 << conf->prev.chunk_shift) *
4503 			 conf->prev.far_copies);
4504 	after_length = ((1 << conf->geo.chunk_shift) *
4505 			conf->geo.far_copies);
4506 
4507 	rdev_for_each(rdev, mddev) {
4508 		if (!test_bit(In_sync, &rdev->flags)
4509 		    && !test_bit(Faulty, &rdev->flags))
4510 			spares++;
4511 		if (rdev->raid_disk >= 0) {
4512 			long long diff = (rdev->new_data_offset
4513 					  - rdev->data_offset);
4514 			if (!mddev->reshape_backwards)
4515 				diff = -diff;
4516 			if (diff < 0)
4517 				diff = 0;
4518 			if (first || diff < min_offset_diff)
4519 				min_offset_diff = diff;
4520 			first = 0;
4521 		}
4522 	}
4523 
4524 	if (max(before_length, after_length) > min_offset_diff)
4525 		return -EINVAL;
4526 
4527 	if (spares < mddev->delta_disks)
4528 		return -EINVAL;
4529 
4530 	conf->offset_diff = min_offset_diff;
4531 	spin_lock_irq(&conf->device_lock);
4532 	if (conf->mirrors_new) {
4533 		memcpy(conf->mirrors_new, conf->mirrors,
4534 		       sizeof(struct raid10_info)*conf->prev.raid_disks);
4535 		smp_mb();
4536 		kfree(conf->mirrors_old);
4537 		conf->mirrors_old = conf->mirrors;
4538 		conf->mirrors = conf->mirrors_new;
4539 		conf->mirrors_new = NULL;
4540 	}
4541 	setup_geo(&conf->geo, mddev, geo_start);
4542 	smp_mb();
4543 	if (mddev->reshape_backwards) {
4544 		sector_t size = raid10_size(mddev, 0, 0);
4545 		if (size < mddev->array_sectors) {
4546 			spin_unlock_irq(&conf->device_lock);
4547 			pr_warn("md/raid10:%s: array size must be reduce before number of disks\n",
4548 				mdname(mddev));
4549 			return -EINVAL;
4550 		}
4551 		mddev->resync_max_sectors = size;
4552 		conf->reshape_progress = size;
4553 	} else
4554 		conf->reshape_progress = 0;
4555 	conf->reshape_safe = conf->reshape_progress;
4556 	spin_unlock_irq(&conf->device_lock);
4557 
4558 	if (mddev->delta_disks && mddev->bitmap) {
4559 		struct mdp_superblock_1 *sb = NULL;
4560 		sector_t oldsize, newsize;
4561 
4562 		oldsize = raid10_size(mddev, 0, 0);
4563 		newsize = raid10_size(mddev, 0, conf->geo.raid_disks);
4564 
4565 		if (!mddev_is_clustered(mddev)) {
4566 			ret = md_bitmap_resize(mddev->bitmap, newsize, 0, 0);
4567 			if (ret)
4568 				goto abort;
4569 			else
4570 				goto out;
4571 		}
4572 
4573 		rdev_for_each(rdev, mddev) {
4574 			if (rdev->raid_disk > -1 &&
4575 			    !test_bit(Faulty, &rdev->flags))
4576 				sb = page_address(rdev->sb_page);
4577 		}
4578 
4579 		/*
4580 		 * some node is already performing reshape, and no need to
4581 		 * call md_bitmap_resize again since it should be called when
4582 		 * receiving BITMAP_RESIZE msg
4583 		 */
4584 		if ((sb && (le32_to_cpu(sb->feature_map) &
4585 			    MD_FEATURE_RESHAPE_ACTIVE)) || (oldsize == newsize))
4586 			goto out;
4587 
4588 		ret = md_bitmap_resize(mddev->bitmap, newsize, 0, 0);
4589 		if (ret)
4590 			goto abort;
4591 
4592 		ret = md_cluster_ops->resize_bitmaps(mddev, newsize, oldsize);
4593 		if (ret) {
4594 			md_bitmap_resize(mddev->bitmap, oldsize, 0, 0);
4595 			goto abort;
4596 		}
4597 	}
4598 out:
4599 	if (mddev->delta_disks > 0) {
4600 		rdev_for_each(rdev, mddev)
4601 			if (rdev->raid_disk < 0 &&
4602 			    !test_bit(Faulty, &rdev->flags)) {
4603 				if (raid10_add_disk(mddev, rdev) == 0) {
4604 					if (rdev->raid_disk >=
4605 					    conf->prev.raid_disks)
4606 						set_bit(In_sync, &rdev->flags);
4607 					else
4608 						rdev->recovery_offset = 0;
4609 
4610 					/* Failure here is OK */
4611 					sysfs_link_rdev(mddev, rdev);
4612 				}
4613 			} else if (rdev->raid_disk >= conf->prev.raid_disks
4614 				   && !test_bit(Faulty, &rdev->flags)) {
4615 				/* This is a spare that was manually added */
4616 				set_bit(In_sync, &rdev->flags);
4617 			}
4618 	}
4619 	/* When a reshape changes the number of devices,
4620 	 * ->degraded is measured against the larger of the
4621 	 * pre and  post numbers.
4622 	 */
4623 	spin_lock_irq(&conf->device_lock);
4624 	mddev->degraded = calc_degraded(conf);
4625 	spin_unlock_irq(&conf->device_lock);
4626 	mddev->raid_disks = conf->geo.raid_disks;
4627 	mddev->reshape_position = conf->reshape_progress;
4628 	set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
4629 
4630 	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
4631 	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
4632 	clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
4633 	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
4634 	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
4635 
4636 	mddev->sync_thread = md_register_thread(md_do_sync, mddev,
4637 						"reshape");
4638 	if (!mddev->sync_thread) {
4639 		ret = -EAGAIN;
4640 		goto abort;
4641 	}
4642 	conf->reshape_checkpoint = jiffies;
4643 	md_wakeup_thread(mddev->sync_thread);
4644 	md_new_event(mddev);
4645 	return 0;
4646 
4647 abort:
4648 	mddev->recovery = 0;
4649 	spin_lock_irq(&conf->device_lock);
4650 	conf->geo = conf->prev;
4651 	mddev->raid_disks = conf->geo.raid_disks;
4652 	rdev_for_each(rdev, mddev)
4653 		rdev->new_data_offset = rdev->data_offset;
4654 	smp_wmb();
4655 	conf->reshape_progress = MaxSector;
4656 	conf->reshape_safe = MaxSector;
4657 	mddev->reshape_position = MaxSector;
4658 	spin_unlock_irq(&conf->device_lock);
4659 	return ret;
4660 }
4661 
4662 /* Calculate the last device-address that could contain
4663  * any block from the chunk that includes the array-address 's'
4664  * and report the next address.
4665  * i.e. the address returned will be chunk-aligned and after
4666  * any data that is in the chunk containing 's'.
4667  */
4668 static sector_t last_dev_address(sector_t s, struct geom *geo)
4669 {
4670 	s = (s | geo->chunk_mask) + 1;
4671 	s >>= geo->chunk_shift;
4672 	s *= geo->near_copies;
4673 	s = DIV_ROUND_UP_SECTOR_T(s, geo->raid_disks);
4674 	s *= geo->far_copies;
4675 	s <<= geo->chunk_shift;
4676 	return s;
4677 }
4678 
4679 /* Calculate the first device-address that could contain
4680  * any block from the chunk that includes the array-address 's'.
4681  * This too will be the start of a chunk
4682  */
4683 static sector_t first_dev_address(sector_t s, struct geom *geo)
4684 {
4685 	s >>= geo->chunk_shift;
4686 	s *= geo->near_copies;
4687 	sector_div(s, geo->raid_disks);
4688 	s *= geo->far_copies;
4689 	s <<= geo->chunk_shift;
4690 	return s;
4691 }
4692 
4693 static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
4694 				int *skipped)
4695 {
4696 	/* We simply copy at most one chunk (smallest of old and new)
4697 	 * at a time, possibly less if that exceeds RESYNC_PAGES,
4698 	 * or we hit a bad block or something.
4699 	 * This might mean we pause for normal IO in the middle of
4700 	 * a chunk, but that is not a problem as mddev->reshape_position
4701 	 * can record any location.
4702 	 *
4703 	 * If we will want to write to a location that isn't
4704 	 * yet recorded as 'safe' (i.e. in metadata on disk) then
4705 	 * we need to flush all reshape requests and update the metadata.
4706 	 *
4707 	 * When reshaping forwards (e.g. to more devices), we interpret
4708 	 * 'safe' as the earliest block which might not have been copied
4709 	 * down yet.  We divide this by previous stripe size and multiply
4710 	 * by previous stripe length to get lowest device offset that we
4711 	 * cannot write to yet.
4712 	 * We interpret 'sector_nr' as an address that we want to write to.
4713 	 * From this we use last_device_address() to find where we might
4714 	 * write to, and first_device_address on the  'safe' position.
4715 	 * If this 'next' write position is after the 'safe' position,
4716 	 * we must update the metadata to increase the 'safe' position.
4717 	 *
4718 	 * When reshaping backwards, we round in the opposite direction
4719 	 * and perform the reverse test:  next write position must not be
4720 	 * less than current safe position.
4721 	 *
4722 	 * In all this the minimum difference in data offsets
4723 	 * (conf->offset_diff - always positive) allows a bit of slack,
4724 	 * so next can be after 'safe', but not by more than offset_diff
4725 	 *
4726 	 * We need to prepare all the bios here before we start any IO
4727 	 * to ensure the size we choose is acceptable to all devices.
4728 	 * The means one for each copy for write-out and an extra one for
4729 	 * read-in.
4730 	 * We store the read-in bio in ->master_bio and the others in
4731 	 * ->devs[x].bio and ->devs[x].repl_bio.
4732 	 */
4733 	struct r10conf *conf = mddev->private;
4734 	struct r10bio *r10_bio;
4735 	sector_t next, safe, last;
4736 	int max_sectors;
4737 	int nr_sectors;
4738 	int s;
4739 	struct md_rdev *rdev;
4740 	int need_flush = 0;
4741 	struct bio *blist;
4742 	struct bio *bio, *read_bio;
4743 	int sectors_done = 0;
4744 	struct page **pages;
4745 
4746 	if (sector_nr == 0) {
4747 		/* If restarting in the middle, skip the initial sectors */
4748 		if (mddev->reshape_backwards &&
4749 		    conf->reshape_progress < raid10_size(mddev, 0, 0)) {
4750 			sector_nr = (raid10_size(mddev, 0, 0)
4751 				     - conf->reshape_progress);
4752 		} else if (!mddev->reshape_backwards &&
4753 			   conf->reshape_progress > 0)
4754 			sector_nr = conf->reshape_progress;
4755 		if (sector_nr) {
4756 			mddev->curr_resync_completed = sector_nr;
4757 			sysfs_notify_dirent_safe(mddev->sysfs_completed);
4758 			*skipped = 1;
4759 			return sector_nr;
4760 		}
4761 	}
4762 
4763 	/* We don't use sector_nr to track where we are up to
4764 	 * as that doesn't work well for ->reshape_backwards.
4765 	 * So just use ->reshape_progress.
4766 	 */
4767 	if (mddev->reshape_backwards) {
4768 		/* 'next' is the earliest device address that we might
4769 		 * write to for this chunk in the new layout
4770 		 */
4771 		next = first_dev_address(conf->reshape_progress - 1,
4772 					 &conf->geo);
4773 
4774 		/* 'safe' is the last device address that we might read from
4775 		 * in the old layout after a restart
4776 		 */
4777 		safe = last_dev_address(conf->reshape_safe - 1,
4778 					&conf->prev);
4779 
4780 		if (next + conf->offset_diff < safe)
4781 			need_flush = 1;
4782 
4783 		last = conf->reshape_progress - 1;
4784 		sector_nr = last & ~(sector_t)(conf->geo.chunk_mask
4785 					       & conf->prev.chunk_mask);
4786 		if (sector_nr + RESYNC_SECTORS < last)
4787 			sector_nr = last + 1 - RESYNC_SECTORS;
4788 	} else {
4789 		/* 'next' is after the last device address that we
4790 		 * might write to for this chunk in the new layout
4791 		 */
4792 		next = last_dev_address(conf->reshape_progress, &conf->geo);
4793 
4794 		/* 'safe' is the earliest device address that we might
4795 		 * read from in the old layout after a restart
4796 		 */
4797 		safe = first_dev_address(conf->reshape_safe, &conf->prev);
4798 
4799 		/* Need to update metadata if 'next' might be beyond 'safe'
4800 		 * as that would possibly corrupt data
4801 		 */
4802 		if (next > safe + conf->offset_diff)
4803 			need_flush = 1;
4804 
4805 		sector_nr = conf->reshape_progress;
4806 		last  = sector_nr | (conf->geo.chunk_mask
4807 				     & conf->prev.chunk_mask);
4808 
4809 		if (sector_nr + RESYNC_SECTORS <= last)
4810 			last = sector_nr + RESYNC_SECTORS - 1;
4811 	}
4812 
4813 	if (need_flush ||
4814 	    time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
4815 		/* Need to update reshape_position in metadata */
4816 		wait_barrier(conf);
4817 		mddev->reshape_position = conf->reshape_progress;
4818 		if (mddev->reshape_backwards)
4819 			mddev->curr_resync_completed = raid10_size(mddev, 0, 0)
4820 				- conf->reshape_progress;
4821 		else
4822 			mddev->curr_resync_completed = conf->reshape_progress;
4823 		conf->reshape_checkpoint = jiffies;
4824 		set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
4825 		md_wakeup_thread(mddev->thread);
4826 		wait_event(mddev->sb_wait, mddev->sb_flags == 0 ||
4827 			   test_bit(MD_RECOVERY_INTR, &mddev->recovery));
4828 		if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
4829 			allow_barrier(conf);
4830 			return sectors_done;
4831 		}
4832 		conf->reshape_safe = mddev->reshape_position;
4833 		allow_barrier(conf);
4834 	}
4835 
4836 	raise_barrier(conf, 0);
4837 read_more:
4838 	/* Now schedule reads for blocks from sector_nr to last */
4839 	r10_bio = raid10_alloc_init_r10buf(conf);
4840 	r10_bio->state = 0;
4841 	raise_barrier(conf, 1);
4842 	atomic_set(&r10_bio->remaining, 0);
4843 	r10_bio->mddev = mddev;
4844 	r10_bio->sector = sector_nr;
4845 	set_bit(R10BIO_IsReshape, &r10_bio->state);
4846 	r10_bio->sectors = last - sector_nr + 1;
4847 	rdev = read_balance(conf, r10_bio, &max_sectors);
4848 	BUG_ON(!test_bit(R10BIO_Previous, &r10_bio->state));
4849 
4850 	if (!rdev) {
4851 		/* Cannot read from here, so need to record bad blocks
4852 		 * on all the target devices.
4853 		 */
4854 		// FIXME
4855 		mempool_free(r10_bio, &conf->r10buf_pool);
4856 		set_bit(MD_RECOVERY_INTR, &mddev->recovery);
4857 		return sectors_done;
4858 	}
4859 
4860 	read_bio = bio_alloc_bioset(GFP_KERNEL, RESYNC_PAGES, &mddev->bio_set);
4861 
4862 	bio_set_dev(read_bio, rdev->bdev);
4863 	read_bio->bi_iter.bi_sector = (r10_bio->devs[r10_bio->read_slot].addr
4864 			       + rdev->data_offset);
4865 	read_bio->bi_private = r10_bio;
4866 	read_bio->bi_end_io = end_reshape_read;
4867 	bio_set_op_attrs(read_bio, REQ_OP_READ, 0);
4868 	r10_bio->master_bio = read_bio;
4869 	r10_bio->read_slot = r10_bio->devs[r10_bio->read_slot].devnum;
4870 
4871 	/*
4872 	 * Broadcast RESYNC message to other nodes, so all nodes would not
4873 	 * write to the region to avoid conflict.
4874 	*/
4875 	if (mddev_is_clustered(mddev) && conf->cluster_sync_high <= sector_nr) {
4876 		struct mdp_superblock_1 *sb = NULL;
4877 		int sb_reshape_pos = 0;
4878 
4879 		conf->cluster_sync_low = sector_nr;
4880 		conf->cluster_sync_high = sector_nr + CLUSTER_RESYNC_WINDOW_SECTORS;
4881 		sb = page_address(rdev->sb_page);
4882 		if (sb) {
4883 			sb_reshape_pos = le64_to_cpu(sb->reshape_position);
4884 			/*
4885 			 * Set cluster_sync_low again if next address for array
4886 			 * reshape is less than cluster_sync_low. Since we can't
4887 			 * update cluster_sync_low until it has finished reshape.
4888 			 */
4889 			if (sb_reshape_pos < conf->cluster_sync_low)
4890 				conf->cluster_sync_low = sb_reshape_pos;
4891 		}
4892 
4893 		md_cluster_ops->resync_info_update(mddev, conf->cluster_sync_low,
4894 							  conf->cluster_sync_high);
4895 	}
4896 
4897 	/* Now find the locations in the new layout */
4898 	__raid10_find_phys(&conf->geo, r10_bio);
4899 
4900 	blist = read_bio;
4901 	read_bio->bi_next = NULL;
4902 
4903 	rcu_read_lock();
4904 	for (s = 0; s < conf->copies*2; s++) {
4905 		struct bio *b;
4906 		int d = r10_bio->devs[s/2].devnum;
4907 		struct md_rdev *rdev2;
4908 		if (s&1) {
4909 			rdev2 = rcu_dereference(conf->mirrors[d].replacement);
4910 			b = r10_bio->devs[s/2].repl_bio;
4911 		} else {
4912 			rdev2 = rcu_dereference(conf->mirrors[d].rdev);
4913 			b = r10_bio->devs[s/2].bio;
4914 		}
4915 		if (!rdev2 || test_bit(Faulty, &rdev2->flags))
4916 			continue;
4917 
4918 		bio_set_dev(b, rdev2->bdev);
4919 		b->bi_iter.bi_sector = r10_bio->devs[s/2].addr +
4920 			rdev2->new_data_offset;
4921 		b->bi_end_io = end_reshape_write;
4922 		bio_set_op_attrs(b, REQ_OP_WRITE, 0);
4923 		b->bi_next = blist;
4924 		blist = b;
4925 	}
4926 
4927 	/* Now add as many pages as possible to all of these bios. */
4928 
4929 	nr_sectors = 0;
4930 	pages = get_resync_pages(r10_bio->devs[0].bio)->pages;
4931 	for (s = 0 ; s < max_sectors; s += PAGE_SIZE >> 9) {
4932 		struct page *page = pages[s / (PAGE_SIZE >> 9)];
4933 		int len = (max_sectors - s) << 9;
4934 		if (len > PAGE_SIZE)
4935 			len = PAGE_SIZE;
4936 		for (bio = blist; bio ; bio = bio->bi_next) {
4937 			/*
4938 			 * won't fail because the vec table is big enough
4939 			 * to hold all these pages
4940 			 */
4941 			bio_add_page(bio, page, len, 0);
4942 		}
4943 		sector_nr += len >> 9;
4944 		nr_sectors += len >> 9;
4945 	}
4946 	rcu_read_unlock();
4947 	r10_bio->sectors = nr_sectors;
4948 
4949 	/* Now submit the read */
4950 	md_sync_acct_bio(read_bio, r10_bio->sectors);
4951 	atomic_inc(&r10_bio->remaining);
4952 	read_bio->bi_next = NULL;
4953 	submit_bio_noacct(read_bio);
4954 	sectors_done += nr_sectors;
4955 	if (sector_nr <= last)
4956 		goto read_more;
4957 
4958 	lower_barrier(conf);
4959 
4960 	/* Now that we have done the whole section we can
4961 	 * update reshape_progress
4962 	 */
4963 	if (mddev->reshape_backwards)
4964 		conf->reshape_progress -= sectors_done;
4965 	else
4966 		conf->reshape_progress += sectors_done;
4967 
4968 	return sectors_done;
4969 }
4970 
4971 static void end_reshape_request(struct r10bio *r10_bio);
4972 static int handle_reshape_read_error(struct mddev *mddev,
4973 				     struct r10bio *r10_bio);
4974 static void reshape_request_write(struct mddev *mddev, struct r10bio *r10_bio)
4975 {
4976 	/* Reshape read completed.  Hopefully we have a block
4977 	 * to write out.
4978 	 * If we got a read error then we do sync 1-page reads from
4979 	 * elsewhere until we find the data - or give up.
4980 	 */
4981 	struct r10conf *conf = mddev->private;
4982 	int s;
4983 
4984 	if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
4985 		if (handle_reshape_read_error(mddev, r10_bio) < 0) {
4986 			/* Reshape has been aborted */
4987 			md_done_sync(mddev, r10_bio->sectors, 0);
4988 			return;
4989 		}
4990 
4991 	/* We definitely have the data in the pages, schedule the
4992 	 * writes.
4993 	 */
4994 	atomic_set(&r10_bio->remaining, 1);
4995 	for (s = 0; s < conf->copies*2; s++) {
4996 		struct bio *b;
4997 		int d = r10_bio->devs[s/2].devnum;
4998 		struct md_rdev *rdev;
4999 		rcu_read_lock();
5000 		if (s&1) {
5001 			rdev = rcu_dereference(conf->mirrors[d].replacement);
5002 			b = r10_bio->devs[s/2].repl_bio;
5003 		} else {
5004 			rdev = rcu_dereference(conf->mirrors[d].rdev);
5005 			b = r10_bio->devs[s/2].bio;
5006 		}
5007 		if (!rdev || test_bit(Faulty, &rdev->flags)) {
5008 			rcu_read_unlock();
5009 			continue;
5010 		}
5011 		atomic_inc(&rdev->nr_pending);
5012 		rcu_read_unlock();
5013 		md_sync_acct_bio(b, r10_bio->sectors);
5014 		atomic_inc(&r10_bio->remaining);
5015 		b->bi_next = NULL;
5016 		submit_bio_noacct(b);
5017 	}
5018 	end_reshape_request(r10_bio);
5019 }
5020 
5021 static void end_reshape(struct r10conf *conf)
5022 {
5023 	if (test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery))
5024 		return;
5025 
5026 	spin_lock_irq(&conf->device_lock);
5027 	conf->prev = conf->geo;
5028 	md_finish_reshape(conf->mddev);
5029 	smp_wmb();
5030 	conf->reshape_progress = MaxSector;
5031 	conf->reshape_safe = MaxSector;
5032 	spin_unlock_irq(&conf->device_lock);
5033 
5034 	if (conf->mddev->queue)
5035 		raid10_set_io_opt(conf);
5036 	conf->fullsync = 0;
5037 }
5038 
5039 static void raid10_update_reshape_pos(struct mddev *mddev)
5040 {
5041 	struct r10conf *conf = mddev->private;
5042 	sector_t lo, hi;
5043 
5044 	md_cluster_ops->resync_info_get(mddev, &lo, &hi);
5045 	if (((mddev->reshape_position <= hi) && (mddev->reshape_position >= lo))
5046 	    || mddev->reshape_position == MaxSector)
5047 		conf->reshape_progress = mddev->reshape_position;
5048 	else
5049 		WARN_ON_ONCE(1);
5050 }
5051 
5052 static int handle_reshape_read_error(struct mddev *mddev,
5053 				     struct r10bio *r10_bio)
5054 {
5055 	/* Use sync reads to get the blocks from somewhere else */
5056 	int sectors = r10_bio->sectors;
5057 	struct r10conf *conf = mddev->private;
5058 	struct r10bio *r10b;
5059 	int slot = 0;
5060 	int idx = 0;
5061 	struct page **pages;
5062 
5063 	r10b = kmalloc(struct_size(r10b, devs, conf->copies), GFP_NOIO);
5064 	if (!r10b) {
5065 		set_bit(MD_RECOVERY_INTR, &mddev->recovery);
5066 		return -ENOMEM;
5067 	}
5068 
5069 	/* reshape IOs share pages from .devs[0].bio */
5070 	pages = get_resync_pages(r10_bio->devs[0].bio)->pages;
5071 
5072 	r10b->sector = r10_bio->sector;
5073 	__raid10_find_phys(&conf->prev, r10b);
5074 
5075 	while (sectors) {
5076 		int s = sectors;
5077 		int success = 0;
5078 		int first_slot = slot;
5079 
5080 		if (s > (PAGE_SIZE >> 9))
5081 			s = PAGE_SIZE >> 9;
5082 
5083 		rcu_read_lock();
5084 		while (!success) {
5085 			int d = r10b->devs[slot].devnum;
5086 			struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev);
5087 			sector_t addr;
5088 			if (rdev == NULL ||
5089 			    test_bit(Faulty, &rdev->flags) ||
5090 			    !test_bit(In_sync, &rdev->flags))
5091 				goto failed;
5092 
5093 			addr = r10b->devs[slot].addr + idx * PAGE_SIZE;
5094 			atomic_inc(&rdev->nr_pending);
5095 			rcu_read_unlock();
5096 			success = sync_page_io(rdev,
5097 					       addr,
5098 					       s << 9,
5099 					       pages[idx],
5100 					       REQ_OP_READ, 0, false);
5101 			rdev_dec_pending(rdev, mddev);
5102 			rcu_read_lock();
5103 			if (success)
5104 				break;
5105 		failed:
5106 			slot++;
5107 			if (slot >= conf->copies)
5108 				slot = 0;
5109 			if (slot == first_slot)
5110 				break;
5111 		}
5112 		rcu_read_unlock();
5113 		if (!success) {
5114 			/* couldn't read this block, must give up */
5115 			set_bit(MD_RECOVERY_INTR,
5116 				&mddev->recovery);
5117 			kfree(r10b);
5118 			return -EIO;
5119 		}
5120 		sectors -= s;
5121 		idx++;
5122 	}
5123 	kfree(r10b);
5124 	return 0;
5125 }
5126 
5127 static void end_reshape_write(struct bio *bio)
5128 {
5129 	struct r10bio *r10_bio = get_resync_r10bio(bio);
5130 	struct mddev *mddev = r10_bio->mddev;
5131 	struct r10conf *conf = mddev->private;
5132 	int d;
5133 	int slot;
5134 	int repl;
5135 	struct md_rdev *rdev = NULL;
5136 
5137 	d = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
5138 	if (repl)
5139 		rdev = conf->mirrors[d].replacement;
5140 	if (!rdev) {
5141 		smp_mb();
5142 		rdev = conf->mirrors[d].rdev;
5143 	}
5144 
5145 	if (bio->bi_status) {
5146 		/* FIXME should record badblock */
5147 		md_error(mddev, rdev);
5148 	}
5149 
5150 	rdev_dec_pending(rdev, mddev);
5151 	end_reshape_request(r10_bio);
5152 }
5153 
5154 static void end_reshape_request(struct r10bio *r10_bio)
5155 {
5156 	if (!atomic_dec_and_test(&r10_bio->remaining))
5157 		return;
5158 	md_done_sync(r10_bio->mddev, r10_bio->sectors, 1);
5159 	bio_put(r10_bio->master_bio);
5160 	put_buf(r10_bio);
5161 }
5162 
5163 static void raid10_finish_reshape(struct mddev *mddev)
5164 {
5165 	struct r10conf *conf = mddev->private;
5166 
5167 	if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))
5168 		return;
5169 
5170 	if (mddev->delta_disks > 0) {
5171 		if (mddev->recovery_cp > mddev->resync_max_sectors) {
5172 			mddev->recovery_cp = mddev->resync_max_sectors;
5173 			set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
5174 		}
5175 		mddev->resync_max_sectors = mddev->array_sectors;
5176 	} else {
5177 		int d;
5178 		rcu_read_lock();
5179 		for (d = conf->geo.raid_disks ;
5180 		     d < conf->geo.raid_disks - mddev->delta_disks;
5181 		     d++) {
5182 			struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev);
5183 			if (rdev)
5184 				clear_bit(In_sync, &rdev->flags);
5185 			rdev = rcu_dereference(conf->mirrors[d].replacement);
5186 			if (rdev)
5187 				clear_bit(In_sync, &rdev->flags);
5188 		}
5189 		rcu_read_unlock();
5190 	}
5191 	mddev->layout = mddev->new_layout;
5192 	mddev->chunk_sectors = 1 << conf->geo.chunk_shift;
5193 	mddev->reshape_position = MaxSector;
5194 	mddev->delta_disks = 0;
5195 	mddev->reshape_backwards = 0;
5196 }
5197 
5198 static struct md_personality raid10_personality =
5199 {
5200 	.name		= "raid10",
5201 	.level		= 10,
5202 	.owner		= THIS_MODULE,
5203 	.make_request	= raid10_make_request,
5204 	.run		= raid10_run,
5205 	.free		= raid10_free,
5206 	.status		= raid10_status,
5207 	.error_handler	= raid10_error,
5208 	.hot_add_disk	= raid10_add_disk,
5209 	.hot_remove_disk= raid10_remove_disk,
5210 	.spare_active	= raid10_spare_active,
5211 	.sync_request	= raid10_sync_request,
5212 	.quiesce	= raid10_quiesce,
5213 	.size		= raid10_size,
5214 	.resize		= raid10_resize,
5215 	.takeover	= raid10_takeover,
5216 	.check_reshape	= raid10_check_reshape,
5217 	.start_reshape	= raid10_start_reshape,
5218 	.finish_reshape	= raid10_finish_reshape,
5219 	.update_reshape_pos = raid10_update_reshape_pos,
5220 };
5221 
5222 static int __init raid_init(void)
5223 {
5224 	return register_md_personality(&raid10_personality);
5225 }
5226 
5227 static void raid_exit(void)
5228 {
5229 	unregister_md_personality(&raid10_personality);
5230 }
5231 
5232 module_init(raid_init);
5233 module_exit(raid_exit);
5234 MODULE_LICENSE("GPL");
5235 MODULE_DESCRIPTION("RAID10 (striped mirror) personality for MD");
5236 MODULE_ALIAS("md-personality-9"); /* RAID10 */
5237 MODULE_ALIAS("md-raid10");
5238 MODULE_ALIAS("md-level-10");
5239 
5240 module_param(max_queued_requests, int, S_IRUGO|S_IWUSR);
5241