| blob | 96f36596830696c2f1ba1bd8bc6fbb24d30a43d8 |
1 /*
2 * raid10.c : Multiple Devices driver for Linux
3 *
4 * Copyright (C) 2000-2004 Neil Brown
5 *
6 * RAID-10 support for md.
7 *
8 * Base on code in raid1.c. See raid1.c for further copyright information.
9 *
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2, or (at your option)
14 * any later version.
15 *
16 * You should have received a copy of the GNU General Public License
17 * (for example /usr/src/linux/COPYING); if not, write to the Free
18 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 */
21 #include <linux/slab.h>
22 #include <linux/delay.h>
23 #include <linux/blkdev.h>
24 #include <linux/module.h>
25 #include <linux/seq_file.h>
26 #include <linux/ratelimit.h>
27 #include <linux/kthread.h>
33 /*
34 * RAID10 provides a combination of RAID0 and RAID1 functionality.
35 * The layout of data is defined by
36 * chunk_size
37 * raid_disks
38 * near_copies (stored in low byte of layout)
39 * far_copies (stored in second byte of layout)
40 * far_offset (stored in bit 16 of layout )
41 * use_far_sets (stored in bit 17 of layout )
42 * use_far_sets_bugfixed (stored in bit 18 of layout )
43 *
44 * The data to be stored is divided into chunks using chunksize. Each device
45 * is divided into far_copies sections. In each section, chunks are laid out
46 * in a style similar to raid0, but near_copies copies of each chunk is stored
47 * (each on a different drive). The starting device for each section is offset
48 * near_copies from the starting device of the previous section. Thus there
49 * are (near_copies * far_copies) of each chunk, and each is on a different
50 * drive. near_copies and far_copies must be at least one, and their product
51 * is at most raid_disks.
52 *
53 * If far_offset is true, then the far_copies are handled a bit differently.
54 * The copies are still in different stripes, but instead of being very far
55 * apart on disk, there are adjacent stripes.
56 *
57 * The far and offset algorithms are handled slightly differently if
58 * 'use_far_sets' is true. In this case, the array's devices are grouped into
59 * sets that are (near_copies * far_copies) in size. The far copied stripes
60 * are still shifted by 'near_copies' devices, but this shifting stays confined
61 * to the set rather than the entire array. This is done to improve the number
62 * of device combinations that can fail without causing the array to fail.
63 * Example 'far' algorithm w/o 'use_far_sets' (each letter represents a chunk
64 * on a device):
65 * A B C D A B C D E
66 * ... ...
67 * D A B C E A B C D
68 * Example 'far' algorithm w/ 'use_far_sets' enabled (sets illustrated w/ []'s):
69 * [A B] [C D] [A B] [C D E]
70 * |...| |...| |...| | ... |
71 * [B A] [D C] [B A] [E C D]
72 */
74 /*
75 * Number of guaranteed r10bios in case of extreme VM load:
76 */
77 #define NR_RAID10_BIOS 256
79 /* when we get a read error on a read-only array, we redirect to another
80 * device without failing the first device, or trying to over-write to
81 * correct the read error. To keep track of bad blocks on a per-bio
82 * level, we store IO_BLOCKED in the appropriate 'bios' pointer
83 */
84 #define IO_BLOCKED ((struct bio *)1)
85 /* When we successfully write to a known bad-block, we need to remove the
86 * bad-block marking which must be done from process context. So we record
87 * the success by setting devs[n].bio to IO_MADE_GOOD
88 */
89 #define IO_MADE_GOOD ((struct bio *)2)
91 #define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
93 /* When there are this many requests queued to be written by
94 * the raid10 thread, we become 'congested' to provide back-pressure
95 * for writeback.
96 */
109 {
113 /* allocate a r10bio with room for raid_disks entries in the
114 * bios array */
116 }
119 {
121 }
123 /* Maximum size of each resync request */
124 #define RESYNC_BLOCK_SIZE (64*1024)
125 #define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
126 /* amount of memory to reserve for resync requests */
127 #define RESYNC_WINDOW (1024*1024)
128 /* maximum number of concurrent requests, memory permitting */
129 #define RESYNC_DEPTH (32*1024*1024/RESYNC_BLOCK_SIZE)
131 /*
132 * When performing a resync, we need to read and compare, so
133 * we need as many pages are there are copies.
134 * When performing a recovery, we need 2 bios, one for read,
135 * one for write (we recover only one drive per r10buf)
136 *
137 */
139 {
154 else
157 /*
158 * Allocate bios.
159 */
171 }
172 /*
173 * Allocate RESYNC_PAGES data pages and attach them
174 * where needed.
175 */
182 /* we can share bv_page's during recovery
183 * and reshape */
195 }
196 }
200 out_free_pages:
207 out_free_bio:
213 }
216 }
219 {
231 }
233 }
237 }
239 }
242 {
254 }
255 }
258 {
263 }
266 {
272 }
275 {
285 /* wake up frozen array... */
289 }
291 /*
292 * raid_end_bio_io() is called when we have finished servicing a mirrored
293 * operation and are ready to return a success/failure code to the buffer
294 * cache layer.
295 */
297 {
314 /*
315 * Wake up any possible resync thread that waits for the device
316 * to go idle.
317 */
319 }
321 }
323 /*
324 * Update disk head position estimator based on IRQ completion info.
325 */
327 {
332 }
334 /*
335 * Find the disk number which triggered given bio
336 */
339 {
349 }
350 }
360 }
363 {
373 /*
374 * this branch is our 'one mirror IO has finished' event handler:
375 */
379 /*
380 * Set R10BIO_Uptodate in our master bio, so that
381 * we will return a good error code to the higher
382 * levels even if IO on some other mirrored buffer fails.
383 *
384 * The 'master' represents the composite IO operation to
385 * user-side. So if something waits for IO, then it will
386 * wait for the 'master' bio.
387 */
390 /* If all other devices that store this block have
391 * failed, we want to return the error upwards rather
392 * than fail the last device. Here we redefine
393 * "uptodate" to mean "Don't want to retry"
394 */
398 }
403 /*
404 * oops, read error - keep the refcount on the rdev
405 */
414 }
415 }
418 {
419 /* clear the bitmap if all writes complete successfully */
425 }
428 {
436 else
438 }
439 }
440 }
443 {
459 }
460 /*
461 * this branch is our 'one mirror IO has finished' event handler:
462 */
465 /* Never record new bad blocks to replacement,
466 * just fail it.
467 */
476 }
478 /*
479 * Set R10BIO_Uptodate in our master bio, so that
480 * we will return a good error code for to the higher
481 * levels even if IO on some other mirrored buffer fails.
482 *
483 * The 'master' represents the composite IO operation to
484 * user-side. So if something waits for IO, then it will
485 * wait for the 'master' bio.
486 */
487 sector_t first_bad;
490 /*
491 * Do not set R10BIO_Uptodate if the current device is
492 * rebuilding or Faulty. This is because we cannot use
493 * such device for properly reading the data back (we could
494 * potentially use it, if the current write would have felt
495 * before rdev->recovery_offset, but for simplicity we don't
496 * check this here.
497 */
502 /* Maybe we can clear some bad blocks. */
510 else
514 }
515 }
517 /*
518 *
519 * Let's see if all mirrored write operations have finished
520 * already.
521 */
525 }
527 /*
528 * RAID10 layout manager
529 * As well as the chunksize and raid_disks count, there are two
530 * parameters: near_copies and far_copies.
531 * near_copies * far_copies must be <= raid_disks.
532 * Normally one of these will be 1.
533 * If both are 1, we get raid0.
534 * If near_copies == raid_disks, we get raid1.
535 *
536 * Chunks are laid out in raid0 style with near_copies copies of the
537 * first chunk, followed by near_copies copies of the next chunk and
538 * so on.
539 * If far_copies > 1, then after 1/far_copies of the array has been assigned
540 * as described above, we start again with a device offset of near_copies.
541 * So we effectively have another copy of the whole array further down all
542 * the drives, but with blocks on different drives.
543 * With this layout, and block is never stored twice on the one device.
544 *
545 * raid10_find_phys finds the sector offset of a given virtual sector
546 * on each device that it is on.
547 *
548 * raid10_find_virt does the reverse mapping, from a device and a
549 * sector offset to a virtual address
550 */
553 {
555 sector_t sector;
556 sector_t chunk;
557 sector_t stripe;
568 /* now calculate first sector/dev */
580 /* and calculate all the others */
587 slot++;
601 }
605 slot++;
606 }
607 dev++;
611 }
612 }
613 }
616 {
628 }
631 {
633 /* Never use conf->prev as this is only called during resync
634 * or recovery, so reshape isn't happening
635 */
649 }
650 }
665 else
667 }
669 }
673 }
675 /*
676 * This routine returns the disk from which the requested read should
677 * be done. There is a per-array 'next expected sequential IO' sector
678 * number - if this matches on the next IO then we use the last disk.
679 * There is also a per-disk 'last know head position' sector that is
680 * maintained from IRQ contexts, both the normal and the resync IO
681 * completion handlers update this position correctly. If there is no
682 * perfect sequential match then we pick the disk whose head is closest.
683 *
684 * If there are 2 mirrors in the same 2 devices, performance degrades
685 * because position is mirror, not device based.
686 *
687 * The rdev for the device selected will have nr_pending incremented.
688 */
690 /*
691 * FIXME: possibly should rethink readbalancing and do it differently
692 * depending on near_copies / far_copies geometry.
693 */
697 {
710 retry:
717 /*
718 * Check if we can balance. We can balance on the whole
719 * device if no resync is going on (recovery is ok), or below
720 * the resync window. We take the first readable disk when
721 * above the resync window.
722 */
728 sector_t first_bad;
730 sector_t dev_sector;
750 /* Already have a better slot */
753 /* Cannot read here. If this is the
754 * 'primary' device, then we must not read
755 * beyond 'bad_sectors' from another device.
756 */
763 sector_t good_sectors =
769 }
771 /* Must read from here */
773 }
781 /* This optimisation is debatable, and completely destroys
782 * sequential read speed for 'far copies' arrays. So only
783 * keep it for 'near' arrays, and review those later.
784 */
788 /* for far > 1 always use the lowest address */
791 else
798 }
799 }
803 }
808 /* Cannot risk returning a device that failed
809 * before we inc'ed nr_pending
810 */
813 }
821 }
824 {
836 i++) {
842 }
843 }
846 }
849 {
850 /* Any writes that have been queued but are awaiting
851 * bitmap updates get flushed here.
852 */
860 /* flush any pending bitmap writes to disk
861 * before proceeding w/ I/O */
870 /* Just ignore it */
872 else
875 }
878 }
880 /* Barriers....
881 * Sometimes we need to suspend IO while we do something else,
882 * either some resync/recovery, or reconfigure the array.
883 * To do this we raise a 'barrier'.
884 * The 'barrier' is a counter that can be raised multiple times
885 * to count how many activities are happening which preclude
886 * normal IO.
887 * We can only raise the barrier if there is no pending IO.
888 * i.e. if nr_pending == 0.
889 * We choose only to raise the barrier if no-one is waiting for the
890 * barrier to go down. This means that as soon as an IO request
891 * is ready, no other operations which require a barrier will start
892 * until the IO request has had a chance.
893 *
894 * So: regular IO calls 'wait_barrier'. When that returns there
895 * is no backgroup IO happening, It must arrange to call
896 * allow_barrier when it has finished its IO.
897 * backgroup IO calls must call raise_barrier. Once that returns
898 * there is no normal IO happeing. It must arrange to call
899 * lower_barrier when the particular background IO completes.
900 */
903 {
907 /* Wait until no block IO is waiting (unless 'force') */
911 /* block any new IO from starting */
914 /* Now wait for all pending IO to complete */
920 }
923 {
929 }
932 {
936 /* Wait for the barrier to drop.
937 * However if there are already pending
938 * requests (preventing the barrier from
939 * rising completely), and the
940 * pre-process bio queue isn't empty,
941 * then don't wait, as we need to empty
942 * that queue to get the nr_pending
943 * count down.
944 */
952 }
955 }
958 {
964 }
967 {
968 /* stop syncio and normal IO and wait for everything to
969 * go quiet.
970 * We increment barrier and nr_waiting, and then
971 * wait until nr_pending match nr_queued+extra
972 * This is called in the context of one normal IO request
973 * that has failed. Thus any sync request that might be pending
974 * will be blocked by nr_pending, and we need to wait for
975 * pending IO requests to complete or be queued for re-try.
976 * Thus the number queued (nr_queued) plus this request (extra)
977 * must match the number of pending IOs (nr_pending) before
978 * we continue.
979 */
989 }
992 {
993 /* reverse the effect of the freeze */
999 }
1003 {
1007 else
1009 }
1015 };
1018 {
1020 cb);
1034 }
1036 /* we aren't scheduling, so we can do the write-out directly. */
1046 /* Just ignore it */
1048 else
1051 }
1053 }
1056 {
1075 /*
1076 * Register the new request and wait if the reconstruction
1077 * thread has put up a bar for new requests.
1078 * Continue immediately if no resync is active currently.
1079 */
1086 /* IO spans the reshape position. Need to wait for
1087 * reshape to pass
1088 */
1093 sectors);
1095 }
1103 /* Need to update reshape_position in metadata */
1112 }
1123 /* We might need to issue multiple reads to different
1124 * devices if there are bad blocks around, so we keep
1125 * track of the number of reads in bio->bi_phys_segments.
1126 * If this is 0, there is only one r10_bio and no locking
1127 * will be needed when the request completes. If it is
1128 * non-zero, then it is the number of not-completed requests.
1129 */
1134 /*
1135 * read balancing logic:
1136 */
1140 read_again:
1145 }
1150 max_sectors);
1163 /* Could not read all from this device, so we will
1164 * need another r10_bio.
1165 */
1172 else
1175 /* Cannot call generic_make_request directly
1176 * as that will be queued in __generic_make_request
1177 * and subsequent mempool_alloc might block
1178 * waiting for it. so hand bio over to raid10d.
1179 */
1189 sectors_handled;
1194 }
1196 /*
1197 * WRITE:
1198 */
1203 }
1204 /* first select target devices under rcu_lock and
1205 * inc refcount on their rdev. Record them by setting
1206 * bios[x] to bio
1207 * If there are known/acknowledged bad blocks on any device
1208 * on which we have seen a write error, we want to avoid
1209 * writing to those blocks. This potentially requires several
1210 * writes to write around the bad blocks. Each set of writes
1211 * gets its own r10_bio with a set of bios attached. The number
1212 * of r10_bios is recored in bio->bi_phys_segments just as with
1213 * the read case.
1214 */
1218 retry_write:
1234 }
1239 }
1251 }
1253 sector_t first_bad;
1259 max_sectors,
1262 /* Mustn't write here until the bad block
1263 * is acknowledged
1264 */
1269 }
1271 /* Cannot write here at all */
1274 /* Mustn't write more than bad_sectors
1275 * to other devices yet
1276 */
1278 /* We don't set R10BIO_Degraded as that
1279 * only applies if the disk is missing,
1280 * so it might be re-added, and we want to
1281 * know to recover this chunk.
1282 * In this case the device is here, and the
1283 * fact that this chunk is not in-sync is
1284 * recorded in the bad block log.
1285 */
1287 }
1292 }
1293 }
1297 }
1301 }
1302 }
1306 /* Have to wait for this device to get unblocked, then retry */
1314 }
1320 /* Race with remove_disk */
1323 }
1325 }
1326 }
1331 }
1334 /* We are splitting this into multiple parts, so
1335 * we need to prepare for allocating another r10_bio.
1336 */
1341 else
1344 }
1358 max_sectors);
1363 rdev));
1376 cb);
1377 else
1386 }
1390 }
1395 /* Replacement just got moved to main 'rdev' */
1398 }
1401 max_sectors);
1420 }
1421 }
1423 /* Don't remove the bias on 'remaining' (one_write_done) until
1424 * after checking if we need to go around again.
1425 */
1429 /* We need another r10_bio. It has already been counted
1430 * in bio->bi_phys_segments.
1431 */
1441 }
1443 }
1446 {
1456 }
1462 /*
1463 * If this request crosses a chunk boundary, we need to split
1464 * it.
1465 */
1478 }
1483 /* In case raid10d snuck in to freeze_array */
1485 }
1488 {
1499 else
1503 }
1511 }
1513 /* check if there are enough drives for
1514 * every block to appear on atleast one.
1515 * Don't consider the device numbered 'ignore'
1516 * as we might be about to remove it.
1517 */
1519 {
1529 }
1541 cnt++;
1543 }
1549 out:
1552 }
1555 {
1556 /* when calling 'enough', both 'prev' and 'geo' must
1557 * be stable.
1558 * This is ensured if ->reconfig_mutex or ->device_lock
1559 * is held.
1560 */
1563 }
1566 {
1571 /*
1572 * If it is not operational, then we have already marked it as dead
1573 * else if it is the last working disks, ignore the error, let the
1574 * next level up know.
1575 * else mark the drive as failed
1576 */
1580 /*
1581 * Don't fail the drive, just return an IO error.
1582 */
1585 }
1588 /*
1589 * If recovery is running, make sure it aborts.
1590 */
1602 }
1605 {
1613 }
1625 }
1626 }
1629 {
1635 }
1638 {
1645 /*
1646 * Find all non-in_sync disks within the RAID10 configuration
1647 * and mark them in_sync
1648 */
1655 /* Replacement has just become active */
1658 count++;
1660 /* Replaced device not technically faulty,
1661 * but we need to be sure it gets removed
1662 * and never re-added.
1663 */
1667 }
1673 count++;
1675 }
1676 }
1683 }
1686 {
1694 /* only hot-add to in-sync arrays, as recovery is
1695 * very different from resync
1696 */
1707 else
1727 }
1741 }
1748 }
1751 {
1763 else
1770 }
1771 /* Only remove faulty devices if recovery
1772 * is not possible.
1773 */
1781 }
1785 /* lost the race, try later */
1790 /* We must have just cleared 'rdev' */
1794 * but will never see neither -- if they are careful.
1795 */
1799 /* We might have just remove the Replacement as faulty
1800 * Clear the flag just in case
1801 */
1806 abort:
1810 }
1813 {
1819 /* this is a reshape read */
1826 else
1827 /* The write handler will notice the lack of
1828 * R10BIO_Uptodate and record any errors etc
1829 */
1833 /* for reconstruct, we always reschedule after a read.
1834 * for resync, only after all reads
1835 */
1839 /* we have read all the blocks,
1840 * do the comparison in process context in raid10d
1841 */
1843 }
1844 }
1847 {
1852 /* the primary of several recovery bios */
1857 else
1866 else
1869 }
1870 }
1871 }
1874 {
1879 sector_t first_bad;
1888 else
1900 }
1910 }
1912 /*
1913 * Note: sync and recover and handled very differently for raid10
1914 * This code is for resync.
1915 * For resync, we read through virtual addresses and read all blocks.
1916 * If there is any error, we schedule a write. The lowest numbered
1917 * drive is authoritative.
1918 * However requests come for physical address, so we need to map.
1919 * For every physical address there are raid_disks/copies virtual addresses,
1920 * which is always are least one, but is not necessarly an integer.
1921 * This means that a physical address can span multiple chunks, so we may
1922 * have to submit multiple io requests for a single sync request.
1923 */
1924 /*
1925 * We check if all blocks are in-sync and only write to blocks that
1926 * aren't in sync
1927 */
1929 {
1937 /* find the first device with a block */
1949 /* now find blocks with errors */
1960 /* We know that the bi_io_vec layout is the same for
1961 * both 'first' and 'i', so we just compare them.
1962 * All vec entries are PAGE_SIZE;
1963 */
1971 len))
1974 }
1979 /* Don't fix anything. */
1981 }
1982 /* Ok, we need to write this bio, either to correct an
1983 * inconsistency or to correct an unreadable block.
1984 * First we need to fixup bv_offset, bv_len and
1985 * bi_vecs, as the read request might have corrupted these
1986 */
2006 }
2008 /* Now write out to any replacement devices
2009 * that are active
2010 */
2025 }
2027 done:
2031 }
2032 }
2034 /*
2035 * Now for the recovery code.
2036 * Recovery happens across physical sectors.
2037 * We recover all non-is_sync drives by finding the virtual address of
2038 * each, and then choose a working drive that also has that virt address.
2039 * There is a separate r10_bio for each non-in_sync drive.
2040 * Only the first two slots are in use. The first for reading,
2041 * The second for writing.
2042 *
2043 */
2045 {
2046 /* We got a read error during recovery.
2047 * We repeat the read in smaller page-sized sections.
2048 * If a read succeeds, write it to the new device or record
2049 * a bad block if we cannot.
2050 * If a read fails, record a bad block on both old and
2051 * new devices.
2052 */
2065 sector_t addr;
2074 addr,
2082 addr,
2092 }
2093 }
2095 /* We don't worry if we cannot set a bad block -
2096 * it really is bad so there is no loss in not
2097 * recording it yet
2098 */
2102 /* need bad block on destination too */
2107 /* just abort the recovery */
2109 "md/raid10:%s: recovery aborted"
2118 }
2119 }
2120 }
2124 idx++;
2125 }
2126 }
2129 {
2138 }
2140 /*
2141 * share the pages with the first bio
2142 * and submit the write request
2143 */
2147 /* Need to test wbio2->bi_end_io before we call
2148 * generic_make_request as if the former is NULL,
2149 * the latter is free to free wbio2.
2150 */
2157 }
2163 }
2164 }
2166 /*
2167 * Used by fix_read_error() to decay the per rdev read_errors.
2168 * We halve the read error count for every hour that has elapsed
2169 * since the last recorded read error.
2170 *
2171 */
2173 {
2182 /* first time we've seen a read error */
2185 }
2192 /*
2193 * if hours_since_last is > the number of bits in read_errors
2194 * just set read errors to 0. We do this to avoid
2195 * overflowing the shift of read_errors by hours_since_last.
2196 */
2199 else
2201 }
2205 {
2206 sector_t first_bad;
2213 /* success */
2220 }
2221 /* need to record an error - either for the block or the device */
2225 }
2227 /*
2228 * This is a kernel thread which:
2229 *
2230 * 1. Retries failed read operations on working mirrors.
2231 * 2. Updates the raid superblock when problems encounter.
2232 * 3. Performs writes following reads for array synchronising.
2233 */
2236 {
2243 /* still own a reference to this rdev, so it cannot
2244 * have been cleared recently.
2245 */
2249 /* drive has already been failed, just ignore any
2250 more fix_read_error() attempts */
2260 "md/raid10:%s: %s: Raid device exceeded "
2270 }
2283 sector_t first_bad;
2296 sect,
2303 }
2304 sl++;
2311 /* Cannot read from anywhere, just mark the block
2312 * as bad on the first device to discourage future
2313 * reads.
2314 */
2319 rdev,
2326 }
2328 }
2331 /* write it back and re-read */
2338 sl--;
2349 sect,
2352 /* Well, this device is dead */
2354 "md/raid10:%s: read correction "
2355 "write failed"
2359 sect +
2361 rdev)),
2367 }
2370 }
2377 sl--;
2388 sect,
2390 READ)) {
2392 /* Well, this device is dead */
2394 "md/raid10:%s: unable to read back "
2395 "corrected sectors"
2399 sect +
2409 "md/raid10:%s: read error corrected"
2413 sect +
2417 }
2421 }
2426 }
2427 }
2430 {
2435 /* bio has the data to be written to slot 'i' where
2436 * we just recently had a write error.
2437 * We repeatedly clone the bio and trim down to one block,
2438 * then try the write. Where the write fails we record
2439 * a bad block.
2440 * It is conceivable that the bio doesn't exactly align with
2441 * blocks. We must handle this.
2442 *
2443 * We currently own a reference to the rdev.
2444 */
2447 sector_t sector;
2466 /* Write at 'sector' for 'sectors' */
2474 /* Failure! */
2483 }
2485 }
2488 {
2497 /* we got a read error. Maybe the drive is bad. Maybe just
2498 * the block and we can fix it.
2499 * We freeze all other IO, and try reading the block from
2500 * other devices. When we find one, we re-write
2501 * and check it that fixes the read error.
2502 * This is all done synchronously while the array is
2503 * frozen.
2504 */
2519 read_more:
2528 }
2533 KERN_ERR
2534 "md/raid10:%s: %s: redirecting "
2551 /* Drat - have to split this up more */
2560 else
2566 GFP_NOIO);
2579 }
2582 {
2583 /* Some sort of write request has finished and it
2584 * succeeded in writing where we thought there was a
2585 * bad block. So forget the bad block.
2586 * Or possibly if failed and we need to record
2587 * a bad block.
2588 */
2601 rdev,
2606 rdev,
2610 }
2617 rdev,
2622 rdev,
2626 }
2627 }
2637 rdev,
2647 }
2649 }
2654 rdev,
2658 }
2659 }
2670 }
2671 }
2672 }
2675 {
2692 }
2696 retry_list);
2705 }
2706 }
2717 }
2737 /* just a partial read to be scheduled from a
2738 * separate context
2739 */
2742 }
2747 }
2749 }
2752 {
2767 }
2769 /*
2770 * perform a "sync" on one "block"
2771 *
2772 * We need to make sure that no normal I/O request - particularly write
2773 * requests - conflict with active sync requests.
2774 *
2775 * This is achieved by tracking pending requests and a 'barrier' concept
2776 * that can be installed to exclude normal IO requests.
2777 *
2778 * Resync and recovery are handled very differently.
2779 * We differentiate by looking at MD_RECOVERY_SYNC in mddev->recovery.
2780 *
2781 * For resync, we iterate over virtual addresses, read all copies,
2782 * and update if there are differences. If only one copy is live,
2783 * skip it.
2784 * For recovery, we iterate over physical addresses, read a good
2785 * value for each non-in_sync drive, and over-write.
2786 *
2787 * So, for recovery we may have several outstanding complex requests for a
2788 * given address, one for each out-of-sync device. We model this by allocating
2789 * a number of r10_bio structures, one for each out-of-sync device.
2790 * As we setup these structures, we collect all bio's together into a list
2791 * which we then process collectively to add pages, and then process again
2792 * to pass to generic_make_request.
2793 *
2794 * The r10_bio structures are linked using a borrowed master_bio pointer.
2795 * This link is counted in ->remaining. When the r10_bio that points to NULL
2796 * has its remaining count decremented to 0, the whole complex operation
2797 * is complete.
2798 *
2799 */
2803 {
2810 sector_t sync_blocks;
2819 /*
2820 * Allow skipping a full rebuild for incremental assembly
2821 * of a clean array, like RAID1 does.
2822 */
2832 }
2834 skipped:
2840 /* If we aborted, we need to abort the
2841 * sync on the 'current' bitmap chucks (there can
2842 * be several when recovering multiple devices).
2843 * as we may have started syncing it but not finished.
2844 * We can find the current address in
2845 * mddev->curr_resync, but for recovery,
2846 * we need to convert that to several
2847 * virtual addresses.
2848 */
2853 }
2860 sector_t sect =
2864 }
2866 /* completed sync */
2870 /* Completed a full sync so the replacements
2871 * are now fully recovered.
2872 */
2876 ->recovery_offset
2878 }
2880 }
2885 }
2891 /* if there has been nothing to do on any drive,
2892 * then there is nothing to do at all..
2893 */
2896 }
2901 /* make sure whole request will fit in a chunk - if chunks
2902 * are meaningful
2903 */
2908 /* Again, very different code for resync and recovery.
2909 * Both must result in an r10bio with a list of bios that
2910 * have bi_end_io, bi_sector, bi_bdev set,
2911 * and bi_private set to the r10bio.
2912 * For recovery, we may actually create several r10bios
2913 * with 2 bios in each, that correspond to the bios in the main one.
2914 * In this case, the subordinate r10bios link back through a
2915 * borrowed master_bio pointer, and the counter in the master
2916 * includes a ref from each subordinate.
2917 */
2918 /* First, we decide what to do and set ->bi_end_io
2919 * To end_sync_read if we want to read, and
2920 * end_sync_write if we will want to write.
2921 */
2925 /* recovery... the complicated one */
2932 sector_t sect;
2939 &&
2946 /* want to reconstruct this device */
2950 /* last stripe is not complete - don't
2951 * try to recover this sector.
2952 */
2954 }
2955 /* Unless we are doing a full sync, or a replacement
2956 * we only need to recover the block if it is set in
2957 * the bitmap
2958 */
2966 /* yep, skip the sync_blocks here, but don't assume
2967 * that there will never be anything to do here
2968 */
2971 }
2987 /* Need to check if the array will still be
2988 * degraded
2989 */
2995 }
3011 /* This is where we read from */
3021 bad_sectors -= (sector
3026 }
3027 }
3040 /* and we write to 'i' (if not in_sync) */
3068 /* and maybe write to replacement */
3073 /* Note: if rdev != NULL, then bio
3074 * cannot be NULL as r10buf_pool_alloc will
3075 * have allocated it.
3076 * So the second test here is pointless.
3077 * But it keeps semantic-checkers happy, and
3078 * this comment keeps human reviewers
3079 * happy.
3080 */
3095 }
3097 /* Cannot recover, so abort the recovery or
3098 * record a bad block */
3100 /* problem is that there are bad blocks
3101 * on other device(s)
3102 */
3120 }
3127 mirror->recovery_disabled
3129 }
3135 }
3136 }
3143 }
3145 }
3147 /* resync. Schedule a read for every block at this virt offset */
3156 /* We can skip this block */
3159 }
3201 }
3202 }
3213 count++;
3220 /* Need to set up for writing to the replacement */
3235 count++;
3236 }
3243 mddev);
3248 mddev);
3249 }
3253 }
3254 }
3272 /* stop here */
3277 /* remove last page from this bio */
3281 }
3283 }
3287 bio_full:
3302 }
3303 }
3306 /* pretend they weren't skipped, it makes
3307 * no important difference in this case
3308 */
3312 giveup:
3313 /* There is nowhere to write, so all non-sync
3314 * drives must be failed or in resync, all drives
3315 * have a bad block, so try the next chunk...
3316 */
3321 chunks_skipped ++;
3324 }
3326 static sector_t
3328 {
3329 sector_t size;
3344 }
3347 {
3348 /* Calculate the number of sectors-per-device that will
3349 * actually be used, and set conf->dev_sectors and
3350 * conf->stride
3351 */
3357 /* 'size' is now the number of chunks in the array */
3358 /* calculate "used chunks per device" */
3361 /* We need to round up when dividing by raid_disks to
3362 * get the stride size.
3363 */
3373 }
3374 }
3378 {
3394 * updated yet. */
3399 }
3417 * actually using this, but leave code here just in case.*/
3427 }
3431 }
3434 {
3447 }
3453 }
3460 /* FIXME calc properly */
3463 GFP_KERNEL);
3486 }
3490 else
3491 /* far_copies must be 1 */
3493 }
3509 out:
3518 }
3520 }
3523 {
3528 sector_t size;
3538 }
3554 else
3557 }
3579 }
3597 }
3603 else
3606 }
3607 /* need to check that every block has at least one working mirror */
3612 }
3615 /* must ensure that shape change is supported */
3622 }
3628 i++) {
3633 /* The replacement is all we have - use it */
3637 }
3646 }
3648 }
3658 /*
3659 * Ok, everything is just fine now
3660 */
3670 /* Calculate max read-ahead size.
3671 * We need to readahead at least twice a whole stripe....
3672 * maybe...
3673 */
3677 }
3691 /* This cannot work */
3694 }
3703 }
3707 out_free_conf:
3714 out:
3716 }
3719 {
3728 }
3731 {
3741 }
3742 }
3745 {
3746 /* Resize of 'far' arrays is not supported.
3747 * For 'near' and 'offset' arrays we can set the
3748 * number of sectors used to be an appropriate multiple
3749 * of the chunk size.
3750 * For 'offset', this is far_copies*chunksize.
3751 * For 'near' the multiplier is the LCM of
3752 * near_copies and raid_disks.
3753 * So if far_copies > 1 && !far_offset, fail.
3754 * Else find LCM(raid_disks, near_copy)*far_copies and
3755 * multiply by chunk_size. Then round to this number.
3756 * This is mostly done by raid10_size()
3757 */
3776 }
3784 }
3789 }
3792 {
3800 }
3803 /* Set new parameters */
3805 /* new layout: far_copies = 1, near_copies = 2 */
3810 /* make sure it will be not marked as dirty */
3820 }
3822 }
3825 }
3828 {
3831 /* raid10 can take over:
3832 * raid0 - providing it has only two drives
3833 */
3835 /* for raid0 takeover only one zone is supported */
3842 }
3846 }
3848 }
3851 {
3852 /* Called when there is a request to change
3853 * - layout (to ->new_layout)
3854 * - chunk size (to ->new_chunk_sectors)
3855 * - raid_disks (by delta_disks)
3856 * or when trying to restart a reshape that was ongoing.
3857 *
3858 * We need to validate the request and possibly allocate
3859 * space if that might be an issue later.
3860 *
3861 * Currently we reject any reshape of a 'far' mode array,
3862 * allow chunk size to change if new is generally acceptable,
3863 * allow raid_disks to increase, and allow
3864 * a switch between 'near' mode and 'offset' mode.
3865 */
3873 /* mustn't change number of copies */
3876 /* Cannot switch to 'far' mode */
3880 /* not factor of array size */
3889 /* allocate new 'mirrors' list */
3894 GFP_KERNEL);
3897 }
3899 }
3901 /*
3902 * Need to check if array has failed when deciding whether to:
3903 * - start an array
3904 * - remove non-faulty devices
3905 * - add a spare
3906 * - allow a reshape
3907 * This determination is simple when no reshape is happening.
3908 * However if there is a reshape, we need to carefully check
3909 * both the before and after sections.
3910 * This is because some failed devices may only affect one
3911 * of the two sections, and some non-in_sync devices may
3912 * be insync in the section most affected by failed devices.
3913 */
3915 {
3921 /* 'prev' section first */
3925 degraded++;
3927 /* When we can reduce the number of devices in
3928 * an array, this might not contribute to
3929 * 'degraded'. It does now.
3930 */
3931 degraded++;
3932 }
3941 degraded2++;
3943 /* If reshape is increasing the number of devices,
3944 * this section has already been recovered, so
3945 * it doesn't contribute to degraded.
3946 * else it does.
3947 */
3949 degraded2++;
3950 }
3951 }
3956 }
3959 {
3960 /* A 'reshape' has been requested. This commits
3961 * the various 'new' fields and sets MD_RECOVER_RESHAPE
3962 * This also checks if there are enough spares and adds them
3963 * to the array.
3964 * We currently require enough spares to make the final
3965 * array non-degraded. We also require that the difference
3966 * between old and new data_offset - on each device - is
3967 * enough that we never risk over-writing.
3968 */
3993 spares++;
4003 }
4004 }
4022 }
4032 }
4047 }
4056 else
4061 }
4064 /* This is a spare that was manually added */
4066 }
4067 }
4068 /* When a reshape changes the number of devices,
4069 * ->degraded is measured against the larger of the
4070 * pre and post numbers.
4071 */
4090 }
4096 abort:
4109 }
4111 /* Calculate the last device-address that could contain
4112 * any block from the chunk that includes the array-address 's'
4113 * and report the next address.
4114 * i.e. the address returned will be chunk-aligned and after
4115 * any data that is in the chunk containing 's'.
4116 */
4118 {
4126 }
4128 /* Calculate the first device-address that could contain
4129 * any block from the chunk that includes the array-address 's'.
4130 * This too will be the start of a chunk
4131 */
4133 {
4140 }
4144 {
4145 /* We simply copy at most one chunk (smallest of old and new)
4146 * at a time, possibly less if that exceeds RESYNC_PAGES,
4147 * or we hit a bad block or something.
4148 * This might mean we pause for normal IO in the middle of
4149 * a chunk, but that is not a problem as mddev->reshape_position
4150 * can record any location.
4151 *
4152 * If we will want to write to a location that isn't
4153 * yet recorded as 'safe' (i.e. in metadata on disk) then
4154 * we need to flush all reshape requests and update the metadata.
4155 *
4156 * When reshaping forwards (e.g. to more devices), we interpret
4157 * 'safe' as the earliest block which might not have been copied
4158 * down yet. We divide this by previous stripe size and multiply
4159 * by previous stripe length to get lowest device offset that we
4160 * cannot write to yet.
4161 * We interpret 'sector_nr' as an address that we want to write to.
4162 * From this we use last_device_address() to find where we might
4163 * write to, and first_device_address on the 'safe' position.
4164 * If this 'next' write position is after the 'safe' position,
4165 * we must update the metadata to increase the 'safe' position.
4166 *
4167 * When reshaping backwards, we round in the opposite direction
4168 * and perform the reverse test: next write position must not be
4169 * less than current safe position.
4170 *
4171 * In all this the minimum difference in data offsets
4172 * (conf->offset_diff - always positive) allows a bit of slack,
4173 * so next can be after 'safe', but not by more than offset_diff
4174 *
4175 * We need to prepare all the bios here before we start any IO
4176 * to ensure the size we choose is acceptable to all devices.
4177 * The means one for each copy for write-out and an extra one for
4178 * read-in.
4179 * We store the read-in bio in ->master_bio and the others in
4180 * ->devs[x].bio and ->devs[x].repl_bio.
4181 */
4195 /* If restarting in the middle, skip the initial sectors */
4208 }
4209 }
4211 /* We don't use sector_nr to track where we are up to
4212 * as that doesn't work well for ->reshape_backwards.
4213 * So just use ->reshape_progress.
4214 */
4216 /* 'next' is the earliest device address that we might
4217 * write to for this chunk in the new layout
4218 */
4222 /* 'safe' is the last device address that we might read from
4223 * in the old layout after a restart
4224 */
4237 /* 'next' is after the last device address that we
4238 * might write to for this chunk in the new layout
4239 */
4242 /* 'safe' is the earliest device address that we might
4243 * read from in the old layout after a restart
4244 */
4247 /* Need to update metadata if 'next' might be beyond 'safe'
4248 * as that would possibly corrupt data
4249 */
4259 }
4263 /* Need to update reshape_position in metadata */
4269 else
4279 }
4282 }
4284 read_more:
4285 /* Now schedule reads for blocks from sector_nr to last */
4298 /* Cannot read from here, so need to record bad blocks
4299 * on all the target devices.
4300 */
4301 // FIXME
4305 }
4322 /* Now find the locations in the new layout */
4338 }
4351 }
4353 /* Now add as many pages as possible to all of these bios. */
4366 /* Didn't fit, must stop */
4370 /* Remove last page from this bio */
4374 }
4376 }
4379 }
4380 bio_full:
4383 /* Now submit the read */
4393 /* Now that we have done the whole section we can
4394 * update reshape_progress
4395 */
4398 else
4402 }
4408 {
4409 /* Reshape read completed. Hopefully we have a block
4410 * to write out.
4411 * If we got a read error then we do sync 1-page reads from
4412 * elsewhere until we find the data - or give up.
4413 */
4419 /* Reshape has been aborted */
4422 }
4424 /* We definitely have the data in the pages, schedule the
4425 * writes.
4426 */
4438 }
4446 }
4448 }
4451 {
4463 /* read-ahead size must cover two whole stripes, which is
4464 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
4465 */
4472 }
4474 }
4478 {
4479 /* Use sync reads to get the blocks from somewhere else */
4505 sector_t addr;
4513 addr,
4519 failed:
4520 slot++;
4525 }
4527 /* couldn't read this block, must give up */
4531 }
4533 idx++;
4534 }
4536 }
4539 {
4554 }
4557 /* FIXME should record badblock */
4559 }
4563 }
4566 {
4572 }
4575 {
4587 }
4595 d++) {
4602 }
4603 }
4609 }
4612 {
4633 };
4636 {
4638 }
4641 {
4643 }