| blob | cd066b63bdafea61ae1175428f2c261575cfd4d1 |
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 *
43 * The data to be stored is divided into chunks using chunksize. Each device
44 * is divided into far_copies sections. In each section, chunks are laid out
45 * in a style similar to raid0, but near_copies copies of each chunk is stored
46 * (each on a different drive). The starting device for each section is offset
47 * near_copies from the starting device of the previous section. Thus there
48 * are (near_copies * far_copies) of each chunk, and each is on a different
49 * drive. near_copies and far_copies must be at least one, and their product
50 * is at most raid_disks.
51 *
52 * If far_offset is true, then the far_copies are handled a bit differently.
53 * The copies are still in different stripes, but instead of being very far
54 * apart on disk, there are adjacent stripes.
55 *
56 * The far and offset algorithms are handled slightly differently if
57 * 'use_far_sets' is true. In this case, the array's devices are grouped into
58 * sets that are (near_copies * far_copies) in size. The far copied stripes
59 * are still shifted by 'near_copies' devices, but this shifting stays confined
60 * to the set rather than the entire array. This is done to improve the number
61 * of device combinations that can fail without causing the array to fail.
62 * Example 'far' algorithm w/o 'use_far_sets' (each letter represents a chunk
63 * on a device):
64 * A B C D A B C D E
65 * ... ...
66 * D A B C E A B C D
67 * Example 'far' algorithm w/ 'use_far_sets' enabled (sets illustrated w/ []'s):
68 * [A B] [C D] [A B] [C D E]
69 * |...| |...| |...| | ... |
70 * [B A] [D C] [B A] [E C D]
71 */
73 /*
74 * Number of guaranteed r10bios in case of extreme VM load:
75 */
76 #define NR_RAID10_BIOS 256
78 /* when we get a read error on a read-only array, we redirect to another
79 * device without failing the first device, or trying to over-write to
80 * correct the read error. To keep track of bad blocks on a per-bio
81 * level, we store IO_BLOCKED in the appropriate 'bios' pointer
82 */
83 #define IO_BLOCKED ((struct bio *)1)
84 /* When we successfully write to a known bad-block, we need to remove the
85 * bad-block marking which must be done from process context. So we record
86 * the success by setting devs[n].bio to IO_MADE_GOOD
87 */
88 #define IO_MADE_GOOD ((struct bio *)2)
90 #define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
92 /* When there are this many requests queued to be written by
93 * the raid10 thread, we become 'congested' to provide back-pressure
94 * for writeback.
95 */
108 {
112 /* allocate a r10bio with room for raid_disks entries in the
113 * bios array */
115 }
118 {
120 }
122 /* Maximum size of each resync request */
123 #define RESYNC_BLOCK_SIZE (64*1024)
124 #define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
125 /* amount of memory to reserve for resync requests */
126 #define RESYNC_WINDOW (1024*1024)
127 /* maximum number of concurrent requests, memory permitting */
128 #define RESYNC_DEPTH (32*1024*1024/RESYNC_BLOCK_SIZE)
130 /*
131 * When performing a resync, we need to read and compare, so
132 * we need as many pages are there are copies.
133 * When performing a recovery, we need 2 bios, one for read,
134 * one for write (we recover only one drive per r10buf)
135 *
136 */
138 {
153 else
156 /*
157 * Allocate bios.
158 */
170 }
171 /*
172 * Allocate RESYNC_PAGES data pages and attach them
173 * where needed.
174 */
181 /* we can share bv_page's during recovery
182 * and reshape */
194 }
195 }
199 out_free_pages:
206 out_free_bio:
212 }
215 }
218 {
230 }
232 }
236 }
238 }
241 {
253 }
254 }
257 {
262 }
265 {
271 }
274 {
284 /* wake up frozen array... */
288 }
290 /*
291 * raid_end_bio_io() is called when we have finished servicing a mirrored
292 * operation and are ready to return a success/failure code to the buffer
293 * cache layer.
294 */
296 {
313 /*
314 * Wake up any possible resync thread that waits for the device
315 * to go idle.
316 */
318 }
320 }
322 /*
323 * Update disk head position estimator based on IRQ completion info.
324 */
326 {
331 }
333 /*
334 * Find the disk number which triggered given bio
335 */
338 {
348 }
349 }
359 }
362 {
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 {
460 }
461 /*
462 * this branch is our 'one mirror IO has finished' event handler:
463 */
466 /* Never record new bad blocks to replacement,
467 * just fail it.
468 */
477 }
479 /*
480 * Set R10BIO_Uptodate in our master bio, so that
481 * we will return a good error code for to the higher
482 * levels even if IO on some other mirrored buffer fails.
483 *
484 * The 'master' represents the composite IO operation to
485 * user-side. So if something waits for IO, then it will
486 * wait for the 'master' bio.
487 */
488 sector_t first_bad;
491 /*
492 * Do not set R10BIO_Uptodate if the current device is
493 * rebuilding or Faulty. This is because we cannot use
494 * such device for properly reading the data back (we could
495 * potentially use it, if the current write would have felt
496 * before rdev->recovery_offset, but for simplicity we don't
497 * check this here.
498 */
503 /* Maybe we can clear some bad blocks. */
511 else
515 }
516 }
518 /*
519 *
520 * Let's see if all mirrored write operations have finished
521 * already.
522 */
526 }
528 /*
529 * RAID10 layout manager
530 * As well as the chunksize and raid_disks count, there are two
531 * parameters: near_copies and far_copies.
532 * near_copies * far_copies must be <= raid_disks.
533 * Normally one of these will be 1.
534 * If both are 1, we get raid0.
535 * If near_copies == raid_disks, we get raid1.
536 *
537 * Chunks are laid out in raid0 style with near_copies copies of the
538 * first chunk, followed by near_copies copies of the next chunk and
539 * so on.
540 * If far_copies > 1, then after 1/far_copies of the array has been assigned
541 * as described above, we start again with a device offset of near_copies.
542 * So we effectively have another copy of the whole array further down all
543 * the drives, but with blocks on different drives.
544 * With this layout, and block is never stored twice on the one device.
545 *
546 * raid10_find_phys finds the sector offset of a given virtual sector
547 * on each device that it is on.
548 *
549 * raid10_find_virt does the reverse mapping, from a device and a
550 * sector offset to a virtual address
551 */
554 {
556 sector_t sector;
557 sector_t chunk;
558 sector_t stripe;
569 /* now calculate first sector/dev */
581 /* and calculate all the others */
588 slot++;
602 }
606 slot++;
607 }
608 dev++;
612 }
613 }
614 }
617 {
629 }
632 {
634 /* Never use conf->prev as this is only called during resync
635 * or recovery, so reshape isn't happening
636 */
650 }
651 }
666 else
668 }
670 }
674 }
676 /**
677 * raid10_mergeable_bvec -- tell bio layer if a two requests can be merged
678 * @q: request queue
679 * @bvm: properties of new bio
680 * @biovec: the request that could be merged to it.
681 *
682 * Return amount of bytes we can accept at this offset
683 * This requires checking for end-of-chunk if near_copies != raid_disks,
684 * and for subordinate merge_bvec_fns if merge_check_needed.
685 */
689 {
708 /* bio_add cannot handle a negative return */
723 /* Cannot give any guidance during reshape */
727 }
744 }
745 }
756 }
757 }
758 }
760 }
762 }
764 /*
765 * This routine returns the disk from which the requested read should
766 * be done. There is a per-array 'next expected sequential IO' sector
767 * number - if this matches on the next IO then we use the last disk.
768 * There is also a per-disk 'last know head position' sector that is
769 * maintained from IRQ contexts, both the normal and the resync IO
770 * completion handlers update this position correctly. If there is no
771 * perfect sequential match then we pick the disk whose head is closest.
772 *
773 * If there are 2 mirrors in the same 2 devices, performance degrades
774 * because position is mirror, not device based.
775 *
776 * The rdev for the device selected will have nr_pending incremented.
777 */
779 /*
780 * FIXME: possibly should rethink readbalancing and do it differently
781 * depending on near_copies / far_copies geometry.
782 */
786 {
799 retry:
806 /*
807 * Check if we can balance. We can balance on the whole
808 * device if no resync is going on (recovery is ok), or below
809 * the resync window. We take the first readable disk when
810 * above the resync window.
811 */
817 sector_t first_bad;
819 sector_t dev_sector;
841 /* Already have a better slot */
844 /* Cannot read here. If this is the
845 * 'primary' device, then we must not read
846 * beyond 'bad_sectors' from another device.
847 */
854 sector_t good_sectors =
860 }
862 /* Must read from here */
864 }
872 /* This optimisation is debatable, and completely destroys
873 * sequential read speed for 'far copies' arrays. So only
874 * keep it for 'near' arrays, and review those later.
875 */
879 /* for far > 1 always use the lowest address */
882 else
889 }
890 }
894 }
899 /* Cannot risk returning a device that failed
900 * before we inc'ed nr_pending
901 */
904 }
912 }
915 {
927 i++) {
933 }
934 }
937 }
941 {
946 }
949 {
950 /* Any writes that have been queued but are awaiting
951 * bitmap updates get flushed here.
952 */
960 /* flush any pending bitmap writes to disk
961 * before proceeding w/ I/O */
970 /* Just ignore it */
972 else
975 }
978 }
980 /* Barriers....
981 * Sometimes we need to suspend IO while we do something else,
982 * either some resync/recovery, or reconfigure the array.
983 * To do this we raise a 'barrier'.
984 * The 'barrier' is a counter that can be raised multiple times
985 * to count how many activities are happening which preclude
986 * normal IO.
987 * We can only raise the barrier if there is no pending IO.
988 * i.e. if nr_pending == 0.
989 * We choose only to raise the barrier if no-one is waiting for the
990 * barrier to go down. This means that as soon as an IO request
991 * is ready, no other operations which require a barrier will start
992 * until the IO request has had a chance.
993 *
994 * So: regular IO calls 'wait_barrier'. When that returns there
995 * is no backgroup IO happening, It must arrange to call
996 * allow_barrier when it has finished its IO.
997 * backgroup IO calls must call raise_barrier. Once that returns
998 * there is no normal IO happeing. It must arrange to call
999 * lower_barrier when the particular background IO completes.
1000 */
1003 {
1007 /* Wait until no block IO is waiting (unless 'force') */
1011 /* block any new IO from starting */
1014 /* Now wait for all pending IO to complete */
1020 }
1023 {
1029 }
1032 {
1036 /* Wait for the barrier to drop.
1037 * However if there are already pending
1038 * requests (preventing the barrier from
1039 * rising completely), and the
1040 * pre-process bio queue isn't empty,
1041 * then don't wait, as we need to empty
1042 * that queue to get the nr_pending
1043 * count down.
1044 */
1052 }
1055 }
1058 {
1064 }
1067 {
1068 /* stop syncio and normal IO and wait for everything to
1069 * go quiet.
1070 * We increment barrier and nr_waiting, and then
1071 * wait until nr_pending match nr_queued+extra
1072 * This is called in the context of one normal IO request
1073 * that has failed. Thus any sync request that might be pending
1074 * will be blocked by nr_pending, and we need to wait for
1075 * pending IO requests to complete or be queued for re-try.
1076 * Thus the number queued (nr_queued) plus this request (extra)
1077 * must match the number of pending IOs (nr_pending) before
1078 * we continue.
1079 */
1089 }
1092 {
1093 /* reverse the effect of the freeze */
1099 }
1103 {
1107 else
1109 }
1115 };
1118 {
1120 cb);
1134 }
1136 /* we aren't scheduling, so we can do the write-out directly. */
1146 /* Just ignore it */
1148 else
1151 }
1153 }
1156 {
1180 }
1182 /* If this request crosses a chunk boundary, we need to
1183 * split it. This will only happen for 1 PAGE (or less) requests.
1184 */
1186 > chunk_sects
1190 /* Sanity check -- queue functions should prevent this happening */
1193 /* This is a one page bio that upper layers
1194 * refuse to split for us, so we need to split it.
1195 */
1199 /* Each of these 'make_request' calls will call 'wait_barrier'.
1200 * If the first succeeds but the second blocks due to the resync
1201 * thread raising the barrier, we will deadlock because the
1202 * IO to the underlying device will be queued in generic_make_request
1203 * and will never complete, so will never reduce nr_pending.
1204 * So increment nr_waiting here so no new raise_barriers will
1205 * succeed, and so the second wait_barrier cannot block.
1206 */
1221 bad_map:
1228 }
1232 /*
1233 * Register the new request and wait if the reconstruction
1234 * thread has put up a bar for new requests.
1235 * Continue immediately if no resync is active currently.
1236 */
1243 /* IO spans the reshape position. Need to wait for
1244 * reshape to pass
1245 */
1251 }
1259 /* Need to update reshape_position in metadata */
1268 }
1279 /* We might need to issue multiple reads to different
1280 * devices if there are bad blocks around, so we keep
1281 * track of the number of reads in bio->bi_phys_segments.
1282 * If this is 0, there is only one r10_bio and no locking
1283 * will be needed when the request completes. If it is
1284 * non-zero, then it is the number of not-completed requests.
1285 */
1290 /*
1291 * read balancing logic:
1292 */
1296 read_again:
1301 }
1306 max_sectors);
1319 /* Could not read all from this device, so we will
1320 * need another r10_bio.
1321 */
1328 else
1331 /* Cannot call generic_make_request directly
1332 * as that will be queued in __generic_make_request
1333 * and subsequent mempool_alloc might block
1334 * waiting for it. so hand bio over to raid10d.
1335 */
1349 }
1351 /*
1352 * WRITE:
1353 */
1358 }
1359 /* first select target devices under rcu_lock and
1360 * inc refcount on their rdev. Record them by setting
1361 * bios[x] to bio
1362 * If there are known/acknowledged bad blocks on any device
1363 * on which we have seen a write error, we want to avoid
1364 * writing to those blocks. This potentially requires several
1365 * writes to write around the bad blocks. Each set of writes
1366 * gets its own r10_bio with a set of bios attached. The number
1367 * of r10_bios is recored in bio->bi_phys_segments just as with
1368 * the read case.
1369 */
1373 retry_write:
1389 }
1394 }
1408 }
1410 sector_t first_bad;
1416 max_sectors,
1419 /* Mustn't write here until the bad block
1420 * is acknowledged
1421 */
1426 }
1428 /* Cannot write here at all */
1431 /* Mustn't write more than bad_sectors
1432 * to other devices yet
1433 */
1435 /* We don't set R10BIO_Degraded as that
1436 * only applies if the disk is missing,
1437 * so it might be re-added, and we want to
1438 * know to recover this chunk.
1439 * In this case the device is here, and the
1440 * fact that this chunk is not in-sync is
1441 * recorded in the bad block log.
1442 */
1444 }
1449 }
1450 }
1454 }
1458 }
1459 }
1463 /* Have to wait for this device to get unblocked, then retry */
1471 }
1477 /* Race with remove_disk */
1480 }
1482 }
1483 }
1488 }
1491 /* We are splitting this into multiple parts, so
1492 * we need to prepare for allocating another r10_bio.
1493 */
1498 else
1501 }
1514 max_sectors);
1519 rdev));
1532 cb);
1533 else
1542 }
1546 }
1551 /* Replacement just got moved to main 'rdev' */
1554 }
1557 max_sectors);
1576 }
1577 }
1579 /* Don't remove the bias on 'remaining' (one_write_done) until
1580 * after checking if we need to go around again.
1581 */
1585 /* We need another r10_bio. It has already been counted
1586 * in bio->bi_phys_segments.
1587 */
1597 }
1600 /* In case raid10d snuck in to freeze_array */
1602 }
1605 {
1616 else
1618 }
1626 }
1628 /* check if there are enough drives for
1629 * every block to appear on atleast one.
1630 * Don't consider the device numbered 'ignore'
1631 * as we might be about to remove it.
1632 */
1634 {
1644 }
1656 cnt++;
1658 }
1664 out:
1667 }
1670 {
1671 /* when calling 'enough', both 'prev' and 'geo' must
1672 * be stable.
1673 * This is ensured if ->reconfig_mutex or ->device_lock
1674 * is held.
1675 */
1678 }
1681 {
1686 /*
1687 * If it is not operational, then we have already marked it as dead
1688 * else if it is the last working disks, ignore the error, let the
1689 * next level up know.
1690 * else mark the drive as failed
1691 */
1695 /*
1696 * Don't fail the drive, just return an IO error.
1697 */
1700 }
1703 /*
1704 * if recovery is running, make sure it aborts.
1705 */
1707 }
1717 }
1720 {
1728 }
1740 }
1741 }
1744 {
1750 }
1753 {
1760 /*
1761 * Find all non-in_sync disks within the RAID10 configuration
1762 * and mark them in_sync
1763 */
1770 /* Replacement has just become active */
1773 count++;
1775 /* Replaced device not technically faulty,
1776 * but we need to be sure it gets removed
1777 * and never re-added.
1778 */
1782 }
1787 count++;
1789 }
1790 }
1797 }
1801 {
1810 /* only hot-add to in-sync arrays, as recovery is
1811 * very different from resync
1812 */
1823 }
1828 else
1848 }
1862 }
1864 /* Some requests might not have seen this new
1865 * merge_bvec_fn. We must wait for them to complete
1866 * before merging the device fully.
1867 * First we make sure any code which has tested
1868 * our function has submitted the request, then
1869 * we wait for all outstanding requests to complete.
1870 */
1875 }
1882 }
1885 {
1897 else
1904 }
1905 /* Only remove faulty devices if recovery
1906 * is not possible.
1907 */
1915 }
1919 /* lost the race, try later */
1924 /* We must have just cleared 'rdev' */
1928 * but will never see neither -- if they are careful.
1929 */
1933 /* We might have just remove the Replacement as faulty
1934 * Clear the flag just in case
1935 */
1940 abort:
1944 }
1948 {
1954 /* this is a reshape read */
1961 else
1962 /* The write handler will notice the lack of
1963 * R10BIO_Uptodate and record any errors etc
1964 */
1968 /* for reconstruct, we always reschedule after a read.
1969 * for resync, only after all reads
1970 */
1974 /* we have read all the blocks,
1975 * do the comparison in process context in raid10d
1976 */
1978 }
1979 }
1982 {
1987 /* the primary of several recovery bios */
1992 else
2001 else
2004 }
2005 }
2006 }
2009 {
2015 sector_t first_bad;
2024 else
2036 }
2046 }
2048 /*
2049 * Note: sync and recover and handled very differently for raid10
2050 * This code is for resync.
2051 * For resync, we read through virtual addresses and read all blocks.
2052 * If there is any error, we schedule a write. The lowest numbered
2053 * drive is authoritative.
2054 * However requests come for physical address, so we need to map.
2055 * For every physical address there are raid_disks/copies virtual addresses,
2056 * which is always are least one, but is not necessarly an integer.
2057 * This means that a physical address can span multiple chunks, so we may
2058 * have to submit multiple io requests for a single sync request.
2059 */
2060 /*
2061 * We check if all blocks are in-sync and only write to blocks that
2062 * aren't in sync
2063 */
2065 {
2073 /* find the first device with a block */
2085 /* now find blocks with errors */
2096 /* We know that the bi_io_vec layout is the same for
2097 * both 'first' and 'i', so we just compare them.
2098 * All vec entries are PAGE_SIZE;
2099 */
2109 /* Don't fix anything. */
2111 }
2112 /* Ok, we need to write this bio, either to correct an
2113 * inconsistency or to correct an unreadable block.
2114 * First we need to fixup bv_offset, bv_len and
2115 * bi_vecs, as the read request might have corrupted these
2116 */
2131 PAGE_SIZE);
2132 }
2143 }
2145 /* Now write out to any replacement devices
2146 * that are active
2147 */
2159 PAGE_SIZE);
2165 }
2167 done:
2171 }
2172 }
2174 /*
2175 * Now for the recovery code.
2176 * Recovery happens across physical sectors.
2177 * We recover all non-is_sync drives by finding the virtual address of
2178 * each, and then choose a working drive that also has that virt address.
2179 * There is a separate r10_bio for each non-in_sync drive.
2180 * Only the first two slots are in use. The first for reading,
2181 * The second for writing.
2182 *
2183 */
2185 {
2186 /* We got a read error during recovery.
2187 * We repeat the read in smaller page-sized sections.
2188 * If a read succeeds, write it to the new device or record
2189 * a bad block if we cannot.
2190 * If a read fails, record a bad block on both old and
2191 * new devices.
2192 */
2205 sector_t addr;
2214 addr,
2222 addr,
2232 }
2233 }
2235 /* We don't worry if we cannot set a bad block -
2236 * it really is bad so there is no loss in not
2237 * recording it yet
2238 */
2242 /* need bad block on destination too */
2247 /* just abort the recovery */
2249 "md/raid10:%s: recovery aborted"
2258 }
2259 }
2260 }
2264 idx++;
2265 }
2266 }
2269 {
2278 }
2280 /*
2281 * share the pages with the first bio
2282 * and submit the write request
2283 */
2291 }
2297 }
2298 }
2301 /*
2302 * Used by fix_read_error() to decay the per rdev read_errors.
2303 * We halve the read error count for every hour that has elapsed
2304 * since the last recorded read error.
2305 *
2306 */
2308 {
2317 /* first time we've seen a read error */
2320 }
2327 /*
2328 * if hours_since_last is > the number of bits in read_errors
2329 * just set read errors to 0. We do this to avoid
2330 * overflowing the shift of read_errors by hours_since_last.
2331 */
2334 else
2336 }
2340 {
2341 sector_t first_bad;
2348 /* success */
2355 }
2356 /* need to record an error - either for the block or the device */
2360 }
2362 /*
2363 * This is a kernel thread which:
2364 *
2365 * 1. Retries failed read operations on working mirrors.
2366 * 2. Updates the raid superblock when problems encounter.
2367 * 3. Performs writes following reads for array synchronising.
2368 */
2371 {
2378 /* still own a reference to this rdev, so it cannot
2379 * have been cleared recently.
2380 */
2384 /* drive has already been failed, just ignore any
2385 more fix_read_error() attempts */
2395 "md/raid10:%s: %s: Raid device exceeded "
2405 }
2418 sector_t first_bad;
2432 sect,
2439 }
2440 sl++;
2447 /* Cannot read from anywhere, just mark the block
2448 * as bad on the first device to discourage future
2449 * reads.
2450 */
2455 rdev,
2462 }
2464 }
2467 /* write it back and re-read */
2474 sl--;
2486 sect,
2489 /* Well, this device is dead */
2491 "md/raid10:%s: read correction "
2492 "write failed"
2496 sect +
2498 rdev)),
2504 }
2507 }
2514 sl--;
2525 sect,
2527 READ)) {
2529 /* Well, this device is dead */
2531 "md/raid10:%s: unable to read back "
2532 "corrected sectors"
2536 sect +
2546 "md/raid10:%s: read error corrected"
2550 sect +
2554 }
2558 }
2563 }
2564 }
2567 {
2572 /* bio has the data to be written to slot 'i' where
2573 * we just recently had a write error.
2574 * We repeatedly clone the bio and trim down to one block,
2575 * then try the write. Where the write fails we record
2576 * a bad block.
2577 * It is conceivable that the bio doesn't exactly align with
2578 * blocks. We must handle this.
2579 *
2580 * We currently own a reference to the rdev.
2581 */
2584 sector_t sector;
2602 /* Write at 'sector' for 'sectors' */
2610 /* Failure! */
2619 }
2621 }
2624 {
2633 /* we got a read error. Maybe the drive is bad. Maybe just
2634 * the block and we can fix it.
2635 * We freeze all other IO, and try reading the block from
2636 * other devices. When we find one, we re-write
2637 * and check it that fixes the read error.
2638 * This is all done synchronously while the array is
2639 * frozen.
2640 */
2655 read_more:
2664 }
2669 KERN_ERR
2670 "md/raid10:%s: %s: redirecting "
2679 max_sectors);
2689 /* Drat - have to split this up more */
2698 else
2704 GFP_NOIO);
2717 }
2720 {
2721 /* Some sort of write request has finished and it
2722 * succeeded in writing where we thought there was a
2723 * bad block. So forget the bad block.
2724 * Or possibly if failed and we need to record
2725 * a bad block.
2726 */
2740 rdev,
2745 rdev,
2749 }
2756 rdev,
2761 rdev,
2765 }
2766 }
2775 rdev,
2785 }
2787 }
2792 rdev,
2796 }
2797 }
2802 }
2803 }
2806 {
2825 }
2845 /* just a partial read to be scheduled from a
2846 * separate context
2847 */
2850 }
2855 }
2857 }
2861 {
2876 }
2878 /*
2879 * perform a "sync" on one "block"
2880 *
2881 * We need to make sure that no normal I/O request - particularly write
2882 * requests - conflict with active sync requests.
2883 *
2884 * This is achieved by tracking pending requests and a 'barrier' concept
2885 * that can be installed to exclude normal IO requests.
2886 *
2887 * Resync and recovery are handled very differently.
2888 * We differentiate by looking at MD_RECOVERY_SYNC in mddev->recovery.
2889 *
2890 * For resync, we iterate over virtual addresses, read all copies,
2891 * and update if there are differences. If only one copy is live,
2892 * skip it.
2893 * For recovery, we iterate over physical addresses, read a good
2894 * value for each non-in_sync drive, and over-write.
2895 *
2896 * So, for recovery we may have several outstanding complex requests for a
2897 * given address, one for each out-of-sync device. We model this by allocating
2898 * a number of r10_bio structures, one for each out-of-sync device.
2899 * As we setup these structures, we collect all bio's together into a list
2900 * which we then process collectively to add pages, and then process again
2901 * to pass to generic_make_request.
2902 *
2903 * The r10_bio structures are linked using a borrowed master_bio pointer.
2904 * This link is counted in ->remaining. When the r10_bio that points to NULL
2905 * has its remaining count decremented to 0, the whole complex operation
2906 * is complete.
2907 *
2908 */
2912 {
2919 sector_t sync_blocks;
2928 /*
2929 * Allow skipping a full rebuild for incremental assembly
2930 * of a clean array, like RAID1 does.
2931 */
2941 }
2943 skipped:
2949 /* If we aborted, we need to abort the
2950 * sync on the 'current' bitmap chucks (there can
2951 * be several when recovering multiple devices).
2952 * as we may have started syncing it but not finished.
2953 * We can find the current address in
2954 * mddev->curr_resync, but for recovery,
2955 * we need to convert that to several
2956 * virtual addresses.
2957 */
2961 }
2968 sector_t sect =
2972 }
2974 /* completed sync */
2978 /* Completed a full sync so the replacements
2979 * are now fully recovered.
2980 */
2984 ->recovery_offset
2986 }
2988 }
2993 }
2999 /* if there has been nothing to do on any drive,
3000 * then there is nothing to do at all..
3001 */
3004 }
3009 /* make sure whole request will fit in a chunk - if chunks
3010 * are meaningful
3011 */
3015 /*
3016 * If there is non-resync activity waiting for us then
3017 * put in a delay to throttle resync.
3018 */
3022 /* Again, very different code for resync and recovery.
3023 * Both must result in an r10bio with a list of bios that
3024 * have bi_end_io, bi_sector, bi_bdev set,
3025 * and bi_private set to the r10bio.
3026 * For recovery, we may actually create several r10bios
3027 * with 2 bios in each, that correspond to the bios in the main one.
3028 * In this case, the subordinate r10bios link back through a
3029 * borrowed master_bio pointer, and the counter in the master
3030 * includes a ref from each subordinate.
3031 */
3032 /* First, we decide what to do and set ->bi_end_io
3033 * To end_sync_read if we want to read, and
3034 * end_sync_write if we will want to write.
3035 */
3039 /* recovery... the complicated one */
3046 sector_t sect;
3053 &&
3060 /* want to reconstruct this device */
3064 /* last stripe is not complete - don't
3065 * try to recover this sector.
3066 */
3068 }
3069 /* Unless we are doing a full sync, or a replacement
3070 * we only need to recover the block if it is set in
3071 * the bitmap
3072 */
3080 /* yep, skip the sync_blocks here, but don't assume
3081 * that there will never be anything to do here
3082 */
3085 }
3100 /* Need to check if the array will still be
3101 * degraded
3102 */
3108 }
3124 /* This is where we read from */
3134 bad_sectors -= (sector
3139 }
3140 }
3152 /* and we write to 'i' (if not in_sync) */
3180 /* and maybe write to replacement */
3185 /* Note: if rdev != NULL, then bio
3186 * cannot be NULL as r10buf_pool_alloc will
3187 * have allocated it.
3188 * So the second test here is pointless.
3189 * But it keeps semantic-checkers happy, and
3190 * this comment keeps human reviewers
3191 * happy.
3192 */
3206 }
3208 /* Cannot recover, so abort the recovery or
3209 * record a bad block */
3215 /* problem is that there are bad blocks
3216 * on other device(s)
3217 */
3235 }
3242 mirror->recovery_disabled
3244 }
3246 }
3247 }
3254 }
3256 }
3258 /* resync. Schedule a read for every block at this virt offset */
3267 /* We can skip this block */
3270 }
3311 }
3312 }
3323 count++;
3330 /* Need to set up for writing to the replacement */
3345 count++;
3346 }
3353 mddev);
3358 mddev);
3359 }
3363 }
3364 }
3382 /* stop here */
3387 /* remove last page from this bio */
3391 }
3393 }
3397 bio_full:
3411 }
3412 }
3415 /* pretend they weren't skipped, it makes
3416 * no important difference in this case
3417 */
3421 giveup:
3422 /* There is nowhere to write, so all non-sync
3423 * drives must be failed or in resync, all drives
3424 * have a bad block, so try the next chunk...
3425 */
3430 chunks_skipped ++;
3433 }
3435 static sector_t
3437 {
3438 sector_t size;
3453 }
3456 {
3457 /* Calculate the number of sectors-per-device that will
3458 * actually be used, and set conf->dev_sectors and
3459 * conf->stride
3460 */
3466 /* 'size' is now the number of chunks in the array */
3467 /* calculate "used chunks per device" */
3470 /* We need to round up when dividing by raid_disks to
3471 * get the stride size.
3472 */
3482 }
3483 }
3487 {
3503 * updated yet. */
3508 }
3525 }
3528 {
3541 }
3547 }
3554 /* FIXME calc properly */
3557 GFP_KERNEL);
3580 }
3584 else
3585 /* far_copies must be 1 */
3587 }
3601 out:
3611 }
3613 }
3616 {
3621 sector_t size;
3631 }
3647 else
3650 }
3672 }
3692 }
3698 else
3701 }
3702 /* need to check that every block has at least one working mirror */
3707 }
3710 /* must ensure that shape change is supported */
3717 }
3723 i++) {
3728 /* The replacement is all we have - use it */
3732 }
3740 }
3742 }
3752 /*
3753 * Ok, everything is just fine now
3754 */
3766 /* Calculate max read-ahead size.
3767 * We need to readahead at least twice a whole stripe....
3768 * maybe...
3769 */
3774 }
3789 /* This cannot work */
3792 }
3802 }
3806 out_free_conf:
3814 out:
3816 }
3819 {
3827 /* the unplug fn references 'conf'*/
3837 }
3840 {
3850 }
3851 }
3854 {
3855 /* Resize of 'far' arrays is not supported.
3856 * For 'near' and 'offset' arrays we can set the
3857 * number of sectors used to be an appropriate multiple
3858 * of the chunk size.
3859 * For 'offset', this is far_copies*chunksize.
3860 * For 'near' the multiplier is the LCM of
3861 * near_copies and raid_disks.
3862 * So if far_copies > 1 && !far_offset, fail.
3863 * Else find LCM(raid_disks, near_copy)*far_copies and
3864 * multiply by chunk_size. Then round to this number.
3865 * This is mostly done by raid10_size()
3866 */
3885 }
3893 }
3898 }
3901 {
3909 }
3911 /* Set new parameters */
3913 /* new layout: far_copies = 1, near_copies = 2 */
3918 /* make sure it will be not marked as dirty */
3927 }
3930 }
3933 {
3936 /* raid10 can take over:
3937 * raid0 - providing it has only two drives
3938 */
3940 /* for raid0 takeover only one zone is supported */
3947 }
3949 }
3951 }
3954 {
3955 /* Called when there is a request to change
3956 * - layout (to ->new_layout)
3957 * - chunk size (to ->new_chunk_sectors)
3958 * - raid_disks (by delta_disks)
3959 * or when trying to restart a reshape that was ongoing.
3960 *
3961 * We need to validate the request and possibly allocate
3962 * space if that might be an issue later.
3963 *
3964 * Currently we reject any reshape of a 'far' mode array,
3965 * allow chunk size to change if new is generally acceptable,
3966 * allow raid_disks to increase, and allow
3967 * a switch between 'near' mode and 'offset' mode.
3968 */
3976 /* mustn't change number of copies */
3979 /* Cannot switch to 'far' mode */
3983 /* not factor of array size */
3992 /* allocate new 'mirrors' list */
3997 GFP_KERNEL);
4000 }
4002 }
4004 /*
4005 * Need to check if array has failed when deciding whether to:
4006 * - start an array
4007 * - remove non-faulty devices
4008 * - add a spare
4009 * - allow a reshape
4010 * This determination is simple when no reshape is happening.
4011 * However if there is a reshape, we need to carefully check
4012 * both the before and after sections.
4013 * This is because some failed devices may only affect one
4014 * of the two sections, and some non-in_sync devices may
4015 * be insync in the section most affected by failed devices.
4016 */
4018 {
4024 /* 'prev' section first */
4028 degraded++;
4030 /* When we can reduce the number of devices in
4031 * an array, this might not contribute to
4032 * 'degraded'. It does now.
4033 */
4034 degraded++;
4035 }
4044 degraded2++;
4046 /* If reshape is increasing the number of devices,
4047 * this section has already been recovered, so
4048 * it doesn't contribute to degraded.
4049 * else it does.
4050 */
4052 degraded2++;
4053 }
4054 }
4059 }
4062 {
4063 /* A 'reshape' has been requested. This commits
4064 * the various 'new' fields and sets MD_RECOVER_RESHAPE
4065 * This also checks if there are enough spares and adds them
4066 * to the array.
4067 * We currently require enough spares to make the final
4068 * array non-degraded. We also require that the difference
4069 * between old and new data_offset - on each device - is
4070 * enough that we never risk over-writing.
4071 */
4096 spares++;
4106 }
4107 }
4125 }
4135 }
4149 }
4158 else
4163 }
4166 /* This is a spare that was manually added */
4168 }
4169 }
4170 /* When a reshape changes the number of devices,
4171 * ->degraded is measured against the larger of the
4172 * pre and post numbers.
4173 */
4191 }
4197 abort:
4209 }
4211 /* Calculate the last device-address that could contain
4212 * any block from the chunk that includes the array-address 's'
4213 * and report the next address.
4214 * i.e. the address returned will be chunk-aligned and after
4215 * any data that is in the chunk containing 's'.
4216 */
4218 {
4226 }
4228 /* Calculate the first device-address that could contain
4229 * any block from the chunk that includes the array-address 's'.
4230 * This too will be the start of a chunk
4231 */
4233 {
4240 }
4244 {
4245 /* We simply copy at most one chunk (smallest of old and new)
4246 * at a time, possibly less if that exceeds RESYNC_PAGES,
4247 * or we hit a bad block or something.
4248 * This might mean we pause for normal IO in the middle of
4249 * a chunk, but that is not a problem was mddev->reshape_position
4250 * can record any location.
4251 *
4252 * If we will want to write to a location that isn't
4253 * yet recorded as 'safe' (i.e. in metadata on disk) then
4254 * we need to flush all reshape requests and update the metadata.
4255 *
4256 * When reshaping forwards (e.g. to more devices), we interpret
4257 * 'safe' as the earliest block which might not have been copied
4258 * down yet. We divide this by previous stripe size and multiply
4259 * by previous stripe length to get lowest device offset that we
4260 * cannot write to yet.
4261 * We interpret 'sector_nr' as an address that we want to write to.
4262 * From this we use last_device_address() to find where we might
4263 * write to, and first_device_address on the 'safe' position.
4264 * If this 'next' write position is after the 'safe' position,
4265 * we must update the metadata to increase the 'safe' position.
4266 *
4267 * When reshaping backwards, we round in the opposite direction
4268 * and perform the reverse test: next write position must not be
4269 * less than current safe position.
4270 *
4271 * In all this the minimum difference in data offsets
4272 * (conf->offset_diff - always positive) allows a bit of slack,
4273 * so next can be after 'safe', but not by more than offset_disk
4274 *
4275 * We need to prepare all the bios here before we start any IO
4276 * to ensure the size we choose is acceptable to all devices.
4277 * The means one for each copy for write-out and an extra one for
4278 * read-in.
4279 * We store the read-in bio in ->master_bio and the others in
4280 * ->devs[x].bio and ->devs[x].repl_bio.
4281 */
4295 /* If restarting in the middle, skip the initial sectors */
4308 }
4309 }
4311 /* We don't use sector_nr to track where we are up to
4312 * as that doesn't work well for ->reshape_backwards.
4313 * So just use ->reshape_progress.
4314 */
4316 /* 'next' is the earliest device address that we might
4317 * write to for this chunk in the new layout
4318 */
4322 /* 'safe' is the last device address that we might read from
4323 * in the old layout after a restart
4324 */
4337 /* 'next' is after the last device address that we
4338 * might write to for this chunk in the new layout
4339 */
4342 /* 'safe' is the earliest device address that we might
4343 * read from in the old layout after a restart
4344 */
4347 /* Need to update metadata if 'next' might be beyond 'safe'
4348 * as that would possibly corrupt data
4349 */
4359 }
4363 /* Need to update reshape_position in metadata */
4369 else
4378 }
4380 read_more:
4381 /* Now schedule reads for blocks from sector_nr to last */
4393 /* Cannot read from here, so need to record bad blocks
4394 * on all the target devices.
4395 */
4396 // FIXME
4399 }
4416 /* Now find the locations in the new layout */
4432 }
4444 }
4446 /* Now add as many pages as possible to all of these bios. */
4459 /* Didn't fit, must stop */
4463 /* Remove last page from this bio */
4467 }
4469 }
4472 }
4473 bio_full:
4476 /* Now submit the read */
4486 /* Now that we have done the whole section we can
4487 * update reshape_progress
4488 */
4491 else
4495 }
4501 {
4502 /* Reshape read completed. Hopefully we have a block
4503 * to write out.
4504 * If we got a read error then we do sync 1-page reads from
4505 * elsewhere until we find the data - or give up.
4506 */
4512 /* Reshape has been aborted */
4515 }
4517 /* We definitely have the data in the pages, schedule the
4518 * writes.
4519 */
4531 }
4539 }
4541 }
4544 {
4555 /* read-ahead size must cover two whole stripes, which is
4556 * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
4557 */
4564 }
4566 }
4571 {
4572 /* Use sync reads to get the blocks from somewhere else */
4598 sector_t addr;
4606 addr,
4612 failed:
4613 slot++;
4618 }
4620 /* couldn't read this block, must give up */
4624 }
4626 idx++;
4627 }
4629 }
4632 {
4648 }
4651 /* FIXME should record badblock */
4653 }
4657 }
4660 {
4666 }
4669 {
4681 }
4689 d++) {
4696 }
4697 }
4703 }
4706 {
4726 };
4729 {
4731 }
4734 {
4736 }