NeilBrown 8e0e99ba64 md/raid5: disable 'DISCARD' by default due to safety concerns. ... It has come to my attention (thanks Martin) that 'discard_zeroes_data' is only a hint. Some devices in some cases don't do what it says on the label. The use of DISCARD in RAID5 depends on reads from discarded regions being predictably zero. If a write to a previously discarded region performs a read-modify-write cycle it assumes that the parity block was consistent with the data blocks. If all were zero, this would be the case. If some are and some aren't this would not be the case. This could lead to data corruption after a device failure when data needs to be reconstructed from the parity. As we cannot trust 'discard_zeroes_data', ignore it by default and so disallow DISCARD on all raid4/5/6 arrays. As many devices are trustworthy, and as there are benefits to using DISCARD, add a module parameter to over-ride this caution and cause DISCARD to work if discard_zeroes_data is set. If a site want to enable DISCARD on some arrays but not on others they should select DISCARD support at the filesystem level, and set the raid456 module parameter. raid456.devices_handle_discard_safely=Y As this is a data-safety issue, I believe this patch is suitable for -stable. DISCARD support for RAID456 was added in 3.7 Cc: Shaohua Li <shli@kernel.org> Cc: "Martin K. Petersen" <martin.petersen@oracle.com> Cc: Mike Snitzer <snitzer@redhat.com> Cc: Heinz Mauelshagen <heinzm@redhat.com> Cc: stable@vger.kernel.org (3.7+) Acked-by: Martin K. Petersen <martin.petersen@oracle.com> Acked-by: Mike Snitzer <snitzer@redhat.com> Fixes: 620125f2bf Signed-off-by: NeilBrown <neilb@suse.de>		2014-10-02 13:45:00 +10:00
..
bcache	bcache: Drop unneeded blk_sync_queue() calls	2014-08-04 15:23:04 -07:00
persistent-data	dm transaction manager: fix corruption due to non-atomic transaction commit	2014-03-27 16:56:23 -04:00
bitmap.c	md/bitmap: remove confusing code from filemap_get_page.	2014-05-29 16:59:47 +10:00
bitmap.h	kernfs: s/sysfs_dirent/kernfs_node/ and rename its friends accordingly	2013-12-11 15:28:36 -08:00
dm-bio-prison.c	dm bio prison: implement per bucket locking in the dm_bio_prison hash table	2014-06-11 16:48:54 -04:00
dm-bio-prison.h	dm thin: return ENOSPC instead of EIO when error_if_no_space enabled	2014-06-03 13:44:08 -04:00
dm-bio-record.h	dm: Refactor for new bio cloning/splitting	2013-11-23 22:33:55 -08:00
dm-bufio.c	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-08-04 16:23:30 -07:00
dm-bufio.h	dm snapshot: use dm-bufio prefetch	2014-01-14 23:23:03 -05:00
dm-builtin.c	dm sysfs: fix a module unload race	2014-01-14 23:23:04 -05:00
dm-cache-block-types.h	dm cache: remove remainder of distinct discard block size	2014-03-27 16:56:23 -04:00
dm-cache-metadata.c	dm cache metadata: use dm-space-map-metadata.h defined size limits	2014-08-01 12:30:33 -04:00
dm-cache-metadata.h	dm cache metadata: use dm-space-map-metadata.h defined size limits	2014-08-01 12:30:33 -04:00
dm-cache-policy-cleaner.c	dm cache: policy change version from string to integer set	2013-03-20 17:21:27 +00:00
dm-cache-policy-internal.h	dm cache: add remove_cblock method to policy interface	2013-11-11 11:37:50 -05:00
dm-cache-policy-mq.c	dm cache mq: fix memory allocation failure for large cache devices	2014-02-28 12:18:29 -05:00
dm-cache-policy.c	dm cache: add policy name to status output	2014-01-16 13:44:11 -05:00
dm-cache-policy.h	dm cache: add policy name to status output	2014-01-16 13:44:11 -05:00
dm-cache-target.c	dm cache: fix race causing dirty blocks to be marked as clean	2014-09-10 11:20:47 -04:00
dm-crypt.c	dm crypt: fix access beyond the end of allocated space	2014-08-28 14:24:09 -04:00
dm-delay.c	Merge branch 'for-3.14/core' of git://git.kernel.dk/linux-block	2014-01-30 11:19:05 -08:00
dm-era-target.c	dm era: check for a non-NULL metadata object before closing it	2014-06-03 13:44:08 -04:00
dm-exception-store.c	dm: replace simple_strtoul	2012-07-27 15:07:59 +01:00
dm-exception-store.h
dm-flakey.c	block: Abstract out bvec iterator	2013-11-23 22:33:47 -08:00
dm-io.c	dm io: simplify dec_count and sync_io	2014-08-01 12:30:30 -04:00
dm-ioctl.c	dm: allow remove to be deferred	2013-11-09 18:20:22 -05:00
dm-kcopyd.c	dm: stop using WQ_NON_REENTRANT	2013-08-23 09:02:13 -04:00
dm-linear.c	block: Abstract out bvec iterator	2013-11-23 22:33:47 -08:00
dm-log-userspace-base.c	dm log userspace: allow mark requests to piggyback on flush requests	2014-01-21 23:46:27 -05:00
dm-log-userspace-transfer.c	connector: add portid to unicast in addition to broadcasting	2014-02-07 15:40:17 -08:00
dm-log-userspace-transfer.h
dm-log.c	dm: use memweight()	2012-07-30 17:25:16 -07:00
dm-mpath.c	dm mpath: eliminate pg_ready() wrapper	2014-08-01 12:30:31 -04:00
dm-mpath.h
dm-path-selector.c
dm-path-selector.h
dm-queue-length.c	dm: reject trailing characters in sccanf input	2012-03-28 18:41:26 +01:00
dm-raid1.c	dm raid1: fix immutable biovec related BUG when retrying read bio	2014-02-18 10:48:57 -05:00
dm-raid.c	MD: Remember the last sync operation that was performed	2013-06-26 12:38:24 +10:00
dm-region-hash.c	block: Abstract out bvec iterator	2013-11-23 22:33:47 -08:00
dm-round-robin.c	dm: reject trailing characters in sccanf input	2012-03-28 18:41:26 +01:00
dm-service-time.c	dm: reject trailing characters in sccanf input	2012-03-28 18:41:26 +01:00
dm-snap-persistent.c	dm snapshot: fix metadata corruption	2014-03-03 17:58:13 -05:00
dm-snap-transient.c
dm-snap.c	sched: Remove proliferation of wait_on_bit() action functions	2014-07-16 15:10:39 +02:00
dm-stats.c	dm stats: initialize read-only module parameter	2013-12-10 19:13:21 -05:00
dm-stats.h	dm: add statistics support	2013-09-05 20:46:06 -04:00
dm-stripe.c	block: Abstract out bvec iterator	2013-11-23 22:33:47 -08:00
dm-switch.c	dm switch: efficiently support repetitive patterns	2014-08-01 12:30:37 -04:00
dm-sysfs.c	dm sysfs: fix a module unload race	2014-01-14 23:23:04 -05:00
dm-table.c	dm table: propagate QUEUE_FLAG_NO_SG_MERGE	2014-08-10 20:54:49 -04:00
dm-target.c	dm: allow error target to replace bio-based and request-based targets	2013-09-05 20:46:05 -04:00
dm-thin-metadata.c	dm thin metadata: do not allow the data block size to change	2014-07-15 14:05:26 -04:00
dm-thin-metadata.h	dm thin: ensure user takes action to validate data and metadata consistency	2014-03-05 15:25:35 -05:00
dm-thin.c	dm thin: set minimum_io_size to pool's data block size	2014-08-01 12:30:35 -04:00
dm-uevent.c
dm-uevent.h
dm-verity.c	dm verity: fix biovecs hash calculation regression	2014-04-15 12:19:24 -04:00
dm-zero.c	dm crypt, dm zero: update author name following legal name change	2014-07-10 16:44:14 -04:00
dm.c	dm: allocate a special workqueue for deferred device removal	2014-07-10 16:44:13 -04:00
dm.h	dm table: make dm_table_supports_discards static	2014-08-01 12:30:34 -04:00
faulty.c	block: Abstract out bvec iterator	2013-11-23 22:33:47 -08:00
Kconfig	dm: add era target	2014-03-27 16:56:23 -04:00
linear.c	block: Introduce new bio_split()	2013-11-23 22:33:57 -08:00
linear.h
Makefile	dm: add era target	2014-03-27 16:56:23 -04:00
md.c	md: don't allow bitmap file to be added to raid0/linear.	2014-08-08 15:43:20 +10:00
md.h	md/bitmap: don't abuse i_writecount for bitmap files.	2014-04-09 12:26:59 +10:00
multipath.c	block: Abstract out bvec iterator	2013-11-23 22:33:47 -08:00
multipath.h
raid0.c	md/raid0: check for bitmap compatability when changing raid levels.	2014-08-08 15:33:17 +10:00
raid0.h	md: add proper merge_bvec handling to RAID0 and Linear.	2012-03-19 12:46:39 +11:00
raid1.c	md/raid1: fix_read_error should act on all non-faulty devices.	2014-09-22 11:26:01 +10:00
raid1.h	raid1: Rewrite the implementation of iobarrier.	2013-11-19 15:19:18 +11:00
raid5.c	md/raid5: disable 'DISCARD' by default due to safety concerns.	2014-10-02 13:45:00 +10:00
raid5.h	raid5: add an option to avoid copy data from bio to stripe cache	2014-05-29 16:59:47 +10:00
raid10.c	md/raid10: always initialise ->state on newly allocated r10_bio	2014-08-19 17:20:27 +10:00
raid10.h	MD RAID10: Improve redundancy for 'far' and 'offset' algorithms (part 1)	2013-02-26 11:55:30 +11:00