summaryrefslogtreecommitdiff
path: root/drivers/md/dm-linear.c
diff options
context:
space:
mode:
authorJun'ichi Nomura <j-nomura@ce.jp.nec.com>2006-03-27 01:17:47 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-27 08:44:58 -0800
commit930d332a23682202c07df0276dd665a57755b37d (patch)
tree0a0202fb581a65a0b63a4a98aa725eb2088a7814 /drivers/md/dm-linear.c
parent76df1c651b66bdf07d60b3d60789feb5f58d73e3 (diff)
[PATCH] drivers/md/dm-raid1.c: Fix inconsistent mirroring after interrupted recovery
dm-mirror has potential data corruption problem: while on-disk log shows that all disk contents are in-sync, actual contents of the disks are not synchronized. This problem occurs if initial recovery (synching) is interrupted and resumed. Attached patch fixes this problem. Background: rh_dec() changes the region state from RH_NOSYNC (out-of-sync) to RH_CLEAN (in-sync), which results in the corresponding bit of clean_bits being set. This is harmful if on-disk log is used and the map is removed/suspended before the initial sync is completed. The clean_bits is written down to the on-disk log at the map removal, and, upon resume, it's read and copied to sync_bits. Since the recovery process refers to the sync_bits to find a region to be recovered, the region whose state was changed from RH_NOSYNC to RH_CLEAN is no longer recovered. If you haven't applied dm-raid1-read-balancing.patch proposed in dm-devel sometimes ago, the contents of the mirrored disk just corrupt silently. If you have, balanced read may get bogus data from out-of-sync disks. The patch keeps RH_NOSYNC state unchanged. It will be changed to RH_RECOVERING when recovery starts and get reclaimed when the recovery completes. So it doesn't leak the region hash entry. Description: Keep RH_NOSYNC state unchanged when I/O on the region completes. rh_dec() changes the region state from RH_NOSYNC (out-of-sync) to RH_CLEAN (in-sync), which results in the corresponding bit of clean_bits being set. This is harmful if on-disk log is used and the map is removed/suspended before the initial sync is completed. The clean_bits is written down to the on-disk log at the map removal, and, upon resume, it's read and copied to sync_bits. Since the recovery process refers to the sync_bits to find a region to be recovered, the region whose state was changed from RH_NOSYNC to RH_CLEAN is no longer recovered. If you haven't applied dm-raid1-read-balancing.patch proposed in dm-devel sometimes ago, the contents of the mirrored disk just corrupt silently. If you have, balanced read may get bogus data from out-of-sync disks. The RH_NOSYNC region will be changed to RH_RECOVERING when recovery starts on the region and get reclaimed when the recovery completes. So it doesn't leak the region hash entry. Alasdair said: I've analysed the relevant part of the state machine and I believe that the patch is correct. (Further work on this code is still needed - this patch has the side-effect of holding onto memory unnecessarily for long periods of time under certain workloads - but better that than corrupting data.) Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Acked-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/md/dm-linear.c')
0 files changed, 0 insertions, 0 deletions