diff options
| author | Dan Williams <dan.j.williams@intel.com> | 2008-06-05 22:45:52 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-06-06 11:29:08 -0700 |
| commit | e0a115e5aa554b93150a8dc1c3fe15467708abb2 (patch) | |
| tree | c8d869cba362f3728c528d696e3985f1c30b0a7b | |
| parent | b2c8daddcbe03a22402ecf943bb88302601c6835 (diff) | |
md: fix prexor vs sync_request race
During the initial array synchronization process there is a window between
when a prexor operation is scheduled to a specific stripe and when it
completes for a sync_request to be scheduled to the same stripe. When
this happens the prexor completes and the stripe is unconditionally marked
"insync", effectively canceling the sync_request for the stripe. Prior to
2.6.23 this was not a problem because the prexor operation was done under
sh->lock. The effect in older kernels being that the prexor would still
erroneously mark the stripe "insync", but sync_request would be held off
and re-mark the stripe as "!in_sync".
Change the write completion logic to not mark the stripe "in_sync" if a
prexor was performed. The effect of the change is to sometimes not set
STRIPE_INSYNC. The worst this can do is cause the resync to stall waiting
for STRIPE_INSYNC to be set. If this were happening, then STRIPE_SYNCING
would be set and handle_issuing_new_read_requests would cause all
available blocks to eventually be read, at which point prexor would never
be used on that stripe any more and STRIPE_INSYNC would eventually be set.
echo repair > /sys/block/mdN/md/sync_action will correct arrays that may
have lost this race.
Cc: <stable@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | drivers/md/raid5.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 425958a76b8..f0f0585c107 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -2645,6 +2645,7 @@ static void handle_stripe5(struct stripe_head *sh) struct r5dev *dev; unsigned long pending = 0; mdk_rdev_t *blocked_rdev = NULL; + int prexor; memset(&s, 0, sizeof(s)); pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d " @@ -2774,9 +2775,11 @@ static void handle_stripe5(struct stripe_head *sh) /* leave prexor set until postxor is done, allows us to distinguish * a rmw from a rcw during biodrain */ + prexor = 0; if (test_bit(STRIPE_OP_PREXOR, &sh->ops.complete) && test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) { + prexor = 1; clear_bit(STRIPE_OP_PREXOR, &sh->ops.complete); clear_bit(STRIPE_OP_PREXOR, &sh->ops.ack); clear_bit(STRIPE_OP_PREXOR, &sh->ops.pending); @@ -2810,6 +2813,8 @@ static void handle_stripe5(struct stripe_head *sh) if (!test_and_set_bit( STRIPE_OP_IO, &sh->ops.pending)) sh->ops.count++; + if (prexor) + continue; if (!test_bit(R5_Insync, &dev->flags) || (i == sh->pd_idx && s.failed == 0)) set_bit(STRIPE_INSYNC, &sh->state); |