diff options
authorDan Williams <dan.j.williams@intel.com>2008-06-06 18:43:58 +0000
committerChris Wright <chrisw@sous-sol.org>2008-06-09 11:27:06 -0700
commitbd1253c627df8150301fbbe6fe79285ca1075188 (patch)
parent16936480e23dcb50b7b9d76f61288876fcbd65f1 (diff)
md: fix prexor vs sync_request race
upstream commit: e0a115e5aa554b93150a8dc1c3fe15467708abb2 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> [chrisw: backport to] Signed-off-by: Chris Wright <chrisw@sous-sol.org>
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 3bd71d9ce352..705fe473c694 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2621,6 +2621,7 @@ static void handle_stripe5(struct stripe_head *sh)
struct stripe_head_state s;
struct r5dev *dev;
unsigned long pending = 0;
+ int prexor;
memset(&s, 0, sizeof(s));
pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d "
@@ -2740,9 +2741,11 @@ 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);
@@ -2776,6 +2779,8 @@ static void handle_stripe5(struct stripe_head *sh)
if (!test_and_set_bit(
STRIPE_OP_IO, &sh->ops.pending))
+ if (prexor)
+ continue;
if (!test_bit(R5_Insync, &dev->flags) ||
(i == sh->pd_idx && s.failed == 0))
set_bit(STRIPE_INSYNC, &sh->state);