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authorNeilBrown <neilb@suse.com>2016-03-09 12:58:25 +1100
committerShaohua Li <shli@fb.com>2016-03-09 09:31:41 -0800
commit550da24f8d62fe81f3c13e3ec27602d6e44d43dc (patch)
treea5403f9c30d4d284ced5ae211df4e171ec32f91c /drivers/md/raid5.c
parent0f9ce866e0938f2e5f9c77277834b429661844b1 (diff)
md/raid5: preserve STRIPE_PREREAD_ACTIVE in break_stripe_batch_list
break_stripe_batch_list breaks up a batch and copies some flags from the batch head to the members, preserving others. It doesn't preserve or copy STRIPE_PREREAD_ACTIVE. This is not normally a problem as STRIPE_PREREAD_ACTIVE is cleared when a stripe_head is added to a batch, and is not set on stripe_heads already in a batch. However there is no locking to ensure one thread doesn't set the flag after it has just been cleared in another. This does occasionally happen. md/raid5 maintains a count of the number of stripe_heads with STRIPE_PREREAD_ACTIVE set: conf->preread_active_stripes. When break_stripe_batch_list clears STRIPE_PREREAD_ACTIVE inadvertently this could becomes incorrect and will never again return to zero. md/raid5 delays the handling of some stripe_heads until preread_active_stripes becomes zero. So when the above mention race happens, those stripe_heads become blocked and never progress, resulting is write to the array handing. So: change break_stripe_batch_list to preserve STRIPE_PREREAD_ACTIVE in the members of a batch. URL: https://bugzilla.kernel.org/show_bug.cgi?id=108741 URL: https://bugzilla.redhat.com/show_bug.cgi?id=1258153 URL: http://thread.gmane.org/5649C0E9.2030204@zoner.cz Reported-by: Martin Svec <martin.svec@zoner.cz> (and others) Tested-by: Tom Weber <linux@junkyard.4t2.com> Fixes: 1b956f7a8f9a ("md/raid5: be more selective about distributing flags across batch.") Cc: stable@vger.kernel.org (v4.1 and later) Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Shaohua Li <shli@fb.com>
Diffstat (limited to 'drivers/md/raid5.c')
-rw-r--r--drivers/md/raid5.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index c25f2fb2e567..32d52878f182 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4239,7 +4239,6 @@ static void break_stripe_batch_list(struct stripe_head *head_sh,
WARN_ON_ONCE(sh->state & ((1 << STRIPE_ACTIVE) |
(1 << STRIPE_SYNCING) |
(1 << STRIPE_REPLACED) |
- (1 << STRIPE_PREREAD_ACTIVE) |
(1 << STRIPE_DELAYED) |
(1 << STRIPE_BIT_DELAY) |
(1 << STRIPE_FULL_WRITE) |
@@ -4254,6 +4253,7 @@ static void break_stripe_batch_list(struct stripe_head *head_sh,
(1 << STRIPE_REPLACED)));
set_mask_bits(&sh->state, ~(STRIPE_EXPAND_SYNC_FLAGS |
+ (1 << STRIPE_PREREAD_ACTIVE) |
(1 << STRIPE_DEGRADED)),
head_sh->state & (1 << STRIPE_INSYNC));