@@ -4236,7 +4236,6 @@ 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) |
@@ -4251,6 +4250,7 @@ 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));
This is a note to let you know that I have just added a patch titled md/raid5: preserve STRIPE_PREREAD_ACTIVE in break_stripe_batch_list to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue This patch is scheduled to be released in version 4.2.8-ckt7. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 4.2.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ---8<------------------------------------------------------------ From f29cb2b6643d86f8533c0e26c5ca27001e6e874c Mon Sep 17 00:00:00 2001 From: NeilBrown <neilb@suse.com> Date: Wed, 9 Mar 2016 12:58:25 +1100 Subject: md/raid5: preserve STRIPE_PREREAD_ACTIVE in break_stripe_batch_list commit 550da24f8d62fe81f3c13e3ec27602d6e44d43dc upstream. 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.") Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/md/raid5.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.7.4