After commit 566c09c53455 ("raid5: relieve lock contention in
get_active_stripe()")
__find_stripe() is called under conf->hash_locks + hash.
But handle_stripe_clean_event() calls remove_hash() under
conf->device_lock.
Under some cirscumstances the hash chain can be circuited,
and we get an infinite loop with disabled interrupts and locked hash
lock in __find_stripe(). This leads to hard lockup on multiple CPUs
and following system crash.
I was able to reproduce this behavior on raid6 over 6 ssd disks.
The devices_handle_discard_safely option should be set to enable trim
support. The following script was used:
for i in `seq 1 32`; do
dd if=/dev/zero of=large$i bs=10M count=100 &
done
Signed-off-by: Roman Gushchin <kl...@yandex-team.ru>
Cc: Neil Brown <ne...@suse.de>
Cc: Shaohua Li <s...@kernel.org>
Cc: linux-r...@vger.kernel.org
Cc: <sta...@vger.kernel.org> # 3.10 - 3.19
---
drivers/md/raid5.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e421016..5fa7549 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3060,6 +3060,8 @@ static void handle_stripe_clean_event(struct r5conf *conf,
}
if (!discard_pending &&
test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags)) {
+ int hash = sh->hash_lock_index;
+
clear_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
if (sh->qd_idx >= 0) {
@@ -3073,9 +3075,9 @@ static void handle_stripe_clean_event(struct r5conf *conf,
* no updated data, so remove it from hash list and the stripe
* will be reinitialized
*/
- spin_lock_irq(&conf->device_lock);
+ spin_lock_irq(conf->hash_locks + hash);
remove_hash(sh);
- spin_unlock_irq(&conf->device_lock);
+ spin_unlock_irq(conf->hash_locks + hash);
if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state))
set_bit(STRIPE_HANDLE, &sh->state);
--
2.4.3
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