This is a note to let you know that I've just added the patch titled md/raid5: fix locking in handle_stripe_clean_event() to the 4.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: md-raid5-fix-locking-in-handle_stripe_clean_event.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From b8a9d66d043ffac116100775a469f05f5158c16f Mon Sep 17 00:00:00 2001 From: Roman Gushchin <klamm@xxxxxxxxxxxxxx> Date: Sat, 31 Oct 2015 10:53:50 +1100 Subject: md/raid5: fix locking in handle_stripe_clean_event() From: Roman Gushchin <klamm@xxxxxxxxxxxxxx> commit b8a9d66d043ffac116100775a469f05f5158c16f upstream. 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 neilb: original was against a 3.x kernel. I forward-ported to 4.3-rc. This verison is suitable for any kernel since Commit: 59fc630b8b5f ("RAID5: batch adjacent full stripe write") (v4.1+). I'll post a version for earlier kernels to stable. Signed-off-by: Roman Gushchin <klamm@xxxxxxxxxxxxxx> Fixes: 566c09c53455 ("raid5: relieve lock contention in get_active_stripe()") Signed-off-by: NeilBrown <neilb@xxxxxxxx> Cc: Shaohua Li <shli@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/raid5.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -3505,6 +3505,7 @@ returnbi: } if (!discard_pending && test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags)) { + int hash; 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) { @@ -3518,16 +3519,17 @@ returnbi: * no updated data, so remove it from hash list and the stripe * will be reinitialized */ - spin_lock_irq(&conf->device_lock); unhash: + hash = sh->hash_lock_index; + spin_lock_irq(conf->hash_locks + hash); remove_hash(sh); + spin_unlock_irq(conf->hash_locks + hash); if (head_sh->batch_head) { sh = list_first_entry(&sh->batch_list, struct stripe_head, batch_list); if (sh != head_sh) goto unhash; } - spin_unlock_irq(&conf->device_lock); sh = head_sh; if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state)) Patches currently in stable-queue which might be from klamm@xxxxxxxxxxxxxx are queue-4.2/md-raid5-fix-locking-in-handle_stripe_clean_event.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html