md/raid5: fix locking in handle_stripe_clean_event()
After commit 566c09c5 ("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: 59fc630b ("RAID5: batch adjacent full stripe write") (v4.1+). I'll post a version for earlier kernels to stable. Signed-off-by:Roman Gushchin <klamm@yandex-team.ru> Fixes: 566c09c5 ("raid5: relieve lock contention in get_active_stripe()") Signed-off-by:
NeilBrown <neilb@suse.com> Cc: Shaohua Li <shli@kernel.org> Cc: <stable@vger.kernel.org> # 3.13 - 4.2
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