Re: [PATCH] md/raid5: fix locking in handle_stripe_clean_event()
From: Roman Gushchin
Date: Thu Oct 29 2015 - 10:26:53 EST
29.10.2015, 03:35, "Neil Brown" <neilb@xxxxxxx>:
> On Wed, Oct 28 2015, Roman Gushchin wrote:
>> 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
>> 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 &
>> Signed-off-by: Roman Gushchin <klamm@xxxxxxxxxxxxxx>
>> Cc: Neil Brown <neilb@xxxxxxx>
>> Cc: Shaohua Li <shli@xxxxxxxxxx>
>> Cc: linux-raid@xxxxxxxxxxxxxxx
>> Cc: <stable@xxxxxxxxxxxxxxx> # 3.10 - 3.19
> Hi Roman,
> thanks for reporting this and providing a fix.
> I'm a bit confused by that stable range: 3.10 - 3.19
> The commit you identify as introducing the bug was added in 3.13, so
> presumably 3.10, 3.11, 3.12 are not affected.
Sure, it's my mistake. Correct range is 3.13 - 3.19. Sorry.
> Also the bug is still present in mainline, so 4.0, 4.1, 4.2 are also
> affected, though the patch needs to be revised a bit for 4.1 and later.
Yes, exactly, but things are a bit more complicated in mainline.
I'll try to prepare a patch for mainline in a couple of days.
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