Re: [BUG] The kernel thread for md RAID1 could cause a md RAID1 array deadlock

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi,

Thank you for the patch.
I have applied the patch to 2.6.23.14 and it works well.

- In case of 2.6.23.14, the problem is reproduced.
- In case of 2.6.23.14 with this patch, raid1 works well so far.
  The fault injection script continues to run, and it doesn't deadlock.
  I will keep it running for a while.

Also, md raid10 seems to have the same problem.
I will test raid10 applying this patch as well.


Neil Brown wrote:
> On Tuesday January 15, k-tanaka@xxxxxxxxxxxxx wrote:
>> This message describes the details about md-RAID1 issue found by
>> testing the md RAID1 using the SCSI fault injection framework.
>>
>> Abstract:
>> Both the error handler for md RAID1 and write access request to the md RAID1
>> use raid1d kernel thread. The nr_pending flag could cause a race condition
>> in raid1d, results in a raid1d deadlock.
> 
> Thanks for finding and reporting this.
> 
> I believe the following patch should fix the deadlock.
> 
> If you are able to repeat your test and confirm this I would
> appreciate it.
> 
> Thanks,
> NeilBrown
> 
> 
> 
> Fix deadlock in md/raid1 when handling a read error.
> 
> When handling a read error, we freeze the array to stop any other
> IO while attempting to over-write with correct data.
> 
> This is done in the raid1d thread and must wait for all submitted IO
> to complete (except for requests that failed and are sitting in the
> retry queue - these are counted in ->nr_queue and will stay there during
> a freeze).
> 
> However write requests need attention from raid1d as bitmap updates
> might be required.  This can cause a deadlock as raid1 is waiting for
> requests to finish that themselves need attention from raid1d.
> 
> So we create a new function 'flush_pending_writes' to give that attention,
> and call it in freeze_array to be sure that we aren't waiting on raid1d.
> 
> Thanks to "K.Tanaka" <k-tanaka@xxxxxxxxxxxxx> for finding and reporting
> this problem.
> 
> Cc: "K.Tanaka" <k-tanaka@xxxxxxxxxxxxx>
> Signed-off-by: Neil Brown <neilb@xxxxxxx>
> 
-- 
---------------------------------------------------------
Kenichi TANAKA    | Open Source Software Platform Development Division
                  | Computers Software Operations Unit, NEC Corporation
                  | k-tanaka@xxxxxxxxxxxxx
-
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Kernel Newbies]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Linux IIO]     [Samba]     [Device Mapper]
  Powered by Linux