Re: Patch "bcache: only permit to recovery read error when cache device is clean" has been added to the 4.9-stable tree

[Jens Axboe <axboe@kernel.dk>]

On 11/27/2017 09:45 AM, Eddie Chapman wrote:
> On 27/11/17 16:06, gregkh@linuxfoundation.org wrote:
>>
>> This is a note to let you know that I've just added the patch titled
>>
>>      bcache: only permit to recovery read error when cache device is clean
>>
>> to the 4.9-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:
>>       bcache-only-permit-to-recovery-read-error-when-cache-device-is-clean.patch
>> and it can be found in the queue-4.9 subdirectory.
>>
>> If you, or anyone else, feels it should not be added to the stable tree,
>> please let <stable@vger.kernel.org> know about it.
> 
> Hi Greg,
> 
> This patch is an important fix for a possible data corruption issue, but 
> it also introduces a bug that can produce read errors under certain 
> circumstances. The issue introduced by this patch is not as severe as 
> the issue it fixes, but can lead to e.g. upper layer fs remounting read 
> only. In my environment upper layer handled it badly and indirectly 
> resulted in data loss (not directly bcache's fault of course).
> 
> Michael Lyle CC'd the stable list with a follow up fix for the issue 
> introduced by this patch, on 24th Nov, subject "bcache: recover data 
> from backing when data is clean".
> 
> However, the followup fix is not in Linus' tree yet, only in Michael's. 
> I guess that means you can't pick it up yet. Never-the-less I felt it 
> important to point this out here.

It's commit e393aa2446150536929140739f09c6ecbcbea7f0 in my tree and will
go upstream shortly - but yes, probably should not add this one, before
both can be pulled in.

-- 
Jens Axboe