Re: loop: fix deadlock when sysfs and LOOP_CLR_FD race against each other

[Kay Sievers]

On Sun, Jul 31, 2011 at 22:20, Jens Axboe <jaxboe@xxxxxxxxxxxx> wrote:
> On 2011-07-30 21:19, Kay Sievers wrote:
>> Instead of taking the lo_ctl_mutex from sysfs code, take the inner
>> lo->lo_lock, to protect the access to the backing_file data.
>>
>> Thanks to Tejun for help debugging and finding a solution.
>
> Looks good, looks like something that should have a stable tag as well?

Right, I think it makes sense to have that in -stable.

It's pretty hard to trigger, I had multiple threads running, crawling
/sys and adding/binding/unbinding/removing 1000s of loop devices, and
it takes several minutes sometimes until its hit. So I only tested it
on top of the 3 loop-control patches, but the issue should exist in
the current code as well.

Thanks,
Kay
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