On Wed, Aug 6, 2014 at 11:06 PM, Ilya Dryomov <[email protected]> wrote:
> On Wed, Aug 6, 2014 at 10:32 PM, Alex Elder <[email protected]> wrote:
>> On 08/05/2014 02:38 AM, Ilya Dryomov wrote:
>>> While it was never a good idea to sleep in request_fn(), commit
>>> 34c6bc2c919a ("locking/mutexes: Add extra reschedule point") made it
>>> a *bad* idea. mutex_lock() since 3.15 may reschedule *before* putting
>>> task on the mutex wait queue, which for tasks in !TASK_RUNNING state
>>> means block forever. request_fn() may be called with !TASK_RUNNING on
>>> the way to schedule() in io_schedule().
>>>
>>> Offload request handling to a workqueue, one per rbd device, to avoid
>>> calling blocking primitives from rbd_request_fn().
>>
>> Off topic... If you supply "--patience" to your git diff command
>> you'll get an easier-to-read result in some cases (like this one).
>> If you like that you can just do:
>> git config --global --add diff.algorithm patience
>
> I'm generally using (and used to review this patch in particular)
> --histogram. In my experience it gives slightly better results than
> --patience. Didn't think of putting it into .gitconfig though.
Looks like --histogram beats --patience in this case too.
alloc_workqueue() hunk is much better, otherwise identical.
Thanks,
Ilya
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