Re: [PATCH] block: don't use blocking queue entered for recursive bio submits

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On Tue, Jul 03, 2018 at 03:20:31PM -0600, Jens Axboe wrote:
> On 7/3/18 3:15 PM, Jens Axboe wrote:
> > commit cd4a4ae4683dc2e09380118e205e057896dcda2b upstream.
> > 
> > If we end up splitting a bio and the queue goes away between
> > the initial submission and the later split submission, then we
> > can block forever in blk_queue_enter() waiting for the reference
> > to drop to zero. This will never happen, since we already hold
> > a reference.
> > 
> > Mark a split bio as already having entered the queue, so we can
> > just use the live non-blocking queue enter variant.
> > 
> > Thanks to Tetsuo Handa for the analysis.
> > 
> > We're running fio tests and the tasks get stuck in a D state forever
> > when systemd-udevd tries to read the partition table. This patch solves
> > it. Please apply to 4.17 stable.
> > 
> > Reported-by: syzbot+c4f9cebf9d651f6e54de@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> > Signed-off-by: Alexandru Moise <00moses.alexander00@xxxxxxxxx>
> 
> WTF? Please don't send out emails with my name. Ever.
> 
Crap, that's the last thing I intended. I need to set fire to my scripts now, along with my lazy eye.
Please accept my most sincere apologies for this stupid mistake.

../Alex
> -- 
> Jens Axboe
> 



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