Re: [PATCH] bcache: add separate workqueue for journal_write to avoid deadlock

[Coly Li]

On 9/27/18 11:53 PM, Eddie Chapman wrote:
> On 27/09/18 16:23, Coly Li wrote:
> > On 9/27/18 9:45 PM, guoju wrote:
> > > After write SSD completed, bcache schedule journal_write work to
> > > system_wq, that is a public workqueue in system, without WQ_MEM_RECLAIM
> > > flag. system_wq is also a bound wq, and there may be no idle kworker on
> > > current processor. Creating a new kworker may unfortunately need to
> > > reclaim memory first, by shrinking cache and slab used by vfs, which
> > > depends on bcache device. That's a deadlock.
> > >
> > > This patch create a new workqueue for journal_write with WQ_MEM_RECLAIM
> > > flag. It's rescuer thread will work to avoid the deadlock.
> > >
> > > Signed-off-by: guoju <fangguoju@xxxxxxxxx>
> >
> > Nice catch, this fix is quite important. I will try to submit to Jens 
> > ASAP.
> >
> > Thanks.
> >
> > Coly Li
>
> Once this goes into 4.19, would this be a candidate for backporting to 
> any stable kernels, or does it only fix something introduced in this 
> cycle?
This bug exists in upstream for quite long time, it should be applied to 
all stable kernels which it can be applied. And it is Cced to 
stable@xxxxxxxxxxxxxxx already.

Coly Li