linux-kernel - Re: [PATCH v2] nbd: Don't use workqueue to handle recv work

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Message-ID: <CACycT3t7=uXfu62WhahwaZpA15WbL42qB_dicB9kb2DS5-R9Qw@mail.gmail.com>
Date:   Tue, 22 Mar 2022 16:10:01 +0800
From:   Yongji Xie <xieyongji@...edance.com>
To:     Josef Bacik <josef@...icpanda.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Jens Axboe <axboe@...nel.dk>,
        Bart Van Assche <bvanassche@....org>,
        linux-block@...r.kernel.org, nbd@...er.debian.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] nbd: Don't use workqueue to handle recv work

Ping.

Hi Josef, any other comments for this approach.

On Sat, Feb 19, 2022 at 9:04 PM Yongji Xie <xieyongji@...edance.com> wrote:
>
> On Fri, Feb 18, 2022 at 11:21 PM Josef Bacik <josef@...icpanda.com> wrote:
> >
> > On Tue, Feb 15, 2022 at 09:17:37PM +0800, Yongji Xie wrote:
> > > Ping again.
> > >
> > > Hi Josef, could you take a look?
> >
> > Sorry Yongji this got lost.  Again in the reconnect case we're still setting up
> > a long running thread, so it's not like it'll happen during a normal reclaim
> > path thing, it'll be acted upon by userspace.  Thanks,
> >
>
> During creating this long running thread, we might trigger memory
> reclaim since workqueue will use GFP_KERNEL allocation for it. Then a
> deadlock can occur if the memory reclaim happens to hit the page cache
> on this reconnecting nbd device.
>
> Thanks,
> Yongji