linux-kernel - Re: Writeback bug causing writeback stalls

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Message-ID: <CAB0TPYHVfkYyFYqp96-PfcP60PKRX6VqrfMHJPkG=UT2956EqQ@mail.gmail.com>
Date:   Wed, 27 May 2020 10:14:09 +0200
From:   Martijn Coenen <maco@...roid.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Jaegeuk Kim <jaegeuk@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, miklos@...redi.hu, tj@...nel.org,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        kernel-team@...roid.com
Subject: Re: Writeback bug causing writeback stalls

Hi Jan,

On Mon, May 25, 2020 at 9:31 AM Jan Kara <jack@...e.cz> wrote:
> Well, most importantly filesystems like ext4, xfs, btrfs don't hold i_rwsem
> when writing back inode and that's deliberate because of performance. We
> don't want to block writes (or event reads in case of XFS) for the inode
> during writeback.

Thanks for clarifying, that makes sense. By the way, do you have an
ETA for your fix? We are under some time pressure to get this fixed in
our downstream kernels, but I'd much rather take a fix from upstream
from somebody who knows this code well. Alternatively, I can take a
stab at the idea you proposed and send a patch to LKML for review this
week.

Thanks,
Martijn


>
>                                                                 Honza
> --
> Jan Kara <jack@...e.com>
> SUSE Labs, CR