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Subject: Re: INFO: task hung in vfs_setxattr (3)
To:     syzbot <syzbot+738cca7d7d9754493513@syzkaller.appspotmail.com>,
        clm@fb.com, dsterba@suse.com, josef@toxicpanda.com,
        linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        viro@zeniv.linux.org.uk
References: <0000000000008a633505af53038f@google.com>
From:   Nikolay Borisov <nborisov@suse.com>
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Message-ID: <c268d760-2230-ec66-01d4-d3cd725ea522@suse.com>
Date:   Tue, 15 Sep 2020 10:26:26 +0300
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On 15.09.20 г. 7:59 ч., syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    7fe10096 Merge branch 'linus' of git://git.kernel.org/pub/..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=140b0853900000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a9075b36a6ae26c9
> dashboard link: https://syzkaller.appspot.com/bug?extid=738cca7d7d9754493513
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=108d45a5900000
> 
> The issue was bisected to:
> 
> commit 6a3c7f5c87854e948c3c234e5f5e745c7c553722
> Author: Nikolay Borisov <nborisov@suse.com>
> Date:   Thu May 28 08:05:13 2020 +0000
> 
>     btrfs: don't balance btree inode pages from buffered write path
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14884d21900000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=16884d21900000
> console output: https://syzkaller.appspot.com/x/log.txt?x=12884d21900000


Unlikely, that patch does change the performance characteristics because
now we don't balance metadata when doing buffered writes but I don't see
how it can lead to a hang.