From: Jan Kara <jack@suse.cz>
To: Hillf Danton <hdanton@sina.com>
Cc: Jan Kara <jack@suse.cz>,
syzbot <syzbot+a7ab8df042baaf42ae3c@syzkaller.appspotmail.com>,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"syzkaller-bugs@googlegroups.com"
<syzkaller-bugs@googlegroups.com>,
Tahsin Erdogan <tahsin@google.com>
Subject: Re: possible deadlock in fs_reclaim_acquire (2)
Date: Thu, 11 Feb 2021 13:12:02 +0100 [thread overview]
Message-ID: <20210211121202.GP19070@quack2.suse.cz> (raw)
In-Reply-To: <20210211120424.86857A3B85@relay2.suse.de>
On Thu 11-02-21 20:04:14, Hillf Danton wrote:
> On Thu 11-02-21 12:07:29, Jan Kara wrote:
> >> Fix 71b565ceff37 ("ext4: drop ext4_kvmalloc()") by restoring the
> >> GFP_NOFS introduced in dec214d00e0d ("ext4: xattr inode deduplication").
> >>
> >> Note this may be the fix also to possible deadlock
> >> Reported-by: syzbot+bfdded10ab7dcd7507ae@syzkaller.appspotmail.com
> >> https://lore.kernel.org/linux-ext4/000000000000563a0205bafb7970@google.com/
> >
> >Please no. Ext4 is using scoping API to limit allocations to GFP_NOFS
> >inside transactions. In this case something didn't work which seems like a
> >lockdep bug at the first sight but I'll talk to mm guys about it.
> >Definitely to problem doesn't seem to be in ext4.
>
> Feel free to elaborate why we can find ext4 in the report?
> Why is ext4 special in this case?
Please read my reply to the syzbot report [1]. It has all the details.
[1] https://lore.kernel.org/lkml/20210211104947.GL19070@quack2.suse.cz
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
prev parent reply other threads:[~2021-02-11 12:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 1:25 possible deadlock in fs_reclaim_acquire (2) syzbot
[not found] ` <20210211040729.12804-1-hdanton@sina.com>
2021-02-11 10:22 ` Jan Kara
2021-02-11 10:50 ` Michal Hocko
2021-02-11 11:49 ` Dan Carpenter
2021-02-11 12:43 ` Michal Hocko
[not found] ` <20210211120424.86857A3B85@relay2.suse.de>
2021-02-11 12:12 ` Jan Kara [this message]
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