linux-ext4 - Re: [PATCH 2/3] ext4: Do not create EA inode under buffer lock

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Date: Thu, 14 Mar 2024 19:12:04 +0100
From: Jan Kara <jack@...e.cz>
To: Theodore Ts'o <tytso@....edu>
Cc: Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org,
	syzbot+a43d4f48b8397d0e41a9@...kaller.appspotmail.com
Subject: Re: [PATCH 2/3] ext4: Do not create EA inode under buffer lock

On Thu 29-02-24 10:59:17, Theodore Ts'o wrote:
> On Fri, Feb 09, 2024 at 12:21:00PM +0100, Jan Kara wrote:
> > ext4_xattr_set_entry() creates new EA inodes while holding buffer lock
> > on the external xattr block. This is problematic as it nests all the
> > allocation locking (which acquires locks on other buffers) under the
> > buffer lock. This can even deadlock when the filesystem is corrupted and
> > e.g. quota file is setup to contain xattr block as data block. Move the
> > allocation of EA inode out of ext4_xattr_set_entry() into the callers.
> > 
> > Reported-by: syzbot+a43d4f48b8397d0e41a9@...kaller.appspotmail.com
> > Signed-off-by: Jan Kara <jack@...e.cz>
> 
> In my testing I've found that this is causing a regression for
> ext4/026 in the encrypt configuration.  This can be replicated using
> "kvm-xfstests -c encrypt ext4/026.   Logs follow below.
> 
> I'll try to take a closer look, but I may end up deciding to drop this
> patch or possible the whole patch series until we can figure out
> what's going on.

OK, I've found the problem. I'll rebase patches on top of rc1 when it
happens and send fixed version. Thanks for catching this!

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