linux-kernel - Re: [PATCH 1/7] vfs - merge path_is_mountpoint() and path_is_mountpoint

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Message-ID: <20161203232912.GE1555@ZenIV.linux.org.uk>
Date:   Sat, 3 Dec 2016 23:29:12 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Ian Kent <raven@...maw.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        autofs mailing list <autofs@...r.kernel.org>,
        Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Omar Sandoval <osandov@...ndov.com>
Subject: Re: [PATCH 1/7] vfs - merge path_is_mountpoint() and
 path_is_mountpoint_rcu()

On Sat, Dec 03, 2016 at 05:13:22AM +0000, Al Viro wrote:
> 	* path_has_submounts() is broken.  At the very least, it's
> AB-BA between mount_lock and rename_lock.  I would suggest trying to
> put read_seqlock_excl(&mount_lock) around the call of d_walk() in there,
> and using __lookup_mnt() in the callback (without retries on the mount_lock,
> of course - read_seqlock_excl done on the outside is enough).  I'm not sure
> if it won't cause trouble with contention, though; that needs testing.  As
> it is, that function is broken in #work.autofs, same as it is in -mm and
> -next.

	Fix for path_has_submounts() (as above) force-pushed.  It does
need testing and profiling, obviously.