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Date: Tue, 3 Jan 2017 01:48:07 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Krister Johansen <kjlx@templeofstupid.com>,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] Fix a race in put_mountpoint.
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On Tue, Jan 03, 2017 at 01:51:36PM +1300, Eric W. Biederman wrote:

> The only significant thing I see is that you have not taken the
> mount_lock on the path where new_mountpoint adds the new struct
> mountpoint into the mountpoint hash table.

Umm...  Point, but I really don't like that bouncing mount_lock up
and down there.  It's not going to cause any serious overhead,
but it just looks ugly... ;-/

Let me think for a while...