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Date: Thu, 17 Apr 2014 23:14:56 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
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        "J. Bruce Fields" <bfields@fieldses.org>,
        Fengguang Wu <fengguang.wu@intel.com>, tytso@mit.edu
Subject: Re: [GIT PULL] Detaching mounts on unlink for 3.15
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On Thu, Apr 17, 2014 at 11:12:03PM +0100, Al Viro wrote:
> 	* *KERNEL* vfsmounts; anything without MNT_INTERNAL is fair game
> as far as ordering of fs shutdown is concerned.  If it wasn't MNT_INTERNAL,
> and we'd done mntput() before destroying some data structures needed for

s/before/just before/, of course ;-)

> fs shutdown, we had been fucked anyway - no warranties that mntput() had
> been the final one.  Moreover, that means going through kern_unmount() or
> simple_release_fs().  Which is trivially dealt with by providing
> mntput_sync(mnt) that *will* wait and using it in those two.  Again, if
> we have an extra reference (e.g. stuffed into a struct file, etc.) -
> we can't rely on mntput() being final.