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Date: Tue, 13 Mar 2018 00:36:47 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: John Ogness <john.ogness@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
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        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: dcache: remove trylock loops (was Re: [BUG] lock_parent()
 breakage when used from shrink_dentry_list())
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On Mon, Mar 12, 2018 at 06:28:30PM -0500, Eric W. Biederman wrote:

> Given that nfs_kill_super calls generic_shutdown_super and
> generic_shutdown_super calls shrink_dcache_for_umount
> I would argue that nfsv2 and nfsv3 are buggy in the same
> case, as shrink_dcache_for_umount is called on something
> that is not the root of the filesystem's dentry tree.

That's not a problem - it will simply evict a subtree first,
then go through ->s_roots and kill each piece.