linux-kernel - Re: dcache shrink list corruption?

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Message-ID: <20140429214842.GL18016@ZenIV.linux.org.uk>
Date:	Tue, 29 Apr 2014 22:48:42 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Dave Chinner <david@...morbit.com>
Cc:	Miklos Szeredi <miklos@...redi.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: dcache shrink list corruption?

On Wed, Apr 30, 2014 at 07:18:51AM +1000, Dave Chinner wrote:

> Seems like it would work, but it seems fragile to me - I'm
> wondering how we can ensure that the private shrink list
> manipulations can be kept private.
> 
> We have a similar situation with the inode cache (private shrink
> list) but the I_FREEING flag is set the entire time the inode is on
> the shrink list. Any new hash lookup or attempt to grab the inode
> that occurs while I_FREEING is set fails, so perhaps dentries also
> need a well defined "being torn down and freed" state where new
> references cannot be taken even though the dentry can still be
> found...

Ummm...  You mean, have d_lookup() et.al. fail on something that is on
a shrink list?
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