linux-kernel - Re: dcache shrink list corruption?

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Message-ID: <CAJfpegu+q3sT=8==9K5t4=qeJH2azFcBGeMXUtK3LVSEEzXTUA@mail.gmail.com>
Date:	Wed, 30 Apr 2014 19:33:38 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Chinner <david@...morbit.com>,
	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 6:03 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Wed, Apr 30, 2014 at 05:49:58PM +0200, Miklos Szeredi wrote:
>> > FWIW, the first two are really straightforward expanding the function
>> > into its only callsite.  The last needs more splitup.  Not sure if the
>> > following is good enough, but it ought to be at least somewhat cleaner.
>> > Combined change is identical to the original, so it doesn't invalidate
>> > the testing so far...
>>
>> Hmm, patches look okay, but I'm wondering if we really need the morgue list and
>> the waiting.  Why not just skip dentries that are presently being handled by
>> dentry_kill()?
>
> Who will be freeing them?  If we do that from dentry_kill(), we are back to
> needing them removed from shrink list by something called by dput().  And
> if we do that from shrink_dentry_list(), we'd damn better wait for
> dentry_iput() et.al. to finish.

We can do it from dput if the shrinker gets there first and from the
shrinker if dput manages to finish before.  See the updated patch in
the previous mail.

Thanks,
Miklos
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