linux-kernel - Re: [PATCH 02/11] vfs: More precise tests in d

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Date:	Sat, 15 Feb 2014 16:03:53 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Rob Landley <rob@...dley.net>,
	Miklos Szeredi <miklos@...redi.hu>,
	Christoph Hellwig <hch@...radead.org>,
	Karel Zak <kzak@...hat.com>,
	"J. Bruce Fields" <bfields@...ldses.org>
Subject: Re: [PATCH 02/11] vfs: More precise tests in d_invalidate

On Sat, Feb 15, 2014 at 3:23 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
>
> Except that today d_invalidate drops the dcache lock and
> calls shrink_dcache_parent.  Which gets you into exactly the same
> complex "walk parents and check all siblings" code.

Hmm. It only does that for directories that have sub-entries, though.

I think you may care just about directories (because that's what your
series is about), but d_invalidate() is used for other cases too,
notably d_revalidate() (ie things like stale NFS lookups of normal
files).

That said, I'll have to think about this more. If d_subdir is empty, I
guess d_walk() will be fairly cheap. It's very different, but maybe
not as disastrous as I thought.

                Linus
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