Re: [PATCH 1/2] VFS: Cut down inode->i_op->xyz accesses in path walking

[Al Viro <viro@ZenIV.linux.org.uk>]

On Fri, Jul 22, 2011 at 10:37:58AM -0700, Linus Torvalds wrote:
> 
> From: Linus Torvalds <torvalds@linux-foundation.org>
> Date: Fri, 22 Jul 2011 08:44:51 -0700
> Subject: [PATCH 1/2] VFS: Cut down inode->i_op->xyz accesses in path walking
> 
> One of the biggest remaining unnecessary costs in path walking is the
> pointer chasing in inode operations.  We already avoided the
> dentry->d_op derferences with the DCACHE_OP_xyz flags, this just starts
> doing the same thing for the i_op->xyz cases.

> +		if (unlikely(inode->i_op->lookup))
> +			dentry->d_flags |= DCACHE_OP_LOOKUP;
> +		if (unlikely(inode->i_op->permission))
> +			dentry->d_flags |= DCACHE_OP_PERMISSION;
> +		if (unlikely(inode->i_op->follow_link))
> +			dentry->d_flags |= DCACHE_OP_FOLLOW_LINK;

I'm not sure about that one...  What happens after ln -s foo bar; rm bar;
touch bar;?  IOW, where do you clean them?

Other than that, it needs rebase on top of #for-next - conflicts with
->permission() series.