linux-kernel - Re: vfs-scale, d_revalidate from nfsd

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Message-ID: <20110114032052.GV19804@ZenIV.linux.org.uk>
Date:	Fri, 14 Jan 2011 03:20:53 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Nick Piggin <npiggin@...il.com>
Cc:	"J. R. Okajima" <hooanon05@...oo.co.jp>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: vfs-scale, d_revalidate from nfsd

On Fri, Jan 14, 2011 at 02:12:35PM +1100, Nick Piggin wrote:
> The main idea here would be to just pass in a flags parameter rather
> thank poking in nd to get the rcu-walk status. That would solve this
> problem and also avoid nd for most filesystems that don't care about
> it.

Start with nd->flags getting passed explicitly, and be ready to see
	* call on the final stage of open split away and folded with
->lookup() and ->open()/->creat()
	* the rest of callers to lose nd completely.
That's what's going to happen in the next cycle.

BTW, why on the earth do you have that:
static int xattr_hide_revalidate(struct dentry *dentry, struct nameidata *nd)
{
        if (nd->flags & LOOKUP_RCU)
                return -ECHILD;
        return -EPERM;
}
when the sole intent of that sucker is to have dentry of /.xattr (pinned
in dcache and hashed all along) rejected on lookups from root?  IOW, WTF
bother with -ECHILD here at all?
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