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

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Date:	Sun, 16 Jan 2011 05:11:01 +1100
From:	Nick Piggin <npiggin@...il.com>
To:	"J. R. Okajima" <hooanon05@...oo.co.jp>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: vfs-scale, d_revalidate from nfsd

On Sat, Jan 15, 2011 at 2:47 PM, J. R. Okajima <hooanon05@...oo.co.jp> wrote:
>
> Nick Piggin:
>> Of course. I was discussing it with Miklos yesterday too, but haven't
>> finished getting a proposal together.
>>
>> 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.
>
> Let me make sure.
> - add a flag parameter to ->d_revalidate. not remove the panameter nd.
> - FS ->d_revalidate() will (probably) return -ECHILD when LOOKUP_RCU is
>  set.
> Right?
>
>
> Then how about the callers?
> Current sequence is
> - NFSD calls lookup_one_len
> - __lookup_hash
> - do_revalidate
> - d_revalidate
> {
>        status = dentry->d_op->d_revalidate(dentry, nd);
>        if (status == -ECHILD) {
>                ;;;
>                status = dentry->d_op->d_revalidate(dentry, nd);
>        }
> }
>
> There will be no change in NFSD but VFS d_revalidate(), such like this?
> VFS d_revalidate()
> {
>        if (nd) {
>                dentry->d_op->d_revalidate(dentry, nd, nd->flags);
>                if (-ECHILD) {
>                        dentry->d_op->d_revalidate(dentry, nd, nd->flags);
>                }
>        } else
>                return dentry->d_op->d_revalidate(dentry, NULL, 0);
> }

Yes that's the idea. I also want to pass a struct inode * parameter, to
facilitate rcu-walk implementations that want to check the inode
(such as fuse).
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