linux-kernel - Re: [PATCH 9/9] nfs: don't open in ->d

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Date:	Tue, 6 Mar 2012 17:47:48 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Miklos Szeredi <miklos@...redi.hu>
CC:	"viro@...IV.linux.org.uk" <viro@...IV.linux.org.uk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hch@...radead.org" <hch@...radead.org>
Subject: Re: [PATCH 9/9] nfs: don't open in ->d_revalidate

On Tue, 2012-03-06 at 18:10 +0100, Miklos Szeredi wrote:
> "Myklebust, Trond" <Trond.Myklebust@...app.com> writes:
> 
> > It makes a big difference to the cache miss case, since not only is the
> > entire path looked up again, but the LOOKUP_REVAL flag gets set, which
> > forces a full lookup of each component (as opposed to just
> > revalidating).
> 
> This is not about a cache miss.  It's about a cache hit (positive cached
> dentry) but changed inode on the server.
> 
> Is this a likely scenario?

Consider something like a git pull on the server, or a distributed
compile across many NFS clients. In both those cases, you are typically
creating and re-creating files with the same name while bypassing the
dcache on your client.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com