linux-kernel - Re: [patch 2/6] fs: no games with DCACHE

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Message-ID: <20091015144137.GA30516@wotan.suse.de>
Date:	Thu, 15 Oct 2009 16:41:37 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, Ian Kent <raven@...maw.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Miklos Szeredi <mszeredi@...e.cz>
Subject: Re: [patch 2/6] fs: no games with DCACHE_UNHASHED

On Thu, Oct 15, 2009 at 07:20:45AM -0600, Matthew Wilcox wrote:
> On Thu, Oct 15, 2009 at 10:29:03AM +0200, Nick Piggin wrote:
> > On Thu, Oct 15, 2009 at 10:13:43AM +0200, Nick Piggin wrote:
> > > Now both sockets and pipes define a d_dname so they are OK, but anon_inodes
> > > does not. I think they should probably be made to just provide a d_dname
> > > anyway so we can have the familiar format of "pseudofs:[ino]" rather than
> > > "[pseudofs]" that we have now.
> > > 
> > > That should make this patch work for anon_inodes.c as well.
> > 
> > So what if we were to do this first? Are there any other reasons I've
> > missed? (btw. this changes the format the link if that is a problem.
> > Probably if we're going to do this change, we should change things like
> > [timerfd] to just timerfd while we're there to improve consistency
> > further.
> > --
> > Pipe and socket pseudo filesystems report their file descriptor link
> > paths as pipe:[ino] and socket:[ino]. anon_inodefs allows subsystems
> > to specify a name, but it does not report an associated inode number.
> 
> I think that's because the inode number is always 0 -- there's just one
> anonymous inode.

OIC. Hmm, well we could give them a unique number I guess. But anyway
for now, let's just make anon_inodefs_dname just print dentry->d_name.name.

> 
> > Implement this with anon_inodefs_dname in the same way pipefs and sockfs
> > are.
> > 
> > ---
> >  fs/anon_inodes.c |   10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > Index: linux-2.6/fs/anon_inodes.c
> > ===================================================================
> > --- linux-2.6.orig/fs/anon_inodes.c
> > +++ linux-2.6/fs/anon_inodes.c
> > @@ -45,6 +45,15 @@ static int anon_inodefs_delete_dentry(st
> >  	return 1;
> >  }
> >  
> > +/*
> > + * anon_inodefs_dname() is called from d_path().
> > + */
> > +static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
> > +{
> > +	return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
> > +				dentry->d_name.name, dentry->d_inode->i_ino);
> > +}
> > +
> >  static struct file_system_type anon_inode_fs_type = {
> >  	.name		= "anon_inodefs",
> >  	.get_sb		= anon_inodefs_get_sb,
> > @@ -52,6 +61,7 @@ static struct file_system_type anon_inod
> >  };
> >  static const struct dentry_operations anon_inodefs_dentry_operations = {
> >  	.d_delete	= anon_inodefs_delete_dentry,
> > +	.d_dname	= anon_inodefs_dname,
> >  };
> >  
> >  /*
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> -- 
> Matthew Wilcox				Intel Open Source Technology Centre
> "Bill, look, we understand that you're interested in selling us this
> operating system, but compare it to ours.  We can't possibly take such
> a retrograde step."
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