linux-kernel - Re: [PATCH v3 1/1] dcache: Translating dentry into pathname without taking rename

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Message-ID: <1378630284.2642.10.camel@perseus.fritz.box>
Date:	Sun, 08 Sep 2013 16:51:24 +0800
From:	Ian Kent <raven@...maw.net>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Waiman Long <Waiman.Long@...com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>,
	George Spelvin <linux@...izon.com>,
	John Stoffel <john@...ffel.org>, Sage Weil <sage@...tank.com>
Subject: Re: [PATCH v3 1/1] dcache: Translating dentry into pathname without
 taking rename_lock

On Sun, 2013-09-08 at 05:58 +0100, Al Viro wrote:
> On Sun, Sep 08, 2013 at 12:15:46PM +0800, Ian Kent wrote:
> > > and *name is never modified in it.  Why not simply pass it by value?
> > > Moreover, I'm not sure I understand what do we need sbi->fs_lock in
> > > there.  Other than that, it's very close to dentry_path() (well, that
> > > and different calling conventions).  Ian?
> > 
> > Yes, it is close to dentry_path() but the path functions used to return
> > the full path to the root, although I don't see where dentry_path() get
> > the root, mmm ... 
> 
> dentry_path(), unlike d_path(), is relative to the root of filesystem
> containing dentry in question.  There are 3 of those suckers:
> 	d_path(): vfsmount/dentry => path to current process' root
> 	d_absolute_path(): ditto, but ignores chroot jails (goes to
> the absolute root of namespace)
> 	dentry_path(): dentry => path from root of fs containing that
> dentry.
> 
> IOW, if you have something mounted on /jail/mnt/foo and are chrooted into
> /jail, passing vfsmount/dentry of /jail/mnt/foo/bar/baz to d_path() will
> yield "/mnt/foo/bar/baz", to d_absolute_path() - "/jail/mnt/foo/bar/baz" and
> passing the same dentry to dentry_path() - "/bar/baz".

Right, so all I need to do is drop the leading "/" and I'll have what I
need. I'll do that.

Thanks
Ian


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