Date: Thu, 11 Dec 2014 18:06:24 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [GIT PULL] vfs.git
Message-ID: <20141211180624.GX22149@ZenIV.linux.org.uk>
References: <20141210191302.GO22149@ZenIV.linux.org.uk>
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On Thu, Dec 11, 2014 at 05:18:21PM +0100, Miklos Szeredi wrote:
> On Wed, Dec 10, 2014 at 8:13 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> 
> >         * killing a bunch of ->f_path.dentry users (and f_dentry macro).
> > Getting that completed will make life much simpler for unionmount/overlayfs,
> > since then we'll be able to limit the places sensitive to file _dentry_
> > to reasonably few.  Which allows to have file_inode(file) pointing to
> > inode in a covered layer, with dentry pointing to (negative) dentry in
> > union one.  Still not complete, but much closer now.
> 
> If we want f_path to point to union path, then shouldn't we be hiding
> it from all but core VFS?  Filesystems have no business looking at the
> mount anyway.  And looking at the union dentry will be just an endless
> source of bugs.
>
> Also some API changes are in order, like passing dentry to ->iterate()
> for "readdirplus" like operations, since f_path.dentry won't be usable
> for that purpose.  Alternatively replace f_inode with f_dentry and
> make file_inode() use that.

Check the remaining users of ->f_path.dentry.  I agree that they ought to
be encapsulated into a sane set of helpers - raw access to ->f_path in
filesystems is asking for serious trouble.  And we have very few such places
remaining.

FWIW, I would prefer to have the whole stack of underlying dentries reachable
in a uniform way...

PS: I'll send review of your multilayer stuff today.
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