Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758644AbXLSPbT (ORCPT ); Wed, 19 Dec 2007 10:31:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754721AbXLSPbC (ORCPT ); Wed, 19 Dec 2007 10:31:02 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:41227 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753141AbXLSPbA (ORCPT ); Wed, 19 Dec 2007 10:31:00 -0500 Date: Wed, 19 Dec 2007 09:30:56 -0600 From: "Serge E. Hallyn" To: Pekka J Enberg Cc: serge@hallyn.com, alan@redhat.com, viro@zeniv.linux.org.uk, hch@infradead.org, peterz@infradead.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC/PATCH 2/8] revoke: inode revoke lock V7 Message-ID: <20071219153056.GA7574@sergelap.austin.ibm.com> References: <20071217222850.GA10076@vino.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1960 Lines: 51 Quoting Pekka J Enberg (penberg@cs.helsinki.fi): > Hi Serge, > > (Thanks for looking at this. I appreciate the review!) > > On Mon, 17 Dec 2007, serge@hallyn.com wrote: > > > struct vfsmount *mnt = nd->mnt; > > > - struct dentry *dentry = __d_lookup(nd->dentry, name); > > > + struct dentry *dentry; > > > > > > +again: > > > + dentry = __d_lookup(nd->dentry, name); > > > if (!dentry) > > > goto need_lookup; > > > + > > > + if (dentry->d_inode && IS_REVOKE_LOCKED(dentry->d_inode)) { > > > > not sure whether this is a problem or not, but dentry->d_inode isn't > > locked here, right? So nothing is keeping do_lookup() returning > > with an inode which gets revoked between here and the return 0 > > a few lines down? > > I assume you mean S_REVOKE_LOCK and not ->i_mutex, right? No I did mean the i_mutex since you take the i_mutex when you set S_REVOKE_LOCK. So between that and the comment above do_lookup(), I assumed you were trying to lock out concurrent do_lookups() returning an inode whose revoke is starting at the same time. But based on your next paragraph it sounds like I misunderstand your locking. > The caller is supposed to block open(2) with chmod(2)/chattr(2) so while > revoke is in progress, you can get references to the _revoked inode_, > which is fine (operations on it will fail with EBADFS). The > ->i_revoke_wait bits are there to make sure that while we revoke, you > can't get a _new reference_ to the inode until we're done. And a new reference means through iget(), so if revoke starts between the IS_REVOKE_LOCKED() check in do_lookup and its return, it's ok bc we'll get a reference later on? I'm a little confused but i'll keep looking. thanks, -serge -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/