Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755351Ab1CVUkL (ORCPT ); Tue, 22 Mar 2011 16:40:11 -0400 Received: from fxip-0047f.externet.hu ([88.209.222.127]:51722 "EHLO pomaz-ex.szeredi.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755030Ab1CVUkI (ORCPT ); Tue, 22 Mar 2011 16:40:08 -0400 To: Miklos Szeredi CC: viro@ZenIV.linux.org.uk, miklos@szeredi.hu, torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, apw@canonical.com, nbd@openwrt.org, neilb@suse.de In-reply-to: (message from Miklos Szeredi on Tue, 22 Mar 2011 21:31:04 +0100) Subject: Re: [PATCH 0/6 v7] overlay filesystem - request for inclusion References: <20110322152602.053930811@szeredi.hu> <20110322183919.GV22723@ZenIV.linux.org.uk> <20110322190002.GW22723@ZenIV.linux.org.uk> <20110322195331.GY22723@ZenIV.linux.org.uk> <20110322201101.GZ22723@ZenIV.linux.org.uk> Message-Id: From: Miklos Szeredi Date: Tue, 22 Mar 2011 21:40:06 +0100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1697 Lines: 44 On Tue, 22 Mar 2011, Miklos Szeredi wrote: > On Tue, 22 Mar 2011, Al Viro wrote: > > On Tue, Mar 22, 2011 at 09:06:38PM +0100, Miklos Szeredi wrote: > > > On Tue, 22 Mar 2011, Al Viro wrote: > > > > Proceeding with rename is not interesting; proceeding with copyup is. > > > > > > > > Who said that by the time we get to copy_up_locked you will still have > > > > dentry (and upper) match lowerpath? Or that ->d_parent on overlay and > > > > on upper will change in sync, for that matter - there are two d_move() > > > > calls involved... > > > > > > If rename is involved, than rename itself already did the copy up. > > > And that's checked before proceeding with the actual copy up. If > > > there was no rename, then that guarantees that things are in sync, at > > > least for the duration of the copy up. > > > > What do you mean, before? It's not atomic... What happens if e.g. > > you get > > > > A: decided to do copy_up_locked > > blocked on i_mutex > > > > B: did copy_up > > did rename(), complete with d_move() > > did unlink() in new place > > > > A: got CPU back, got i_mutex > > Here it can check if the file was copied up or not. OK, I see the > code doesn't quite get that right. > > Patch below would fix it, I think. Scratch that, d_move() on overlayfs would also have to be under i_mutex of upper. But that should be doable as well. I'll fix that tomorrow when my brain is a little fresher. Thanks, Miklos -- 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/