From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CBE9FC43334 for ; Wed, 29 Jun 2022 21:48:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230323AbiF2Vs0 (ORCPT ); Wed, 29 Jun 2022 17:48:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230214AbiF2VsZ (ORCPT ); Wed, 29 Jun 2022 17:48:25 -0400 Received: from mail104.syd.optusnet.com.au (mail104.syd.optusnet.com.au [211.29.132.246]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C9262A1B1 for ; Wed, 29 Jun 2022 14:48:23 -0700 (PDT) Received: from dread.disaster.area (pa49-181-2-147.pa.nsw.optusnet.com.au [49.181.2.147]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 1F0685ED05F; Thu, 30 Jun 2022 07:48:23 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1o6fXp-00Ccmk-O8; Thu, 30 Jun 2022 07:48:21 +1000 Date: Thu, 30 Jun 2022 07:48:21 +1000 From: Dave Chinner To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 8/9] xfs: add log item precommit operation Message-ID: <20220629214821.GA227878@dread.disaster.area> References: <20220627004336.217366-1-david@fromorbit.com> <20220627004336.217366-9-david@fromorbit.com> <20220629213437.GX227878@dread.disaster.area> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.4 cv=e9dl9Yl/ c=1 sm=1 tr=0 ts=62bcc8a7 a=ivVLWpVy4j68lT4lJFbQgw==:117 a=ivVLWpVy4j68lT4lJFbQgw==:17 a=kj9zAlcOel0A:10 a=JPEYwPQDsx4A:10 a=7-415B0cAAAA:8 a=NatiyMxR-QzUNClV8JkA:9 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, Jun 29, 2022 at 02:42:43PM -0700, Darrick J. Wong wrote: > On Thu, Jun 30, 2022 at 07:34:37AM +1000, Dave Chinner wrote: > > On Wed, Jun 29, 2022 at 02:16:03PM -0700, Darrick J. Wong wrote: > > > On Mon, Jun 27, 2022 at 10:43:35AM +1000, Dave Chinner wrote: > > > > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c > > > > index 82cf0189c0db..0acb31093d9f 100644 > > > > --- a/fs/xfs/xfs_trans.c > > > > +++ b/fs/xfs/xfs_trans.c > > > > @@ -844,6 +844,90 @@ xfs_trans_committed_bulk( > > > > spin_unlock(&ailp->ail_lock); > > > > } > > > > > > > > +/* > > > > + * Sort transaction items prior to running precommit operations. This will > > > > + * attempt to order the items such that they will always be locked in the same > > > > + * order. Items that have no sort function are moved to the end of the list > > > > + * and so are locked last (XXX: need to check the logic matches the comment). > > > > + * > > > > + * This may need refinement as different types of objects add sort functions. > > > > + * > > > > + * Function is more complex than it needs to be because we are comparing 64 bit > > > > + * values and the function only returns 32 bit values. > > > > + */ > > > > +static int > > > > +xfs_trans_precommit_sort( > > > > + void *unused_arg, > > > > + const struct list_head *a, > > > > + const struct list_head *b) > > > > +{ > > > > + struct xfs_log_item *lia = container_of(a, > > > > + struct xfs_log_item, li_trans); > > > > + struct xfs_log_item *lib = container_of(b, > > > > + struct xfs_log_item, li_trans); > > > > + int64_t diff; > > > > + > > > > + /* > > > > + * If both items are non-sortable, leave them alone. If only one is > > > > + * sortable, move the non-sortable item towards the end of the list. > > > > + */ > > > > + if (!lia->li_ops->iop_sort && !lib->li_ops->iop_sort) > > > > + return 0; > > > > + if (!lia->li_ops->iop_sort) > > > > + return 1; > > > > + if (!lib->li_ops->iop_sort) > > > > + return -1; > > > > + > > > > + diff = lia->li_ops->iop_sort(lia) - lib->li_ops->iop_sort(lib); > > > > > > I'm kinda surprised the iop_sort method doesn't take both log item > > > pointers, like most sorting-comparator functions? But I'll see, maybe > > > you're doing something clever wrt ordering of log items of differing > > > types, and hence the ->iop_sort implementations are required to return > > > some absolute priority or something. > > > > Nope, we have to order item locking based on an unchanging > > characteristic of the object. log items can come and go, we want to > > lock items in consistent ascending order, so it has to be based on > > some kind of physical characteristic, like inode number, block > > address, etc. > > > > e.g. If all objects are ordered by the physical location, we naturally > > get a lock order that can be applied sanely across differing object > > types e.g. AG headers will naturally sort and lock before buffers > > in the AG itself. e.g. inode cluster buffers for unlinked list > > manipulations will always get locked after the AGI.... > > So if (say) we were going to add dquots to this scheme, we'd > probably want to shift all the iop_sort functions to return (say) the > xfs_daddr_t of the associated item? No, I don't want to tie it specifically to physical address. ip->i_ino is not a daddr, but it would order just fine against one. > (Practically speaking, I don't know that I'd want to tie things down to > the disk address quite this soon, and since it's all incore code anyway > I don't think the precise type of the return values matter.) Indeed, I don't even want to tie this specifically to a 64 bit value; it's intended that objects will return a sort key, and as we add more object types we'll have to think harder about the specific key values we use. Cheers, Dave. -- Dave Chinner david@fromorbit.com