From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org X-Spam-Level: X-Spam-Status: No, score=1.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_SOFTFAIL autolearn=no autolearn_force=no version=3.4.6 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8A5AC433F5 for ; Tue, 26 Apr 2022 22:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235035AbiDZW5s (ORCPT ); Tue, 26 Apr 2022 18:57:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237257AbiDZW5r (ORCPT ); Tue, 26 Apr 2022 18:57:47 -0400 Received: from mail105.syd.optusnet.com.au (mail105.syd.optusnet.com.au [211.29.132.249]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AE53718E1BA; Tue, 26 Apr 2022 15:54:38 -0700 (PDT) Received: from dread.disaster.area (pa49-195-62-197.pa.nsw.optusnet.com.au [49.195.62.197]) by mail105.syd.optusnet.com.au (Postfix) with ESMTPS id 72EB210E5E0F; Wed, 27 Apr 2022 08:54:37 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1njU4q-004vMz-MN; Wed, 27 Apr 2022 08:54:36 +1000 Date: Wed, 27 Apr 2022 08:54:36 +1000 From: Dave Chinner To: Stefan Roesch Cc: io-uring@vger.kernel.org, kernel-team@fb.com, linux-mm@kvack.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH v1 06/18] xfs: add iomap async buffered write support Message-ID: <20220426225436.GQ1544202@dread.disaster.area> References: <20220426174335.4004987-1-shr@fb.com> <20220426174335.4004987-7-shr@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220426174335.4004987-7-shr@fb.com> X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.4 cv=deDjYVbe c=1 sm=1 tr=0 ts=6268782d a=KhGSFSjofVlN3/cgq4AT7A==:117 a=KhGSFSjofVlN3/cgq4AT7A==:17 a=kj9zAlcOel0A:10 a=z0gMJWrwH1QA:10 a=FOH2dFAWAAAA:8 a=7-415B0cAAAA:8 a=R3nUgBtQJk3RGZ7wdW8A:9 a=CjuIK1q_8ugA:10 a=L5iZDtUwO0cA:10 a=i3VuKzQdj-NEYjvDI-p3:22 a=biEYGPWJfzWAr4FL6Ov7:22 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Tue, Apr 26, 2022 at 10:43:23AM -0700, Stefan Roesch wrote: > This adds the async buffered write support to the iomap layer of XFS. If > a lock cannot be acquired or additional reads need to be performed, the > request will return -EAGAIN in case this is an async buffered write request. > > Signed-off-by: Stefan Roesch > --- > fs/xfs/xfs_iomap.c | 33 +++++++++++++++++++++++++++++++-- > 1 file changed, 31 insertions(+), 2 deletions(-) > > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c > index e552ce541ec2..80b6c48e88af 100644 > --- a/fs/xfs/xfs_iomap.c > +++ b/fs/xfs/xfs_iomap.c > @@ -881,18 +881,28 @@ xfs_buffered_write_iomap_begin( > bool eof = false, cow_eof = false, shared = false; > int allocfork = XFS_DATA_FORK; > int error = 0; > + bool no_wait = (flags & IOMAP_NOWAIT); > > if (xfs_is_shutdown(mp)) > return -EIO; > > /* we can't use delayed allocations when using extent size hints */ > - if (xfs_get_extsz_hint(ip)) > + if (xfs_get_extsz_hint(ip)) { > + if (no_wait) > + return -EAGAIN; > + > return xfs_direct_write_iomap_begin(inode, offset, count, > flags, iomap, srcmap); Why can't we do IOMAP_NOWAIT allocation here? xfs_direct_write_iomap_begin() supports IOMAP_NOWAIT semantics just fine - that's what the direct IO path uses... > + } > > ASSERT(!XFS_IS_REALTIME_INODE(ip)); > > - xfs_ilock(ip, XFS_ILOCK_EXCL); > + if (no_wait) { > + if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) > + return -EAGAIN; > + } else { > + xfs_ilock(ip, XFS_ILOCK_EXCL); > + } handled by xfs_ilock_for_iomap(). > > if (XFS_IS_CORRUPT(mp, !xfs_ifork_has_extents(&ip->i_df)) || > XFS_TEST_ERROR(false, mp, XFS_ERRTAG_BMAPIFORMAT)) { > @@ -902,6 +912,11 @@ xfs_buffered_write_iomap_begin( > > XFS_STATS_INC(mp, xs_blk_mapw); > > + if (no_wait && xfs_need_iread_extents(XFS_IFORK_PTR(ip, XFS_DATA_FORK))) { > + error = -EAGAIN; > + goto out_unlock; > + } > + Also handled by xfs_ilock_for_iomap(). > error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK); > if (error) > goto out_unlock; > @@ -933,6 +948,10 @@ xfs_buffered_write_iomap_begin( > if (xfs_is_cow_inode(ip)) { > if (!ip->i_cowfp) { > ASSERT(!xfs_is_reflink_inode(ip)); > + if (no_wait) { > + error = -EAGAIN; > + goto out_unlock; > + } > xfs_ifork_init_cow(ip); > } Also handled by xfs_ilock_for_iomap(). > cow_eof = !xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, > @@ -956,6 +975,11 @@ xfs_buffered_write_iomap_begin( > goto found_imap; > } > > + if (no_wait) { > + error = -EAGAIN; > + goto out_unlock; > + } > + Won't get here because this is COW path, and xfs_ilock_for_iomap() handles returning -EAGAIN for that case. > xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb); > > /* Trim the mapping to the nearest shared extent boundary. */ > @@ -993,6 +1017,11 @@ xfs_buffered_write_iomap_begin( > allocfork = XFS_COW_FORK; > } > > + if (no_wait) { > + error = -EAGAIN; > + goto out_unlock; > + } Why? Delayed allocation doesn't block... Cheers, Dave. -- Dave Chinner david@fromorbit.com