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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11D55C4CEC4 for ; Wed, 18 Sep 2019 17:52:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE3B421907 for ; Wed, 18 Sep 2019 17:52:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="DpaDlXQm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729330AbfIRRwj (ORCPT ); Wed, 18 Sep 2019 13:52:39 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:41166 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728523AbfIRRwi (ORCPT ); Wed, 18 Sep 2019 13:52:38 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x8IHd1j1100434; Wed, 18 Sep 2019 17:52:32 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2019-08-05; bh=cgxeaOMY0qSxoZT/LWRWDSDADbr7L2IP+dx0dwUZwkI=; b=DpaDlXQmw6PXX2UVdmLc6VWvo2NNbX4hq696EMrT2bqsAgeh6NXiHUwTIYAV4lzYnsSs CFV6hjc1wYl4wnTLD/7Q8bxxkIt8YRkM8Ucaxttd4NHTURPPcHDSNyqggFc8icNbZmeE WdntIW81ey5CHiK76yQODFq4WjAjYm5U5JxQR+zlmfxMoc5rNeWlYWPcUNjXAAOw5dSE d8LNDfapWeQ05svHQ+lpymkWz+SlZNMmJCWvDzjO7pkfkwfbXdkOOkCiwPltoRkPCZ1F n84JHJq7T7EE24PLIup5R+g5eo4PLjI338wuQZALVvdC+hcRZXDLM5hOUp5W22E/BM7Q FA== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2130.oracle.com with ESMTP id 2v385dwhx7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 18 Sep 2019 17:52:32 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x8IHd6SM054458; Wed, 18 Sep 2019 17:52:32 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 2v37maxs2y-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 18 Sep 2019 17:52:32 +0000 Received: from abhmp0017.oracle.com (abhmp0017.oracle.com [141.146.116.23]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x8IHqUdd031944; Wed, 18 Sep 2019 17:52:31 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 18 Sep 2019 10:52:29 -0700 Date: Wed, 18 Sep 2019 10:52:28 -0700 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Goldwyn Rodrigues , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 12/19] xfs: fill out the srcmap in iomap_begin Message-ID: <20190918175228.GE2229799@magnolia> References: <20190909182722.16783-1-hch@lst.de> <20190909182722.16783-13-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190909182722.16783-13-hch@lst.de> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9384 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909180160 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9384 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909180160 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Sep 09, 2019 at 08:27:15PM +0200, Christoph Hellwig wrote: > Replace our local hacks to report the source block in the main iomap > with the proper scrmap reporting. > > Signed-off-by: Christoph Hellwig > --- > fs/xfs/xfs_iomap.c | 49 +++++++++++++++++++++++----------------------- > 1 file changed, 24 insertions(+), 25 deletions(-) > > diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c > index 18a0f8a5d8c9..d12eacdc9bba 100644 > --- a/fs/xfs/xfs_iomap.c > +++ b/fs/xfs/xfs_iomap.c > @@ -527,7 +527,8 @@ xfs_file_iomap_begin_delay( > loff_t offset, > loff_t count, > unsigned flags, > - struct iomap *iomap) > + struct iomap *iomap, > + struct iomap *srcmap) > { > struct xfs_inode *ip = XFS_I(inode); > struct xfs_mount *mp = ip->i_mount; > @@ -721,11 +722,13 @@ xfs_file_iomap_begin_delay( > found_cow: > xfs_iunlock(ip, XFS_ILOCK_EXCL); > if (imap.br_startoff <= offset_fsb) { > - /* ensure we only report blocks we have a reservation for */ > - xfs_trim_extent(&imap, cmap.br_startoff, cmap.br_blockcount); > - return xfs_bmbt_to_iomap(ip, iomap, &imap, IOMAP_F_SHARED); > + error = xfs_bmbt_to_iomap(ip, srcmap, &imap, 0); > + if (error) > + return error; > + } else { > + xfs_trim_extent(&cmap, offset_fsb, > + imap.br_startoff - offset_fsb); > } > - xfs_trim_extent(&cmap, offset_fsb, imap.br_startoff - offset_fsb); > return xfs_bmbt_to_iomap(ip, iomap, &cmap, IOMAP_F_SHARED); > > out_unlock: > @@ -933,7 +936,7 @@ xfs_file_iomap_begin( > { > struct xfs_inode *ip = XFS_I(inode); > struct xfs_mount *mp = ip->i_mount; > - struct xfs_bmbt_irec imap; > + struct xfs_bmbt_irec imap, cmap; > xfs_fileoff_t offset_fsb, end_fsb; > int nimaps = 1, error = 0; > bool shared = false; > @@ -947,7 +950,7 @@ xfs_file_iomap_begin( > !IS_DAX(inode) && !xfs_get_extsz_hint(ip)) { > /* Reserve delalloc blocks for regular writeback. */ > return xfs_file_iomap_begin_delay(inode, offset, length, flags, > - iomap); > + iomap, srcmap); > } > > /* > @@ -987,9 +990,6 @@ xfs_file_iomap_begin( > * been done up front, so we don't need to do them here. > */ > if (xfs_is_cow_inode(ip)) { > - struct xfs_bmbt_irec cmap; > - bool directio = (flags & IOMAP_DIRECT); > - > /* if zeroing doesn't need COW allocation, then we are done. */ > if ((flags & IOMAP_ZERO) && > !needs_cow_for_zeroing(&imap, nimaps)) > @@ -997,23 +997,11 @@ xfs_file_iomap_begin( > > /* may drop and re-acquire the ilock */ > error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared, > - &lockmode, directio); > + &lockmode, flags & IOMAP_DIRECT); > if (error) > goto out_unlock; > - > - /* > - * For buffered writes we need to report the address of the > - * previous block (if there was any) so that the higher level > - * write code can perform read-modify-write operations; we > - * won't need the CoW fork mapping until writeback. For direct > - * I/O, which must be block aligned, we need to report the > - * newly allocated address. If the data fork has a hole, copy > - * the COW fork mapping to avoid allocating to the data fork. > - */ > - if (shared && > - (directio || imap.br_startblock == HOLESTARTBLOCK)) > - imap = cmap; > - > + if (shared) > + goto out_found_cow; > end_fsb = imap.br_startoff + imap.br_blockcount; > length = XFS_FSB_TO_B(mp, end_fsb) - offset; > } > @@ -1067,6 +1055,17 @@ xfs_file_iomap_begin( > trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap); > goto out_finish; > > +out_found_cow: > + xfs_iunlock(ip, lockmode); > + length = XFS_FSB_TO_B(mp, cmap.br_startoff + cmap.br_blockcount); > + trace_xfs_iomap_found(ip, offset, length - offset, XFS_COW_FORK, &cmap); > + if (imap.br_startblock != HOLESTARTBLOCK) { TBH I've been wondering for a while now if it would make more sense to do this in iomap_apply (and the open-coded versions in dax.c): struct iomap srcmap = { .type = IOMAP_HOLE }; in the iomap_apply function (and change the "if (!srcmap.type)" checks to "if (srcmap.type != IOMAP_HOLE)"). That would get rid of the weird situation where iomap.h doesn't define an iomap type name corresponding to 0 but clearly it has some special meaning because the iomap code changes behavior based on that. It also strikes me as weird that for the @imap parameter, type == 0 would be considered a coding error but for @srcmap, we use type == 0 to mean "no mapping" but we don't do that for @srcmap.type == IOMAP_HOLE. I mention that because, if some ->iomap_begin function returns IOMAP_HOLE then iomap_apply will pass the (hole) srcmap as the second parameter to the ->actor function. When that happens, iomap_write_begin call will try to fill in the rest of the page from @srcmap (which is hole), not the @iomap (which might not be a hole) which seems wrong. As for this function, if we made the above change, then the conditional becomes unneccessary -- we know this is a COW write, so we call xfs_bmbt_to_iomap on both mappings and exit. No need for special casing. --D > + error = xfs_bmbt_to_iomap(ip, srcmap, &imap, 0); > + if (error) > + return error; > + } > + return xfs_bmbt_to_iomap(ip, iomap, &cmap, IOMAP_F_SHARED); > + > out_unlock: > xfs_iunlock(ip, lockmode); > return error; > -- > 2.20.1 >