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=-8.4 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, USER_AGENT_SANE_1 autolearn=ham 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 D98BCCA9EAE for ; Tue, 29 Oct 2019 23:33:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A0D4E20659 for ; Tue, 29 Oct 2019 23:33:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="q54RCWjZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726271AbfJ2Xdn (ORCPT ); Tue, 29 Oct 2019 19:33:43 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:53888 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725974AbfJ2Xdn (ORCPT ); Tue, 29 Oct 2019 19:33:43 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x9TNXeBT020517; Tue, 29 Oct 2019 23:33:40 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=SVLTlTzMY3Sf3vzFpevoiOvvBFqEzAUib8r+x5vqP3g=; b=q54RCWjZbUh5JD+iXw61CpLYE9INPovZuo5MrzwpHdWiSVz+Fx3zMHHtfGdYFoU4Zy70 KGPpDEsTr3Vkqn5zXTKOixK/4wQmIoXGq6YTCtCkFb+JZwOZs6IA7LpdZKg98cvBK0JP A0iv736+2Ulecx+CaSghaOtL7zcrZfyQoArPpIqvN4P7hv+qhbSz7FhfdFYS3Q8hcQu/ Q3Jf9s/1EpvqowiCt8XRDCjTzKM25arVuQSyc7w0Hmvnds4ZAJq88GApEA6ESsBYDbi/ KUMPRPP/xp5J9kMt9m9w8nhWG7kBeKyW8xp1tnD+6lDhDlaxx3jsJy8HYFK+aM/zu4A9 lQ== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2120.oracle.com with ESMTP id 2vxwhf8b99-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 29 Oct 2019 23:33:39 +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 x9TNXLbT193875; Tue, 29 Oct 2019 23:33:39 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 2vxwj84cec-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 29 Oct 2019 23:33:39 +0000 Received: from abhmp0007.oracle.com (abhmp0007.oracle.com [141.146.116.13]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x9TNXcx3007944; Tue, 29 Oct 2019 23:33:38 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 29 Oct 2019 16:33:38 -0700 Date: Tue, 29 Oct 2019 16:33:37 -0700 From: "Darrick J. Wong" To: Dave Chinner Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH V2] xfs: properly serialise fallocate against AIO+DIO Message-ID: <20191029233337.GH15222@magnolia> References: <20191029223752.28562-1-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191029223752.28562-1-david@fromorbit.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9425 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 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-1910290207 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9425 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 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-1910290207 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, Oct 30, 2019 at 09:37:52AM +1100, Dave Chinner wrote: > From: Dave Chinner > > AIO+DIO can extend the file size on IO completion, and it holds > no inode locks while the IO is in flight. Therefore, a race > condition exists in file size updates if we do something like this: > > aio-thread fallocate-thread > > lock inode > submit IO beyond inode->i_size > unlock inode > ..... > lock inode > break layouts > if (off + len > inode->i_size) > new_size = off + len > ..... > inode_dio_wait() > > ..... > completes > inode->i_size updated > inode_dio_done() > .... > > > if (new_size) > xfs_vn_setattr(inode, new_size) > > > Yup, that attempt to extend the file size in the fallocate code > turns into a truncate - it removes the whatever the aio write > allocated and put to disk, and reduced the inode size back down to > where the fallocate operation ends. > > Fundamentally, xfs_file_fallocate() not compatible with racing > AIO+DIO completions, so we need to move the inode_dio_wait() call > up to where the lock the inode and break the layouts. > > Secondly, storing the inode size and then using it unchecked without > holding the ILOCK is not safe; we can only do such a thing if we've > locked out and drained all IO and other modification operations, > which we don't do initially in xfs_file_fallocate. > > It should be noted that some of the fallocate operations are > compound operations - they are made up of multiple manipulations > that may zero data, and so we may need to flush and invalidate the > file multiple times during an operation. However, we only need to > lock out IO and other space manipulation operations once, as that > lockout is maintained until the entire fallocate operation has been > completed. > > Signed-off-by: Dave Chinner Looks reasonable to me; what do you think of my regression test? Reviewed-by: Darrick J. Wong --D > --- > fs/xfs/xfs_bmap_util.c | 8 +------- > fs/xfs/xfs_file.c | 23 +++++++++++++++++++++++ > fs/xfs/xfs_ioctl.c | 1 + > 3 files changed, 25 insertions(+), 7 deletions(-) > > diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c > index fb31d7d6701e..dea68308fb64 100644 > --- a/fs/xfs/xfs_bmap_util.c > +++ b/fs/xfs/xfs_bmap_util.c > @@ -1040,6 +1040,7 @@ xfs_unmap_extent( > goto out_unlock; > } > > +/* Caller must first wait for the completion of any pending DIOs if required. */ > int > xfs_flush_unmap_range( > struct xfs_inode *ip, > @@ -1051,9 +1052,6 @@ xfs_flush_unmap_range( > xfs_off_t rounding, start, end; > int error; > > - /* wait for the completion of any pending DIOs */ > - inode_dio_wait(inode); > - > rounding = max_t(xfs_off_t, 1 << mp->m_sb.sb_blocklog, PAGE_SIZE); > start = round_down(offset, rounding); > end = round_up(offset + len, rounding) - 1; > @@ -1085,10 +1083,6 @@ xfs_free_file_space( > if (len <= 0) /* if nothing being freed */ > return 0; > > - error = xfs_flush_unmap_range(ip, offset, len); > - if (error) > - return error; > - > startoffset_fsb = XFS_B_TO_FSB(mp, offset); > endoffset_fsb = XFS_B_TO_FSBT(mp, offset + len); > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index 525b29b99116..46fc5629369b 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -817,6 +817,29 @@ xfs_file_fallocate( > if (error) > goto out_unlock; > > + /* > + * Must wait for all AIO to complete before we continue as AIO can > + * change the file size on completion without holding any locks we > + * currently hold. We must do this first because AIO can update both > + * the on disk and in memory inode sizes, and the operations that follow > + * require the in-memory size to be fully up-to-date. > + */ > + inode_dio_wait(inode); > + > + /* > + * Now that AIO and DIO has drained we can flush and (if necessary) > + * invalidate the cached range over the first operation we are about to > + * run. We include zero and collapse here because they both start with a > + * hole punch over the target range. Insert and collapse both invalidate > + * the broader range affected by the shift in xfs_prepare_shift(). > + */ > + if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE | > + FALLOC_FL_COLLAPSE_RANGE)) { > + error = xfs_flush_unmap_range(ip, offset, len); > + if (error) > + goto out_unlock; > + } > + > if (mode & FALLOC_FL_PUNCH_HOLE) { > error = xfs_free_file_space(ip, offset, len); > if (error) > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > index 287f83eb791f..800f07044636 100644 > --- a/fs/xfs/xfs_ioctl.c > +++ b/fs/xfs/xfs_ioctl.c > @@ -623,6 +623,7 @@ xfs_ioc_space( > error = xfs_break_layouts(inode, &iolock, BREAK_UNMAP); > if (error) > goto out_unlock; > + inode_dio_wait(inode); > > switch (bf->l_whence) { > case 0: /*SEEK_SET*/ > -- > 2.24.0.rc0 >