From patchwork Wed Sep 14 10:01:26 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 9331049 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 33CC1607FD for ; Wed, 14 Sep 2016 10:02:01 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 24FE029C31 for ; Wed, 14 Sep 2016 10:02:01 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 19E5429C35; Wed, 14 Sep 2016 10:02:01 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 04EC029C31 for ; Wed, 14 Sep 2016 10:01:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932671AbcINKB5 (ORCPT ); Wed, 14 Sep 2016 06:01:57 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:51780 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932581AbcINKB4 (ORCPT ); Wed, 14 Sep 2016 06:01:56 -0400 Received: from [80.188.228.195] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.85_2 #1 (Red Hat Linux)) id 1bk70t-0005dS-NP; Wed, 14 Sep 2016 10:01:56 +0000 From: Christoph Hellwig To: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@ml01.01.org Cc: ross.zwisler@linux.intel.com Subject: [PATCH 07/12] xfs: fix locking for DAX writes Date: Wed, 14 Sep 2016 12:01:26 +0200 Message-Id: <1473847291-18913-8-git-send-email-hch@lst.de> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1473847291-18913-1-git-send-email-hch@lst.de> References: <1473847291-18913-1-git-send-email-hch@lst.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP So far DAX writes inherited the locking from direct I/O writes, but the direct I/O model of using shared locks for writes is actually wrong for DAX. For direct I/O we're out of any standards and don't have to provide the Posix required exclusion between writers, but for DAX which gets transparently enable on applications without any knowledge of it we can't simply drop the requirement. Even worse this only happens for aligned writes and thus doesn't show up for many typical use cases. Signed-off-by: Christoph Hellwig --- fs/xfs/xfs_file.c | 20 +------------------- 1 file changed, 1 insertion(+), 19 deletions(-) diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index e612a02..62649cc 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -714,24 +714,11 @@ xfs_file_dax_write( struct address_space *mapping = iocb->ki_filp->f_mapping; struct inode *inode = mapping->host; struct xfs_inode *ip = XFS_I(inode); - struct xfs_mount *mp = ip->i_mount; ssize_t ret = 0; - int unaligned_io = 0; - int iolock; + int iolock = XFS_IOLOCK_EXCL; struct iov_iter data; - /* "unaligned" here means not aligned to a filesystem block */ - if ((iocb->ki_pos & mp->m_blockmask) || - ((iocb->ki_pos + iov_iter_count(from)) & mp->m_blockmask)) { - unaligned_io = 1; - iolock = XFS_IOLOCK_EXCL; - } else if (mapping->nrpages) { - iolock = XFS_IOLOCK_EXCL; - } else { - iolock = XFS_IOLOCK_SHARED; - } xfs_rw_ilock(ip, iolock); - ret = xfs_file_aio_write_checks(iocb, from, &iolock); if (ret) goto out; @@ -758,11 +745,6 @@ xfs_file_dax_write( WARN_ON_ONCE(ret); } - if (iolock == XFS_IOLOCK_EXCL && !unaligned_io) { - xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL); - iolock = XFS_IOLOCK_SHARED; - } - trace_xfs_file_dax_write(ip, iov_iter_count(from), iocb->ki_pos); data = *from;