From patchwork Wed Jun 22 15:27:16 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 9193221 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 84D8D6075F for ; Wed, 22 Jun 2016 16:02:03 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 75CEA2237D for ; Wed, 22 Jun 2016 16:02:03 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6A9E32840F; Wed, 22 Jun 2016 16:02:03 +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 E9A972237D for ; Wed, 22 Jun 2016 16:02:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752472AbcFVQB4 (ORCPT ); Wed, 22 Jun 2016 12:01:56 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:57641 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752259AbcFVQB4 (ORCPT ); Wed, 22 Jun 2016 12:01:56 -0400 Received: from [83.175.99.196] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.85_2 #1 (Red Hat Linux)) id 1bFk44-0006kD-5H; Wed, 22 Jun 2016 15:27:40 +0000 From: Christoph Hellwig To: xfs@oss.sgi.com Cc: linux-nvdimm@ml01.01.org, linux-fsdevel@vger.kernel.org Subject: [PATCH 8/8] xfs: fix locking for DAX writes Date: Wed, 22 Jun 2016 17:27:16 +0200 Message-Id: <1466609236-23801-9-git-send-email-hch@lst.de> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1466609236-23801-1-git-send-email-hch@lst.de> References: <1466609236-23801-1-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 0e74325..413c9e0 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; @@ -747,11 +734,6 @@ 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;