From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p7REgsDC207243 for ; Sat, 27 Aug 2011 09:42:56 -0500 Received: from bombadil.infradead.org (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 3991B11EE17 for ; Sat, 27 Aug 2011 07:42:53 -0700 (PDT) Received: from bombadil.infradead.org (173-166-109-252-newengland.hfc.comcastbusiness.net [173.166.109.252]) by cuda.sgi.com with ESMTP id tXekAo5wzI6FwsaF for ; Sat, 27 Aug 2011 07:42:53 -0700 (PDT) Received: from hch by bombadil.infradead.org with local (Exim 4.76 #1 (Red Hat Linux)) id 1QxK61-0004Iw-FZ for xfs@oss.sgi.com; Sat, 27 Aug 2011 14:42:53 +0000 Date: Sat, 27 Aug 2011 10:42:53 -0400 From: Christoph Hellwig Subject: [PATCH] xfs: avoid direct I/O write vs buffered I/O race Message-ID: <20110827144253.GA16381@infradead.org> MIME-Version: 1.0 Content-Disposition: inline List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: xfs@oss.sgi.com Currently a buffered reader or writer can add pages to the pagecache while we are waiting for the iolock in xfs_file_dio_aio_write. Prevent this by re-checking mapping->nrpages after we got the iolock, and if nessecary upgrade the lock to exclusive mode. To simplify this a bit only take the ilock inside of xfs_file_aio_write_checks. Signed-off-by: Christoph Hellwig Index: xfs/fs/xfs/xfs_file.c =================================================================== --- xfs.orig/fs/xfs/xfs_file.c 2011-08-27 08:22:18.537779834 +0200 +++ xfs/fs/xfs/xfs_file.c 2011-08-27 08:31:43.296278506 +0200 @@ -680,6 +680,7 @@ xfs_file_aio_write_checks( xfs_fsize_t new_size; int error = 0; + xfs_rw_ilock(ip, XFS_ILOCK_EXCL); *new_sizep = 0; restart: error = generic_write_checks(file, pos, count, S_ISBLK(inode->i_mode)); @@ -802,14 +803,24 @@ xfs_file_dio_aio_write( *iolock = XFS_IOLOCK_EXCL; else *iolock = XFS_IOLOCK_SHARED; - xfs_rw_ilock(ip, XFS_ILOCK_EXCL | *iolock); + xfs_rw_ilock(ip, *iolock); + + /* + * Recheck if there are cached pages that need invalidate after we got + * the iolock to protect against other threads adding new pages while + * we were waiting for the iolock. + */ + if (mapping->nrpages && *iolock == XFS_IOLOCK_SHARED) { + xfs_rw_iunlock(ip, *iolock); + *iolock = XFS_IOLOCK_EXCL; + xfs_rw_ilock(ip, *iolock); + } ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock); if (ret) return ret; if (mapping->nrpages) { - WARN_ON(*iolock != XFS_IOLOCK_EXCL); ret = -xfs_flushinval_pages(ip, (pos & PAGE_CACHE_MASK), -1, FI_REMAPF_LOCKED); if (ret) @@ -855,7 +866,7 @@ xfs_file_buffered_aio_write( size_t count = ocount; *iolock = XFS_IOLOCK_EXCL; - xfs_rw_ilock(ip, XFS_ILOCK_EXCL | *iolock); + xfs_rw_ilock(ip, *iolock); ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock); if (ret) _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs