From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 75A676B025E for ; Mon, 25 Sep 2017 19:14:28 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id m30so18531955pgn.2 for ; Mon, 25 Sep 2017 16:14:28 -0700 (PDT) Received: from mga07.intel.com (mga07.intel.com. [134.134.136.100]) by mx.google.com with ESMTPS id 142si4752383pgg.395.2017.09.25.16.14.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 25 Sep 2017 16:14:27 -0700 (PDT) From: Ross Zwisler Subject: [PATCH 3/7] xfs: protect S_DAX transitions in XFS read path Date: Mon, 25 Sep 2017 17:14:00 -0600 Message-Id: <20170925231404.32723-4-ross.zwisler@linux.intel.com> In-Reply-To: <20170925231404.32723-1-ross.zwisler@linux.intel.com> References: <20170925231404.32723-1-ross.zwisler@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , linux-kernel@vger.kernel.org Cc: Ross Zwisler , "Darrick J. Wong" , "J. Bruce Fields" , Christoph Hellwig , Dan Williams , Dave Chinner , Jan Kara , Jeff Layton , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-xfs@vger.kernel.org In the current XFS read I/O path we check IS_DAX() in xfs_file_read_iter() to decide whether to do DAX I/O, direct I/O or buffered I/O. This check is done without holding the XFS_IOLOCK, though, which means that if we allow S_DAX to be manipulated via the inode flag we can run into this race: CPU 0 CPU 1 ----- ----- xfs_file_read_iter() IS_DAX() << returns false xfs_ioctl_setattr() xfs_ioctl_setattr_dax_invalidate() xfs_ilock(XFS_MMAPLOCK|XFS_IOLOCK) sets S_DAX releases XFS_MMAPLOCK and XFS_IOLOCK xfs_file_buffered_aio_read() does buffered I/O to DAX inode, death Fix this by ensuring that we only check S_DAX when we hold the XFS_IOLOCK in the read path. Signed-off-by: Ross Zwisler --- fs/xfs/xfs_file.c | 42 +++++++++++++----------------------------- 1 file changed, 13 insertions(+), 29 deletions(-) diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index ebdd0bd..ca4c8fd 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -207,7 +207,6 @@ xfs_file_dio_aio_read( { struct xfs_inode *ip = XFS_I(file_inode(iocb->ki_filp)); size_t count = iov_iter_count(to); - ssize_t ret; trace_xfs_file_direct_read(ip, count, iocb->ki_pos); @@ -215,12 +214,7 @@ xfs_file_dio_aio_read( return 0; /* skip atime */ file_accessed(iocb->ki_filp); - - xfs_ilock(ip, XFS_IOLOCK_SHARED); - ret = iomap_dio_rw(iocb, to, &xfs_iomap_ops, NULL); - xfs_iunlock(ip, XFS_IOLOCK_SHARED); - - return ret; + return iomap_dio_rw(iocb, to, &xfs_iomap_ops, NULL); } static noinline ssize_t @@ -230,23 +224,14 @@ xfs_file_dax_read( { struct xfs_inode *ip = XFS_I(iocb->ki_filp->f_mapping->host); size_t count = iov_iter_count(to); - ssize_t ret = 0; trace_xfs_file_dax_read(ip, count, iocb->ki_pos); if (!count) return 0; /* skip atime */ - if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED)) { - if (iocb->ki_flags & IOCB_NOWAIT) - return -EAGAIN; - xfs_ilock(ip, XFS_IOLOCK_SHARED); - } - ret = dax_iomap_rw(iocb, to, &xfs_iomap_ops); - xfs_iunlock(ip, XFS_IOLOCK_SHARED); - file_accessed(iocb->ki_filp); - return ret; + return dax_iomap_rw(iocb, to, &xfs_iomap_ops); } STATIC ssize_t @@ -255,19 +240,9 @@ xfs_file_buffered_aio_read( struct iov_iter *to) { struct xfs_inode *ip = XFS_I(file_inode(iocb->ki_filp)); - ssize_t ret; trace_xfs_file_buffered_read(ip, iov_iter_count(to), iocb->ki_pos); - - if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED)) { - if (iocb->ki_flags & IOCB_NOWAIT) - return -EAGAIN; - xfs_ilock(ip, XFS_IOLOCK_SHARED); - } - ret = generic_file_read_iter(iocb, to); - xfs_iunlock(ip, XFS_IOLOCK_SHARED); - - return ret; + return generic_file_read_iter(iocb, to); } STATIC ssize_t @@ -276,7 +251,8 @@ xfs_file_read_iter( struct iov_iter *to) { struct inode *inode = file_inode(iocb->ki_filp); - struct xfs_mount *mp = XFS_I(inode)->i_mount; + struct xfs_inode *ip = XFS_I(inode); + struct xfs_mount *mp = ip->i_mount; ssize_t ret = 0; XFS_STATS_INC(mp, xs_read_calls); @@ -284,6 +260,12 @@ xfs_file_read_iter( if (XFS_FORCED_SHUTDOWN(mp)) return -EIO; + if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED)) { + if (iocb->ki_flags & IOCB_NOWAIT) + return -EAGAIN; + xfs_ilock(ip, XFS_IOLOCK_SHARED); + } + if (IS_DAX(inode)) ret = xfs_file_dax_read(iocb, to); else if (iocb->ki_flags & IOCB_DIRECT) @@ -291,6 +273,8 @@ xfs_file_read_iter( else ret = xfs_file_buffered_aio_read(iocb, to); + xfs_iunlock(ip, XFS_IOLOCK_SHARED); + if (ret > 0) XFS_STATS_ADD(mp, xs_read_bytes, ret); return ret; -- 2.9.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org