Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751514AbdILFGo (ORCPT ); Tue, 12 Sep 2017 01:06:44 -0400 Received: from mga09.intel.com ([134.134.136.24]:5341 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751119AbdILFFa (ORCPT ); Tue, 12 Sep 2017 01:05:30 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,381,1500966000"; d="scan'208";a="899352289" From: Ross Zwisler To: "Theodore Ts'o" , Jan Kara , linux-kernel@vger.kernel.org Cc: Ross Zwisler , Andreas Dilger , Christoph Hellwig , Dan Williams , Dave Chinner , linux-ext4@vger.kernel.org, linux-nvdimm@lists.01.org, stable@vger.kernel.org Subject: [PATCH v2 1/5] ext4: prevent data corruption with inline data + DAX Date: Mon, 11 Sep 2017 23:05:22 -0600 Message-Id: <20170912050526.7627-2-ross.zwisler@linux.intel.com> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20170912050526.7627-1-ross.zwisler@linux.intel.com> References: <20170912050526.7627-1-ross.zwisler@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2570 Lines: 74 If an inode has inline data it is currently prevented from using DAX by a check in ext4_set_inode_flags(). When the inode grows inline data via ext4_create_inline_data() or removes its inline data via ext4_destroy_inline_data_nolock(), the value of S_DAX can change. Currently these changes are unsafe because we don't hold off page faults and I/O, write back dirty radix tree entries and invalidate all mappings. There are also issues with mm-level races when changing the value of S_DAX, as well as issues with the VM_MIXEDMAP flag: https://www.spinics.net/lists/linux-xfs/msg09859.html The unsafe transition of S_DAX can reliably cause data corruption, as shown by the following fstest: https://patchwork.kernel.org/patch/9948381/ Fix this issue by preventing the DAX mount option from being used on filesystems that were created to support inline data. Inline data is an option given to mkfs.ext4. Signed-off-by: Ross Zwisler CC: stable@vger.kernel.org --- fs/ext4/inline.c | 10 ---------- fs/ext4/super.c | 5 +++++ 2 files changed, 5 insertions(+), 10 deletions(-) diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 28c5c3a..fd95019 100644 --- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c @@ -302,11 +302,6 @@ static int ext4_create_inline_data(handle_t *handle, EXT4_I(inode)->i_inline_size = len + EXT4_MIN_INLINE_DATA_SIZE; ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS); ext4_set_inode_flag(inode, EXT4_INODE_INLINE_DATA); - /* - * Propagate changes to inode->i_flags as well - e.g. S_DAX may - * get cleared - */ - ext4_set_inode_flags(inode); get_bh(is.iloc.bh); error = ext4_mark_iloc_dirty(handle, inode, &is.iloc); @@ -451,11 +446,6 @@ static int ext4_destroy_inline_data_nolock(handle_t *handle, } } ext4_clear_inode_flag(inode, EXT4_INODE_INLINE_DATA); - /* - * Propagate changes to inode->i_flags as well - e.g. S_DAX may - * get set. - */ - ext4_set_inode_flags(inode); get_bh(is.iloc.bh); error = ext4_mark_iloc_dirty(handle, inode, &is.iloc); diff --git a/fs/ext4/super.c b/fs/ext4/super.c index c9e7be5..4251e50 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3707,6 +3707,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) } if (sbi->s_mount_opt & EXT4_MOUNT_DAX) { + if (ext4_has_feature_inline_data(sb)) { + ext4_msg(sb, KERN_ERR, "Cannot use DAX on a filesystem" + " that may contain inline data"); + goto failed_mount; + } err = bdev_dax_supported(sb, blocksize); if (err) goto failed_mount; -- 2.9.5