From: Hidehiro Kawai Subject: [RFC][PATCH] ext3: don't read inode block if the buffer has a write error Date: Mon, 23 Jun 2008 20:25:22 +0900 Message-ID: <485F8822.5030205@hitachi.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, jack@suse.cz, sugita , Satoshi OSHIMA To: akpm@linux-foundation.org, sct@redhat.com, adilger@sun.com Return-path: Received: from mail9.hitachi.co.jp ([133.145.228.44]:42487 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752837AbYFWLZb (ORCPT ); Mon, 23 Jun 2008 07:25:31 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: A transient I/O error can corrupt inode data. Here is the scenario: (1) update inode_A at the block_B (2) pdflush writes out new inode_A to the filesystem, but it results in write I/O error, at this point, BH_Uptodate flag of the buffer for block_B is cleared and BH_Write_EIO is set (3) create new inode_C which located at block_B, and __ext3_get_inode_loc() tries to read on-disk block_B because the buffer is not uptodate (4) if it can read on-disk block_B successfully, inode_A is overwritten by old data This patch makes __ext3_get_inode_loc() not read the inode block if the buffer has BH_Write_EIO flag. In this case, the buffer should have the latest information, so setting the uptodate flag to the buffer (this avoids WARN_ON_ONCE() in mark_buffer_dirty().) According to this change, we would need to test BH_Write_EIO flag for the error checking. Currently nobody checks write I/O errors on metadata buffers, but it will be done in other patches I'm working on. Signed-off-by: Hidehiro Kawai --- fs/ext3/inode.c | 10 ++++++++++ 1 file changed, 10 insertions(+) Index: linux-2.6.26-rc5-mm3/fs/ext3/inode.c =================================================================== --- linux-2.6.26-rc5-mm3.orig/fs/ext3/inode.c +++ linux-2.6.26-rc5-mm3/fs/ext3/inode.c @@ -2516,6 +2516,16 @@ static int __ext3_get_inode_loc(struct i } if (!buffer_uptodate(bh)) { lock_buffer(bh); + + /* + * If the buffer has the write error flag, we have failed + * to write out another inode in the same block. In this + * case, we don't have to read the block because we may + * read the old inode data successfully. + */ + if (buffer_write_io_error(bh) && !buffer_uptodate(bh)) + set_buffer_uptodate(bh); + if (buffer_uptodate(bh)) { /* someone brought it uptodate while we waited */ unlock_buffer(bh);