From: Curt Wohlgemuth Subject: [PATCH] ext4: Fix ext4_should_writeback_data() for no-journal mode Date: Fri, 12 Aug 2011 08:53:34 -0700 Message-ID: <1313164414-24204-1-git-send-email-curtw@google.com> Cc: linux-ext4@vger.kernel.org, Curt Wohlgemuth To: tytso@mit.edu, adilger.kernel@dilger.ca Return-path: Received: from smtp-out.google.com ([216.239.44.51]:15427 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751269Ab1HLPxr (ORCPT ); Fri, 12 Aug 2011 11:53:47 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: ext4_should_writeback_data() had an incorrect sequence of tests to determine if it should return 0 or 1: in particular, even in no-journal mode, 0 was being returned for a non-regular-file inode. This meant that, in non-journal mode, we would use ext4_journalled_aops for directories, symlinks, and other non-regular files. However, calling journalled aop callbacks when there is no valid handle, can cause problems. This would cause a kernel crash with Jan Kara's commit 2d859db3e4 ("ext4: fix data corruption in inodes with journalled data"), because we now dereference 'handle' in ext4_journalled_write_end(). I also added BUG_ONs to check for a valid handle in the obviously journal-only aops callbacks. I tested this running xfstests with a scratch device in these modes: - no-journal - data=ordered - data=writeback - data=journal All work fine; the data=journal run has many failures and a crash in xfstests 074, but this is no different from a vanilla kernel. Signed-off-by: Curt Wohlgemuth --- fs/ext4/ext4_jbd2.h | 4 ++-- fs/ext4/inode.c | 4 ++++ 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h index bb85757..5802fa1 100644 --- a/fs/ext4/ext4_jbd2.h +++ b/fs/ext4/ext4_jbd2.h @@ -289,10 +289,10 @@ static inline int ext4_should_order_data(struct inode *inode) static inline int ext4_should_writeback_data(struct inode *inode) { - if (!S_ISREG(inode->i_mode)) - return 0; if (EXT4_JOURNAL(inode) == NULL) return 1; + if (!S_ISREG(inode->i_mode)) + return 0; if (ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA)) return 0; if (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_WRITEBACK_DATA) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index d47264c..ad3a7ca 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -983,6 +983,8 @@ static int ext4_journalled_write_end(struct file *file, from = pos & (PAGE_CACHE_SIZE - 1); to = from + len; + BUG_ON(!ext4_handle_valid(handle)); + if (copied < len) { if (!PageUptodate(page)) copied = 0; @@ -1699,6 +1701,8 @@ static int __ext4_journalled_writepage(struct page *page, goto out; } + BUG_ON(!ext4_handle_valid(handle)); + ret = walk_page_buffers(handle, page_bufs, 0, len, NULL, do_journal_get_write_access); -- 1.7.3.1