Dear Dmitry Monakhov, I see a race condition, __ext4_abort() ... EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED; ... smp_wmb() [if scheduled at this point ] ... sb->s_flags |= MS_RDONLY; if schedule occur above point(in red). There comes race condition the s_mount_flags set to EXT4_MF_FS_ABORTED. On the other hand sb->s_flags is not set to MS_RDONLY. Now if ext4_fsync_file() is called from some process, the check s_flags to MS_RDONLY will fail, and it will flush unwritten io and not return -EORFS. thanks ----- Original Message ----- From: Dmitry Monakhov Sent: 05/16/13 05:58 PM Subject: [PATCH 1/4] ext4: Fix fsync error handling after filesysteb abort. If filesystem was aborted after inode's write back complete but before it's metadata was updated we may return success due to (sb->s_flags & MS_RDONLY) which is incorrect and result in data loss. In order to handle fs abort correctly we have to check fs state once we discover that it is in MS_RDONLY state Test case: http://patchwork.ozlabs.org/patch/244297/ Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx> --- fs/ext4/fsync.c | 8 ++++++-- fs/ext4/super.c | 13 ++++++++++++- 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c index e0ba8a4..d7df2f1 100644 --- a/fs/ext4/fsync.c +++ b/fs/ext4/fsync.c @@ -129,9 +129,13 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync) return ret; mutex_lock(&inode->i_mutex); - if (inode->i_sb->s_flags & MS_RDONLY) + if (inode->i_sb->s_flags & MS_RDONLY) { + /* Make shure that we read updated s_mount_flags value */ + smp_rmb(); + if (EXT4_SB(inode->i_sb)->s_mount_flags & EXT4_MF_FS_ABORTED) + ret = -EROFS; goto out; - + } ret = ext4_flush_unwritten_io(inode); if (ret < 0) goto out; diff --git a/fs/ext4/super.c b/fs/ext4/super.c index dbc7c09..6c91c8e 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -398,6 +398,11 @@ static void ext4_handle_error(struct super_block *sb) } if (test_opt(sb, ERRORS_RO)) { ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only"); + /* + * Make shure updated value of ->s_mount_flags will be visiable + * before ->s_flags update + */ + smp_wmb(); sb->s_flags |= MS_RDONLY; } if (test_opt(sb, ERRORS_PANIC)) @@ -552,6 +557,7 @@ void __ext4_std_error(struct super_block *sb, const char *function, * * We unconditionally force the filesystem into an ABORT|READONLY state, * unless the error response on the fs has been set to panic in which + * case we take the easy way out and panic immediately. */ @@ -570,8 +576,13 @@ void __ext4_abort(struct super_block *sb, const char *function, if ((sb->s_flags & MS_RDONLY) == 0) { ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only"); - sb->s_flags |= MS_RDONLY; EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED; + /* + * Make shure updated value of ->s_mount_flags will be visiable + * before ->s_flags update + */ + smp_wmb(); + sb->s_flags |= MS_RDONLY; if (EXT4_SB(sb)->s_journal) jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO); save_error_info(sb, function, line); -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
