FAILED: patch "[PATCH] Btrfs: fix fsync not persisting changed attributes of a" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 60d9f50308e5df19bc18c2fefab0eba4a843900a Mon Sep 17 00:00:00 2001
From: Filipe Manana <[email protected]>
Date: Thu, 16 May 2019 15:48:55 +0100
Subject: [PATCH] Btrfs: fix fsync not persisting changed attributes of a
directory

While logging an inode we follow its ancestors and for each one we mark it as logged in the current transaction, even if we have not logged it. As a consequence if we change an attribute of an ancestor, such as the UID or GID for example, and then explicitly fsync it, we end up not logging the inode at all despite returning success to user space, which results in the attribute being lost if a power failure happens after the fsync.

Sample reproducer:

  $ mkfs.btrfs -f /dev/sdb
  $ mount /dev/sdb /mnt

  $ mkdir /mnt/dir
  $ chown 6007:6007 /mnt/dir

  $ sync

  $ chown 9003:9003 /mnt/dir
  $ touch /mnt/dir/file
  $ xfs_io -c fsync /mnt/dir/file

  # fsync our directory after fsync'ing the new file, should persist the
  # new values for the uid and gid.
  $ xfs_io -c fsync /mnt/dir

<power failure>

  $ mount /dev/sdb /mnt
  $ stat -c %u:%g /mnt/dir
  6007:6007

--> should be 9003:9003, the uid and gid were not persisted, despite
the explicit fsync on the directory prior to the power failure

Fix this by not updating the logged_trans field of ancestor inodes when logging an inode, since we have not logged them. Let only future calls to btrfs_log_inode() to mark inodes as logged.

This could be triggered by my recent fsync fuzz tester for fstests, for which an fstests patch exists titled "fstests: generic, fsync fuzz tester with fsstress".

index 6c47f6ed3e94..de729acee738 100644
@@ -5478,7 +5478,6 @@ static noinline int check_parent_dirs_for_sync(struct btrfs_trans_handle *trans,
 {
 	int ret = 0;
 	struct dentry *old_parent = NULL;
-	struct btrfs_inode *orig_inode = inode;
 
 	/*
 	 * for regular files, if its inode is already on disk, we don't

@@ -5498,16 +5497,6 @@ static noinline int check_parent_dirs_for_sync(struct btrfs_trans_handle *trans,
 	}
 
 	while (1) {
-		/*
-		 * If we are logging a directory then we start with our inode,
-		 * not our parent's inode, so we need to skip setting the
-		 * logged_trans so that further down in the log code we don't
-		 * think this inode has already been logged.
-		 */
-		if (inode != orig_inode)
-			inode->logged_trans = trans->transid;
-		smp_mb();
-
 		if (btrfs_must_commit_transaction(trans, inode)) {
 			ret = 1;
 			break;

@@ -6384,7 +6373,6 @@ void btrfs_record_unlink_dir(struct btrfs_trans_handle *trans,
 	 * if this directory was already logged any new
 	 * names for this file/dir will get recorded
 	 */
-	smp_mb();
 	if (dir->logged_trans == trans->transid)
 		return;