FAILED: patch "[PATCH] btrfs: abort the transaction if we fail to inc ref in" failed to apply to 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org>.

thanks,

greg k-h

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

From 867ed321f90d06aaba84e2c91de51cd3038825ef Mon Sep 17 00:00:00 2001
From: Josef Bacik <josef@toxicpanda.com>
Date: Thu, 14 Jan 2021 14:02:46 -0500
Subject: [PATCH] btrfs: abort the transaction if we fail to inc ref in
 btrfs_copy_root

While testing my error handling patches, I added a error injection site
at btrfs_inc_extent_ref, to validate the error handling I added was
doing the correct thing.  However I hit a pretty ugly corruption while
doing this check, with the following error injection stack trace:

btrfs_inc_extent_ref
  btrfs_copy_root
    create_reloc_root
      btrfs_init_reloc_root
	btrfs_record_root_in_trans
	  btrfs_start_transaction
	    btrfs_update_inode
	      btrfs_update_time
		touch_atime
		  file_accessed
		    btrfs_file_mmap

This is because we do not catch the error from btrfs_inc_extent_ref,
which in practice would be ENOMEM, which means we lose the extent
references for a root that has already been allocated and inserted,
which is the problem.  Fix this by aborting the transaction if we fail
to do the reference modification.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 56e132d825a2..95d9bae764ab 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -221,9 +221,10 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
 		ret = btrfs_inc_ref(trans, root, cow, 1);
 	else
 		ret = btrfs_inc_ref(trans, root, cow, 0);
-
-	if (ret)
+	if (ret) {
+		btrfs_abort_transaction(trans, ret);
 		return ret;
+	}
 
 	btrfs_mark_buffer_dirty(cow);
 	*cow_ret = cow;