FAILED: patch "[PATCH] btrfs: fix transaction leak in btrfs_recover_relocation" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-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 1402d17dfd9657be0da8458b2079d03c2d61c86a Mon Sep 17 00:00:00 2001
From: Xiyu Yang <[email protected]>
Date: Mon, 20 Apr 2020 13:39:39 +0800
Subject: [PATCH] btrfs: fix transaction leak in btrfs_recover_relocation

btrfs_recover_relocation() invokes btrfs_join_transaction(), which joins a btrfs_trans_handle object into transactions and returns a reference of it with increased refcount to "trans".

When btrfs_recover_relocation() returns, "trans" becomes invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of btrfs_recover_relocation(). When read_fs_root() failed, the refcnt increased by btrfs_join_transaction() is not decreased, causing a refcnt leak.

Fix this issue by calling btrfs_end_transaction() on this error path when read_fs_root() failed.

index d35936c934ab..03bc7134e8cb 100644
@@ -4559,6 +4559,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
 		if (IS_ERR(fs_root)) {
 			err = PTR_ERR(fs_root);
 			list_add_tail(&reloc_root->root_list, &reloc_roots);
+			btrfs_end_transaction(trans);
 			goto out_unset;
 		}