[PATCH] btrfs: tests: Fix memory leak in btrfs_test_qgroups()

[Zilin Guan]

btrfs_alloc_dummy_root() allocates a root with a reference count of 1.
Then btrfs_insert_fs_root() is used to insert the root into the fs_info.
On success, it increments the reference count. On failure, it does not.

Currently, if btrfs_insert_fs_root() fails, the error handling path
jumps to the out label immediately without decrementing the reference
count of tmp_root, leading to a memory leak.

Fix this by calling btrfs_put_root() unconditionally after
btrfs_insert_fs_root(). This correctly handles both cases: on success,
it drops the local reference, leaving the root with the reference held
by fs_info; on failure, it drops the sole reference, freeing the root.

Fixes: 4785e24fa5d23 ("btrfs: don't take an extra root ref at allocation time")
Signed-off-by: Zilin Guan <zilin@xxxxxxxxxx>
---
 fs/btrfs/tests/qgroup-tests.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/tests/qgroup-tests.c b/fs/btrfs/tests/qgroup-tests.c
index e9124605974b..0d51e0abaeac 100644
--- a/fs/btrfs/tests/qgroup-tests.c
+++ b/fs/btrfs/tests/qgroup-tests.c
@@ -517,11 +517,11 @@ int btrfs_test_qgroups(u32 sectorsize, u32 nodesize)
 	tmp_root->root_key.objectid = BTRFS_FS_TREE_OBJECTID;
 	root->fs_info->fs_root = tmp_root;
 	ret = btrfs_insert_fs_root(root->fs_info, tmp_root);
+	btrfs_put_root(tmp_root);
 	if (ret) {
 		test_err("couldn't insert fs root %d", ret);
 		goto out;
 	}
-	btrfs_put_root(tmp_root);
 
 	tmp_root = btrfs_alloc_dummy_root(fs_info);
 	if (IS_ERR(tmp_root)) {
@@ -532,11 +532,11 @@ int btrfs_test_qgroups(u32 sectorsize, u32 nodesize)
 
 	tmp_root->root_key.objectid = BTRFS_FIRST_FREE_OBJECTID;
 	ret = btrfs_insert_fs_root(root->fs_info, tmp_root);
+	btrfs_put_root(tmp_root);
 	if (ret) {
 		test_err("couldn't insert fs root %d", ret);
 		goto out;
 	}
-	btrfs_put_root(tmp_root);
 
 	test_msg("running qgroup tests");
 	ret = test_no_shared_qgroup(root, sectorsize, nodesize);
-- 
2.34.1