btrfs: move locking into btrfs_get_reloc_bg_bytenr()

It does not make sense for the single caller to have the responsability
to lock the relocation mutex before calling the function and then have
the function to assert the lock is held. As this is a function in
relocation.c, move the locking details into it.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: fdmanana

fs/btrfs/inode.c

@@ -226,9 +226,7 @@ static void print_data_reloc_error(const struct btrfs_inode *inode, u64 file_off
 	u32 item_size;
 	int ret;
 
-	mutex_lock(&fs_info->reloc_mutex);
 	logical = btrfs_get_reloc_bg_bytenr(fs_info);
-	mutex_unlock(&fs_info->reloc_mutex);
 
 	if (logical == U64_MAX) {
 		btrfs_warn_rl(fs_info, "has data reloc tree but no running relocation");

fs/btrfs/relocation.c

@@ -5863,14 +5863,15 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
  *
  * Return U64_MAX if no running relocation.
  */
-u64 btrfs_get_reloc_bg_bytenr(const struct btrfs_fs_info *fs_info)
+u64 btrfs_get_reloc_bg_bytenr(struct btrfs_fs_info *fs_info)
 {
 	u64 logical = U64_MAX;
 
-	lockdep_assert_held(&fs_info->reloc_mutex);
-
+	mutex_lock(&fs_info->reloc_mutex);
 	if (fs_info->reloc_ctl && fs_info->reloc_ctl->block_group)
 		logical = fs_info->reloc_ctl->block_group->start;
+	mutex_unlock(&fs_info->reloc_mutex);
+
 	return logical;
 }
 

fs/btrfs/relocation.h

@@ -41,7 +41,7 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
 int btrfs_should_cancel_balance(const struct btrfs_fs_info *fs_info);
 struct btrfs_root *find_reloc_root(struct btrfs_fs_info *fs_info, u64 bytenr);
 bool btrfs_should_ignore_reloc_root(const struct btrfs_root *root);
-u64 btrfs_get_reloc_bg_bytenr(const struct btrfs_fs_info *fs_info);
+u64 btrfs_get_reloc_bg_bytenr(struct btrfs_fs_info *fs_info);
 int btrfs_translate_remap(struct btrfs_fs_info *fs_info, u64 *logical, u64 *length);
 int btrfs_remove_extent_from_remap_tree(struct btrfs_trans_handle *trans,
 					struct btrfs_path *path,