btrfs: expand btrfs_find_item if found_key is NULL

If the found_key is NULL, then btrfs_find_item becomes a verbose wrapper
for simple btrfs_search_slot.

After we've removed all such callers, passing a NULL key is not valid
anymore.
Signed-off-by: NDavid Sterba <dsterba@suse.cz>

fs/btrfs/ctree.c

@@ -2618,13 +2618,14 @@ int btrfs_find_item(struct btrfs_root *fs_root, struct btrfs_path *path,
 	struct extent_buffer *eb;
 
 	ASSERT(path);
+	ASSERT(found_key);
 
 	key.type = key_type;
 	key.objectid = iobjectid;
 	key.offset = ioff;
 
 	ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
-	if ((ret < 0) || (found_key == NULL))
+	if (ret < 0)
 		return ret;
 
 	eb = path->nodes[0];

fs/btrfs/disk-io.c

@@ -1631,6 +1631,7 @@ struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
 {
 	struct btrfs_root *root;
 	struct btrfs_path *path;
+	struct btrfs_key key;
 	int ret;
 
 	if (location->objectid == BTRFS_ROOT_TREE_OBJECTID)
@@ -1675,8 +1676,11 @@ struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
 		ret = -ENOMEM;
 		goto fail;
 	}
-	ret = btrfs_find_item(fs_info->tree_root, path, BTRFS_ORPHAN_OBJECTID,
-			location->objectid, BTRFS_ORPHAN_ITEM_KEY, NULL);
+	key.objectid = BTRFS_ORPHAN_OBJECTID;
+	key.type = BTRFS_ORPHAN_ITEM_KEY;
+	key.offset = location->objectid;
+
+	ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
 	btrfs_free_path(path);
 	if (ret < 0)
 		goto fail;

fs/btrfs/inode.c

@@ -5009,6 +5009,7 @@ static int fixup_tree_root_location(struct btrfs_root *root,
 	struct btrfs_root *new_root;
 	struct btrfs_root_ref *ref;
 	struct extent_buffer *leaf;
+	struct btrfs_key key;
 	int ret;
 	int err = 0;
 
@@ -5019,9 +5020,12 @@ static int fixup_tree_root_location(struct btrfs_root *root,
 	}
 
 	err = -ENOENT;
-	ret = btrfs_find_item(root->fs_info->tree_root, path,
-				BTRFS_I(dir)->root->root_key.objectid,
-				location->objectid, BTRFS_ROOT_REF_KEY, NULL);
+	key.objectid = BTRFS_I(dir)->root->root_key.objectid;
+	key.type = BTRFS_ROOT_REF_KEY;
+	key.offset = location->objectid;
+
+	ret = btrfs_search_slot(NULL, root->fs_info->tree_root, &key, path,
+				0, 0);
 	if (ret) {
 		if (ret < 0)
 			err = ret;

fs/btrfs/scrub.c

@@ -520,6 +520,7 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 	struct inode_fs_paths *ipath = NULL;
 	struct btrfs_root *local_root;
 	struct btrfs_key root_key;
+	struct btrfs_key key;
 
 	root_key.objectid = root;
 	root_key.type = BTRFS_ROOT_ITEM_KEY;
@@ -533,8 +534,11 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
 	/*
 	 * this makes the path point to (inum INODE_ITEM ioff)
 	 */
-	ret = btrfs_find_item(local_root, swarn->path, inum, 0,
-			BTRFS_INODE_ITEM_KEY, NULL);
+	key.objectid = inum;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot(NULL, local_root, &key, swarn->path, 0, 0);
 	if (ret) {
 		btrfs_release_path(swarn->path);
 		goto err;