btrfs: bootstrap generic btrfs_find_item interface

There are many btrfs functions that manually search the tree for an
item. They all reimplement the same mechanism and differ in the
conditions that they use to find the item. __inode_info() is one such
example. Zach Brown proposed creating a new interface to take the place
of these functions.

This patch is the first step to creating the interface. A new function,
btrfs_find_item, has been added to ctree.c and prototyped in ctree.h.
It is identical to __inode_info, except that the order of the parameters
has been rearranged to more closely those of similar functions elsewhere
in the code (now, root and path come first, then the objectid, offset
and type, and the key to be filled in last). __inode_info's callers have
been set to call this new function instead, and __inode_info itself has
been removed.

Signed-off-by: Kelley Nielsen <kelleynnn@gmail.com>
Suggested-by: Zach Brown <zab@redhat.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/backref.c

@@ -1107,38 +1107,6 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
-
-static int __inode_info(u64 inum, u64 ioff, u8 key_type,
-			struct btrfs_root *fs_root, struct btrfs_path *path,
-			struct btrfs_key *found_key)
-{
-	int ret;
-	struct btrfs_key key;
-	struct extent_buffer *eb;
-
-	key.type = key_type;
-	key.objectid = inum;
-	key.offset = ioff;
-
-	ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
-	if (ret < 0)
-		return ret;
-
-	eb = path->nodes[0];
-	if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
-		ret = btrfs_next_leaf(fs_root, path);
-		if (ret)
-			return ret;
-		eb = path->nodes[0];
-	}
-
-	btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
-	if (found_key->type != key.type || found_key->objectid != key.objectid)
-		return 1;
-
-	return 0;
-}
-
 /*
  * this makes the path point to (inum INODE_ITEM ioff)
  */
@@ -1146,16 +1114,16 @@ int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
 			struct btrfs_path *path)
 {
 	struct btrfs_key key;
-	return __inode_info(inum, ioff, BTRFS_INODE_ITEM_KEY, fs_root, path,
-				&key);
+	return btrfs_find_item(fs_root, path, inum, ioff,
+			BTRFS_INODE_ITEM_KEY, &key);
 }
 
 static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
 				struct btrfs_path *path,
 				struct btrfs_key *found_key)
 {
-	return __inode_info(inum, ioff, BTRFS_INODE_REF_KEY, fs_root, path,
-				found_key);
+	return btrfs_find_item(fs_root, path, inum, ioff,
+			BTRFS_INODE_REF_KEY, found_key);
 }
 
 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,

fs/btrfs/ctree.c

@@ -2461,6 +2461,43 @@ static int key_search(struct extent_buffer *b, struct btrfs_key *key,
 	return 0;
 }
 
+/* Proposed generic search function, meant to take the place of the
+* various small search helper functions throughout the code and standardize
+* the search interface. Right now, it only replaces the former __inode_info
+* in backref.c.
+*/
+int btrfs_find_item(struct btrfs_root *fs_root, struct btrfs_path *path,
+		u64 iobjectid, u64 ioff, u8 key_type,
+		struct btrfs_key *found_key)
+{
+	int ret;
+	struct btrfs_key key;
+	struct extent_buffer *eb;
+
+	key.type = key_type;
+	key.objectid = iobjectid;
+	key.offset = ioff;
+
+	ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
+	if (ret < 0)
+		return ret;
+
+	eb = path->nodes[0];
+	if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
+		ret = btrfs_next_leaf(fs_root, path);
+		if (ret)
+			return ret;
+		eb = path->nodes[0];
+	}
+
+	btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
+	if (found_key->type != key.type ||
+			found_key->objectid != key.objectid)
+		return 1;
+
+	return 0;
+}
+
 /*
  * look for key in the tree.  path is filled in with nodes along the way
  * if key is found, we return zero and you can find the item in the leaf

fs/btrfs/ctree.h

@@ -3371,6 +3371,8 @@ int btrfs_duplicate_item(struct btrfs_trans_handle *trans,
 			 struct btrfs_root *root,
 			 struct btrfs_path *path,
 			 struct btrfs_key *new_key);
+int btrfs_find_item(struct btrfs_root *fs_root, struct btrfs_path *path,
+		u64 inum, u64 ioff, u8 key_type, struct btrfs_key *found_key);
 int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
 		      *root, struct btrfs_key *key, struct btrfs_path *p, int
 		      ins_len, int cow);