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Commit 2f38b3e1 authored by Arne Jansen's avatar Arne Jansen Committed by Jan Schmidt
Browse files

Btrfs: add helper for tree enumeration 



Often no exact match is wanted but just the next lower or
higher item. There's a lot of duplicated code throughout
btrfs to deal with the corner cases. This patch adds a
helper function that can facilitate searching.

Signed-off-by: default avatarArne Jansen <sensille@gmx.net>
parent 630dc772

fs/btrfs/ctree.c

+72 −0
Original line number Diff line number Diff line
@@ -2788,6 +2788,78 @@ done: 
	return ret;

}



/*

 * helper to use instead of search slot if no exact match is needed but

 * instead the next or previous item should be returned.

 * When find_higher is true, the next higher item is returned, the next lower

 * otherwise.

 * When return_any and find_higher are both true, and no higher item is found,

 * return the next lower instead.

 * When return_any is true and find_higher is false, and no lower item is found,

 * return the next higher instead.

 * It returns 0 if any item is found, 1 if none is found (tree empty), and

 * < 0 on error

 */

int btrfs_search_slot_for_read(struct btrfs_root *root,

			       struct btrfs_key *key, struct btrfs_path *p,

			       int find_higher, int return_any)

{

	int ret;

	struct extent_buffer *leaf;



again:

	ret = btrfs_search_slot(NULL, root, key, p, 0, 0);

	if (ret <= 0)

		return ret;

	/*

	 * a return value of 1 means the path is at the position where the

	 * item should be inserted. Normally this is the next bigger item,

	 * but in case the previous item is the last in a leaf, path points

	 * to the first free slot in the previous leaf, i.e. at an invalid

	 * item.

	 */

	leaf = p->nodes[0];



	if (find_higher) {

		if (p->slots[0] >= btrfs_header_nritems(leaf)) {

			ret = btrfs_next_leaf(root, p);

			if (ret <= 0)

				return ret;

			if (!return_any)

				return 1;

			/*

			 * no higher item found, return the next

			 * lower instead

			 */

			return_any = 0;

			find_higher = 0;

			btrfs_release_path(p);

			goto again;

		}

	} else {

		if (p->slots[0] >= btrfs_header_nritems(leaf)) {

			/* we're sitting on an invalid slot */

			if (p->slots[0] == 0) {

				ret = btrfs_prev_leaf(root, p);

				if (ret <= 0)

					return ret;

				if (!return_any)

					return 1;

				/*

				 * no lower item found, return the next

				 * higher instead

				 */

				return_any = 0;

				find_higher = 1;

				btrfs_release_path(p);

				goto again;

			}

			--p->slots[0];

		}

	}

	return 0;

}



/*

 * adjust the pointers going up the tree, starting at level

 * making sure the right key of each node is points to 'key'.

fs/btrfs/ctree.h

+3 −0
Original line number Diff line number Diff line
@@ -2856,6 +2856,9 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root 
		      ins_len, int cow);

int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key,

			  struct btrfs_path *p, u64 time_seq);

int btrfs_search_slot_for_read(struct btrfs_root *root,

			       struct btrfs_key *key, struct btrfs_path *p,

			       int find_higher, int return_any);

int btrfs_realloc_node(struct btrfs_trans_handle *trans,

		       struct btrfs_root *root, struct extent_buffer *parent,

		       int start_slot, int cache_only, u64 *last_ret,