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btrfs: introduce btrfs_search_backwards function
It's a common practice to start a search using offset (u64)-1, which is the u64 maximum value, meaning that we want the search_slot function to be set in the last item with the same objectid and type. Once we are in this position, it's a matter to start a search backwards by calling btrfs_previous_item, which will check if we'll need to go to a previous leaf and other necessary checks, only to be sure that we are in last offset of the same object and type. The new btrfs_search_backwards function does the all these steps when necessary, and can be used to avoid code duplication. Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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@ -2101,6 +2101,27 @@ again:
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return 0;
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}
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/*
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* Execute search and call btrfs_previous_item to traverse backwards if the item
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* was not found.
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*
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* Return 0 if found, 1 if not found and < 0 if error.
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*/
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int btrfs_search_backwards(struct btrfs_root *root, struct btrfs_key *key,
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struct btrfs_path *path)
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{
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int ret;
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ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
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if (ret > 0)
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ret = btrfs_previous_item(root, path, key->objectid, key->type);
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if (ret == 0)
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btrfs_item_key_to_cpu(path->nodes[0], key, path->slots[0]);
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return ret;
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}
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/*
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* adjust the pointers going up the tree, starting at level
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* making sure the right key of each node is points to 'key'.
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@ -2908,6 +2908,10 @@ static inline int btrfs_insert_empty_item(struct btrfs_trans_handle *trans,
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int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path);
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int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
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u64 time_seq);
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int btrfs_search_backwards(struct btrfs_root *root, struct btrfs_key *key,
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struct btrfs_path *path);
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static inline int btrfs_next_old_item(struct btrfs_root *root,
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struct btrfs_path *p, u64 time_seq)
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{
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@ -2389,23 +2389,16 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
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key.offset = (u64)-1;
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while (1) {
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ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
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ret = btrfs_search_backwards(root, &key, path);
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if (ret < 0)
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goto out;
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else if (ret > 0) {
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ret = btrfs_previous_item(root, path, dirid,
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BTRFS_INODE_REF_KEY);
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if (ret < 0)
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goto out;
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else if (ret > 0) {
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ret = -ENOENT;
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goto out;
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}
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ret = -ENOENT;
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goto out;
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}
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l = path->nodes[0];
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slot = path->slots[0];
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btrfs_item_key_to_cpu(l, &key, slot);
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iref = btrfs_item_ptr(l, slot, struct btrfs_inode_ref);
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len = btrfs_inode_ref_name_len(l, iref);
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@ -2480,23 +2473,16 @@ static int btrfs_search_path_in_tree_user(struct inode *inode,
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key.type = BTRFS_INODE_REF_KEY;
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key.offset = (u64)-1;
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while (1) {
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ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
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if (ret < 0) {
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ret = btrfs_search_backwards(root, &key, path);
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if (ret < 0)
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goto out_put;
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else if (ret > 0) {
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ret = -ENOENT;
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goto out_put;
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} else if (ret > 0) {
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ret = btrfs_previous_item(root, path, dirid,
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BTRFS_INODE_REF_KEY);
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if (ret < 0) {
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goto out_put;
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} else if (ret > 0) {
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ret = -ENOENT;
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goto out_put;
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}
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}
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leaf = path->nodes[0];
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slot = path->slots[0];
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btrfs_item_key_to_cpu(leaf, &key, slot);
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iref = btrfs_item_ptr(leaf, slot, struct btrfs_inode_ref);
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len = btrfs_inode_ref_name_len(leaf, iref);
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@ -1201,21 +1201,14 @@ char *btrfs_get_subvol_name_from_objectid(struct btrfs_fs_info *fs_info,
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key.type = BTRFS_ROOT_BACKREF_KEY;
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key.offset = (u64)-1;
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ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
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ret = btrfs_search_backwards(root, &key, path);
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if (ret < 0) {
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goto err;
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} else if (ret > 0) {
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ret = btrfs_previous_item(root, path, subvol_objectid,
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BTRFS_ROOT_BACKREF_KEY);
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if (ret < 0) {
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goto err;
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} else if (ret > 0) {
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ret = -ENOENT;
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goto err;
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}
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ret = -ENOENT;
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goto err;
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}
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btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
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subvol_objectid = key.offset;
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root_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
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@ -1248,21 +1241,14 @@ char *btrfs_get_subvol_name_from_objectid(struct btrfs_fs_info *fs_info,
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key.type = BTRFS_INODE_REF_KEY;
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key.offset = (u64)-1;
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ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
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ret = btrfs_search_backwards(fs_root, &key, path);
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if (ret < 0) {
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goto err;
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} else if (ret > 0) {
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ret = btrfs_previous_item(fs_root, path, dirid,
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BTRFS_INODE_REF_KEY);
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if (ret < 0) {
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goto err;
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} else if (ret > 0) {
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ret = -ENOENT;
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goto err;
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}
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ret = -ENOENT;
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goto err;
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}
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btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
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dirid = key.offset;
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inode_ref = btrfs_item_ptr(path->nodes[0],
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@ -1586,14 +1586,9 @@ again:
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key.offset = search_start;
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key.type = BTRFS_DEV_EXTENT_KEY;
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ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
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ret = btrfs_search_backwards(root, &key, path);
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if (ret < 0)
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goto out;
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if (ret > 0) {
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ret = btrfs_previous_item(root, path, key.objectid, key.type);
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if (ret < 0)
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goto out;
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}
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while (1) {
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l = path->nodes[0];
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