From c921aa20c3682456b59574be8cf3df589d909950 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Wed, 24 Jun 2020 18:03:05 +0200 Subject: fs: btrfs: Implement btrfs_lookup_path() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is the extent buffer based path lookup routine. To implement this, btrfs_lookup_dir_item() is crossported from btrfs-progs, and implements btrfs_lookup_path() from scratch. Unlike the existing __btrfs_lookup_path(), since btrfs_read_fs_root() will check whether a root is a orphan at read time, there is no need to check root backref, this makes the code a little easier to read. Signed-off-by: Qu Wenruo Reviewed-by: Marek Behún --- fs/btrfs/inode.c | 250 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 250 insertions(+) (limited to 'fs/btrfs/inode.c') diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index da2a5e90a1..2e3fcad5a8 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -162,6 +162,115 @@ int __btrfs_readlink(const struct __btrfs_root *root, u64 inr, char *target) return 0; } +static int lookup_root_ref(struct btrfs_fs_info *fs_info, + u64 rootid, u64 *root_ret, u64 *dir_ret) +{ + struct btrfs_root *root = fs_info->tree_root; + struct btrfs_root_ref *root_ref; + struct btrfs_path path; + struct btrfs_key key; + int ret; + + btrfs_init_path(&path); + key.objectid = rootid; + key.type = BTRFS_ROOT_BACKREF_KEY; + key.offset = (u64)-1; + + ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0); + if (ret < 0) + return ret; + /* Should not happen */ + if (ret == 0) { + ret = -EUCLEAN; + goto out; + } + ret = btrfs_previous_item(root, &path, rootid, BTRFS_ROOT_BACKREF_KEY); + if (ret < 0) + goto out; + if (ret > 0) { + ret = -ENOENT; + goto out; + } + btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]); + root_ref = btrfs_item_ptr(path.nodes[0], path.slots[0], + struct btrfs_root_ref); + *root_ret = key.offset; + *dir_ret = btrfs_root_ref_dirid(path.nodes[0], root_ref); +out: + btrfs_release_path(&path); + return ret; +} + +/* + * To get the parent inode of @ino of @root. + * + * @root_ret and @ino_ret will be filled. + * + * NOTE: This function is not reliable. It can only get one parent inode. + * The get the proper parent inode, we need a full VFS inodes stack to + * resolve properly. + */ +static int get_parent_inode(struct btrfs_root *root, u64 ino, + struct btrfs_root **root_ret, u64 *ino_ret) +{ + struct btrfs_fs_info *fs_info = root->fs_info; + struct btrfs_path path; + struct btrfs_key key; + int ret; + + if (ino == BTRFS_FIRST_FREE_OBJECTID) { + u64 parent_root = -1; + + /* It's top level already, no more parent */ + if (root->root_key.objectid == BTRFS_FS_TREE_OBJECTID) { + *root_ret = fs_info->fs_root; + *ino_ret = BTRFS_FIRST_FREE_OBJECTID; + return 0; + } + + ret = lookup_root_ref(fs_info, root->root_key.objectid, + &parent_root, ino_ret); + if (ret < 0) + return ret; + + key.objectid = parent_root; + key.type = BTRFS_ROOT_ITEM_KEY; + key.offset = (u64)-1; + *root_ret = btrfs_read_fs_root(fs_info, &key); + if (IS_ERR(*root_ret)) + return PTR_ERR(*root_ret); + + return 0; + } + + btrfs_init_path(&path); + key.objectid = ino; + key.type = BTRFS_INODE_REF_KEY; + key.offset = (u64)-1; + + ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0); + if (ret < 0) + return ret; + /* Should not happen */ + if (ret == 0) { + ret = -EUCLEAN; + goto out; + } + ret = btrfs_previous_item(root, &path, ino, BTRFS_INODE_REF_KEY); + if (ret < 0) + goto out; + if (ret > 0) { + ret = -ENOENT; + goto out; + } + btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]); + *root_ret = root; + *ino_ret = key.offset; +out: + btrfs_release_path(&path); + return ret; +} + /* inr must be a directory (for regular files with multiple hard links this function returns only one of the parents of the file) */ static u64 __get_parent_inode(struct __btrfs_root *root, u64 inr, @@ -240,6 +349,147 @@ static inline const char *skip_current_directories(const char *cur) return cur; } +/* + * Resolve one filename of @ino of @root. + * + * key_ret: The child key (either INODE_ITEM or ROOT_ITEM type) + * type_ret: BTRFS_FT_* of the child inode. + * + * Return 0 with above members filled. + * Return <0 for error. + */ +static int resolve_one_filename(struct btrfs_root *root, u64 ino, + const char *name, int namelen, + struct btrfs_key *key_ret, u8 *type_ret) +{ + struct btrfs_dir_item *dir_item; + struct btrfs_path path; + int ret = 0; + + btrfs_init_path(&path); + + dir_item = btrfs_lookup_dir_item(NULL, root, &path, ino, name, + namelen, 0); + if (IS_ERR(dir_item)) { + ret = PTR_ERR(dir_item); + goto out; + } + + btrfs_dir_item_key_to_cpu(path.nodes[0], dir_item, key_ret); + *type_ret = btrfs_dir_type(path.nodes[0], dir_item); +out: + btrfs_release_path(&path); + return ret; +} + +/* + * Resolve a full path @filename. The start point is @ino of @root. + * + * The result will be filled into @root_ret, @ino_ret and @type_ret. + */ +int btrfs_lookup_path(struct btrfs_root *root, u64 ino, const char *filename, + struct btrfs_root **root_ret, u64 *ino_ret, + u8 *type_ret, int symlink_limit) +{ + struct btrfs_fs_info *fs_info = root->fs_info; + struct btrfs_root *next_root; + struct btrfs_key key; + const char *cur = filename; + u64 next_ino; + u8 next_type; + u8 type; + int len; + int ret = 0; + + /* If the path is absolute path, also search from fs root */ + if (*cur == '/') { + root = fs_info->fs_root; + ino = btrfs_root_dirid(&root->root_item); + type = BTRFS_FT_DIR; + } + + while (*cur != '\0') { + cur = skip_current_directories(cur); + + len = next_length(cur); + if (len > BTRFS_NAME_LEN) { + error("%s: Name too long at \"%.*s\"", __func__, + BTRFS_NAME_LEN, cur); + return -ENAMETOOLONG; + } + + if (len == 1 && cur[0] == '.') + break; + + if (len == 2 && cur[0] == '.' && cur[1] == '.') { + /* Go one level up */ + ret = get_parent_inode(root, ino, &next_root, &next_ino); + if (ret < 0) + return ret; + root = next_root; + ino = next_ino; + goto next; + } + + if (!*cur) + break; + + ret = resolve_one_filename(root, ino, cur, len, &key, &type); + if (ret < 0) + return ret; + + if (key.type == BTRFS_ROOT_ITEM_KEY) { + /* Child inode is a subvolume */ + + next_root = btrfs_read_fs_root(fs_info, &key); + if (IS_ERR(next_root)) + return PTR_ERR(next_root); + root = next_root; + ino = btrfs_root_dirid(&root->root_item); + } else if (type == BTRFS_FT_SYMLINK && symlink_limit >= 0) { + /* Child inode is a symlink */ + + char *target; + + if (symlink_limit == 0) { + error("%s: Too much symlinks!", __func__); + return -EMLINK; + } + target = malloc(fs_info->sectorsize); + if (!target) + return -ENOMEM; + ret = btrfs_readlink(root, key.objectid, target); + if (ret < 0) { + free(target); + return ret; + } + target[ret] = '\0'; + + ret = btrfs_lookup_path(root, ino, target, &next_root, + &next_ino, &next_type, + symlink_limit); + if (ret < 0) + return ret; + root = next_root; + ino = next_ino; + type = next_type; + } else { + /* Child inode is an inode */ + ino = key.objectid; + } +next: + cur += len; + } + + if (!ret) { + *root_ret = root; + *ino_ret = ino; + *type_ret = type; + } + + return ret; +} + u64 __btrfs_lookup_path(struct __btrfs_root *root, u64 inr, const char *path, u8 *type_p, struct btrfs_inode_item *inode_item_p, int symlink_limit) -- cgit