[PATCH U-BOOT 18/26] fs: btrfs: Implement btrfs_lookup_path()

Qu Wenruo
2020-04-22T06:50:01Z

This is the extent buffer based path lookup routine.

To implement this, btrfs_lookup_dir_item() is cross ported from
btrfs-progs, and implement btrfs_lookup_path() from scratch.

Unlike the existing __btrfs_lookup_path(), since btrfs_read_fs_root()
will check whether a root is orphan at read time, there is no need to
check root backref, this make the code a little easier to read.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/ctree.h | 4 +
fs/btrfs/dir-item.c | 106 +++++++++++++++++++
fs/btrfs/inode.c | 245 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 355 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index f702eaff293c..78f7746d1f32 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1284,6 +1284,10 @@ struct btrfs_dir_item *btrfs_lookup_dir_item(struct btrfs_trans_handle *trans,
struct btrfs_path *path, u64 dir,
const char *name, int name_len,
int mod);
+/* inode.c */
+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);

/* ctree.c */
int btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2);
diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index aea621c72bb3..4bf45c2fa925 100644
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -8,6 +8,112 @@
#include "btrfs.h"
#include "disk-io.h"

+static int verify_dir_item(struct btrfs_root *root,
+ struct extent_buffer *leaf,
+ struct btrfs_dir_item *dir_item)
+{
+ u16 namelen = BTRFS_NAME_LEN;
+ u8 type = btrfs_dir_type(leaf, dir_item);
+
+ if (type == BTRFS_FT_XATTR)
+ namelen = XATTR_NAME_MAX;
+
+ if (btrfs_dir_name_len(leaf, dir_item) > namelen) {
+ fprintf(stderr, "invalid dir item name len: %u\n",
+ (unsigned)btrfs_dir_data_len(leaf, dir_item));
+ return 1;
+ }
+
+ /* BTRFS_MAX_XATTR_SIZE is the same for all dir items */
+ if ((btrfs_dir_data_len(leaf, dir_item) +
+ btrfs_dir_name_len(leaf, dir_item)) >
+ BTRFS_MAX_XATTR_SIZE(root->fs_info)) {
+ fprintf(stderr, "invalid dir item name + data len: %u + %u\n",
+ (unsigned)btrfs_dir_name_len(leaf, dir_item),
+ (unsigned)btrfs_dir_data_len(leaf, dir_item));
+ return 1;
+ }
+
+ return 0;
+}
+
+struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_root *root,
+ struct btrfs_path *path,
+ const char *name, int name_len)
+{
+ struct btrfs_dir_item *dir_item;
+ unsigned long name_ptr;
+ u32 total_len;
+ u32 cur = 0;
+ u32 this_len;
+ struct extent_buffer *leaf;
+
+ leaf = path->nodes[0];
+ dir_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dir_item);
+ total_len = btrfs_item_size_nr(leaf, path->slots[0]);
+ if (verify_dir_item(root, leaf, dir_item))
+ return NULL;
+
+ while(cur < total_len) {
+ this_len = sizeof(*dir_item) +
+ btrfs_dir_name_len(leaf, dir_item) +
+ btrfs_dir_data_len(leaf, dir_item);
+ if (this_len > (total_len - cur)) {
+ fprintf(stderr, "invalid dir item size\n");
+ return NULL;
+ }
+
+ name_ptr = (unsigned long)(dir_item + 1);
+
+ if (btrfs_dir_name_len(leaf, dir_item) == name_len &&
+ memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0)
+ return dir_item;
+
+ cur += this_len;
+ dir_item = (struct btrfs_dir_item *)((char *)dir_item +
+ this_len);
+ }
+ return NULL;
+}
+
+struct btrfs_dir_item *btrfs_lookup_dir_item(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root,
+ struct btrfs_path *path, u64 dir,
+ const char *name, int name_len,
+ int mod)
+{
+ int ret;
+ struct btrfs_key key;
+ int ins_len = mod < 0 ? -1 : 0;
+ int cow = mod != 0;
+ struct btrfs_key found_key;
+ struct extent_buffer *leaf;
+
+ key.objectid = dir;
+ key.type = BTRFS_DIR_ITEM_KEY;
+
+ key.offset = btrfs_name_hash(name, name_len);
+
+ ret = btrfs_search_slot(trans, root, &key, path, ins_len, cow);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ if (ret > 0) {
+ if (path->slots[0] == 0)
+ return NULL;
+ path->slots[0]--;
+ }
+
+ leaf = path->nodes[0];
+ btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+
+ if (found_key.objectid != dir ||
+ found_key.type != BTRFS_DIR_ITEM_KEY ||
+ found_key.offset != key.offset)
+ return NULL;
+
+ return btrfs_match_dir_item_name(root, path, name, name_len);
+}
+
static int __verify_dir_item(struct btrfs_dir_item *item, u32 start, u32 total)
{
u16 max_len = BTRFS_NAME_LEN;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index df2f6590bb40..af4f30bbd50c 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -161,6 +161,115 @@ 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;
+
+ /* 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,
@@ -235,6 +344,142 @@ 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) {
+ printf("%s: Name too long at \"%.*s\"\n", __func__,
+ BTRFS_NAME_LEN, cur);
+ return -ENAMETOOLONG;
+ }
+ if (len == 1 && cur[0] == '.')
+ break;
+ /* Go one level up */
+ if (len == 2 && cur[0] == '.' && cur[1] == '.') {
+ 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;
+ /* Child inode is a subvolume */
+ if (key.type == BTRFS_ROOT_ITEM_KEY) {
+
+ 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);
+ goto next;
+ }
+ /* Child inode is a symlink */
+ if (type == BTRFS_FT_SYMLINK && symlink_limit >= 0) {
+ char *target;
+
+ if (symlink_limit == 0) {
+ printf("%s: Too much symlinks!\n", __func__);
+ return -EMLINK;
+ }
+ target = malloc(fs_info->sectorsize);
+ if (!target)
+ return -ENOMEM;
+ ret = btrfs_readlink(root, ino, 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;
+ goto next;
+ }
+ /* 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)
--
2.26.0