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

[Su Yue <Damenly_Su@gmx.com>]

On Wed 22 Apr 2020 at 14:50, Qu Wenruo <wqu@suse.com> wrote:

> 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) {

next_length() promises @len <= BTRFS_NAME_LEN, so the check is
trivial.

> +			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';

It was done in btrfs_readlink() already.
> +
> +			ret = btrfs_lookup_path(root, ino, target, &next_root,
> +						&next_ino, &next_type,
> +						symlink_limit);

Just notify gentlely this is a recursive call here. I don't know
whether uboot cares about stack things. But, recursion makes
coding simpler :).

--
Su
> +			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)