Btrfs: prevent loops in the directory tree when creating snapshots (ea9e8b11) · Commits · 戴 / test

fs/btrfs/ctree.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -1801,6 +1801,9 @@ int btrfs_drop_subtree(struct btrfs_trans_handle *trans,
		struct extent_buffer *node,
		struct extent_buffer *parent);
		/* root-item.c */
		int btrfs_find_root_ref(struct btrfs_root *tree_root,
		struct btrfs_path *path,
		u64 root_id, u64 ref_id);
		int btrfs_add_root_ref(struct btrfs_trans_handle *trans,
		struct btrfs_root *tree_root,
		u64 root_id, u8 type, u64 ref_id,

fs/btrfs/disk-io.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -1129,7 +1129,7 @@ struct btrfs_root btrfs_read_fs_root(struct btrfs_fs_info fs_info,
		kfree(root);
		return ERR_PTR(ret);
		}

		#if 0
		ret = btrfs_sysfs_add_root(root);
		if (ret) {
		free_extent_buffer(root->node);
		@@ -1137,6 +1137,7 @@ struct btrfs_root btrfs_read_fs_root(struct btrfs_fs_info fs_info,
		kfree(root);
		return ERR_PTR(ret);
		}
		#endif
		root->in_sysfs = 1;
		return root;
		}
		@@ -1963,8 +1964,10 @@ int btrfs_free_fs_root(struct btrfs_fs_info fs_info, struct btrfs_root root)
		down_write(&root->anon_super.s_umount);
		kill_anon_super(&root->anon_super);
		}
		#if 0
		if (root->in_sysfs)
		btrfs_sysfs_del_root(root);
		#endif
		if (root->node)
		free_extent_buffer(root->node);
		if (root->commit_root)

fs/btrfs/ioctl.c

+50 −0

Original line number	Diff line number	Diff line
		@@ -284,6 +284,56 @@ static noinline int btrfs_mksubvol(struct path parent, char name,
		* subvolume with specific mode bits.
		*/
		if (snap_src) {
		struct dentry *dir = dentry->d_parent;
		struct dentry *test = dir->d_parent;
		struct btrfs_path *path = btrfs_alloc_path();
		int ret;
		u64 test_oid;
		u64 parent_oid = BTRFS_I(dir->d_inode)->root->root_key.objectid;

		test_oid = snap_src->root_key.objectid;

		ret = btrfs_find_root_ref(snap_src->fs_info->tree_root,
		path, parent_oid, test_oid);
		if (ret == 0)
		goto create;
		btrfs_release_path(snap_src->fs_info->tree_root, path);

		/* we need to make sure we aren't creating a directory loop
		* by taking a snapshot of something that has our current
		* subvol in its directory tree. So, this loops through
		* the dentries and checks the forward refs for each subvolume
		* to see if is references the subvolume where we are
		* placing this new snapshot.
		*/
		while(1) {
		if (!test \|\|
		dir == snap_src->fs_info->sb->s_root \|\|
		test == snap_src->fs_info->sb->s_root \|\|
		test->d_inode->i_sb != snap_src->fs_info->sb) {
		break;
		}
		if (S_ISLNK(test->d_inode->i_mode)) {
		printk("Symlink in snapshot path, failed\n");
		error = -EMLINK;
		btrfs_free_path(path);
		goto out_drop_write;
		}
		test_oid =
		BTRFS_I(test->d_inode)->root->root_key.objectid;
		ret = btrfs_find_root_ref(snap_src->fs_info->tree_root,
		path, test_oid, parent_oid);
		if (ret == 0) {
		printk("Snapshot creation failed, looping\n");
		error = -EMLINK;
		btrfs_free_path(path);
		goto out_drop_write;
		}
		btrfs_release_path(snap_src->fs_info->tree_root, path);
		test = test->d_parent;
		}
		create:
		btrfs_free_path(path);
		error = create_snapshot(snap_src, dentry, name, namelen);
		} else {
		error = create_subvol(BTRFS_I(parent->dentry->d_inode)->root,

fs/btrfs/root-tree.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -300,6 +300,22 @@ int btrfs_del_root_ref(struct btrfs_trans_handle *trans,
		return ret;
		}

		int btrfs_find_root_ref(struct btrfs_root *tree_root,
		struct btrfs_path *path,
		u64 root_id, u64 ref_id)
		{
		struct btrfs_key key;
		int ret;

		key.objectid = root_id;
		key.type = BTRFS_ROOT_REF_KEY;
		key.offset = ref_id;

		ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
		return ret;
		}


		/*
		* add a btrfs_root_ref item. type is either BTRFS_ROOT_REF_KEY
		* or BTRFS_ROOT_BACKREF_KEY.

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