From 4df27c4d5cc1dda54ed7d0a8389347f2df359cf9 Mon Sep 17 00:00:00 2001 From: "Yan, Zheng" Date: Mon, 21 Sep 2009 15:56:00 -0400 Subject: Btrfs: change how subvolumes are organized btrfs allows subvolumes and snapshots anywhere in the directory tree. If we snapshot a subvolume that contains a link to other subvolume called subvolA, subvolA can be accessed through both the original subvolume and the snapshot. This is similar to creating hard link to directory, and has the very similar problems. The aim of this patch is enforcing there is only one access point to each subvolume. Only the first directory entry (the one added when the subvolume/snapshot was created) is treated as valid access point. The first directory entry is distinguished by checking root forward reference. If the corresponding root forward reference is missing, we know the entry is not the first one. This patch also adds snapshot/subvolume rename support, the code allows rename subvolume link across subvolumes. Signed-off-by: Yan Zheng Signed-off-by: Chris Mason --- fs/btrfs/root-tree.c | 69 ++++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 51 insertions(+), 18 deletions(-) (limited to 'fs/btrfs/root-tree.c') diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c index 0ddc6d61c55a..5ef72599a581 100644 --- a/fs/btrfs/root-tree.c +++ b/fs/btrfs/root-tree.c @@ -278,31 +278,57 @@ out: return ret; } -#if 0 /* this will get used when snapshot deletion is implemented */ int btrfs_del_root_ref(struct btrfs_trans_handle *trans, struct btrfs_root *tree_root, - u64 root_id, u8 type, u64 ref_id) + u64 root_id, u64 ref_id, u64 dirid, u64 *sequence, + const char *name, int name_len) + { + struct btrfs_path *path; + struct btrfs_root_ref *ref; + struct extent_buffer *leaf; struct btrfs_key key; + unsigned long ptr; + int err = 0; int ret; - struct btrfs_path *path; path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; key.objectid = root_id; - key.type = type; + key.type = BTRFS_ROOT_BACKREF_KEY; key.offset = ref_id; - +again: ret = btrfs_search_slot(trans, tree_root, &key, path, -1, 1); - BUG_ON(ret); - - ret = btrfs_del_item(trans, tree_root, path); - BUG_ON(ret); + BUG_ON(ret < 0); + if (ret == 0) { + leaf = path->nodes[0]; + ref = btrfs_item_ptr(leaf, path->slots[0], + struct btrfs_root_ref); + + WARN_ON(btrfs_root_ref_dirid(leaf, ref) != dirid); + WARN_ON(btrfs_root_ref_name_len(leaf, ref) != name_len); + ptr = (unsigned long)(ref + 1); + WARN_ON(memcmp_extent_buffer(leaf, name, ptr, name_len)); + *sequence = btrfs_root_ref_sequence(leaf, ref); + + ret = btrfs_del_item(trans, tree_root, path); + BUG_ON(ret); + } else + err = -ENOENT; + + if (key.type == BTRFS_ROOT_BACKREF_KEY) { + btrfs_release_path(tree_root, path); + key.objectid = ref_id; + key.type = BTRFS_ROOT_REF_KEY; + key.offset = root_id; + goto again; + } btrfs_free_path(path); - return ret; + return err; } -#endif int btrfs_find_root_ref(struct btrfs_root *tree_root, struct btrfs_path *path, @@ -319,7 +345,6 @@ int btrfs_find_root_ref(struct btrfs_root *tree_root, return ret; } - /* * add a btrfs_root_ref item. type is either BTRFS_ROOT_REF_KEY * or BTRFS_ROOT_BACKREF_KEY. @@ -335,8 +360,7 @@ int btrfs_find_root_ref(struct btrfs_root *tree_root, */ int btrfs_add_root_ref(struct btrfs_trans_handle *trans, struct btrfs_root *tree_root, - u64 root_id, u8 type, u64 ref_id, - u64 dirid, u64 sequence, + u64 root_id, u64 ref_id, u64 dirid, u64 sequence, const char *name, int name_len) { struct btrfs_key key; @@ -346,13 +370,14 @@ int btrfs_add_root_ref(struct btrfs_trans_handle *trans, struct extent_buffer *leaf; unsigned long ptr; - path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; key.objectid = root_id; - key.type = type; + key.type = BTRFS_ROOT_BACKREF_KEY; key.offset = ref_id; - +again: ret = btrfs_insert_empty_item(trans, tree_root, path, &key, sizeof(*ref) + name_len); BUG_ON(ret); @@ -366,6 +391,14 @@ int btrfs_add_root_ref(struct btrfs_trans_handle *trans, write_extent_buffer(leaf, name, ptr, name_len); btrfs_mark_buffer_dirty(leaf); + if (key.type == BTRFS_ROOT_BACKREF_KEY) { + btrfs_release_path(tree_root, path); + key.objectid = ref_id; + key.type = BTRFS_ROOT_REF_KEY; + key.offset = root_id; + goto again; + } + btrfs_free_path(path); - return ret; + return 0; } -- cgit v1.2.3-58-ga151