Btrfs: Add back pointers from the inode to the directory that references it

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 136 insertions, 0 deletions

diff --git a/fs/btrfs/inode-item.c b/fs/btrfs/inode-item.c
index 35d2608f8918..cba30b6cc6fe 100644
--- a/fs/btrfs/inode-item.c
+++ b/fs/btrfs/inode-item.c
@@ -20,6 +20,142 @@
 #include "disk-io.h"
 #include "transaction.h"
 
+int find_name_in_backref(struct btrfs_path *path, const char * name,
+                         int name_len, struct btrfs_inode_ref **ref_ret)
+{
+        struct extent_buffer *leaf;
+        struct btrfs_inode_ref *ref;
+        unsigned long ptr;
+        unsigned long name_ptr;
+        u32 item_size;
+        u32 cur_offset = 0;
+        int len;
+
+        leaf = path->nodes[0];
+        item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+        ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
+        while (cur_offset < item_size) {
+                ref = (struct btrfs_inode_ref *)(ptr + cur_offset);
+                len = btrfs_inode_ref_name_len(leaf, ref);
+                name_ptr = (unsigned long)(ref + 1);
+                cur_offset += len + sizeof(*ref);
+                if (len != name_len)
+                        continue;
+                if (memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0) {
+                        *ref_ret = ref;
+                        return 1;
+                }
+        }
+        return 0;
+}
+
+int btrfs_del_inode_ref(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root,
+                           const char *name, int name_len,
+                           u64 inode_objectid, u64 ref_objectid)
+{
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        struct btrfs_inode_ref *ref;
+        struct extent_buffer *leaf;
+        unsigned long ptr;
+        unsigned long item_start;
+        u32 item_size;
+        u32 sub_item_len;
+        int ret;
+        int del_len = name_len + sizeof(*ref);
+
+        key.objectid = inode_objectid;
+        key.offset = ref_objectid;
+        btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+        if (ret > 0) {
+                ret = -ENOENT;
+                goto out;
+        } else if (ret < 0) {
+                goto out;
+        }
+        if (!find_name_in_backref(path, name, name_len, &ref)) {
+                ret = -ENOENT;
+                goto out;
+        }
+        leaf = path->nodes[0];
+        item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+        if (del_len == item_size) {
+                ret = btrfs_del_item(trans, root, path);
+                goto out;
+        }
+        ptr = (unsigned long)ref;
+        sub_item_len = name_len + sizeof(*ref);
+        item_start = btrfs_item_ptr_offset(leaf, path->slots[0]);
+        memmove_extent_buffer(leaf, ptr, ptr + sub_item_len,
+                              item_size - (ptr + sub_item_len - item_start));
+        ret = btrfs_truncate_item(trans, root, path,
+                                  item_size - sub_item_len, 1);
+        BUG_ON(ret);
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+int btrfs_insert_inode_ref(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root,
+                           const char *name, int name_len,
+                           u64 inode_objectid, u64 ref_objectid)
+{
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        struct btrfs_inode_ref *ref;
+        unsigned long ptr;
+        int ret;
+        int ins_len = name_len + sizeof(*ref);
+
+        key.objectid = inode_objectid;
+        key.offset = ref_objectid;
+        btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        ret = btrfs_insert_empty_item(trans, root, path, &key,
+                                      ins_len);
+        if (ret == -EEXIST) {
+                u32 old_size;
+
+                if (find_name_in_backref(path, name, name_len, &ref))
+                        goto out;
+
+                old_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
+                ret = btrfs_extend_item(trans, root, path, ins_len);
+                BUG_ON(ret);
+                ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                     struct btrfs_inode_ref);
+                ref = (struct btrfs_inode_ref *)((unsigned long)ref + old_size);
+                btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
+                ptr = (unsigned long)(ref + 1);
+                ret = 0;
+        } else if (ret < 0) {
+                goto out;
+        } else {
+                ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                     struct btrfs_inode_ref);
+                btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
+                ptr = (unsigned long)(ref + 1);
+        }
+        write_extent_buffer(path->nodes[0], name, ptr, name_len);
+        btrfs_mark_buffer_dirty(path->nodes[0]);
+
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
 int btrfs_insert_empty_inode(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct btrfs_path *path, u64 objectid)