+static int btrfs_block_can_be_shared(struct btrfs_root *root,
+ struct extent_buffer *buf)
+{
+ /*
+ * Tree blocks not in reference counted trees and tree roots
+ * are never shared. If a block was allocated after the last
+ * snapshot and the block was not allocated by tree relocation,
+ * we know the block is not shared.
+ */
+ if (root->ref_cows &&
+ buf != root->node && buf != root->commit_root &&
+ (btrfs_header_generation(buf) <=
+ btrfs_root_last_snapshot(&root->root_item) ||
+ btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)))
+ return 1;
+#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
+ if (root->ref_cows &&
+ btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
+ return 1;
+#endif
+ return 0;
+}
+
+static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root,
+ struct extent_buffer *buf,
+ struct extent_buffer *cow)
+{
+ u64 refs;
+ u64 owner;
+ u64 flags;
+ u64 new_flags = 0;
+ int ret;
+
+ /*
+ * Backrefs update rules:
+ *
+ * Always use full backrefs for extent pointers in tree block
+ * allocated by tree relocation.
+ *
+ * If a shared tree block is no longer referenced by its owner
+ * tree (btrfs_header_owner(buf) == root->root_key.objectid),
+ * use full backrefs for extent pointers in tree block.
+ *
+ * If a tree block is been relocating
+ * (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID),
+ * use full backrefs for extent pointers in tree block.
+ * The reason for this is some operations (such as drop tree)
+ * are only allowed for blocks use full backrefs.
+ */
+
+ if (btrfs_block_can_be_shared(root, buf)) {
+ ret = btrfs_lookup_extent_info(trans, root, buf->start,
+ btrfs_header_level(buf), 1,
+ &refs, &flags);
+ BUG_ON(ret);
+ BUG_ON(refs == 0);
+ } else {
+ refs = 1;
+ if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
+ btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
+ flags = BTRFS_BLOCK_FLAG_FULL_BACKREF;
+ else
+ flags = 0;
+ }
+
+ owner = btrfs_header_owner(buf);
+ BUG_ON(!(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) &&
+ owner == BTRFS_TREE_RELOC_OBJECTID);
+
+ if (refs > 1) {
+ if ((owner == root->root_key.objectid ||
+ root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) &&
+ !(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)) {
+ ret = btrfs_inc_ref(trans, root, buf, 1);
+ BUG_ON(ret);
+
+ if (root->root_key.objectid ==
+ BTRFS_TREE_RELOC_OBJECTID) {
+ ret = btrfs_dec_ref(trans, root, buf, 0);
+ BUG_ON(ret);
+ ret = btrfs_inc_ref(trans, root, cow, 1);
+ BUG_ON(ret);
+ }
+ new_flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
+ } else {
+
+ if (root->root_key.objectid ==
+ BTRFS_TREE_RELOC_OBJECTID)
+ ret = btrfs_inc_ref(trans, root, cow, 1);
+ else
+ ret = btrfs_inc_ref(trans, root, cow, 0);
+ BUG_ON(ret);
+ }
+ if (new_flags != 0) {
+ ret = btrfs_set_block_flags(trans, root, buf->start,
+ btrfs_header_level(buf),
+ new_flags);
+ BUG_ON(ret);
+ }
+ } else {
+ if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
+ if (root->root_key.objectid ==
+ BTRFS_TREE_RELOC_OBJECTID)
+ ret = btrfs_inc_ref(trans, root, cow, 1);
+ else
+ ret = btrfs_inc_ref(trans, root, cow, 0);
+ BUG_ON(ret);
+ ret = btrfs_dec_ref(trans, root, buf, 1);
+ BUG_ON(ret);
+ }
+ clean_tree_block(trans, root, buf);
+ }
+ return 0;
+}
+
+int __btrfs_cow_block(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root,
+ struct extent_buffer *buf,
+ struct extent_buffer *parent, int parent_slot,
+ struct extent_buffer **cow_ret,
+ u64 search_start, u64 empty_size)
+{
+ struct extent_buffer *cow;
+ struct btrfs_disk_key disk_key;
+ int level;
+
+ WARN_ON(root->ref_cows && trans->transid !=
+ root->fs_info->running_transaction->transid);
+ WARN_ON(root->ref_cows && trans->transid != root->last_trans);
+
+ level = btrfs_header_level(buf);
+
+ if (level == 0)
+ btrfs_item_key(buf, &disk_key, 0);
+ else
+ btrfs_node_key(buf, &disk_key, 0);
+
+ cow = btrfs_alloc_free_block(trans, root, buf->len,
+ root->root_key.objectid, &disk_key,
+ level, search_start, empty_size);
+ if (IS_ERR(cow))
+ return PTR_ERR(cow);
+
+ copy_extent_buffer(cow, buf, 0, 0, cow->len);
+ btrfs_set_header_bytenr(cow, cow->start);
+ btrfs_set_header_generation(cow, trans->transid);
+ btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
+ btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN |
+ BTRFS_HEADER_FLAG_RELOC);
+ if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
+ btrfs_set_header_flag(cow, BTRFS_HEADER_FLAG_RELOC);
+ else
+ btrfs_set_header_owner(cow, root->root_key.objectid);
+
+ write_extent_buffer(cow, root->fs_info->fsid,
+ btrfs_header_fsid(), BTRFS_FSID_SIZE);
+
+ WARN_ON(!(buf->flags & EXTENT_BAD_TRANSID) &&
+ btrfs_header_generation(buf) > trans->transid);
+
+ update_ref_for_cow(trans, root, buf, cow);
+
+ if (buf == root->node) {
+ root->node = cow;
+ extent_buffer_get(cow);
+
+ btrfs_free_extent(trans, root, buf->start, buf->len,
+ 0, root->root_key.objectid, level, 0);
+ free_extent_buffer(buf);
+ add_root_to_dirty_list(root);
+ } else {
+ btrfs_set_node_blockptr(parent, parent_slot,
+ cow->start);
+ WARN_ON(trans->transid == 0);
+ btrfs_set_node_ptr_generation(parent, parent_slot,
+ trans->transid);
+ btrfs_mark_buffer_dirty(parent);
+ WARN_ON(btrfs_header_generation(parent) != trans->transid);
+
+ btrfs_free_extent(trans, root, buf->start, buf->len,
+ 0, root->root_key.objectid, level, 1);
+ }
+ if (!list_empty(&buf->recow)) {
+ list_del_init(&buf->recow);
+ free_extent_buffer(buf);
+ }
+ free_extent_buffer(buf);
+ btrfs_mark_buffer_dirty(cow);
+ *cow_ret = cow;
+ return 0;
+}
+
+static inline int should_cow_block(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root,
+ struct extent_buffer *buf)
+{
+ if (btrfs_header_generation(buf) == trans->transid &&
+ !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN) &&
+ !(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID &&
+ btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)))
+ return 0;
+ return 1;
+}
+
+int btrfs_cow_block(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root, struct extent_buffer *buf,
+ struct extent_buffer *parent, int parent_slot,
+ struct extent_buffer **cow_ret)
+{
+ u64 search_start;
+ int ret;
+ /*
+ if (trans->transaction != root->fs_info->running_transaction) {
+ printk(KERN_CRIT "trans %Lu running %Lu\n", trans->transid,
+ root->fs_info->running_transaction->transid);
+ WARN_ON(1);
+ }
+ */
+ if (trans->transid != root->fs_info->generation) {
+ printk(KERN_CRIT "trans %llu running %llu\n",
+ (unsigned long long)trans->transid,
+ (unsigned long long)root->fs_info->generation);
+ WARN_ON(1);
+ }
+ if (!should_cow_block(trans, root, buf)) {
+ *cow_ret = buf;
+ return 0;
+ }
+
+ search_start = buf->start & ~((u64)SZ_1G - 1);
+ ret = __btrfs_cow_block(trans, root, buf, parent,
+ parent_slot, cow_ret, search_start, 0);
+ return ret;
+}
+
+int btrfs_comp_cpu_keys(struct btrfs_key *k1, struct btrfs_key *k2)