Btrfs: Add back pointers from extents to the btree or file referencing them

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

8 files changed, 577 insertions, 105 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 5697705f7530..fd8233e05cf4 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -77,13 +77,37 @@ static int __btrfs_cow_block(struct btrfs_trans_handle *trans,
                              struct extent_buffer **cow_ret,
                              u64 search_start, u64 empty_size)
 {
+        u64 root_gen;
         struct extent_buffer *cow;
+        u32 nritems;
         int ret = 0;
         int different_trans = 0;
+        int level;
+        struct btrfs_key first_key;
+
+        if (root->ref_cows) {
+                root_gen = trans->transid;
+        } else {
+                root_gen = 0;
+        }
 
+        WARN_ON(root->ref_cows && trans->transid !=
+                root->fs_info->running_transaction->transid);
         WARN_ON(root->ref_cows && trans->transid != root->last_trans);
 
-        cow = btrfs_alloc_free_block(trans, root, buf->len,
+        level = btrfs_header_level(buf);
+        nritems = btrfs_header_nritems(buf);
+        if (nritems) {
+                if (level == 0)
+                        btrfs_item_key_to_cpu(buf, &first_key, 0);
+                else
+                        btrfs_node_key_to_cpu(buf, &first_key, 0);
+        } else {
+                first_key.objectid = 0;
+        }
+        cow = __btrfs_alloc_free_block(trans, root, buf->len,
+                                     root->root_key.objectid,
+                                     root_gen, first_key.objectid, level,
                                      search_start, empty_size);
         if (IS_ERR(cow))
                 return PTR_ERR(cow);
@@ -104,14 +128,17 @@ static int __btrfs_cow_block(struct btrfs_trans_handle *trans,
         }
 
         if (buf == root->node) {
+                root_gen = btrfs_header_generation(buf);
                 root->node = cow;
                 extent_buffer_get(cow);
                 if (buf != root->commit_root) {
                         btrfs_free_extent(trans, root, buf->start,
-                                          buf->len, 1);
+                                          buf->len, root->root_key.objectid,
+                                          root_gen, 0, 0, 1);
                 }
                 free_extent_buffer(buf);
         } else {
+                root_gen = btrfs_header_generation(parent);
                 btrfs_set_node_blockptr(parent, parent_slot,
                                         cow->start);
                 WARN_ON(trans->transid == 0);
@@ -119,7 +146,9 @@ static int __btrfs_cow_block(struct btrfs_trans_handle *trans,
                                               trans->transid);
                 btrfs_mark_buffer_dirty(parent);
                 WARN_ON(btrfs_header_generation(parent) != trans->transid);
-                btrfs_free_extent(trans, root, buf->start, buf->len, 1);
+                btrfs_free_extent(trans, root, buf->start, buf->len,
+                                  btrfs_header_owner(parent), root_gen,
+                                  0, 0, 1);
         }
         free_extent_buffer(buf);
         btrfs_mark_buffer_dirty(cow);
@@ -606,6 +635,8 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
                 return 0;
 
         mid = path->nodes[level];
+        WARN_ON(btrfs_header_generation(mid) != trans->transid);
+
         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
 
         if (level < BTRFS_MAX_LEVEL - 1)
@@ -631,7 +662,9 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
                 wait_on_tree_block_writeback(root, mid);
                 /* once for the path */
                 free_extent_buffer(mid);
-                ret = btrfs_free_extent(trans, root, mid->start, mid->len, 1);
+                ret = btrfs_free_extent(trans, root, mid->start, mid->len,
+                                        root->root_key.objectid,
+                                        btrfs_header_generation(mid), 0, 0, 1);
                 /* once for the root ptr */
                 free_extent_buffer(mid);
                 return ret;
@@ -681,6 +714,7 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
                         ret = wret;
                 if (btrfs_header_nritems(right) == 0) {
                         u64 bytenr = right->start;
+                        u64 generation = btrfs_header_generation(parent);
                         u32 blocksize = right->len;
 
                         clean_tree_block(trans, root, right);
@@ -692,7 +726,9 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
                         if (wret)
                                 ret = wret;
                         wret = btrfs_free_extent(trans, root, bytenr,
-                                                 blocksize, 1);
+                                                 blocksize,
+                                                 btrfs_header_owner(parent),
+                                                 generation, 0, 0, 1);
                         if (wret)
                                 ret = wret;
                 } else {
@@ -722,6 +758,7 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
         }
         if (btrfs_header_nritems(mid) == 0) {
                 /* we've managed to empty the middle node, drop it */
+                u64 root_gen = btrfs_header_generation(parent);
                 u64 bytenr = mid->start;
                 u32 blocksize = mid->len;
                 clean_tree_block(trans, root, mid);
@@ -731,7 +768,9 @@ static int balance_level(struct btrfs_trans_handle *trans, struct btrfs_root
                 wret = del_ptr(trans, root, path, level + 1, pslot);
                 if (wret)
                         ret = wret;
-                wret = btrfs_free_extent(trans, root, bytenr, blocksize, 1);
+                wret = btrfs_free_extent(trans, root, bytenr, blocksize,
+                                         btrfs_header_owner(parent),
+                                         root_gen, 0, 0, 1);
                 if (wret)
                         ret = wret;
         } else {
@@ -788,6 +827,7 @@ static int push_nodes_for_insert(struct btrfs_trans_handle *trans,
                 return 1;
 
         mid = path->nodes[level];
+        WARN_ON(btrfs_header_generation(mid) != trans->transid);
         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
 
         if (level < BTRFS_MAX_LEVEL - 1)
@@ -1113,6 +1153,8 @@ static int push_node_left(struct btrfs_trans_handle *trans, struct btrfs_root
         src_nritems = btrfs_header_nritems(src);
         dst_nritems = btrfs_header_nritems(dst);
         push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
+        WARN_ON(btrfs_header_generation(src) != trans->transid);
+        WARN_ON(btrfs_header_generation(dst) != trans->transid);
 
         if (push_items <= 0) {
                 return 1;
@@ -1159,6 +1201,9 @@ static int balance_node_right(struct btrfs_trans_handle *trans,
         int dst_nritems;
         int ret = 0;
 
+        WARN_ON(btrfs_header_generation(src) != trans->transid);
+        WARN_ON(btrfs_header_generation(dst) != trans->transid);
+
         src_nritems = btrfs_header_nritems(src);
         dst_nritems = btrfs_header_nritems(dst);
         push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
@@ -1202,6 +1247,8 @@ static int insert_new_root(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root,
                            struct btrfs_path *path, int level)
 {
+        u64 root_gen;
+        u64 lower_gen;
         struct extent_buffer *lower;
         struct extent_buffer *c;
         struct btrfs_disk_key lower_key;
@@ -1209,7 +1256,20 @@ static int insert_new_root(struct btrfs_trans_handle *trans,
         BUG_ON(path->nodes[level]);
         BUG_ON(path->nodes[level-1] != root->node);
 
-        c = btrfs_alloc_free_block(trans, root, root->nodesize,
+        if (root->ref_cows)
+                root_gen = trans->transid;
+        else
+                root_gen = 0;
+
+        lower = path->nodes[level-1];
+        if (level == 1)
+                btrfs_item_key(lower, &lower_key, 0);
+        else
+                btrfs_node_key(lower, &lower_key, 0);
+
+        c = __btrfs_alloc_free_block(trans, root, root->nodesize,
+                                   root->root_key.objectid,
+                                   root_gen, lower_key.objectid, level,
                                    root->node->start, 0);
         if (IS_ERR(c))
                 return PTR_ERR(c);
@@ -1219,19 +1279,16 @@ static int insert_new_root(struct btrfs_trans_handle *trans,
         btrfs_set_header_bytenr(c, c->start);
         btrfs_set_header_generation(c, trans->transid);
         btrfs_set_header_owner(c, root->root_key.objectid);
-        lower = path->nodes[level-1];
 
         write_extent_buffer(c, root->fs_info->fsid,
                             (unsigned long)btrfs_header_fsid(c),
                             BTRFS_FSID_SIZE);
-        if (level == 1)
-                btrfs_item_key(lower, &lower_key, 0);
-        else
-                btrfs_node_key(lower, &lower_key, 0);
         btrfs_set_node_key(c, &lower_key, 0);
         btrfs_set_node_blockptr(c, 0, lower->start);
-        WARN_ON(btrfs_header_generation(lower) == 0);
-        btrfs_set_node_ptr_generation(c, 0, btrfs_header_generation(lower));
+        lower_gen = btrfs_header_generation(lower);
+        WARN_ON(lower_gen == 0);
+
+        btrfs_set_node_ptr_generation(c, 0, lower_gen);
 
         btrfs_mark_buffer_dirty(c);
 
@@ -1241,6 +1298,18 @@ static int insert_new_root(struct btrfs_trans_handle *trans,
         extent_buffer_get(c);
         path->nodes[level] = c;
         path->slots[level] = 0;
+
+        if (root->ref_cows && lower_gen != trans->transid) {
+                struct btrfs_path *back_path = btrfs_alloc_path();
+                int ret;
+                ret = btrfs_insert_extent_backref(trans,
+                                                  root->fs_info->extent_root,
+                                                  path, lower->start,
+                                                  root->root_key.objectid,
+                                                  trans->transid, 0, 0);
+                BUG_ON(ret);
+                btrfs_free_path(back_path);
+        }
         return 0;
 }
 
@@ -1294,6 +1363,7 @@ static int insert_ptr(struct btrfs_trans_handle *trans, struct btrfs_root
 static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
                       *root, struct btrfs_path *path, int level)
 {
+        u64 root_gen;
         struct extent_buffer *c;
         struct extent_buffer *split;
         struct btrfs_disk_key disk_key;
@@ -1303,6 +1373,7 @@ static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
         u32 c_nritems;
 
         c = path->nodes[level];
+        WARN_ON(btrfs_header_generation(c) != trans->transid);
         if (c == root->node) {
                 /* trying to split the root, lets make a new one */
                 ret = insert_new_root(trans, root, path, level + 1);
@@ -1319,8 +1390,17 @@ static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
         }
 
         c_nritems = btrfs_header_nritems(c);
-        split = btrfs_alloc_free_block(trans, root, root->nodesize,
-                                       c->start, 0);
+        if (root->ref_cows)
+                root_gen = trans->transid;
+        else
+                root_gen = 0;
+
+        btrfs_node_key(c, &disk_key, 0);
+        split = __btrfs_alloc_free_block(trans, root, root->nodesize,
+                                         root->root_key.objectid,
+                                         root_gen,
+                                         btrfs_disk_key_objectid(&disk_key),
+                                         level, c->start, 0);
         if (IS_ERR(split))
                 return PTR_ERR(split);
 
@@ -1789,6 +1869,7 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
                       *root, struct btrfs_key *ins_key,
                       struct btrfs_path *path, int data_size, int extend)
 {
+        u64 root_gen;
         struct extent_buffer *l;
         u32 nritems;
         int mid;
@@ -1807,6 +1888,11 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
         if (extend)
                 space_needed = data_size;
 
+        if (root->ref_cows)
+                root_gen = trans->transid;
+        else
+                root_gen = 0;
+
         /* first try to make some room by pushing left and right */
         if (ins_key->type != BTRFS_DIR_ITEM_KEY) {
                 wret = push_leaf_right(trans, root, path, data_size, 0);
@@ -1837,8 +1923,12 @@ again:
         nritems = btrfs_header_nritems(l);
         mid = (nritems + 1)/ 2;
 
-        right = btrfs_alloc_free_block(trans, root, root->leafsize,
-                                       l->start, 0);
+        btrfs_item_key(l, &disk_key, 0);
+
+        right = __btrfs_alloc_free_block(trans, root, root->leafsize,
+                                         root->root_key.objectid,
+                                         root_gen, disk_key.objectid, 0,
+                                         l->start, 0);
         if (IS_ERR(right))
                 return PTR_ERR(right);
 
@@ -2413,13 +2503,16 @@ int btrfs_del_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                 if (leaf == root->node) {
                         btrfs_set_header_level(leaf, 0);
                 } else {
+                        u64 root_gen = btrfs_header_generation(path->nodes[1]);
                         clean_tree_block(trans, root, leaf);
                         wait_on_tree_block_writeback(root, leaf);
                         wret = del_ptr(trans, root, path, 1, path->slots[1]);
                         if (wret)
                                 ret = wret;
                         wret = btrfs_free_extent(trans, root,
-                                                 leaf->start, leaf->len, 1);
+                                         leaf->start, leaf->len,
+                                         btrfs_header_owner(path->nodes[1]),
+                                         root_gen, 0, 0, 1);
                         if (wret)
                                 ret = wret;
                 }
@@ -2456,9 +2549,13 @@ int btrfs_del_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                         }
 
                         if (btrfs_header_nritems(leaf) == 0) {
+                                u64 root_gen;
                                 u64 bytenr = leaf->start;
                                 u32 blocksize = leaf->len;
 
+                                root_gen = btrfs_header_generation(
+                                                           path->nodes[1]);
+
                                 clean_tree_block(trans, root, leaf);
                                 wait_on_tree_block_writeback(root, leaf);
 
@@ -2468,7 +2565,9 @@ int btrfs_del_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 
                                 free_extent_buffer(leaf);
                                 wret = btrfs_free_extent(trans, root, bytenr,
-                                                         blocksize, 1);
+                                             blocksize,
+                                             btrfs_header_owner(path->nodes[1]),
+                                             root_gen, 0, 0, 1);
                                 if (wret)
                                         ret = wret;
                         } else {
@@ -2483,6 +2582,61 @@ int btrfs_del_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 }
 
 /*
+ * walk up the tree as far as required to find the previous leaf.
+ * returns 0 if it found something or 1 if there are no lesser leaves.
+ * returns < 0 on io errors.
+ */
+int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
+{
+        int slot;
+        int level = 1;
+        u64 bytenr;
+        struct extent_buffer *c;
+        struct extent_buffer *next = NULL;
+
+        while(level < BTRFS_MAX_LEVEL) {
+                if (!path->nodes[level])
+                        return 1;
+
+                slot = path->slots[level];
+                c = path->nodes[level];
+                if (slot == 0) {
+                        level++;
+                        if (level == BTRFS_MAX_LEVEL)
+                                return 1;
+                        continue;
+                }
+                slot--;
+
+                bytenr = btrfs_node_blockptr(c, slot);
+                if (next)
+                        free_extent_buffer(next);
+
+                if (path->reada < 0)
+                        reada_for_search(root, path, level, slot);
+
+                next = read_tree_block(root, bytenr,
+                                       btrfs_level_size(root, level - 1));
+                break;
+        }
+        path->slots[level] = slot;
+        while(1) {
+                level--;
+                c = path->nodes[level];
+                free_extent_buffer(c);
+                path->nodes[level] = next;
+                path->slots[level] = 0;
+                if (!level)
+                        break;
+                if (path->reada)
+                        reada_for_search(root, path, level, 0);
+                next = read_tree_block(root, btrfs_node_blockptr(next, 0),
+                                       btrfs_level_size(root, level - 1));
+        }
+        return 0;
+}
+
+/*
  * walk up the tree as far as required to find the next leaf.
  * returns 0 if it found something or 1 if there are no greater leaves.
  * returns < 0 on io errors.
@@ -2503,6 +2657,8 @@ int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
                 c = path->nodes[level];
                 if (slot >= btrfs_header_nritems(c)) {
                         level++;
+                        if (level == BTRFS_MAX_LEVEL)
+                                return 1;
                         continue;
                 }
 
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fd58dd846e61..cb1b156d954e 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -544,11 +544,12 @@ BTRFS_SETGET_FUNCS(ref_generation, struct btrfs_extent_ref, generation, 64);
 BTRFS_SETGET_FUNCS(ref_objectid, struct btrfs_extent_ref, objectid, 64);
 BTRFS_SETGET_FUNCS(ref_offset, struct btrfs_extent_ref, offset, 64);
 
-BTRFS_SETGET_STACK_FUNCS(ref_root, struct btrfs_extent_ref, root, 64);
-BTRFS_SETGET_STACK_FUNCS(ref_generation, struct btrfs_extent_ref,
+BTRFS_SETGET_STACK_FUNCS(stack_ref_root, struct btrfs_extent_ref, root, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_ref_generation, struct btrfs_extent_ref,
                          generation, 64);
-BTRFS_SETGET_STACK_FUNCS(ref_objectid, struct btrfs_extent_ref, objectid, 64);
-BTRFS_SETGET_STACK_FUNCS(ref_offset, struct btrfs_extent_ref, offset, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_ref_objectid, struct btrfs_extent_ref,
+                         objectid, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_ref_offset, struct btrfs_extent_ref, offset, 64);
 
 BTRFS_SETGET_STACK_FUNCS(stack_extent_refs, struct btrfs_extent_item,
                          refs, 32);
@@ -914,24 +915,45 @@ struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
                                                  *hint, u64 search_start,
                                                  int data, int owner);
 int btrfs_inc_root_ref(struct btrfs_trans_handle *trans,
-                       struct btrfs_root *root);
+                       struct btrfs_root *root, u64 owner_objectid);
 struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                                             struct btrfs_root *root, u32 size,
+                                            u64 root_objectid,
                                             u64 hint, u64 empty_size);
+struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
+                                             struct btrfs_root *root,
+                                             u32 blocksize,
+                                             u64 root_objectid,
+                                             u64 ref_generation,
+                                             u64 first_objectid,
+                                             int level,
+                                             u64 hint,
+                                             u64 empty_size);
+int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
+                                 struct btrfs_root *root,
+                                 struct btrfs_path *path, u64 bytenr,
+                                 u64 root_objectid, u64 ref_generation,
+                                 u64 owner, u64 owner_offset);
 int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
-                       struct btrfs_root *root, u64 owner,
-                       u64 num_bytes, u64 empty_size, u64 search_start,
+                       struct btrfs_root *root,
+                       u64 num_bytes, u64 root_objectid, u64 ref_generation,
+                       u64 owner, u64 owner_offset,
+                       u64 empty_size, u64 hint_byte,
                        u64 search_end, struct btrfs_key *ins, int data);
 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                   struct extent_buffer *buf);
 int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
-                      *root, u64 bytenr, u64 num_bytes, int pin);
+                      *root, u64 bytenr, u64 num_bytes,
+                      u64 root_objectid, u64 ref_generation,
+                      u64 owner_objectid, u64 owner_offset, int pin);
 int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct extent_map_tree *unpin);
 int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
-                                u64 bytenr, u64 num_bytes);
+                                u64 bytenr, u64 num_bytes,
+                                u64 root_objectid, u64 ref_generation,
+                                u64 owner, u64 owner_offset);
 int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root);
 int btrfs_free_block_groups(struct btrfs_fs_info *info);
@@ -966,6 +988,7 @@ int btrfs_insert_empty_item(struct btrfs_trans_handle *trans, struct btrfs_root
                             *root, struct btrfs_path *path, struct btrfs_key
                             *cpu_key, u32 data_size);
 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path);
+int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path);
 int btrfs_leaf_free_space(struct btrfs_root *root, struct extent_buffer *leaf);
 int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
                         *root);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 60a30da6af00..0ac21e3aac87 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -210,7 +210,7 @@ static int btree_writepages(struct address_space *mapping,
 {
         struct extent_map_tree *tree;
         tree = &BTRFS_I(mapping->host)->extent_tree;
-        if (wbc->sync_mode == WB_SYNC_NONE) {
+        if (0 && wbc->sync_mode == WB_SYNC_NONE) {
                 u64 num_dirty;
                 u64 start = 0;
                 unsigned long thresh = 96 * 1024 * 1024;
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 0f1ebdd4e925..32991f73e9db 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/sched.h>
+#include <linux/crc32c.h>
 #include "hash.h"
 #include "ctree.h"
 #include "disk-io.h"
@@ -89,7 +90,8 @@ static int cache_block_group(struct btrfs_root *root,
 
                 btrfs_item_key_to_cpu(leaf, &key, slot);
                 if (key.objectid < block_group->key.objectid) {
-                        if (key.objectid + key.offset > first_free)
+                        if (btrfs_key_type(&key) != BTRFS_EXTENT_REF_KEY &&
+                            key.objectid + key.offset > first_free)
                                 first_free = key.objectid + key.offset;
                         goto next;
                 }
@@ -353,7 +355,7 @@ found:
         return found_group;
 }
 
-static u64 hash_extent_ref(u64 root_objectid, u64 root_generation,
+static u64 hash_extent_ref(u64 root_objectid, u64 ref_generation,
                            u64 owner, u64 owner_offset)
 {
         u32 high_crc = ~(u32)0;
@@ -362,53 +364,149 @@ static u64 hash_extent_ref(u64 root_objectid, u64 root_generation,
 
         lenum = cpu_to_le64(root_objectid);
         high_crc = crc32c(high_crc, &lenum, sizeof(lenum));
-        lenum = cpu_to_le64(root_generation);
-        high_crc = crc32c(high_crc, &lenum, sizeof(lenum));
+        lenum = cpu_to_le64(ref_generation);
+        low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
 
+#if 0
         lenum = cpu_to_le64(owner);
         low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
-
         lenum = cpu_to_le64(owner_offset);
         low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
-
+#endif
         return ((u64)high_crc << 32) | (u64)low_crc;
 }
 
-int insert_extent_ref(struct btrfs_trans_handle *trans,
-                                struct btrfs_root *root,
-                                struct btrfs_path *path,
-                                u64 bytenr,
-                                u64 root_objectid, u64 root_generation,
-                                u64 owner, u64 owner_offset)
+static int match_extent_ref(struct extent_buffer *leaf,
+                            struct btrfs_extent_ref *disk_ref,
+                            struct btrfs_extent_ref *cpu_ref)
+{
+        int ret;
+        int len;
+
+        if (cpu_ref->objectid)
+                len = sizeof(*cpu_ref);
+        else
+                len = 2 * sizeof(u64);
+        ret = memcmp_extent_buffer(leaf, cpu_ref, (unsigned long)disk_ref,
+                                   len);
+        return ret == 0;
+}
+
+static int lookup_extent_backref(struct btrfs_trans_handle *trans,
+                                 struct btrfs_root *root,
+                                 struct btrfs_path *path, u64 bytenr,
+                                 u64 root_objectid, u64 ref_generation,
+                                 u64 owner, u64 owner_offset, int del)
 {
         u64 hash;
         struct btrfs_key key;
+        struct btrfs_key found_key;
         struct btrfs_extent_ref ref;
-        struct extent_buffer *l;
-        struct btrfs_extent_item *item;
+        struct extent_buffer *leaf;
+        struct btrfs_extent_ref *disk_ref;
+        int ret;
+        int ret2;
+
+        btrfs_set_stack_ref_root(&ref, root_objectid);
+        btrfs_set_stack_ref_generation(&ref, ref_generation);
+        btrfs_set_stack_ref_objectid(&ref, owner);
+        btrfs_set_stack_ref_offset(&ref, owner_offset);
+
+        hash = hash_extent_ref(root_objectid, ref_generation, owner,
+                               owner_offset);
+        key.offset = hash;
+        key.objectid = bytenr;
+        key.type = BTRFS_EXTENT_REF_KEY;
+
+        while (1) {
+                ret = btrfs_search_slot(trans, root, &key, path,
+                                        del ? -1 : 0, del);
+                if (ret < 0)
+                        goto out;
+                leaf = path->nodes[0];
+                if (ret != 0) {
+                        u32 nritems = btrfs_header_nritems(leaf);
+                        if (path->slots[0] >= nritems) {
+                                ret2 = btrfs_next_leaf(root, path);
+                                if (ret2)
+                                        goto out;
+                                leaf = path->nodes[0];
+                        }
+                        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+                        if (found_key.objectid != bytenr ||
+                            found_key.type != BTRFS_EXTENT_REF_KEY)
+                                goto out;
+                        key.offset = found_key.offset;
+                        if (del) {
+                                btrfs_release_path(root, path);
+                                continue;
+                        }
+                }
+                disk_ref = btrfs_item_ptr(path->nodes[0],
+                                          path->slots[0],
+                                          struct btrfs_extent_ref);
+                if (match_extent_ref(path->nodes[0], disk_ref, &ref)) {
+                        ret = 0;
+                        goto out;
+                }
+                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+                key.offset = found_key.offset + 1;
+                btrfs_release_path(root, path);
+        }
+out:
+        return ret;
+}
+
+int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
+                                 struct btrfs_root *root,
+                                 struct btrfs_path *path, u64 bytenr,
+                                 u64 root_objectid, u64 ref_generation,
+                                 u64 owner, u64 owner_offset)
+{
+        u64 hash;
+        struct btrfs_key key;
+        struct btrfs_extent_ref ref;
+        struct btrfs_extent_ref *disk_ref;
         int ret;
 
         btrfs_set_stack_ref_root(&ref, root_objectid);
-        btrfs_set_stack_ref_generation(&ref, root_generation);
+        btrfs_set_stack_ref_generation(&ref, ref_generation);
         btrfs_set_stack_ref_objectid(&ref, owner);
         btrfs_set_stack_ref_offset(&ref, owner_offset);
 
-        ret = btrfs_name_hash(&ref, sizeof(ref), &hash);
+        hash = hash_extent_ref(root_objectid, ref_generation, owner,
+                               owner_offset);
         key.offset = hash;
         key.objectid = bytenr;
         key.type = BTRFS_EXTENT_REF_KEY;
 
         ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(ref));
         while (ret == -EEXIST) {
-
+                disk_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                          struct btrfs_extent_ref);
+                if (match_extent_ref(path->nodes[0], disk_ref, &ref))
+                        goto out;
+                key.offset++;
+                btrfs_release_path(root, path);
+                ret = btrfs_insert_empty_item(trans, root, path, &key,
+                                              sizeof(ref));
         }
-
+        if (ret)
+                goto out;
+        disk_ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                  struct btrfs_extent_ref);
+        write_extent_buffer(path->nodes[0], &ref, (unsigned long)disk_ref,
+                            sizeof(ref));
+        btrfs_mark_buffer_dirty(path->nodes[0]);
+out:
+        btrfs_release_path(root, path);
+        return ret;
 }
 
 int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 u64 bytenr, u64 num_bytes,
-                                u64 root_objectid, u64 root_generation,
+                                u64 root_objectid, u64 ref_generation,
                                 u64 owner, u64 owner_offset)
 {
         struct btrfs_path *path;
@@ -441,6 +539,11 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
         btrfs_mark_buffer_dirty(path->nodes[0]);
 
         btrfs_release_path(root->fs_info->extent_root, path);
+
+        ret = btrfs_insert_extent_backref(trans, root->fs_info->extent_root,
+                                          path, bytenr, root_objectid,
+                                          ref_generation, owner, owner_offset);
+        BUG_ON(ret);
         finish_current_insert(trans, root->fs_info->extent_root);
         del_pending_extents(trans, root->fs_info->extent_root);
 
@@ -489,10 +592,29 @@ out:
 }
 
 int btrfs_inc_root_ref(struct btrfs_trans_handle *trans,
-                       struct btrfs_root *root)
+                       struct btrfs_root *root, u64 owner_objectid)
 {
+        u64 generation;
+        u64 key_objectid;
+        u64 level;
+        u32 nritems;
+        struct btrfs_disk_key disk_key;
+
+        level = btrfs_header_level(root->node);
+        generation = trans->transid;
+        nritems = btrfs_header_nritems(root->node);
+        if (nritems > 0) {
+                if (level == 0)
+                        btrfs_item_key(root->node, &disk_key, 0);
+                else
+                        btrfs_node_key(root->node, &disk_key, 0);
+                key_objectid = btrfs_disk_key_objectid(&disk_key);
+        } else {
+                key_objectid = 0;
+        }
         return btrfs_inc_extent_ref(trans, root, root->node->start,
-                                    root->node->len);
+                                    root->node->len, owner_objectid,
+                                    generation, 0, 0);
 }
 
 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
@@ -506,7 +628,6 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
         int level;
         int ret;
         int faili;
-        int err;
 
         if (!root->ref_cows)
                 return 0;
@@ -528,7 +649,9 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                         if (disk_bytenr == 0)
                                 continue;
                         ret = btrfs_inc_extent_ref(trans, root, disk_bytenr,
-                                    btrfs_file_extent_disk_num_bytes(buf, fi));
+                                    btrfs_file_extent_disk_num_bytes(buf, fi),
+                                    root->root_key.objectid, trans->transid,
+                                    key.objectid, key.offset);
                         if (ret) {
                                 faili = i;
                                 goto fail;
@@ -536,7 +659,9 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                 } else {
                         bytenr = btrfs_node_blockptr(buf, i);
                         ret = btrfs_inc_extent_ref(trans, root, bytenr,
-                                           btrfs_level_size(root, level - 1));
+                                           btrfs_level_size(root, level - 1),
+                                           root->root_key.objectid,
+                                           trans->transid, 0, 0);
                         if (ret) {
                                 faili = i;
                                 goto fail;
@@ -546,6 +671,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
         return 0;
 fail:
         WARN_ON(1);
+#if 0
         for (i =0; i < faili; i++) {
                 if (level == 0) {
                         u64 disk_bytenr;
@@ -571,6 +697,7 @@ fail:
                         BUG_ON(err);
                 }
         }
+#endif
         return ret;
 }
 
@@ -809,18 +936,18 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
 static int finish_current_insert(struct btrfs_trans_handle *trans, struct
                                  btrfs_root *extent_root)
 {
+        u64 start;
+        u64 end;
+        struct btrfs_fs_info *info = extent_root->fs_info;
+        struct btrfs_path *path;
         struct btrfs_key ins;
         struct btrfs_extent_item extent_item;
         int ret;
         int err = 0;
-        u64 start;
-        u64 end;
-        struct btrfs_fs_info *info = extent_root->fs_info;
 
         btrfs_set_stack_extent_refs(&extent_item, 1);
         btrfs_set_key_type(&ins, BTRFS_EXTENT_ITEM_KEY);
-        btrfs_set_stack_extent_owner(&extent_item,
-                                     extent_root->root_key.objectid);
+        path = btrfs_alloc_path();
 
         while(1) {
                 ret = find_first_extent_bit(&info->extent_ins, 0, &start,
@@ -834,7 +961,12 @@ static int finish_current_insert(struct btrfs_trans_handle *trans, struct
                                         &extent_item, sizeof(extent_item));
                 clear_extent_bits(&info->extent_ins, start, end, EXTENT_LOCKED,
                                   GFP_NOFS);
+                err = btrfs_insert_extent_backref(trans, extent_root, path,
+                                          start, extent_root->root_key.objectid,
+                                          0, 0, 0);
+                BUG_ON(err);
         }
+        btrfs_free_path(path);
         return 0;
 }
 
@@ -871,7 +1003,9 @@ static int pin_down_bytes(struct btrfs_root *root, u64 bytenr, u32 num_bytes,
  * remove an extent from the root, returns 0 on success
  */
 static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
-                         *root, u64 bytenr, u64 num_bytes, int pin,
+                         *root, u64 bytenr, u64 num_bytes,
+                         u64 root_objectid, u64 ref_generation,
+                         u64 owner_objectid, u64 owner_offset, int pin,
                          int mark_free)
 {
         struct btrfs_path *path;
@@ -891,6 +1025,24 @@ static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
         if (!path)
                 return -ENOMEM;
 
+        if (ref_generation && owner_objectid == 0 && root_objectid == 3) {
+//printk("drop backref root %Lu gen %Lu byte %Lu\n", root_objectid, ref_generation, bytenr );
+        }
+        ret = lookup_extent_backref(trans, extent_root, path,
+                                    bytenr, root_objectid,
+                                    ref_generation,
+                                    owner_objectid, owner_offset, 1);
+        if (ret == 0) {
+                ret = btrfs_del_item(trans, extent_root, path);
+        } else {
+                btrfs_print_leaf(extent_root, path->nodes[0]);
+                WARN_ON(1);
+                printk("Unable to find ref byte nr %Lu root %Lu "
+                       " gen %Lu owner %Lu offset %Lu\n", bytenr,
+                       root_objectid, ref_generation, owner_objectid,
+                       owner_offset);
+        }
+        btrfs_release_path(extent_root, path);
         ret = btrfs_search_slot(trans, extent_root, &key, path, -1, 1);
         if (ret < 0)
                 return ret;
@@ -965,7 +1117,9 @@ static int del_pending_extents(struct btrfs_trans_handle *trans, struct
                 clear_extent_bits(pending_del, start, end, EXTENT_LOCKED,
                                   GFP_NOFS);
                 ret = __free_extent(trans, extent_root,
-                                     start, end + 1 - start, 0, 0);
+                                     start, end + 1 - start,
+                                     extent_root->root_key.objectid,
+                                     0, 0, 0, 0, 0);
                 if (ret)
                         err = ret;
         }
@@ -976,18 +1130,25 @@ static int del_pending_extents(struct btrfs_trans_handle *trans, struct
  * remove an extent from the root, returns 0 on success
  */
 int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
-                      *root, u64 bytenr, u64 num_bytes, int pin)
+                      *root, u64 bytenr, u64 num_bytes,
+                      u64 root_objectid, u64 ref_generation,
+                      u64 owner_objectid, u64 owner_offset, int pin)
 {
         struct btrfs_root *extent_root = root->fs_info->extent_root;
         int pending_ret;
         int ret;
 
         WARN_ON(num_bytes < root->sectorsize);
+        if (!root->ref_cows)
+                ref_generation = 0;
+
         if (root == extent_root) {
                 pin_down_bytes(root, bytenr, num_bytes, 1);
                 return 0;
         }
-        ret = __free_extent(trans, root, bytenr, num_bytes, pin, pin == 0);
+        ret = __free_extent(trans, root, bytenr, num_bytes, root_objectid,
+                            ref_generation, owner_objectid, owner_offset,
+                            pin, pin == 0);
         pending_ret = del_pending_extents(trans, root->fs_info->extent_root);
         return ret ? ret : pending_ret;
 }
@@ -1080,23 +1241,26 @@ check_failed:
         btrfs_item_key_to_cpu(l, &key, path->slots[0]);
 
         /*
-         * a rare case, go back one key if we hit a block group item
-         * instead of an extent item
+         * walk backwards to find the first extent item key
          */
-        if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY &&
-            key.objectid + key.offset >= search_start) {
-                ins->objectid = key.objectid;
-                ins->offset = key.offset - 1;
-                btrfs_release_path(root, path);
-                ret = btrfs_search_slot(trans, root, ins, path, 0, 0);
-                if (ret < 0)
-                        goto error;
-
-                if (path->slots[0] > 0) {
+        while(btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY) {
+                if (path->slots[0] == 0) {
+                        ret = btrfs_prev_leaf(root, path);
+                        if (ret != 0) {
+                                ret = btrfs_search_slot(trans, root, ins,
+                                                        path, 0, 0);
+                                if (ret < 0)
+                                        goto error;
+                                if (path->slots[0] > 0)
+                                        path->slots[0]--;
+                                break;
+                        }
+                } else {
                         path->slots[0]--;
                 }
+                l = path->nodes[0];
+                btrfs_item_key_to_cpu(l, &key, path->slots[0]);
         }
-
         while (1) {
                 l = path->nodes[0];
                 slot = path->slots[0];
@@ -1146,7 +1310,8 @@ check_failed:
                         }
                 }
                 if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY) {
-                        if (!start_found) {
+                        if (!start_found && btrfs_key_type(&key) ==
+                            BTRFS_BLOCK_GROUP_ITEM_KEY) {
                                 last_byte = key.objectid;
                                 start_found = 1;
                         }
@@ -1244,8 +1409,10 @@ error:
  * returns 0 if everything worked, non-zero otherwise.
  */
 int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
-                       struct btrfs_root *root, u64 owner,
-                       u64 num_bytes, u64 empty_size, u64 hint_byte,
+                       struct btrfs_root *root,
+                       u64 num_bytes, u64 root_objectid, u64 ref_generation,
+                       u64 owner, u64 owner_offset,
+                       u64 empty_size, u64 hint_byte,
                        u64 search_end, struct btrfs_key *ins, int data)
 {
         int ret;
@@ -1255,9 +1422,9 @@ int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
         struct btrfs_fs_info *info = root->fs_info;
         struct btrfs_root *extent_root = info->extent_root;
         struct btrfs_extent_item extent_item;
+        struct btrfs_path *path;
 
         btrfs_set_stack_extent_refs(&extent_item, 1);
-        btrfs_set_stack_extent_owner(&extent_item, owner);
 
         WARN_ON(num_bytes < root->sectorsize);
         ret = find_free_extent(trans, root, num_bytes, empty_size,
@@ -1296,8 +1463,16 @@ int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
 
         trans->alloc_exclude_start = 0;
         trans->alloc_exclude_nr = 0;
+        BUG_ON(ret);
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        ret = btrfs_insert_extent_backref(trans, extent_root, path,
+                                          ins->objectid, root_objectid,
+                                          ref_generation, owner, owner_offset);
 
         BUG_ON(ret);
+        btrfs_free_path(path);
         finish_current_insert(trans, extent_root);
         pending_ret = del_pending_extents(trans, extent_root);
 
@@ -1321,15 +1496,43 @@ update_block:
  */
 struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
                                              struct btrfs_root *root,
-                                             u32 blocksize, u64 hint,
+                                             u32 blocksize,
+                                             u64 root_objectid, u64 hint,
+                                             u64 empty_size)
+{
+        u64 ref_generation;
+
+        if (root->ref_cows)
+                ref_generation = trans->transid;
+        else
+                ref_generation = 0;
+
+
+        return __btrfs_alloc_free_block(trans, root, blocksize, root_objectid,
+                                        ref_generation, 0, 0, hint, empty_size);
+}
+
+/*
+ * helper function to allocate a block for a given tree
+ * returns the tree buffer or NULL.
+ */
+struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
+                                             struct btrfs_root *root,
+                                             u32 blocksize,
+                                             u64 root_objectid,
+                                             u64 ref_generation,
+                                             u64 first_objectid,
+                                             int level,
+                                             u64 hint,
                                              u64 empty_size)
 {
         struct btrfs_key ins;
         int ret;
         struct extent_buffer *buf;
 
-        ret = btrfs_alloc_extent(trans, root, root->root_key.objectid,
-                                 blocksize, empty_size, hint,
+        ret = btrfs_alloc_extent(trans, root, blocksize,
+                                 root_objectid, ref_generation,
+                                 first_objectid, level, empty_size, hint,
                                  (u64)-1, &ins, 0);
         if (ret) {
                 BUG_ON(ret > 0);
@@ -1337,7 +1540,9 @@ struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
         }
         buf = btrfs_find_create_tree_block(root, ins.objectid, blocksize);
         if (!buf) {
-                btrfs_free_extent(trans, root, ins.objectid, blocksize, 0);
+                btrfs_free_extent(trans, root, ins.objectid, blocksize,
+                                  root->root_key.objectid, ref_generation,
+                                  0, 0, 0);
                 return ERR_PTR(-ENOMEM);
         }
         btrfs_set_buffer_uptodate(buf);
@@ -1355,6 +1560,8 @@ struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 static int drop_leaf_ref(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, struct extent_buffer *leaf)
 {
+        u64 leaf_owner;
+        u64 leaf_generation;
         struct btrfs_key key;
         struct btrfs_file_extent_item *fi;
         int i;
@@ -1363,6 +1570,9 @@ static int drop_leaf_ref(struct btrfs_trans_handle *trans,
 
         BUG_ON(!btrfs_is_leaf(leaf));
         nritems = btrfs_header_nritems(leaf);
+        leaf_owner = btrfs_header_owner(leaf);
+        leaf_generation = btrfs_header_generation(leaf);
+
         for (i = 0; i < nritems; i++) {
                 u64 disk_bytenr;
 
@@ -1381,7 +1591,9 @@ static int drop_leaf_ref(struct btrfs_trans_handle *trans,
                 if (disk_bytenr == 0)
                         continue;
                 ret = btrfs_free_extent(trans, root, disk_bytenr,
-                                btrfs_file_extent_disk_num_bytes(leaf, fi), 0);
+                                btrfs_file_extent_disk_num_bytes(leaf, fi),
+                                leaf_owner, leaf_generation,
+                                key.objectid, key.offset, 0);
                 BUG_ON(ret);
         }
         return 0;
@@ -1423,9 +1635,12 @@ static void reada_walk_down(struct btrfs_root *root,
 static int walk_down_tree(struct btrfs_trans_handle *trans, struct btrfs_root
                           *root, struct btrfs_path *path, int *level)
 {
+        u64 root_owner;
+        u64 root_gen;
+        u64 bytenr;
         struct extent_buffer *next;
         struct extent_buffer *cur;
-        u64 bytenr;
+        struct extent_buffer *parent;
         u32 blocksize;
         int ret;
         u32 refs;
@@ -1466,9 +1681,13 @@ static int walk_down_tree(struct btrfs_trans_handle *trans, struct btrfs_root
                 ret = lookup_extent_ref(trans, root, bytenr, blocksize, &refs);
                 BUG_ON(ret);
                 if (refs != 1) {
+                        parent = path->nodes[*level];
+                        root_owner = btrfs_header_owner(parent);
+                        root_gen = btrfs_header_generation(parent);
                         path->slots[*level]++;
                         ret = btrfs_free_extent(trans, root, bytenr,
-                                                blocksize, 1);
+                                                blocksize, root_owner,
+                                                root_gen, 0, 0, 1);
                         BUG_ON(ret);
                         continue;
                 }
@@ -1484,10 +1703,16 @@ static int walk_down_tree(struct btrfs_trans_handle *trans, struct btrfs_root
                                                 blocksize, &refs);
                         BUG_ON(ret);
                         if (refs != 1) {
+                                parent = path->nodes[*level];
+                                root_owner = btrfs_header_owner(parent);
+                                root_gen = btrfs_header_generation(parent);
+
                                 path->slots[*level]++;
                                 free_extent_buffer(next);
-                                ret = btrfs_free_extent(trans, root,
-                                                        bytenr, blocksize, 1);
+                                ret = btrfs_free_extent(trans, root, bytenr,
+                                                        blocksize,
+                                                        root_owner,
+                                                        root_gen, 0, 0, 1);
                                 BUG_ON(ret);
                                 continue;
                         }
@@ -1502,8 +1727,19 @@ static int walk_down_tree(struct btrfs_trans_handle *trans, struct btrfs_root
 out:
         WARN_ON(*level < 0);
         WARN_ON(*level >= BTRFS_MAX_LEVEL);
+
+        if (path->nodes[*level] == root->node) {
+                root_owner = root->root_key.objectid;
+                parent = path->nodes[*level];
+        } else {
+                parent = path->nodes[*level + 1];
+                root_owner = btrfs_header_owner(parent);
+        }
+
+        root_gen = btrfs_header_generation(parent);
         ret = btrfs_free_extent(trans, root, path->nodes[*level]->start,
-                                path->nodes[*level]->len, 1);
+                                path->nodes[*level]->len,
+                                root_owner, root_gen, 0, 0, 1);
         free_extent_buffer(path->nodes[*level]);
         path->nodes[*level] = NULL;
         *level += 1;
@@ -1519,10 +1755,12 @@ out:
 static int walk_up_tree(struct btrfs_trans_handle *trans, struct btrfs_root
                         *root, struct btrfs_path *path, int *level)
 {
+        u64 root_owner;
+        u64 root_gen;
+        struct btrfs_root_item *root_item = &root->root_item;
         int i;
         int slot;
         int ret;
-        struct btrfs_root_item *root_item = &root->root_item;
 
         for(i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
                 slot = path->slots[i];
@@ -1539,9 +1777,20 @@ static int walk_up_tree(struct btrfs_trans_handle *trans, struct btrfs_root
                         root_item->drop_level = i;
                         return 0;
                 } else {
+                        if (path->nodes[*level] == root->node) {
+                                root_owner = root->root_key.objectid;
+                                root_gen =
+                                   btrfs_header_generation(path->nodes[*level]);
+                        } else {
+                                struct extent_buffer *node;
+                                node = path->nodes[*level + 1];
+                                root_owner = btrfs_header_owner(node);
+                                root_gen = btrfs_header_generation(node);
+                        }
                         ret = btrfs_free_extent(trans, root,
                                                 path->nodes[*level]->start,
-                                                path->nodes[*level]->len, 1);
+                                                path->nodes[*level]->len,
+                                                root_owner, root_gen, 0, 0, 1);
                         BUG_ON(ret);
                         free_extent_buffer(path->nodes[*level]);
                         path->nodes[*level] = NULL;
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index b0d637787264..5b1f90f06e03 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -496,7 +496,10 @@ next_slot:
                                                    sizeof(old));
                                 if (disk_bytenr != 0) {
                                         ret = btrfs_inc_extent_ref(trans, root,
-                                                 disk_bytenr, disk_num_bytes);
+                                                 disk_bytenr, disk_num_bytes,
+                                                 root->root_key.objectid,
+                                                 trans->transid,
+                                                 key.objectid, end);
                                         BUG_ON(ret);
                                 }
                         }
@@ -541,6 +544,14 @@ next_slot:
                         u64 disk_bytenr = 0;
                         u64 disk_num_bytes = 0;
                         u64 extent_num_bytes = 0;
+                        u64 root_gen;
+
+                        if (leaf != root->node) {
+                                root_gen =
+                                        btrfs_header_generation(path->nodes[1]);
+                        } else {
+                                root_gen = btrfs_header_generation(leaf);
+                        }
                         if (found_extent) {
                                 disk_bytenr =
                                       btrfs_file_extent_disk_bytenr(leaf,
@@ -562,8 +573,11 @@ next_slot:
                         if (found_extent && disk_bytenr != 0) {
                                 inode->i_blocks -= extent_num_bytes >> 9;
                                 ret = btrfs_free_extent(trans, root,
-                                                        disk_bytenr,
-                                                        disk_num_bytes, 0);
+                                                disk_bytenr,
+                                                disk_num_bytes,
+                                                root->root_key.objectid,
+                                                root_gen, inode->i_ino,
+                                                key.offset, 0);
                         }
 
                         BUG_ON(ret);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d0af0807d9f8..bb70db0c9df4 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -93,7 +93,9 @@ static int run_delalloc_range(struct inode *inode, u64 start, u64 end)
         if (alloc_hint == EXTENT_MAP_INLINE)
                 goto out;
 
-        ret = btrfs_alloc_extent(trans, root, inode->i_ino, num_bytes, 0,
+        ret = btrfs_alloc_extent(trans, root, num_bytes,
+                                 root->root_key.objectid, trans->transid,
+                                 inode->i_ino, start, 0,
                                  alloc_hint, (u64)-1, &ins, 1);
         if (ret) {
                 WARN_ON(1);
@@ -560,6 +562,7 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
         u64 extent_start = 0;
         u64 extent_num_bytes = 0;
         u64 item_end = 0;
+        u64 root_gen = 0;
         int found_extent;
         int del_item;
         int extent_type = -1;
@@ -670,6 +673,15 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
                                         found_extent = 1;
                                         inode->i_blocks -= num_dec;
                                 }
+                                if (leaf == root->node) {
+                                        root_gen =
+                                                btrfs_header_generation(leaf);
+                                } else {
+                                        struct extent_buffer *parent;
+                                        parent = path->nodes[1];
+                                        root_gen =
+                                                btrfs_header_generation(parent);
+                                }
                         }
                 } else if (extent_type == BTRFS_FILE_EXTENT_INLINE &&
                            !del_item) {
@@ -690,7 +702,10 @@ delete:
                 btrfs_release_path(root, path);
                 if (found_extent) {
                         ret = btrfs_free_extent(trans, root, extent_start,
-                                                extent_num_bytes, 0);
+                                                extent_num_bytes,
+                                                root->root_key.objectid,
+                                                root_gen, inode->i_ino,
+                                                found_key.offset, 0);
                         BUG_ON(ret);
                 }
         }
@@ -1900,7 +1915,14 @@ static int create_subvol(struct btrfs_root *root, char *name, int namelen)
         trans = btrfs_start_transaction(root, 1);
         BUG_ON(!trans);
 
-        leaf = btrfs_alloc_free_block(trans, root, root->leafsize, 0, 0);
+        ret = btrfs_find_free_objectid(trans, root->fs_info->tree_root,
+                                       0, &objectid);
+        if (ret)
+                goto fail;
+
+        leaf = __btrfs_alloc_free_block(trans, root, root->leafsize,
+                                        objectid, trans->transid, 0, 0,
+                                        0, 0);
         if (IS_ERR(leaf))
                 return PTR_ERR(leaf);
 
@@ -1908,7 +1930,8 @@ static int create_subvol(struct btrfs_root *root, char *name, int namelen)
         btrfs_set_header_level(leaf, 0);
         btrfs_set_header_bytenr(leaf, leaf->start);
         btrfs_set_header_generation(leaf, trans->transid);
-        btrfs_set_header_owner(leaf, root->root_key.objectid);
+        btrfs_set_header_owner(leaf, objectid);
+
         write_extent_buffer(leaf, root->fs_info->fsid,
                             (unsigned long)btrfs_header_fsid(leaf),
                             BTRFS_FSID_SIZE);
@@ -1933,11 +1956,6 @@ static int create_subvol(struct btrfs_root *root, char *name, int namelen)
         free_extent_buffer(leaf);
         leaf = NULL;
 
-        ret = btrfs_find_free_objectid(trans, root->fs_info->tree_root,
-                                       0, &objectid);
-        if (ret)
-                goto fail;
-
         btrfs_set_root_dirid(&root_item, new_dirid);
 
         key.objectid = objectid;
@@ -2056,7 +2074,7 @@ static int create_snapshot(struct btrfs_root *root, char *name, int namelen)
         if (ret)
                 goto fail;
 
-        ret = btrfs_inc_root_ref(trans, root);
+        ret = btrfs_inc_root_ref(trans, root, objectid);
         if (ret)
                 goto fail;
 fail:
diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
index 030324febf6c..da0b4dcf3617 100644
--- a/fs/btrfs/print-tree.c
+++ b/fs/btrfs/print-tree.c
@@ -33,6 +33,7 @@ void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *l)
         struct btrfs_file_extent_item *fi;
         struct btrfs_key key;
         struct btrfs_key found_key;
+        struct btrfs_extent_ref *ref;
         u32 type;
 
         printk("leaf %llu total ptrs %d free space %d\n",
@@ -73,6 +74,15 @@ void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *l)
                         printk("\t\textent data refs %u\n",
                                 btrfs_extent_refs(l, ei));
                         break;
+                case BTRFS_EXTENT_REF_KEY:
+                        ref = btrfs_item_ptr(l, i, struct btrfs_extent_ref);
+                        printk("\t\textent back ref root %llu gen %llu "
+                               "owner %llu offset %llu\n",
+                               (unsigned long long)btrfs_ref_root(l, ref),
+                               (unsigned long long)btrfs_ref_generation(l, ref),
+                               (unsigned long long)btrfs_ref_objectid(l, ref),
+                               (unsigned long long)btrfs_ref_offset(l, ref));
+                        break;
 
                 case BTRFS_EXTENT_DATA_KEY:
                         fi = btrfs_item_ptr(l, i,
diff --git a/fs/btrfs/tree-defrag.c b/fs/btrfs/tree-defrag.c
index 3994795edfeb..5c58630dce03 100644
--- a/fs/btrfs/tree-defrag.c
+++ b/fs/btrfs/tree-defrag.c
@@ -78,6 +78,8 @@ static int defrag_walk_down(struct btrfs_trans_handle *trans,
                         break;
 
                 if (*level == 1) {
+                        WARN_ON(btrfs_header_generation(path->nodes[*level]) !=
+                                                        trans->transid);
                         ret = btrfs_realloc_node(trans, root,
                                                  path->nodes[*level],
                                                  path->slots[*level],