Btrfs: use the tree modification log for backref resolving

This enables backref resolving on life trees while they are changing. This
is a prerequisite for quota groups and just nice to have for everything
else.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

2 files changed, 29 insertions, 17 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index fd13101aafa3..0ac47f2834d1 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -231,6 +231,7 @@ add_parent:
  */
 static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
                                         int search_commit_root,
+                                        u64 time_seq,
                                         struct __prelim_ref *ref,
                                         struct ulist *parents,
                                         const u64 *extent_item_pos)
@@ -266,7 +267,7 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
                 goto out;
 
         path->lowest_level = level;
-        ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path, 0, 0);
+        ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
                  "%d for key (%llu %u %llu)\n",
                  (unsigned long long)ref->root_id, level, ref->count, ret,
@@ -305,7 +306,7 @@ out:
  * resolve all indirect backrefs from the list
  */
 static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
-                                   int search_commit_root,
+                                   int search_commit_root, u64 time_seq,
                                    struct list_head *head,
                                    const u64 *extent_item_pos)
 {
@@ -333,7 +334,8 @@ static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
                 if (ref->count == 0)
                         continue;
                 err = __resolve_indirect_ref(fs_info, search_commit_root,
-                                             ref, parents, extent_item_pos);
+                                             time_seq, ref, parents,
+                                             extent_item_pos);
                 if (err) {
                         if (ret == 0)
                                 ret = err;
@@ -750,7 +752,8 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
  */
 static int find_parent_nodes(struct btrfs_trans_handle *trans,
                              struct btrfs_fs_info *fs_info, u64 bytenr,
-                             u64 seq, struct ulist *refs, struct ulist *roots,
+                             u64 delayed_ref_seq, u64 time_seq,
+                             struct ulist *refs, struct ulist *roots,
                              const u64 *extent_item_pos)
 {
         struct btrfs_key key;
@@ -813,7 +816,8 @@ again:
                                 btrfs_put_delayed_ref(&head->node);
                                 goto again;
                         }
-                        ret = __add_delayed_refs(head, seq, &prefs_delayed);
+                        ret = __add_delayed_refs(head, delayed_ref_seq,
+                                                 &prefs_delayed);
                         if (ret) {
                                 spin_unlock(&delayed_refs->lock);
                                 goto out;
@@ -854,8 +858,8 @@ again:
         if (ret)
                 goto out;
 
-        ret = __resolve_indirect_refs(fs_info, search_commit_root, &prefs,
-                                      extent_item_pos);
+        ret = __resolve_indirect_refs(fs_info, search_commit_root, time_seq,
+                                      &prefs, extent_item_pos);
         if (ret)
                 goto out;
 
@@ -945,7 +949,8 @@ static void free_leaf_list(struct ulist *blocks)
  */
 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
                                 struct btrfs_fs_info *fs_info, u64 bytenr,
-                                u64 seq, struct ulist **leafs,
+                                u64 delayed_ref_seq, u64 time_seq,
+                                struct ulist **leafs,
                                 const u64 *extent_item_pos)
 {
         struct ulist *tmp;
@@ -960,8 +965,8 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
                 return -ENOMEM;
         }
 
-        ret = find_parent_nodes(trans, fs_info, bytenr, seq, *leafs, tmp,
-                                extent_item_pos);
+        ret = find_parent_nodes(trans, fs_info, bytenr, delayed_ref_seq,
+                                time_seq, *leafs, tmp, extent_item_pos);
         ulist_free(tmp);
 
         if (ret < 0 && ret != -ENOENT) {
@@ -987,7 +992,8 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
  */
 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
                                 struct btrfs_fs_info *fs_info, u64 bytenr,
-                                u64 seq, struct ulist **roots)
+                                u64 delayed_ref_seq, u64 time_seq,
+                                struct ulist **roots)
 {
         struct ulist *tmp;
         struct ulist_node *node = NULL;
@@ -1005,8 +1011,8 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
 
         ULIST_ITER_INIT(&uiter);
         while (1) {
-                ret = find_parent_nodes(trans, fs_info, bytenr, seq,
-                                        tmp, *roots, NULL);
+                ret = find_parent_nodes(trans, fs_info, bytenr, delayed_ref_seq,
+                                        time_seq, tmp, *roots, NULL);
                 if (ret < 0 && ret != -ENOENT) {
                         ulist_free(tmp);
                         ulist_free(*roots);
@@ -1338,7 +1344,8 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
         struct ulist *roots = NULL;
         struct ulist_node *ref_node = NULL;
         struct ulist_node *root_node = NULL;
-        struct seq_list seq_elem;
+        struct seq_list seq_elem = {};
+        struct seq_list tree_mod_seq_elem = {};
         struct ulist_iterator ref_uiter;
         struct ulist_iterator root_uiter;
         struct btrfs_delayed_ref_root *delayed_refs = NULL;
@@ -1357,17 +1364,20 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
                 spin_lock(&delayed_refs->lock);
                 btrfs_get_delayed_seq(delayed_refs, &seq_elem);
                 spin_unlock(&delayed_refs->lock);
+                btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
         }
 
         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
-                                   seq_elem.seq, &refs, &extent_item_pos);
+                                   seq_elem.seq, tree_mod_seq_elem.seq, &refs,
+                                   &extent_item_pos);
         if (ret)
                 goto out;
 
         ULIST_ITER_INIT(&ref_uiter);
         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
                 ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
-                                                seq_elem.seq, &roots);
+                                                seq_elem.seq,
+                                                tree_mod_seq_elem.seq, &roots);
                 if (ret)
                         break;
                 ULIST_ITER_INIT(&root_uiter);
@@ -1388,6 +1398,7 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
         ulist_free(roots);
 out:
         if (!search_commit_root) {
+                btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
                 btrfs_put_delayed_seq(delayed_refs, &seq_elem);
                 btrfs_end_transaction(trans, fs_info->extent_root);
         }
diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h
index 94ba1b2e733b..c18d8ac7b795 100644
--- a/fs/btrfs/backref.h
+++ b/fs/btrfs/backref.h
@@ -58,7 +58,8 @@ int paths_from_inode(u64 inum, struct inode_fs_paths *ipath);
 
 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
                                 struct btrfs_fs_info *fs_info, u64 bytenr,
-                                u64 seq, struct ulist **roots);
+                                u64 delayed_ref_seq, u64 time_seq,
+                                struct ulist **roots);
 
 struct btrfs_data_container *init_data_container(u32 total_bytes);
 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,