btrfs: backref: Add special time_seq == (u64)-1 case for

btrfs_find_all_roots().

Allow btrfs_find_all_roots() to skip all delayed_ref_head lock and tree
lock to do tree search.

This is important for later qgroup implement which will call
find_all_roots() after fs trees are committed.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 29 insertions, 6 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 49bc5a41c1f8..802fabb30e15 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -250,8 +250,12 @@ static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
          * the first item to check. But sometimes, we may enter it with
          * slot==nritems. In that case, go to the next leaf before we continue.
          */
-        if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
-                ret = btrfs_next_old_leaf(root, path, time_seq);
+        if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
+                if (time_seq == (u64)-1)
+                        ret = btrfs_next_leaf(root, path);
+                else
+                        ret = btrfs_next_old_leaf(root, path, time_seq);
+        }
 
         while (!ret && count < total_refs) {
                 eb = path->nodes[0];
@@ -291,7 +295,10 @@ static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
                         eie = NULL;
                 }
 next:
-                ret = btrfs_next_old_item(root, path, time_seq);
+                if (time_seq == (u64)-1)
+                        ret = btrfs_next_item(root, path);
+                else
+                        ret = btrfs_next_old_item(root, path, time_seq);
         }
 
         if (ret > 0)
@@ -334,6 +341,8 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 
         if (path->search_commit_root)
                 root_level = btrfs_header_level(root->commit_root);
+        else if (time_seq == (u64)-1)
+                root_level = btrfs_header_level(root->node);
         else
                 root_level = btrfs_old_root_level(root, time_seq);
 
@@ -343,7 +352,12 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
         }
 
         path->lowest_level = level;
-        ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
+        if (time_seq == (u64)-1)
+                ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path,
+                                        0, 0);
+        else
+                ret = btrfs_search_old_slot(root, &ref->key_for_search, path,
+                                            time_seq);
 
         /* root node has been locked, we can release @subvol_srcu safely here */
         srcu_read_unlock(&fs_info->subvol_srcu, index);
@@ -879,6 +893,11 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
  *
  * NOTE: This can return values > 0
  *
+ * If time_seq is set to (u64)-1, it will not search delayed_refs, and behave
+ * much like trans == NULL case, the difference only lies in it will not
+ * commit root.
+ * The special case is for qgroup to search roots in commit_transaction().
+ *
  * FIXME some caching might speed things up
  */
 static int find_parent_nodes(struct btrfs_trans_handle *trans,
@@ -917,6 +936,9 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
                 path->skip_locking = 1;
         }
 
+        if (time_seq == (u64)-1)
+                path->skip_locking = 1;
+
         /*
          * grab both a lock on the path and a lock on the delayed ref head.
          * We need both to get a consistent picture of how the refs look
@@ -931,9 +953,10 @@ again:
         BUG_ON(ret == 0);
 
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
-        if (trans && likely(trans->type != __TRANS_DUMMY)) {
+        if (trans && likely(trans->type != __TRANS_DUMMY) &&
+            time_seq != (u64)-1) {
 #else
-        if (trans) {
+        if (trans && time_seq != (u64)-1) {
 #endif
                 /*
                  * look if there are updates for this ref queued and lock the