Btrfs: add btrfs_next_old_leaf

To make sense of the tree mod log, the backref walker not only needs
btrfs_search_old_slot, but it also called btrfs_next_leaf, which in turn was
calling btrfs_search_slot. This obviously didn't give the correct result.

This commit adds btrfs_next_old_leaf, a drop-in replacement for
btrfs_next_leaf with a time_seq parameter. If it is zero, it behaves exactly
like btrfs_next_leaf. If it is non-zero, it will use btrfs_search_old_slot
with this time_seq parameter.

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

3 files changed, 16 insertions, 4 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 579131de1b3b..8f7d1237b7a0 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -179,7 +179,8 @@ static int __add_prelim_ref(struct list_head *head, u64 root_id,
 
 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
                                 struct ulist *parents, int level,
-                                struct btrfs_key *key, u64 wanted_disk_byte,
+                                struct btrfs_key *key, u64 time_seq,
+                                u64 wanted_disk_byte,
                                 const u64 *extent_item_pos)
 {
         int ret;
@@ -212,7 +213,7 @@ add_parent:
          */
         while (1) {
                 eie = NULL;
-                ret = btrfs_next_leaf(root, path);
+                ret = btrfs_next_old_leaf(root, path, time_seq);
                 if (ret < 0)
                         return ret;
                 if (ret)
@@ -297,7 +298,7 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
         if (level == 0)
                 btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
 
-        ret = add_all_parents(root, path, parents, level, &key,
+        ret = add_all_parents(root, path, parents, level, &key, time_seq,
                                 ref->wanted_disk_byte, extent_item_pos);
 out:
         btrfs_free_path(path);
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 50d7c99ddce7..cb76b2a1b908 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -5017,6 +5017,12 @@ next:
  */
 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
 {
+        return btrfs_next_old_leaf(root, path, 0);
+}
+
+int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
+                        u64 time_seq)
+{
         int slot;
         int level;
         struct extent_buffer *c;
@@ -5041,7 +5047,10 @@ again:
         path->keep_locks = 1;
         path->leave_spinning = 1;
 
-        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        if (time_seq)
+                ret = btrfs_search_old_slot(root, &key, path, time_seq);
+        else
+                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
         path->keep_locks = 0;
 
         if (ret < 0)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0151ca1ac657..db15e9e7b91c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2753,6 +2753,8 @@ static inline int btrfs_insert_empty_item(struct btrfs_trans_handle *trans,
 }
 
 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path);
+int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
+                        u64 time_seq);
 static inline int btrfs_next_item(struct btrfs_root *root, struct btrfs_path *p)
 {
         ++p->slots[0];