bcachefs: Snapshot whiteout fix

When fully overwriting an existing extent, we may need to generate a
whiteout - not just if the extent being overwritten was in an older
snapshot, but also if it was overwriting an extent in an older snapshot.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/btree_update_leaf.c b/fs/bcachefs/btree_update_leaf.c
index 0fc98b43a07337bba846036ba135c3802e9829c2..544b90b152609be56dedcc139085ad189e7ab740 100644 (file)
--- a/fs/bcachefs/btree_update_leaf.c
+++ b/fs/bcachefs/btree_update_leaf.c
@@ -1307,6 +1307,39 @@ static noinline int extent_back_merge(struct btree_trans *trans,
        return 0;
 }
 
+/*
+ * When deleting, check if we need to emit a whiteout (because we're overwriting
+ * something in an ancestor snapshot)
+ */
+static int need_whiteout_for_snapshot(struct btree_trans *trans,
+                                     enum btree_id btree_id, struct bpos pos)
+{
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       u32 snapshot = pos.snapshot;
+       int ret;
+
+       if (!bch2_snapshot_parent(trans->c, pos.snapshot))
+               return 0;
+
+       pos.snapshot++;
+
+       for_each_btree_key_norestart(trans, iter, btree_id, pos,
+                          BTREE_ITER_ALL_SNAPSHOTS|
+                          BTREE_ITER_NOPRESERVE, k, ret) {
+               if (!bkey_eq(k.k->p, pos))
+                       break;
+
+               if (bch2_snapshot_is_ancestor(trans->c, snapshot,
+                                             k.k->p.snapshot)) {
+                       ret = !bkey_whiteout(k.k);
+                       break;
+               }
+       }
+       bch2_trans_iter_exit(trans, &iter);
+
+       return ret;
+}
 int bch2_trans_update_extent(struct btree_trans *trans,
                             struct btree_iter *orig_iter,
                             struct bkey_i *insert,
@@ -1388,12 +1421,12 @@ int bch2_trans_update_extent(struct btree_trans *trans,
 
                        bkey_init(&update->k);
                        update->k.p = k.k->p;
+                       update->k.p.snapshot = insert->k.p.snapshot;
 
-                       if (insert->k.p.snapshot != k.k->p.snapshot) {
-                               update->k.p.snapshot = insert->k.p.snapshot;
+                       if (insert->k.p.snapshot != k.k->p.snapshot ||
+                           (btree_type_has_snapshots(btree_id) &&
+                            need_whiteout_for_snapshot(trans, btree_id, update->k.p)))
                                update->k.type = KEY_TYPE_whiteout;
-                       }
-
 
                        ret = bch2_btree_insert_nonextent(trans, btree_id, update,
                                                  BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|flags);
@@ -1448,40 +1481,6 @@ err:
        return ret;
 }
 
-/*
- * When deleting, check if we need to emit a whiteout (because we're overwriting
- * something in an ancestor snapshot)
- */
-static int need_whiteout_for_snapshot(struct btree_trans *trans,
-                                     enum btree_id btree_id, struct bpos pos)
-{
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       u32 snapshot = pos.snapshot;
-       int ret;
-
-       if (!bch2_snapshot_parent(trans->c, pos.snapshot))
-               return 0;
-
-       pos.snapshot++;
-
-       for_each_btree_key_norestart(trans, iter, btree_id, pos,
-                          BTREE_ITER_ALL_SNAPSHOTS|
-                          BTREE_ITER_NOPRESERVE, k, ret) {
-               if (!bkey_eq(k.k->p, pos))
-                       break;
-
-               if (bch2_snapshot_is_ancestor(trans->c, snapshot,
-                                             k.k->p.snapshot)) {
-                       ret = !bkey_whiteout(k.k);
-                       break;
-               }
-       }
-       bch2_trans_iter_exit(trans, &iter);
-
-       return ret;
-}
-
 static int __must_check
 bch2_trans_update_by_path_trace(struct btree_trans *trans, struct btree_path *path,
                                struct bkey_i *k, enum btree_update_flags flags,