bcachefs: bch2_btree_iter_fix_key_modified()

This is considerably cheaper than bch2_btree_node_iter_fix(), for cases
where the key was only modified and key ordering isn't changing.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -501,6 +501,30 @@ static void btree_node_iter_set_set_pos(struct btree_node_iter *iter,
 	bch2_btree_node_iter_push(iter, b, k, btree_bkey_last(b, t));
 }
 
+static void __bch2_btree_iter_fix_key_modified(struct btree_iter *iter,
+						    struct btree *b,
+						    struct bkey_packed *where)
+{
+	struct btree_node_iter *node_iter = &iter->l[0].iter;
+
+	if (where == bch2_btree_node_iter_peek_all(node_iter, b)) {
+		bkey_disassemble(b, where, &iter->k);
+		btree_iter_set_dirty(iter, BTREE_ITER_NEED_PEEK);
+	}
+}
+
+void bch2_btree_iter_fix_key_modified(struct btree_iter *iter,
+				      struct btree *b,
+				      struct bkey_packed *where)
+{
+	struct btree_iter *linked;
+
+	trans_for_each_iter_with_node(iter->trans, b, linked) {
+		__bch2_btree_iter_fix_key_modified(linked, b, where);
+		__bch2_btree_iter_verify(linked, b);
+	}
+}
+
 static void __bch2_btree_node_iter_fix(struct btree_iter *iter,
 				      struct btree *b,
 				      struct btree_node_iter *node_iter,

fs/bcachefs/btree_iter.h

@@ -104,6 +104,8 @@ static inline void bch2_btree_iter_verify(struct btree_iter *iter,
 static inline void bch2_btree_trans_verify_locks(struct btree_trans *iter) {}
 #endif
 
+void bch2_btree_iter_fix_key_modified(struct btree_iter *, struct btree *,
+					   struct bkey_packed *);
 void bch2_btree_node_iter_fix(struct btree_iter *, struct btree *,
 			      struct btree_node_iter *, struct bkey_packed *,
 			      unsigned, unsigned);

fs/bcachefs/extents.c

@@ -1091,8 +1091,7 @@ extent_squash(struct bch_fs *c, struct btree_iter *iter,
 		__bch2_cut_front(insert->k.p, k);
 		EBUG_ON(bkey_deleted(k.k));
 		extent_save(l->b, _k, k.k);
-		bch2_btree_node_iter_fix(iter, l->b, &l->iter,
-					 _k, _k->u64s, _k->u64s);
+		bch2_btree_iter_fix_key_modified(iter, l->b, _k);
 		break;
 
 	case BCH_EXTENT_OVERLAP_BACK:
@@ -1127,8 +1126,7 @@ extent_squash(struct bch_fs *c, struct btree_iter *iter,
 						 _k, u64s, 0);
 		} else {
 			extent_save(l->b, _k, k.k);
-			bch2_btree_node_iter_fix(iter, l->b, &l->iter,
-						 _k, _k->u64s, _k->u64s);
+			bch2_btree_iter_fix_key_modified(iter, l->b, _k);
 		}
 
 		break;
@@ -1158,8 +1156,7 @@ extent_squash(struct bch_fs *c, struct btree_iter *iter,
 		__bch2_cut_front(insert->k.p, k);
 		BUG_ON(bkey_deleted(k.k));
 		extent_save(l->b, _k, k.k);
-		bch2_btree_node_iter_fix(iter, l->b, &l->iter,
-					 _k, _k->u64s, _k->u64s);
+		bch2_btree_iter_fix_key_modified(iter, l->b, _k);
 
 		extent_bset_insert(c, iter, &split.k);
 		break;
@@ -1259,8 +1256,8 @@ void bch2_insert_fixup_extent(struct btree_trans *trans,
 				btree_account_key_drop(l->b, _k);
 				_k->type = KEY_TYPE_discard;
 				reserve_whiteout(l->b, _k);
-				bch2_btree_node_iter_fix(iter, l->b, &l->iter,
-							_k, _k->u64s, _k->u64s);
+				bch2_btree_iter_fix_key_modified(iter,
+								 l->b, _k);
 			}
 			break;
 		}