bcachefs: bch2_foreground_maybe_merge() now correctly reports lock restarts

This means that btree node splits don't have to automatically trigger a
transaction restart.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_update_interior.c

@@ -1527,12 +1527,12 @@ int bch2_btree_split_leaf(struct bch_fs *c, struct btree_iter *iter,
 	bch2_btree_update_done(as);
 
 	for (l = iter->level + 1; btree_iter_node(iter, l) && !ret; l++)
-		bch2_foreground_maybe_merge(c, iter, l, flags);
+		ret = bch2_foreground_maybe_merge(c, iter, l, flags);
 
 	return ret;
 }
 
-void __bch2_foreground_maybe_merge(struct bch_fs *c,
+int __bch2_foreground_maybe_merge(struct bch_fs *c,
 				  struct btree_iter *iter,
 				  unsigned level,
 				  unsigned flags,
@@ -1547,10 +1547,7 @@ void __bch2_foreground_maybe_merge(struct bch_fs *c,
 	struct btree *b, *m, *n, *prev, *next, *parent;
 	struct bpos sib_pos;
 	size_t sib_u64s;
-	int ret = 0;
-
-	if (trans->nounlock)
-		return;
+	int ret = 0, ret2 = 0;
 
 	BUG_ON(!btree_node_locked(iter, level));
 retry:
@@ -1689,17 +1686,16 @@ void __bch2_foreground_maybe_merge(struct bch_fs *c,
 	 * split path, and downgrading to read locks in there is potentially
 	 * confusing:
 	 */
-	return;
+	return ret ?: ret2;
 err:
 	bch2_trans_iter_put(trans, sib_iter);
 	sib_iter = NULL;
 
-	if (ret == -EINTR && bch2_trans_relock(trans)) {
-		ret = 0;
+	if (ret == -EINTR && bch2_trans_relock(trans))
 		goto retry;
-	}
 
 	if (ret == -EINTR && !(flags & BTREE_INSERT_NOUNLOCK)) {
+		ret2 = ret;
 		ret = bch2_btree_iter_traverse_all(trans);
 		if (!ret)
 			goto retry;

fs/bcachefs/btree_update_interior.h

@@ -132,10 +132,10 @@ void bch2_btree_insert_node(struct btree_update *, struct btree *,
 			    unsigned);
 int bch2_btree_split_leaf(struct bch_fs *, struct btree_iter *, unsigned);
 
-void __bch2_foreground_maybe_merge(struct bch_fs *, struct btree_iter *,
+int __bch2_foreground_maybe_merge(struct bch_fs *, struct btree_iter *,
 				  unsigned, unsigned, enum btree_node_sibling);
 
-static inline void bch2_foreground_maybe_merge_sibling(struct bch_fs *c,
+static inline int bch2_foreground_maybe_merge_sibling(struct bch_fs *c,
 					struct btree_iter *iter,
 					unsigned level, unsigned flags,
 					enum btree_node_sibling sib)
@@ -143,25 +143,25 @@ static inline void bch2_foreground_maybe_merge_sibling(struct bch_fs *c,
 	struct btree *b;
 
 	if (iter->uptodate >= BTREE_ITER_NEED_TRAVERSE)
-		return;
+		return 0;
 
 	if (!bch2_btree_node_relock(iter, level))
-		return;
+		return 0;
 
 	b = iter->l[level].b;
 	if (b->sib_u64s[sib] > c->btree_foreground_merge_threshold)
-		return;
+		return 0;
 
-	__bch2_foreground_maybe_merge(c, iter, level, flags, sib);
+	return __bch2_foreground_maybe_merge(c, iter, level, flags, sib);
 }
 
-static inline void bch2_foreground_maybe_merge(struct bch_fs *c,
+static inline int bch2_foreground_maybe_merge(struct bch_fs *c,
 					       struct btree_iter *iter,
 					       unsigned level,
 					       unsigned flags)
 {
-	bch2_foreground_maybe_merge_sibling(c, iter, level, flags,
-					    btree_prev_sib);
+	return  bch2_foreground_maybe_merge_sibling(c, iter, level, flags,
+						    btree_prev_sib) ?:
 		bch2_foreground_maybe_merge_sibling(c, iter, level, flags,
 						    btree_next_sib);
 }