bcachefs: iter->update_path

With BTREE_ITER_FILTER_SNAPSHOTS, we have to distinguish between the
path where the key was found, and the path for inserting into the
current snapshot. This adds a new field to struct btree_iter for saving
a path for the current snapshot, and plumbs it through
bch2_trans_update().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -704,6 +704,8 @@ static void bch2_btree_iter_verify(struct btree_iter *iter)
 	       (iter->flags & BTREE_ITER_ALL_SNAPSHOTS) &&
 	       !btree_type_has_snapshots(iter->btree_id));
 
+	if (iter->update_path)
+		bch2_btree_path_verify(trans, iter->update_path);
 	bch2_btree_path_verify(trans, iter->path);
 }
 
@@ -2311,13 +2313,7 @@ static struct bkey_s_c __bch2_btree_iter_peek(struct btree_iter *iter, struct bp
 			goto out;
 		}
 	}
-
-	iter->path = btree_path_set_pos(trans, iter->path, k.k->p,
-				iter->flags & BTREE_ITER_INTENT);
-	BUG_ON(!iter->path->nodes_locked);
 out:
-	iter->path->should_be_locked = true;
-
 	bch2_btree_iter_verify(iter);
 
 	return k;
@@ -2334,6 +2330,12 @@ struct bkey_s_c bch2_btree_iter_peek(struct btree_iter *iter)
 	struct bkey_s_c k;
 	int ret;
 
+	if (iter->update_path) {
+		bch2_path_put(trans, iter->update_path,
+			      iter->flags & BTREE_ITER_INTENT);
+		iter->update_path = NULL;
+	}
+
 	bch2_btree_iter_verify_entry_exit(iter);
 
 	while (1) {
@@ -2341,6 +2343,41 @@ struct bkey_s_c bch2_btree_iter_peek(struct btree_iter *iter)
 		if (!k.k || bkey_err(k))
 			goto out;
 
+		if (iter->update_path &&
+		    bkey_cmp(iter->update_path->pos, k.k->p)) {
+			bch2_path_put(trans, iter->update_path,
+				      iter->flags & BTREE_ITER_INTENT);
+			iter->update_path = NULL;
+		}
+
+		if ((iter->flags & BTREE_ITER_FILTER_SNAPSHOTS) &&
+		    (iter->flags & BTREE_ITER_INTENT) &&
+		    !(iter->flags & BTREE_ITER_IS_EXTENTS) &&
+		    !iter->update_path) {
+			struct bpos pos = k.k->p;
+
+			if (pos.snapshot < iter->snapshot) {
+				search_key = bpos_successor(k.k->p);
+				continue;
+			}
+
+			pos.snapshot = iter->snapshot;
+
+			/*
+			 * advance, same as on exit for iter->path, but only up
+			 * to snapshot
+			 */
+			__btree_path_get(iter->path, iter->flags & BTREE_ITER_INTENT);
+			iter->update_path = iter->path;
+
+			iter->update_path = btree_path_set_pos(trans,
+						iter->update_path, pos,
+						iter->flags & BTREE_ITER_INTENT);
+
+			BUG_ON(!(iter->update_path->nodes_locked & 1));
+			iter->update_path->should_be_locked = true;
+		}
+
 		/*
 		 * We can never have a key in a leaf node at POS_MAX, so
 		 * we don't have to check these successor() calls:
@@ -2370,7 +2407,17 @@ struct bkey_s_c bch2_btree_iter_peek(struct btree_iter *iter)
 		iter->pos = k.k->p;
 	else if (bkey_cmp(bkey_start_pos(k.k), iter->pos) > 0)
 		iter->pos = bkey_start_pos(k.k);
+
+	iter->path = btree_path_set_pos(trans, iter->path, k.k->p,
+				iter->flags & BTREE_ITER_INTENT);
+	BUG_ON(!iter->path->nodes_locked);
 out:
+	if (iter->update_path) {
+		BUG_ON(!(iter->update_path->nodes_locked & 1));
+		iter->update_path->should_be_locked = true;
+	}
+	iter->path->should_be_locked = true;
+
 	if (!(iter->flags & BTREE_ITER_ALL_SNAPSHOTS))
 		iter->pos.snapshot = iter->snapshot;
 
@@ -2774,7 +2821,11 @@ void bch2_trans_iter_exit(struct btree_trans *trans, struct btree_iter *iter)
 	if (iter->path)
 		bch2_path_put(trans, iter->path,
 			      iter->flags & BTREE_ITER_INTENT);
+	if (iter->update_path)
+		bch2_path_put(trans, iter->update_path,
+			      iter->flags & BTREE_ITER_INTENT);
 	iter->path = NULL;
+	iter->update_path = NULL;
 }
 
 static void __bch2_trans_iter_init(struct btree_trans *trans,
@@ -2803,6 +2854,7 @@ static void __bch2_trans_iter_init(struct btree_trans *trans,
 
 	iter->trans	= trans;
 	iter->path	= NULL;
+	iter->update_path = NULL;
 	iter->btree_id	= btree_id;
 	iter->min_depth	= depth;
 	iter->flags	= flags;
@@ -2848,6 +2900,8 @@ void bch2_trans_copy_iter(struct btree_iter *dst, struct btree_iter *src)
 	*dst = *src;
 	if (src->path)
 		__btree_path_get(src->path, src->flags & BTREE_ITER_INTENT);
+	if (src->update_path)
+		__btree_path_get(src->update_path, src->flags & BTREE_ITER_INTENT);
 }
 
 void *bch2_trans_kmalloc(struct btree_trans *trans, size_t size)

fs/bcachefs/btree_iter.h

@@ -258,6 +258,11 @@ static inline void __bch2_btree_iter_set_pos(struct btree_iter *iter, struct bpo
 
 static inline void bch2_btree_iter_set_pos(struct btree_iter *iter, struct bpos new_pos)
 {
+	if (unlikely(iter->update_path))
+		bch2_path_put(iter->trans, iter->update_path,
+			      iter->flags & BTREE_ITER_INTENT);
+	iter->update_path = NULL;
+
 	if (!(iter->flags & BTREE_ITER_ALL_SNAPSHOTS))
 		new_pos.snapshot = iter->snapshot;
 

fs/bcachefs/btree_types.h

@@ -276,6 +276,7 @@ static inline struct btree_path_level *path_l(struct btree_path *path)
 struct btree_iter {
 	struct btree_trans	*trans;
 	struct btree_path	*path;
+	struct btree_path	*update_path;
 
 	enum btree_id		btree_id:4;
 	unsigned		min_depth:4;

fs/bcachefs/btree_update.h

@@ -73,8 +73,14 @@ int bch2_btree_node_update_key(struct btree_trans *, struct btree_iter *,
 int bch2_btree_node_update_key_get_iter(struct btree_trans *,
 				struct btree *, struct bkey_i *, bool);
 
+int bch2_trans_update_extent(struct btree_trans *, struct btree_iter *,
+			     struct bkey_i *, enum btree_update_flags);
+
+int __must_check bch2_trans_update_by_path(struct btree_trans *, struct btree_path *,
+				   struct bkey_i *, enum btree_update_flags);
 int __must_check bch2_trans_update(struct btree_trans *, struct btree_iter *,
 				   struct bkey_i *, enum btree_update_flags);
+
 void bch2_trans_commit_hook(struct btree_trans *,
 			    struct btree_trans_commit_hook *);
 int __bch2_trans_commit(struct btree_trans *);

fs/bcachefs/btree_update_leaf.c

@@ -1181,10 +1181,10 @@ static noinline int extent_back_merge(struct btree_trans *trans,
 	return 0;
 }
 
-static int bch2_trans_update_extent(struct btree_trans *trans,
-				    struct btree_iter *orig_iter,
-				    struct bkey_i *insert,
-				    enum btree_update_flags flags)
+int bch2_trans_update_extent(struct btree_trans *trans,
+			     struct btree_iter *orig_iter,
+			     struct bkey_i *insert,
+			     enum btree_update_flags flags)
 {
 	struct btree_iter iter, update_iter;
 	struct bpos start = bkey_start_pos(&insert->k);
@@ -1308,13 +1308,9 @@ static int bch2_trans_update_extent(struct btree_trans *trans,
 			bkey_reassemble(update, k);
 			bch2_cut_front(insert->k.p, update);
 
-			bch2_trans_copy_iter(&update_iter, &iter);
-			update_iter.pos = update->k.p;
-			ret   = bch2_trans_update(trans, &update_iter, update,
+			ret = bch2_trans_update_by_path(trans, iter.path, update,
 						  BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|
 						  flags);
-			bch2_trans_iter_exit(trans, &update_iter);
-
 			if (ret)
 				goto err;
 			goto out;
@@ -1385,26 +1381,23 @@ static int need_whiteout_for_snapshot(struct btree_trans *trans,
 	return ret;
 }
 
-int __must_check bch2_trans_update(struct btree_trans *trans, struct btree_iter *iter,
+int __must_check bch2_trans_update_by_path(struct btree_trans *trans, struct btree_path *path,
 				   struct bkey_i *k, enum btree_update_flags flags)
 {
 	struct btree_insert_entry *i, n;
 
-	BUG_ON(!iter->path->should_be_locked);
-
-	if (iter->flags & BTREE_ITER_IS_EXTENTS)
-		return bch2_trans_update_extent(trans, iter, k, flags);
+	BUG_ON(!path->should_be_locked);
 
 	BUG_ON(trans->nr_updates >= BTREE_ITER_MAX);
-	BUG_ON(bpos_cmp(k->k.p, iter->path->pos));
+	BUG_ON(bpos_cmp(k->k.p, path->pos));
 
 	n = (struct btree_insert_entry) {
 		.flags		= flags,
-		.bkey_type	= __btree_node_type(iter->path->level, iter->btree_id),
-		.btree_id	= iter->btree_id,
-		.level		= iter->path->level,
-		.cached		= iter->flags & BTREE_ITER_CACHED,
-		.path		= iter->path,
+		.bkey_type	= __btree_node_type(path->level, path->btree_id),
+		.btree_id	= path->btree_id,
+		.level		= path->level,
+		.cached		= path->cached,
+		.path		= path,
 		.k		= k,
 		.ip_allocated	= _RET_IP_,
 	};
@@ -1415,16 +1408,6 @@ int __must_check bch2_trans_update(struct btree_trans *trans, struct btree_iter
 		       btree_insert_entry_cmp(i - 1, i) >= 0);
 #endif
 
-	if (bkey_deleted(&n.k->k) &&
-	    (iter->flags & BTREE_ITER_FILTER_SNAPSHOTS)) {
-		int ret = need_whiteout_for_snapshot(trans, n.btree_id, n.k->k.p);
-		if (unlikely(ret < 0))
-			return ret;
-
-		if (ret)
-			n.k->k.type = KEY_TYPE_whiteout;
-	}
-
 	/*
 	 * Pending updates are kept sorted: first, find position of new update,
 	 * then delete/trim any updates the new update overwrites:
@@ -1455,10 +1438,29 @@ int __must_check bch2_trans_update(struct btree_trans *trans, struct btree_iter
 				  i - trans->updates, n);
 
 	__btree_path_get(n.path, true);
-
 	return 0;
 }
 
+int __must_check bch2_trans_update(struct btree_trans *trans, struct btree_iter *iter,
+				   struct bkey_i *k, enum btree_update_flags flags)
+{
+	if (iter->flags & BTREE_ITER_IS_EXTENTS)
+		return bch2_trans_update_extent(trans, iter, k, flags);
+
+	if (bkey_deleted(&k->k) &&
+	    (iter->flags & BTREE_ITER_FILTER_SNAPSHOTS)) {
+		int ret = need_whiteout_for_snapshot(trans, iter->btree_id, k->k.p);
+		if (unlikely(ret < 0))
+			return ret;
+
+		if (ret)
+			k->k.type = KEY_TYPE_whiteout;
+	}
+
+	return bch2_trans_update_by_path(trans, iter->update_path ?: iter->path,
+					 k, flags);
+}
+
 void bch2_trans_commit_hook(struct btree_trans *trans,
 			    struct btree_trans_commit_hook *h)
 {