bcachefs: Introduce bch2_journal_keys_peek_(upto|slot)()

When many journal replay keys have been overwritten,
bch2_journal_keys_peek() was taking excessively long to scan before it
found a key to return.

Fix this by introducing bch2_journal_keys_peek_upto() which takes a
parameter for the end of the range we want, so that we can terminate the
search much sooner, and replace all uses of bch2_journal_keys_peek()
with peek_upto() or peek_slot().
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_iter.c

@@ -2225,10 +2225,10 @@ static noinline
 struct bkey_s_c btree_trans_peek_slot_journal(struct btree_trans *trans,
 					      struct btree_iter *iter)
 {
-	struct bkey_i *k = bch2_journal_keys_peek(trans->c, iter->btree_id, 0,
-						  iter->path->pos);
+	struct bkey_i *k = bch2_journal_keys_peek_slot(trans->c, iter->btree_id,
+						       0, iter->path->pos);
 
-	if (k && !bpos_cmp(k->k.p, iter->path->pos)) {
+	if (k) {
 		iter->k = k->k;
 		return bkey_i_to_s_c(k);
 	} else {
@@ -2242,12 +2242,11 @@ struct bkey_s_c btree_trans_peek_journal(struct btree_trans *trans,
 					 struct bkey_s_c k)
 {
 	struct bkey_i *next_journal =
-		bch2_journal_keys_peek(trans->c, iter->btree_id, 0,
-				       iter->path->pos);
+		bch2_journal_keys_peek_upto(trans->c, iter->btree_id, 0,
+				iter->path->pos,
+				k.k ? k.k->p : iter->path->l[0].b->key.k.p);
 
-	if (next_journal &&
-	    bpos_cmp(next_journal->k.p,
-		     k.k ? k.k->p : iter->path->l[0].b->key.k.p) <= 0) {
+	if (next_journal) {
 		iter->k = next_journal->k;
 		k = bkey_i_to_s_c(next_journal);
 	}

fs/bcachefs/btree_update_leaf.c

@@ -670,9 +670,10 @@ bch2_trans_commit_write_locked(struct btree_trans *trans,
 
 		if (unlikely(!test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags))) {
 			struct bkey_i *j_k =
-				bch2_journal_keys_peek(c, i->btree_id, i->level, i->k->k.p);
+				bch2_journal_keys_peek_slot(c, i->btree_id, i->level,
+							    i->k->k.p);
 
-			if (j_k && !bpos_cmp(j_k->k.p, i->k->k.p)) {
+			if (j_k) {
 				i->old_k = j_k->k;
 				i->old_v = &j_k->v;
 			}
@@ -1550,9 +1551,9 @@ bch2_trans_update_by_path_trace(struct btree_trans *trans, struct btree_path *pa
 
 		if (unlikely(trans->journal_replay_not_finished)) {
 			struct bkey_i *j_k =
-				bch2_journal_keys_peek(c, n.btree_id, n.level, k->k.p);
+				bch2_journal_keys_peek_slot(c, n.btree_id, n.level, k->k.p);
 
-			if (j_k && !bpos_cmp(j_k->k.p, i->k->k.p)) {
+			if (j_k) {
 				i->old_k = j_k->k;
 				i->old_v = &j_k->v;
 			}

fs/bcachefs/recovery.c

@@ -109,26 +109,34 @@ size_t bch2_journal_key_search(struct journal_keys *keys,
 	return idx_to_pos(keys, l);
 }
 
-struct bkey_i *bch2_journal_keys_peek(struct bch_fs *c, enum btree_id btree_id,
-				      unsigned level, struct bpos pos)
+struct bkey_i *bch2_journal_keys_peek_upto(struct bch_fs *c, enum btree_id btree_id,
+					   unsigned level, struct bpos pos,
+					   struct bpos end_pos)
 {
 	struct journal_keys *keys = &c->journal_keys;
 	size_t idx = bch2_journal_key_search(keys, btree_id, level, pos);
 
 	while (idx < keys->size &&
-	       keys->d[idx].overwritten) {
+	       keys->d[idx].btree_id == btree_id &&
+	       keys->d[idx].level == level &&
+	       bpos_cmp(keys->d[idx].k->k.p, end_pos) <= 0) {
+		if (!keys->d[idx].overwritten)
+			return keys->d[idx].k;
+
 		idx++;
 		if (idx == keys->gap)
 			idx += keys->size - keys->nr;
 	}
 
-	if (idx < keys->size &&
-	    keys->d[idx].btree_id == btree_id &&
-	    keys->d[idx].level == level)
-		return keys->d[idx].k;
 	return NULL;
 }
 
+struct bkey_i *bch2_journal_keys_peek_slot(struct bch_fs *c, enum btree_id btree_id,
+					   unsigned level, struct bpos pos)
+{
+	return bch2_journal_keys_peek_upto(c, btree_id, level, pos, pos);
+}
+
 static void journal_iters_fix(struct bch_fs *c)
 {
 	struct journal_keys *keys = &c->journal_keys;

fs/bcachefs/recovery.h

@@ -30,8 +30,10 @@ struct btree_and_journal_iter {
 
 size_t bch2_journal_key_search(struct journal_keys *, enum btree_id,
 			       unsigned, struct bpos);
-struct bkey_i *bch2_journal_keys_peek(struct bch_fs *, enum btree_id,
-				      unsigned, struct bpos pos);
+struct bkey_i *bch2_journal_keys_peek_upto(struct bch_fs *, enum btree_id,
+					   unsigned, struct bpos, struct bpos);
+struct bkey_i *bch2_journal_keys_peek_slot(struct bch_fs *, enum btree_id,
+					   unsigned, struct bpos);
 
 int bch2_journal_key_insert_take(struct bch_fs *, enum btree_id,
 				 unsigned, struct bkey_i *);