bcachefs: Make journal replay more efficient

Journal replay now first attempts to replay keys in sorted order,
similar to how the btree write buffer flush path works.

Any keys that can not be replayed due to journal deadlock are then left
for later and replayed in journal order, unpinning journal entries as we
go.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/errcode.h

@@ -73,7 +73,6 @@
 	x(ENOMEM,			ENOMEM_fsck_add_nlink)			\
 	x(ENOMEM,			ENOMEM_journal_key_insert)		\
 	x(ENOMEM,			ENOMEM_journal_keys_sort)		\
-	x(ENOMEM,			ENOMEM_journal_replay)			\
 	x(ENOMEM,			ENOMEM_read_superblock_clean)		\
 	x(ENOMEM,			ENOMEM_fs_alloc)			\
 	x(ENOMEM,			ENOMEM_fs_name_alloc)			\

fs/bcachefs/recovery.c

@@ -99,6 +99,9 @@ static int bch2_journal_replay_key(struct btree_trans *trans,
 	unsigned update_flags = BTREE_TRIGGER_NORUN;
 	int ret;
 
+	if (k->overwritten)
+		return 0;
+
 	trans->journal_res.seq = k->journal_seq;
 
 	/*
@@ -142,24 +145,14 @@ static int journal_sort_seq_cmp(const void *_l, const void *_r)
 static int bch2_journal_replay(struct bch_fs *c)
 {
 	struct journal_keys *keys = &c->journal_keys;
-	struct journal_key **keys_sorted, *k;
+	DARRAY(struct journal_key *) keys_sorted = { 0 };
+	struct journal_key **kp;
 	struct journal *j = &c->journal;
 	u64 start_seq	= c->journal_replay_seq_start;
 	u64 end_seq	= c->journal_replay_seq_start;
-	size_t i;
+	struct btree_trans *trans = bch2_trans_get(c);
 	int ret = 0;
 
-	keys_sorted = kvmalloc_array(keys->nr, sizeof(*keys_sorted), GFP_KERNEL);
-	if (!keys_sorted)
-		return -BCH_ERR_ENOMEM_journal_replay;
-
-	for (i = 0; i < keys->nr; i++)
-		keys_sorted[i] = &keys->d[i];
-
-	sort(keys_sorted, keys->nr,
-	     sizeof(keys_sorted[0]),
-	     journal_sort_seq_cmp, NULL);
-
 	if (keys->nr) {
 		ret = bch2_journal_log_msg(c, "Starting journal replay (%zu keys in entries %llu-%llu)",
 					   keys->nr, start_seq, end_seq);
@@ -169,25 +162,66 @@ static int bch2_journal_replay(struct bch_fs *c)
 
 	BUG_ON(!atomic_read(&keys->ref));
 
-	for (i = 0; i < keys->nr; i++) {
-		k = keys_sorted[i];
+	/*
+	 * First, attempt to replay keys in sorted order. This is more
+	 * efficient - better locality of btree access -  but some might fail if
+	 * that would cause a journal deadlock.
+	 */
+	for (size_t i = 0; i < keys->nr; i++) {
+		cond_resched();
+
+		struct journal_key *k = keys->d + i;
 
+		/* Skip fastpath if we're low on space in the journal */
+		ret = c->journal.watermark ? -1 :
+			commit_do(trans, NULL, NULL,
+				  BTREE_INSERT_NOFAIL|
+				  BTREE_INSERT_JOURNAL_RECLAIM|
+				  (!k->allocated ? BTREE_INSERT_JOURNAL_REPLAY : 0),
+			     bch2_journal_replay_key(trans, k));
+		BUG_ON(!ret && !k->overwritten);
+		if (ret) {
+			ret = darray_push(&keys_sorted, k);
+			if (ret)
+				goto err;
+		}
+	}
+
+	/*
+	 * Now, replay any remaining keys in the order in which they appear in
+	 * the journal, unpinning those journal entries as we go:
+	 */
+	sort(keys_sorted.data, keys_sorted.nr,
+	     sizeof(keys_sorted.data[0]),
+	     journal_sort_seq_cmp, NULL);
+
+	darray_for_each(keys_sorted, kp) {
 		cond_resched();
 
+		struct journal_key *k = *kp;
+
 		replay_now_at(j, k->journal_seq);
 
-		ret = bch2_trans_do(c, NULL, NULL,
+		ret = commit_do(trans, NULL, NULL,
 				BTREE_INSERT_NOFAIL|
 				(!k->allocated
 				 ? BTREE_INSERT_JOURNAL_REPLAY|BCH_WATERMARK_reclaim
 				 : 0),
 			     bch2_journal_replay_key(trans, k));
-		if (ret) {
-			bch_err(c, "journal replay: error while replaying key at btree %s level %u: %s",
-				bch2_btree_id_str(k->btree_id), k->level, bch2_err_str(ret));
+		bch_err_msg(c, ret, "while replaying key at btree %s level %u:",
+			    bch2_btree_id_str(k->btree_id), k->level);
+		if (ret)
 			goto err;
+
+		BUG_ON(!k->overwritten);
 	}
-	}
+
+	/*
+	 * We need to put our btree_trans before calling flush_all_pins(), since
+	 * that will use a btree_trans internally
+	 */
+	bch2_trans_put(trans);
+	trans = NULL;
 
 	if (!c->opts.keep_journal)
 		bch2_journal_keys_put_initial(c);
@@ -202,9 +236,9 @@ static int bch2_journal_replay(struct bch_fs *c)
 	if (keys->nr && !ret)
 		bch2_journal_log_msg(c, "journal replay finished");
 err:
-	kvfree(keys_sorted);
-
-	if (ret)
+	if (trans)
+		bch2_trans_put(trans);
+	darray_exit(&keys_sorted);
 	bch_err_fn(c, ret);
 	return ret;
 }