bcachefs: Handle last journal write being torn

If the last journal write didn't complete sucessfully due to a torn
write, we'll detect it as a checksum error. In that case, we should just
pretend that journal entry was never written.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/journal_io.c

@@ -1106,7 +1106,7 @@ int bch2_journal_read(struct bch_fs *c, u64 *blacklist_seq, u64 *start_seq)
 	struct bch_dev *ca;
 	unsigned iter;
 	struct printbuf buf = PRINTBUF;
-	bool degraded = false;
+	bool degraded = false, last_write_torn = false;
 	u64 seq, last_seq = 0;
 	int ret = 0;
 
@@ -1142,8 +1142,13 @@ int bch2_journal_read(struct bch_fs *c, u64 *blacklist_seq, u64 *start_seq)
 	/*
 	 * Find most recent flush entry, and ignore newer non flush entries -
 	 * those entries will be blacklisted:
+	 *
+	 *
+	 * XXX check for torn write on last journal entry
 	 */
 	genradix_for_each_reverse(&c->journal_entries, radix_iter, _i) {
+		int write = READ;
+
 		i = *_i;
 
 		if (!i || i->ignore)
@@ -1152,8 +1157,17 @@ int bch2_journal_read(struct bch_fs *c, u64 *blacklist_seq, u64 *start_seq)
 		if (!*start_seq)
 			*blacklist_seq = *start_seq = le64_to_cpu(i->j.seq) + 1;
 
-		if (!JSET_NO_FLUSH(&i->j)) {
-			int write = READ;
+		if (JSET_NO_FLUSH(&i->j)) {
+			journal_replay_free(c, i);
+			continue;
+		}
+
+		if (!last_write_torn && !i->csum_good) {
+			last_write_torn = true;
+			journal_replay_free(c, i);
+			continue;
+		}
+
 		if (journal_entry_err_on(le64_to_cpu(i->j.last_seq) > le64_to_cpu(i->j.seq),
 					 c, &i->j, NULL,
 					 "invalid journal entry: last_seq > seq (%llu > %llu)",
@@ -1166,9 +1180,6 @@ int bch2_journal_read(struct bch_fs *c, u64 *blacklist_seq, u64 *start_seq)
 		break;
 	}
 
-		journal_replay_free(c, i);
-	}
-
 	if (!*start_seq) {
 		bch_info(c, "journal read done, but no entries found");
 		return 0;