bcachefs: Recover from blacklisted journal entries

If it so happens that we crash while dirty, meaning we don't have the
superblock clean section, and we erroneously mark a journal entry we
wrote as blacklisted, we won't be able to recover.

This patch fixes this by adding a fallback: if we've got no superblock
clean section, and no non-ignored journal entries, we try the most
recent ignored journal entry.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/journal_io.c

@@ -1123,9 +1123,6 @@ 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;
@@ -1139,13 +1136,13 @@ int bch2_journal_read(struct bch_fs *c, u64 *blacklist_seq, u64 *start_seq)
 			*blacklist_seq = *start_seq = le64_to_cpu(i->j.seq) + 1;
 
 		if (JSET_NO_FLUSH(&i->j)) {
-			journal_replay_free(c, i);
+			i->ignore = true;
 			continue;
 		}
 
 		if (!last_write_torn && !i->csum_good) {
 			last_write_torn = true;
-			journal_replay_free(c, i);
+			i->ignore = true;
 			continue;
 		}
 
@@ -1194,8 +1191,7 @@ int bch2_journal_read(struct bch_fs *c, u64 *blacklist_seq, u64 *start_seq)
 		if (bch2_journal_seq_is_blacklisted(c, seq, true)) {
 			fsck_err_on(!JSET_NO_FLUSH(&i->j), c,
 				    "found blacklisted journal entry %llu", seq);
-
-			journal_replay_free(c, i);
+			i->ignore = true;
 		}
 	}
 

fs/bcachefs/recovery.c

@@ -1137,7 +1137,15 @@ int bch2_fs_recovery(struct bch_fs *c)
 
 		if (!last_journal_entry) {
 			fsck_err_on(!c->sb.clean, c, "no journal entries found");
-			goto use_clean;
+			if (clean)
+				goto use_clean;
+
+			genradix_for_each_reverse(&c->journal_entries, iter, i)
+				if (*i) {
+					last_journal_entry = &(*i)->j;
+					(*i)->ignore = false;
+					break;
+				}
 		}
 
 		ret = journal_keys_sort(c);