On Thu, 18 Jul 2024, Kent Overstreet wrote:
On Wed, Jul 17, 2024 at 06:02:39PM GMT, Camila Alvarez wrote:
last_seq and last_empty_seq suffered from an off by one error when the
journal has no entries.
The indexes were fixed and an assertion is added to check that the
last_empty_seq is always kept under the next valid seq number.
oh nice. I'm going to need to stare at this some more, I still feel like
this code needs to be clearer and less fiddly.
Sure! Please let me know if there's anything I can do to help.
Reported-by: syzbot+4093905737cf289b6...@syzkaller.appspotmail.com
Signed-off-by: Camila Alvarez <cam.alvare...@gmail.com>
---
fs/bcachefs/journal.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
index 10b19791ec98..7bbbf4b149e9 100644
--- a/fs/bcachefs/journal.c
+++ b/fs/bcachefs/journal.c
@@ -1201,7 +1201,7 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq)
struct journal_replay *i, **_i;
struct genradix_iter iter;
bool had_entries = false;
- u64 last_seq = cur_seq, nr, seq;
+ u64 last_written_seq = cur_seq - 1, last_seq = cur_seq - 1, nr, seq;
genradix_for_each_reverse(&c->journal_entries, iter, _i) {
i = *_i;
@@ -1209,11 +1209,11 @@ int bch2_fs_journal_start(struct journal *j, u64
cur_seq)
if (journal_replay_ignore(i))
continue;
- last_seq = le64_to_cpu(i->j.last_seq);
+ last_written_seq = le64_to_cpu(i->j.last_seq);
break;
}
- nr = cur_seq - last_seq;
+ nr = cur_seq - last_written_seq;
if (nr + 1 > j->pin.size) {
free_fifo(&j->pin);
@@ -1224,14 +1224,14 @@ int bch2_fs_journal_start(struct journal *j, u64
cur_seq)
}
}
- j->replay_journal_seq = last_seq;
+ j->replay_journal_seq = last_written_seq;
j->replay_journal_seq_end = cur_seq;
- j->last_seq_ondisk = last_seq;
- j->flushed_seq_ondisk = cur_seq - 1;
- j->seq_ondisk = cur_seq - 1;
- j->pin.front = last_seq;
+ j->last_seq_ondisk = last_written_seq;
+ j->flushed_seq_ondisk = last_seq;
+ j->seq_ondisk = last_seq;
+ j->pin.front = last_written_seq;
j->pin.back = cur_seq;
- atomic64_set(&j->seq, cur_seq - 1);
+ atomic64_set(&j->seq, last_seq);
fifo_for_each_entry_ptr(p, &j->pin, seq)
journal_pin_list_init(p, 1);
@@ -1261,7 +1261,10 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq)
}
if (!had_entries)
- j->last_empty_seq = cur_seq;
+ j->last_empty_seq = last_seq;
+
+ WARN(j->last_empty_seq >= cur_seq, "journal startup error: last empty seq
%llu is higher or equal than the next seq number to be used (%llu)",
+ j->last_empty_seq, cur_seq);
spin_lock(&j->lock);
--
2.34.1