Re: [syzbot] [PATCH v2] bcachefs: fix last_seq and last_empty_seq in bch2_fs_journal_start()

syzbot
2024-05-20T02:34:05Z

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Subject: [PATCH v2] bcachefs: fix last_seq and last_empty_seq in bch2_fs_journal_start()
Author: cam.alvarez.i@gmail.com

#syz test
Values were left as the next possible sequence number when there were no
entries.

The fix involves updating the last_seq initial value and
setting last_empty_seq to cur_seq - 1.

Signed-off-by: Camila Alvarez <cam.alvarez.i@gmail.com>
---
fs/bcachefs/journal.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
index adec8e1ea73e..99fc32f0382d 100644
--- a/fs/bcachefs/journal.c
+++ b/fs/bcachefs/journal.c
@@ -1195,8 +1195,8 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq)
struct journal_entry_pin_list *p;
struct journal_replay *i, **_i;
struct genradix_iter iter;
- bool had_entries = false;
- u64 last_seq = cur_seq, nr, seq;
+ bool had_entries = false;
+ 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;
@@ -1204,11 +1204,11 @@ 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);
@@ -1219,14 +1219,14 @@ 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);
@@ -1256,7 +1256,7 @@ 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;

spin_lock(&j->lock);

--
2.34.1