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

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

[Camila Alvarez]

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.

Reported-by: syzbot+10b936c5eaee2819b49b@syzkaller.appspotmail.com
Signed-off-by: Camila Alvarez <cam.alvarez.i@gmail.com>
---
Changes in v2:
- Introduce a new variable to distinguish the last sequence number, from
  the last written sequence number
- Abstract `cur_seq - 1` into a variable named `last_seq`
- Reference to the last sequence number are changed from `cur_seq - 1`
  to `last_seq`
---
 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

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

[Camila Alvarez Inostroza]

Hello,
I was wondering if you had had the time to take a look at this.
Please let me know if there's something I'm missing.

Thanks!

On Sun, 19 May 2024, Camila Alvarez wrote:

> 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.
>
> Reported-by: syzbot+10b936c5eaee2819b49b@syzkaller.appspotmail.com
> Signed-off-by: Camila Alvarez <cam.alvarez.i@gmail.com>
> ---
> Changes in v2:
> - Introduce a new variable to distinguish the last sequence number, from
>  the last written sequence number
> - Abstract `cur_seq - 1` into a variable named `last_seq`
> - Reference to the last sequence number are changed from `cur_seq - 1`
>  to `last_seq`
> ---
> 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
>
>

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

[Kent Overstreet]

On Mon, May 27, 2024 at 03:25:39PM -0400, Camila Alvarez Inostroza wrote:
> Hello,
> I was wondering if you had had the time to take a look at this.
> Please let me know if there's something I'm missing.

Sorry, I'll get to it - I'm going to need to stare at this one and try
and figure out what the assertions should be