Re: [PATCH 1/4] ext4: fix incorrect tid assumption in ext4_wait_for_tail_page_commit()

Jan Kara
2024-07-24T09:17:19Z

On Tue 23-07-24 16:43:59, Luis Henriques (SUSE) wrote:
> Function ext4_wait_for_tail_page_commit() assumes that '0' is not a valid
> value for transaction IDs, which is incorrect. Don't assume that and invoke
> jbd2_log_wait_commit() if the journal had a committing transaction instead.
>
> Signed-off-by: Luis Henriques (SUSE) <luis.henriques@linux.dev>
> ---
> fs/ext4/inode.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 941c1c0d5c6e..e65fc2086701 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5279,8 +5279,9 @@ static void ext4_wait_for_tail_page_commit(struct inode *inode)
> {
> unsigned offset;
> journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
> - tid_t commit_tid = 0;
> + tid_t commit_tid;
> int ret;
> + bool has_transaction = false;
>
> offset = inode->i_size & (PAGE_SIZE - 1);
> /*
> @@ -5305,12 +5306,13 @@ static void ext4_wait_for_tail_page_commit(struct inode *inode)
> folio_put(folio);
> if (ret != -EBUSY)
> return;
> - commit_tid = 0;

We should set "has_transaction = false" here to make things work properly
when looping... Otherwise looks good.

Honza

> read_lock(&journal->j_state_lock);
> - if (journal->j_committing_transaction)
> + if (journal->j_committing_transaction) {
> commit_tid = journal->j_committing_transaction->t_tid;
> + has_transaction = true;
> + }
> read_unlock(&journal->j_state_lock);
> - if (commit_tid)
> + if (has_transaction)
> jbd2_log_wait_commit(journal, commit_tid);
> }
> }
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR