Re: [PATCH 7/9] jbd2: make the whole kjournald2 kthread NOFS safe

[Jan Kara]

On Thu 15-12-16 15:07:13, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
> 
> kjournald2 is central to the transaction commit processing. As such any
> potential allocation from this kernel thread has to be GFP_NOFS. Make
> sure to mark the whole kernel thread GFP_NOFS by the memalloc_nofs_save.
> 
> Suggested-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza

> ---
>  fs/jbd2/journal.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 8ed971eeab44..6dad8c5d6ddf 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -206,6 +206,13 @@ static int kjournald2(void *arg)
>  	wake_up(&journal->j_wait_done_commit);
>  
>  	/*
> +	 * Make sure that no allocations from this kernel thread will ever recurse
> +	 * to the fs layer because we are responsible for the transaction commit
> +	 * and any fs involvement might get stuck waiting for the trasn. commit.
> +	 */
> +	memalloc_nofs_save();
> +
> +	/*
>  	 * And now, wait forever for commit wakeup events.
>  	 */
>  	write_lock(&journal->j_state_lock);
> -- 
> 2.10.2
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR