On 2022/06/01 23:51, Jan Kara wrote:
> ioprio_get(2) can be asked to return the best IO priority from several
> tasks (IOPRIO_WHO_PGRP, IOPRIO_WHO_USER). Currently the call treats
> tasks without set IO priority as having priority
> IOPRIO_CLASS_BE/IOPRIO_BE_NORM however this does not really reflect the
> IO priority the task will get (which depends on task's nice value) and
> with the following fix it will not even match returned IO priority for a
> single task. So fix IO priority comparison to treat unset IO priority as
> the lowest possible one. This way we will return IOPRIO_CLASS_NONE
> priority only if none of the considered tasks has explicitely set IO
> priority, otherwise we return the highest set IO priority. This changes
> userspace visible behavior but hopefully the results are clearer and
> nothing breaks.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> block/ioprio.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/block/ioprio.c b/block/ioprio.c
> index 2fe068fcaad5..62890391fc80 100644
> --- a/block/ioprio.c
> +++ b/block/ioprio.c
> @@ -157,10 +157,9 @@ static int get_task_ioprio(struct task_struct *p)
> int ioprio_best(unsigned short aprio, unsigned short bprio)
> {
> if (!ioprio_valid(aprio))
> - aprio = IOPRIO_DEFAULT;
> + return bprio;
bprio may not be valid...
> if (!ioprio_valid(bprio))
> - bprio = IOPRIO_DEFAULT;
> -
> + return aprio;
> return min(aprio, bprio);
> }
>
--
Damien Le Moal
Western Digital Research
