On Fri, Jun 3, 2022 at 5:40 PM Zach O'Keefe <zokeefe@xxxxxxxxxx> wrote:
>
> Allow MADV_COLLAPSE behavior for process_madvise(2) if caller has
> CAP_SYS_ADMIN or is requesting collapse of it's own memory.
It is fine to me. But I'd like to hear more from other folks.
>
> This is useful for the development of userspace agents that seek to
> optimize THP utilization system-wide by using userspace signals to
> prioritize what memory is most deserving of being THP-backed.
>
> Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx>
> ---
> mm/madvise.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index eccac2620226..b19e2f4b924c 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1171,13 +1171,15 @@ madvise_behavior_valid(int behavior)
> }
>
> static bool
> -process_madvise_behavior_valid(int behavior)
> +process_madvise_behavior_valid(int behavior, struct task_struct *task)
> {
> switch (behavior) {
> case MADV_COLD:
> case MADV_PAGEOUT:
> case MADV_WILLNEED:
> return true;
> + case MADV_COLLAPSE:
> + return task == current || capable(CAP_SYS_ADMIN);
> default:
> return false;
> }
> @@ -1455,7 +1457,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
> goto free_iov;
> }
>
> - if (!process_madvise_behavior_valid(behavior)) {
> + if (!process_madvise_behavior_valid(behavior, task)) {
> ret = -EINVAL;
> goto release_task;
> }
> --
> 2.36.1.255.ge46751e96f-goog
>
