On Tue, Feb 18, 2020 at 5:44 PM Minchan Kim <minchan@xxxxxxxxxx> wrote:
>
> From: Oleksandr Natalenko <oleksandr@xxxxxxxxxx>
>
> Do the very same trick as we already do since 04f5866e41fb. KSM hints
> will require locking mmap_sem for write since they modify vm_flags, so
> for remote KSM hinting this additional check is needed.
>
> Signed-off-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxx>
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
> mm/madvise.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index f6d9b9e66243..c55a18fe71f9 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1118,6 +1118,8 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
> if (write) {
> if (down_write_killable(&mm->mmap_sem))
> return -EINTR;
> + if (current->mm != mm && !mmget_still_valid(mm))
mmget_still_valid() seems pretty light-weight, so why not just use
that without checking that the mm belongs to the current process
first?
> + goto skip_mm;
> } else {
> down_read(&mm->mmap_sem);
> }
> @@ -1169,6 +1171,7 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
> }
> out:
> blk_finish_plug(&plug);
> +skip_mm:
> if (write)
> up_write(&mm->mmap_sem);
> else
> --
> 2.25.0.265.gbab2e86ba0-goog
>
