On 9/3/20 12:12 AM, Souptick Joarder wrote:
On Wed, Aug 19, 2020 at 11:45 PM John Hubbard <jhubbard@xxxxxxxxxx> wrote:
On 8/19/20 4:01 AM, Barry Song wrote:
gug prohibits users from calling get_user_pages() with FOLL_PIN. But it
Maybe Andrew can fix the typo above: gug --> gup.
allows users to call get_user_pages() with FOLL_LONGTERM only. It seems
insensible.
since FOLL_LONGTERM is a stricter case of FOLL_PIN, we should prohibit
users from calling get_user_pages() with FOLL_LONGTERM while not with
FOLL_PIN.
mm/gup_benchmark.c used to be the only user who did this improperly.
But it has been fixed by moving to use pin_user_pages().
For future patches, you don't have to write everything in the
commit log. Some things are better placed in a cover letter or after
the "---" line, because they don't need to be recorded forever.
Anyway, the diffs seem fine, assuming that you've audited the call sites.
We can use is_valid_gup_flags() inside ->
get_user_pages_locked(),
get_user_pages_unlocked(),
pin_user_pages_locked() as well.
Probably it's best to discern between valid pup flags, and valid gup flags.
As in: separate functions for those. Maybe one is a subset of the other, but
still.
Are you planning to add it in future patches ?
It's not on my list. I don't see anything wrong with doing so, other
than avoiding the minor pitfall I called out above. So if you want to
do that, then feel free...
thanks,
--
John Hubbard
NVIDIA
