On 8/20/19 1:18 AM, Michal Hocko wrote:
On Mon 19-08-19 12:30:18, John Hubbard wrote:
On 8/19/19 12:06 PM, Bharath Vedartham wrote:
On Mon, Aug 19, 2019 at 07:56:11AM -0500, Dimitri Sivanich wrote:
...
Conversion of gup/put_page sites:
Before:
get_user_pages(...);
...
for each page:
put_page();
After:
gup_flags |= FOLL_PIN; (maybe FOLL_LONGTERM in some cases)
vaddr_pin_user_pages(...gup_flags...)
I was hoping that FOLL_PIN would be handled by vaddr_pin_user_pages.
Good point: now that we've got the 4 cases summarized, it turns out
that either FOLL_PIN is required, or there is no need to call
vaddr_pin_user_pages() at all. So we can go back to setting FOLL_PIN
inside it, which is of course much better for maintenance. Great!
...
vaddr_unpin_user_pages(); /* which invokes put_user_page() */
Fortunately, it's not harmful for the simpler conversion from put_page()
to put_user_page() to happen first, and in fact those have usually led
to simplifications, paving the way to make it easier to call
vaddr_unpin_user_pages(), once it's ready. (And showing exactly what
to convert, too.)
If that makes the later conversion easier then no real objections from
me. Assuming that the current put_user_page conversions are correct of
course (I have the mlock one and potentials that falls into the same
category in mind).
Agreed: only correct conversions should be done. Not the incorrect
ones. ahem. :)
thanks,
--
John Hubbard
NVIDIA
