Messages in this thread | | | Subject | Re: [Linux-kernel-mentees][PATCH v6 1/2] sgi-gru: Convert put_page() to put_user_page*() | From | John Hubbard <> | Date | Tue, 20 Aug 2019 13:50:18 -0700 |
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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
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