Messages in this thread | | | Subject | Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages_remote() | From | John Hubbard <> | Date | Mon, 12 Aug 2019 17:07:32 -0700 |
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On 8/12/19 4:49 PM, Ira Weiny wrote: > On Sun, Aug 11, 2019 at 06:50:44PM -0700, john.hubbard@gmail.com wrote: >> From: John Hubbard <jhubbard@nvidia.com> ... >> diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c >> index 53085896d718..fdff034a8a30 100644 >> --- a/drivers/infiniband/core/umem_odp.c >> +++ b/drivers/infiniband/core/umem_odp.c >> @@ -534,7 +534,7 @@ static int ib_umem_odp_map_dma_single_page( >> } >> >> out: >> - put_user_page(page); >> + vaddr_unpin_pages(&page, 1, &umem_odp->umem.vaddr_pin); >> >> if (remove_existing_mapping) { >> ib_umem_notifier_start_account(umem_odp); >> @@ -635,9 +635,10 @@ int ib_umem_odp_map_dma_pages(struct ib_umem_odp *umem_odp, u64 user_virt, >> * complex (and doesn't gain us much performance in most use >> * cases). >> */ >> - npages = get_user_pages_remote(owning_process, owning_mm, >> + npages = vaddr_pin_pages_remote(owning_process, owning_mm, >> user_virt, gup_num_pages, >> - flags, local_page_list, NULL, NULL); >> + flags, local_page_list, NULL, NULL, >> + &umem_odp->umem.vaddr_pin); > > Thinking about this part of the patch... is this pin really necessary? This > code is not doing a long term pin. The page just needs a reference while we > map it into the devices page tables. Once that is done we should get notifiers > if anything changes and we can adjust. right? >
OK, now it's a little interesting: the FOLL_PIN is necessary, but maybe not FOLL_LONGTERM. Illustrating once again that it's actually necessary to allow these flags to vary independently.
And that leads to another API refinement idea: let's set FOLL_PIN within the vaddr_pin_pages*() wrappers, and set FOLL_LONGTER in the *callers* of those wrappers, yes?
thanks, -- John Hubbard NVIDIA
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