Messages in this thread | | | Subject | Re: [PATCH] mm/gup: remove unnecessary check against CMA in __gup_longterm_locked() | From | "Aneesh Kumar K.V" <> | Date | Tue, 4 Jun 2019 14:00:29 +0530 |
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On 6/4/19 12:56 PM, Pingfan Liu wrote: > The PF_MEMALLOC_NOCMA is set by memalloc_nocma_save(), which is finally > cast to ~_GFP_MOVABLE. So __get_user_pages_locked() will get pages from > non CMA area and pin them. There is no need to > check_and_migrate_cma_pages().
That is not completely correct. We can fault in that pages outside get_user_pages_longterm at which point those pages can get allocated from CMA region. memalloc_nocma_save() as added as an optimization to avoid unnecessary page migration.
-aneesh
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