Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH v8 10/10] mm: Renumber FOLL_PIN and FOLL_GET down | Date | Tue, 24 Jan 2023 14:11:50 +0000 |
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Jason Gunthorpe <jgg@nvidia.com> wrote:
> if (cleanup_flags & PAGE_CLEANUP_UNPIN) > gup_put_folio(folio, 1, true); > else if (cleanup_flags & PAGE_CLEANUP_PUT) > gup_put_folio(folio, 1, false);
gup_put_folio() doesn't take a bool - it takes FOLL_PIN and FOLL_GET:
static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
though I could do:
if (cleanup_flags & PAGE_CLEANUP_UNPIN) gup_put_folio(folio, 1, FOLL_PIN); else if (cleanup_flags & PAGE_CLEANUP_PUT) gup_put_folio(folio, 1, FOLL_GET);
But the reason I wrote it like this:
gup_flags |= cleanup_flags & PAGE_CLEANUP_UNPIN ? FOLL_PIN : 0; gup_flags |= cleanup_flags & PAGE_CLEANUP_PUT ? FOLL_GET : 0;
is that if PAGE_CLEANUP_UNPIN == FOLL_PIN and PAGE_CLEANUP_PUT == FOLL_GET, the C compiler optimiser should be able to turn all of that into a single AND instruction.
David
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