Messages in this thread Patch in this message | | | Date | Sat, 23 May 2020 10:25:19 -0700 | From | Matthew Wilcox <> | Subject | Re: [linux-next RFC] mm/gup.c: Convert to use get_user_pages_fast_only() |
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On Sat, May 23, 2020 at 10:11:12PM +0530, Souptick Joarder wrote: > Renaming the API __get_user_pages_fast() to get_user_pages_ > fast_only() to align with pin_user_pages_fast_only().
Please don't split a function name across lines. That messes up people who are grepping for the function name in the changelog.
> As part of this we will get rid of write parameter. > Instead caller will pass FOLL_WRITE to get_user_pages_fast_only(). > This will not change any existing functionality of the API. > > All the callers are changed to pass FOLL_WRITE. > > Updated the documentation of the API.
Everything you have done here is an improvement, and I'd be happy to see it go in (after fixing the bug I note below).
But in reading through it, I noticed almost every user ...
> - if (__get_user_pages_fast(hva, 1, 1, &page) == 1) { > + if (get_user_pages_fast_only(hva, 1, FOLL_WRITE, &page) == 1) {
passes '1' as the second parameter. So do we want to add:
static inline bool get_user_page_fast_only(unsigned long addr, unsigned int gup_flags, struct page **pagep) { return get_user_pages_fast_only(addr, 1, gup_flags, pagep) == 1; }
> @@ -2797,10 +2803,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, > * FOLL_FAST_ONLY is required in order to match the API description of > * this routine: no fall back to regular ("slow") GUP. > */ > - unsigned int gup_flags = FOLL_GET | FOLL_FAST_ONLY; > - > - if (write) > - gup_flags |= FOLL_WRITE; > + gup_flags = FOLL_GET | FOLL_FAST_ONLY;
Er ... gup_flags |=, surely?
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