Messages in this thread | | | Date | Wed, 30 Jul 2008 10:29:28 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 1/2] Export get_user_pages_fast |
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On Wed, 30 Jul 2008 20:23:01 +0300 Avi Kivity <avi@qumranet.com> wrote:
> Andrew Morton wrote: > >> o other arch > >> would define CONFIG_HAVE_GET_USER_PAGES_FAST. > >> > >> > > > > That's presently true in Linus mainline. The powerpc implementation is > > in -mm, but apprarently needs a bit more work. > > Wouldn't a generic get_user_pages_fast() implementation which calls > get_user_pages_slow() if the arch hadn't implemented the former reduce a > lot of #ifdefs in call sites? >
That is how it is presently implemented.
#ifdef CONFIG_HAVE_GET_USER_PAGES_FAST /* * get_user_pages_fast provides equivalent functionality to get_user_pages, * operating on current and current->mm (force=0 and doesn't return any vmas). * * get_user_pages_fast may take mmap_sem and page tables, so no assumptions * can be made about locking. get_user_pages_fast is to be implemented in a * way that is advantageous (vs get_user_pages()) when the user memory area is * already faulted in and present in ptes. However if the pages have to be * faulted in, it may turn out to be slightly slower). */ int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages);
#else /* * Should probably be moved to asm-generic, and architectures can include it if * they don't implement their own get_user_pages_fast. */ #define get_user_pages_fast(start, nr_pages, write, pages) \ ({ \ struct mm_struct *mm = current->mm; \ int ret; \ \ down_read(&mm->mmap_sem); \ ret = get_user_pages(current, mm, start, nr_pages, \ write, 0, pages, NULL); \ up_read(&mm->mmap_sem); \ \ ret; \ }) #endif
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