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    SubjectRe: [PATCH 1/2] Export get_user_pages_fast
    On Thu, 31 Jul 2008 09:43:59 +0300 Avi Kivity <avi@qumranet.com> wrote:

    > > #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
    > >
    > >
    >
    > Surprised. Why not an out-of-line function? Would eliminate the
    > present discussion as well.

    Excellent question!


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