On Sun, May 12, 2013 at 9:23 AM, Kirill A. Shutemov
<kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
>
> Let's add helpers to clear huge page segment(s). They provide the same
> functionallity as zero_user_segment and zero_user, but for huge pages.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> ---
> include/linux/mm.h | 7 +++++++
> mm/memory.c | 36 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 43 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index c05d7cf..5e156fb 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1797,6 +1797,13 @@ extern void dump_page(struct page *page);
> extern void clear_huge_page(struct page *page,
> unsigned long addr,
> unsigned int pages_per_huge_page);
> +extern void zero_huge_user_segment(struct page *page,
> + unsigned start, unsigned end);
> +static inline void zero_huge_user(struct page *page,
> + unsigned start, unsigned len)
> +{
> + zero_huge_user_segment(page, start, start + len);
> +}
> extern void copy_user_huge_page(struct page *dst, struct page *src,
> unsigned long addr, struct vm_area_struct *vma,
> unsigned int pages_per_huge_page);
> diff --git a/mm/memory.c b/mm/memory.c
> index f7a1fba..f02a8be 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4266,6 +4266,42 @@ void clear_huge_page(struct page *page,
> }
> }
>
> +void zero_huge_user_segment(struct page *page, unsigned start, unsigned end)
> +{
> + int i;
> + unsigned start_idx, end_idx;
> + unsigned start_off, end_off;
> +
> + BUG_ON(end < start);
> +
> + might_sleep();
> +
> + if (start == end)
> + return;
> +
> + start_idx = start >> PAGE_SHIFT;
> + start_off = start & ~PAGE_MASK;
> + end_idx = (end - 1) >> PAGE_SHIFT;
> + end_off = ((end - 1) & ~PAGE_MASK) + 1;
> +
> + /*
> + * if start and end are on the same small page we can call
> + * zero_user_segment() once and save one kmap_atomic().
> + */
> + if (start_idx == end_idx)
> + return zero_user_segment(page + start_idx, start_off, end_off);
> +
> + /* zero the first (possibly partial) page */
> + zero_user_segment(page + start_idx, start_off, PAGE_SIZE);
> + for (i = start_idx + 1; i < end_idx; i++) {
> + cond_resched();
> + clear_highpage(page + i);
> + flush_dcache_page(page + i);
Can we use the function again?
zero_user_segment(page + i, 0, PAGE_SIZE);
> + }
> + /* zero the last (possibly partial) page */
> + zero_user_segment(page + end_idx, 0, end_off);
> +}
> +
> static void copy_user_gigantic_page(struct page *dst, struct page *src,
> unsigned long addr,
> struct vm_area_struct *vma,
> --
> 1.7.10.4
>
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