On Sun 22-02-15 15:42:18, Shachar Raindel wrote:
> The do_wp_page function is extremely long. Extract the logic for
> handling a page belonging to a shared vma into a function of its own.
>
> This helps the readability of the code, without doing any functional
> change in it.
>
> Signed-off-by: Shachar Raindel <raindel@xxxxxxxxxxxx>
> Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxx>
> Acked-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Acked-by: Haggai Eran <haggaie@xxxxxxxxxxxx>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Cc: Peter Feiner <pfeiner@xxxxxxxxxx>
> Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/memory.c | 86 ++++++++++++++++++++++++++++++++++---------------------------
> 1 file changed, 48 insertions(+), 38 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index a06e705..b246d22 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2181,6 +2181,52 @@ oom:
> return VM_FAULT_OOM;
> }
>
> +static int wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
> + unsigned long address, pte_t *page_table,
> + pmd_t *pmd, spinlock_t *ptl, pte_t orig_pte,
> + struct page *old_page)
> + __releases(ptl)
> +{
> + int page_mkwrite = 0;
> +
> + page_cache_get(old_page);
> +
> + /*
> + * Only catch write-faults on shared writable pages,
> + * read-only shared pages can get COWed by
> + * get_user_pages(.write=1, .force=1).
> + */
> + if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
> + int tmp;
> +
> + pte_unmap_unlock(page_table, ptl);
> + tmp = do_page_mkwrite(vma, old_page, address);
> + if (unlikely(!tmp || (tmp &
> + (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
> + page_cache_release(old_page);
> + return tmp;
> + }
> + /*
> + * Since we dropped the lock we need to revalidate
> + * the PTE as someone else may have changed it. If
> + * they did, we just return, as we can count on the
> + * MMU to tell us if they didn't also make it writable.
> + */
> + page_table = pte_offset_map_lock(mm, pmd, address,
> + &ptl);
> + if (!pte_same(*page_table, orig_pte)) {
> + unlock_page(old_page);
> + pte_unmap_unlock(page_table, ptl);
> + page_cache_release(old_page);
> + return 0;
> + }
> + page_mkwrite = 1;
> + }
> +
> + return wp_page_reuse(mm, vma, address, page_table, ptl,
> + orig_pte, old_page, page_mkwrite, 1);
> +}
> +
> /*
> * This routine handles present pages, when users try to write
> * to a shared page. It is done by copying the page to a new address
> @@ -2259,44 +2305,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
> unlock_page(old_page);
> } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
> (VM_WRITE|VM_SHARED))) {
> - int page_mkwrite = 0;
> -
> - page_cache_get(old_page);
> -
> - /*
> - * Only catch write-faults on shared writable pages,
> - * read-only shared pages can get COWed by
> - * get_user_pages(.write=1, .force=1).
> - */
> - if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
> - int tmp;
> -
> - pte_unmap_unlock(page_table, ptl);
> - tmp = do_page_mkwrite(vma, old_page, address);
> - if (unlikely(!tmp || (tmp &
> - (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
> - page_cache_release(old_page);
> - return tmp;
> - }
> - /*
> - * Since we dropped the lock we need to revalidate
> - * the PTE as someone else may have changed it. If
> - * they did, we just return, as we can count on the
> - * MMU to tell us if they didn't also make it writable.
> - */
> - page_table = pte_offset_map_lock(mm, pmd, address,
> - &ptl);
> - if (!pte_same(*page_table, orig_pte)) {
> - unlock_page(old_page);
> - pte_unmap_unlock(page_table, ptl);
> - page_cache_release(old_page);
> - return 0;
> - }
> - page_mkwrite = 1;
> - }
> -
> - return wp_page_reuse(mm, vma, address, page_table, ptl,
> - orig_pte, old_page, page_mkwrite, 1);
> + return wp_page_shared(mm, vma, address, page_table, pmd,
> + ptl, orig_pte, old_page);
> }
>
> /*
> --
> 1.7.11.2
>
> --
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--
Michal Hocko
SUSE Labs
--
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