On Mon, Dec 01, 2014 at 06:56:17PM +0200, 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>
Few nitpicks below.
> ---
> mm/memory.c | 90 +++++++++++++++++++++++++++++++++++--------------------------
> 1 file changed, 52 insertions(+), 38 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index c7c0df2..c0dd47a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2227,6 +2227,56 @@ 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;
> + int ret;
> +
> + /*
> + * Only catch write-faults on shared writable pages,
> + * read-only shared pages can get COWed by
> + * get_user_pages(.write=1, .force=1).
> + */
Reformat of the comment and comment below would safe few lines.
> + if (!vma->vm_ops || !vma->vm_ops->page_mkwrite)
> + goto no_mkwrite;
> +
> +
Redundant newline.
> + page_cache_get(old_page);
> + pte_unmap_unlock(page_table, ptl);
> + ret = do_page_mkwrite(vma, old_page, address);
> + if (unlikely(!ret || (ret &
> + (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
This would fit one line now.
> + page_cache_release(old_page);
> + return ret;
> + }
> + /*
> + * 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);
ditto.
> + 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;
> +
> +no_mkwrite:
> + get_page(old_page);
> +
> + return wp_page_reuse(mm, vma, address, page_table, ptl, orig_pte,
> + old_page, 1, page_mkwrite);
> +}
> +
> /*
> * 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
--
Kirill A. Shutemov
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