On Sun 22-02-15 15:42:16, Shachar Raindel wrote:
> When do_wp_page is ending, in several cases it needs to unlock the
> pages and ptls it was accessing.
>
> Currently, this logic was "called" by using a goto jump. This makes
> following the control flow of the function harder. Readability was
> further hampered by the unlock case containing large amount of logic
> needed only in one of the 3 cases.
>
> Using goto for cleanup is generally allowed. However, moving the
> trivial unlocking flows to the relevant call sites allow deeper
> refactoring in the next patch.
>
> 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>
Neat!
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/memory.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 7a04414..3afd9ce 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2066,7 +2066,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
> {
> struct page *old_page, *new_page = NULL;
> pte_t entry;
> - int ret = 0;
> + int page_copied = 0;
> unsigned long mmun_start = 0; /* For mmu_notifiers */
> unsigned long mmun_end = 0; /* For mmu_notifiers */
> struct mem_cgroup *memcg;
> @@ -2101,7 +2101,9 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
> &ptl);
> if (!pte_same(*page_table, orig_pte)) {
> unlock_page(old_page);
> - goto unlock;
> + pte_unmap_unlock(page_table, ptl);
> + page_cache_release(old_page);
> + return 0;
> }
> page_cache_release(old_page);
> }
> @@ -2148,7 +2150,9 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
> &ptl);
> if (!pte_same(*page_table, orig_pte)) {
> unlock_page(old_page);
> - goto unlock;
> + pte_unmap_unlock(page_table, ptl);
> + page_cache_release(old_page);
> + return 0;
> }
> page_mkwrite = 1;
> }
> @@ -2246,29 +2250,28 @@ gotten:
>
> /* Free the old page.. */
> new_page = old_page;
> - ret |= VM_FAULT_WRITE;
> + page_copied = 1;
> } else
> mem_cgroup_cancel_charge(new_page, memcg);
>
> if (new_page)
> page_cache_release(new_page);
> -unlock:
> +
> pte_unmap_unlock(page_table, ptl);
> - if (mmun_end > mmun_start)
> - mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
> + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
> if (old_page) {
> /*
> * Don't let another task, with possibly unlocked vma,
> * keep the mlocked page.
> */
> - if ((ret & VM_FAULT_WRITE) && (vma->vm_flags & VM_LOCKED)) {
> + if (page_copied && (vma->vm_flags & VM_LOCKED)) {
> lock_page(old_page); /* LRU manipulation */
> munlock_vma_page(old_page);
> unlock_page(old_page);
> }
> page_cache_release(old_page);
> }
> - return ret;
> + return page_copied ? VM_FAULT_WRITE : 0;
> oom_free_new:
> page_cache_release(new_page);
> oom:
> --
> 1.7.11.2
>
> --
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--
Michal Hocko
SUSE Labs
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