diff options
| -rw-r--r-- | mm/memory.c | 117 |
1 files changed, 68 insertions, 49 deletions
diff --git a/mm/memory.c b/mm/memory.c index 97839f5c8c30..e70685f3e836 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1983,6 +1983,65 @@ static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page, } /* + * Handle write page faults for pages that can be reused in the current vma + * + * This can happen either due to the mapping being with the VM_SHARED flag, + * or due to us being the last reference standing to the page. In either + * case, all we need to do here is to mark the page as writable and update + * any related book-keeping. + */ +static inline int wp_page_reuse(struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long address, + pte_t *page_table, spinlock_t *ptl, pte_t orig_pte, + struct page *page, int page_mkwrite, + int dirty_shared) + __releases(ptl) +{ + pte_t entry; + /* + * Clear the pages cpupid information as the existing + * information potentially belongs to a now completely + * unrelated process. + */ + if (page) + page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1); + + flush_cache_page(vma, address, pte_pfn(orig_pte)); + entry = pte_mkyoung(orig_pte); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + if (ptep_set_access_flags(vma, address, page_table, entry, 1)) + update_mmu_cache(vma, address, page_table); + pte_unmap_unlock(page_table, ptl); + + if (dirty_shared) { + struct address_space *mapping; + int dirtied; + + if (!page_mkwrite) + lock_page(page); + + dirtied = set_page_dirty(page); + VM_BUG_ON_PAGE(PageAnon(page), page); + mapping = page->mapping; + unlock_page(page); + page_cache_release(page); + + if ((dirtied || page_mkwrite) && mapping) { + /* + * Some device drivers do not set page.mapping + * but still dirty their pages + */ + balance_dirty_pages_ratelimited(mapping); + } + + if (!page_mkwrite) + file_update_time(vma->vm_file); + } + + return VM_FAULT_WRITE; +} + +/* * 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 * and decrementing the shared-page counter for the old page. @@ -2008,8 +2067,6 @@ 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_mkwrite = 0; - bool dirty_shared = false; unsigned long mmun_start = 0; /* For mmu_notifiers */ unsigned long mmun_end = 0; /* For mmu_notifiers */ struct mem_cgroup *memcg; @@ -2026,7 +2083,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, */ if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) == (VM_WRITE|VM_SHARED)) - goto reuse; + return wp_page_reuse(mm, vma, address, page_table, ptl, + orig_pte, old_page, 0, 0); goto gotten; } @@ -2055,12 +2113,16 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, */ page_move_anon_rmap(old_page, vma, address); unlock_page(old_page); - goto reuse; + return wp_page_reuse(mm, vma, address, page_table, ptl, + orig_pte, old_page, 0, 0); } 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 @@ -2091,51 +2153,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, page_mkwrite = 1; } - dirty_shared = true; - -reuse: - /* - * Clear the pages cpupid information as the existing - * information potentially belongs to a now completely - * unrelated process. - */ - if (old_page) - page_cpupid_xchg_last(old_page, (1 << LAST_CPUPID_SHIFT) - 1); - - flush_cache_page(vma, address, pte_pfn(orig_pte)); - entry = pte_mkyoung(orig_pte); - entry = maybe_mkwrite(pte_mkdirty(entry), vma); - if (ptep_set_access_flags(vma, address, page_table, entry,1)) - update_mmu_cache(vma, address, page_table); - pte_unmap_unlock(page_table, ptl); - ret |= VM_FAULT_WRITE; - - if (dirty_shared) { - struct address_space *mapping; - int dirtied; - - if (!page_mkwrite) - lock_page(old_page); - - dirtied = set_page_dirty(old_page); - VM_BUG_ON_PAGE(PageAnon(old_page), old_page); - mapping = old_page->mapping; - unlock_page(old_page); - page_cache_release(old_page); - - if ((dirtied || page_mkwrite) && mapping) { - /* - * Some device drivers do not set page.mapping - * but still dirty their pages - */ - balance_dirty_pages_ratelimited(mapping); - } - - if (!page_mkwrite) - file_update_time(vma->vm_file); - } - - return ret; + return wp_page_reuse(mm, vma, address, page_table, ptl, + orig_pte, old_page, page_mkwrite, 1); } /* |