diff options
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 42 |
1 files changed, 17 insertions, 25 deletions
diff --git a/mm/memory.c b/mm/memory.c index 09a57fe6ae01..0c69908d3eed 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2399,39 +2399,31 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, * Take out anonymous pages first, anonymous shared vmas are * not dirty accountable. */ - if (PageAnon(old_page) && !PageKsm(old_page)) { - if (!trylock_page(old_page)) { - page_cache_get(old_page); - pte_unmap_unlock(page_table, ptl); - lock_page(old_page); - 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_cache_release(old_page); - } - if (reuse_swap_page(old_page)) { - /* - * The page is all ours. Move it to our anon_vma so - * the rmap code will not search our parent or siblings. - * Protected against the rmap code by the page lock. - */ - page_move_anon_rmap(old_page, vma, address); + if (PageAnon(old_page)) { + /* PageKsm() doesn't necessarily raise the page refcount */ + if (PageKsm(old_page) || page_count(old_page) != 1) + goto copy; + if (!trylock_page(old_page)) + goto copy; + if (PageKsm(old_page) || page_mapcount(old_page) != 1 || page_count(old_page) != 1) { unlock_page(old_page); - return wp_page_reuse(mm, vma, address, page_table, ptl, - orig_pte, old_page, 0, 0); + goto copy; } + /* + * Ok, we've got the only map reference, and the only + * page count reference, and the page is locked, + * it's dark out, and we're wearing sunglasses. Hit it. + */ unlock_page(old_page); + wp_page_reuse(mm, vma, address, page_table, ptl, + orig_pte, old_page, 0, 0); + return VM_FAULT_WRITE; } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) == (VM_WRITE|VM_SHARED))) { return wp_page_shared(mm, vma, address, page_table, pmd, ptl, orig_pte, old_page); } - +copy: /* * Ok, we need to copy. Oh, well.. */ |