diff options
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 25 |
1 files changed, 2 insertions, 23 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index 9827409eb7c7..08ac5c7fa91f 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -247,8 +247,8 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) * * On success returns with mapped pte and locked mm->page_table_lock. */ -static pte_t *page_check_address(struct page *page, struct mm_struct *mm, - unsigned long address) +pte_t *page_check_address(struct page *page, struct mm_struct *mm, + unsigned long address) { pgd_t *pgd; pud_t *pud; @@ -539,27 +539,6 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma) goto out_unmap; } - /* - * Don't pull an anonymous page out from under get_user_pages. - * GUP carefully breaks COW and raises page count (while holding - * page_table_lock, as we have here) to make sure that the page - * cannot be freed. If we unmap that page here, a user write - * access to the virtual address will bring back the page, but - * its raised count will (ironically) be taken to mean it's not - * an exclusive swap page, do_wp_page will replace it by a copy - * page, and the user never get to see the data GUP was holding - * the original page for. - * - * This test is also useful for when swapoff (unuse_process) has - * to drop page lock: its reference to the page stops existing - * ptes from being unmapped, so swapoff can make progress. - */ - if (PageSwapCache(page) && - page_count(page) != page_mapcount(page) + 2) { - ret = SWAP_FAIL; - goto out_unmap; - } - /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); pteval = ptep_clear_flush(vma, address, pte); |