From 3ca7b3c5b64d35fe02c35b5d44c2c58b49499fee Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 14 Dec 2009 17:58:57 -0800 Subject: mm: define PAGE_MAPPING_FLAGS At present we define PageAnon(page) by the low PAGE_MAPPING_ANON bit set in page->mapping, with the higher bits a pointer to the anon_vma; and have defined PageKsm(page) as that with NULL anon_vma. But KSM swapping will need to store a pointer there: so in preparation for that, now define PAGE_MAPPING_FLAGS as the low two bits, including PAGE_MAPPING_KSM (always set along with PAGE_MAPPING_ANON, until some other use for the bit emerges). Declare page_rmapping(page) to return the pointer part of page->mapping, and page_anon_vma(page) to return the anon_vma pointer when that's what it is. Use these in a few appropriate places: notably, unuse_vma() has been testing page->mapping, but is better to be testing page_anon_vma() (cases may be added in which flag bits are set without any pointer). Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Nick Piggin Cc: KOSAKI Motohiro Reviewed-by: Rik van Riel Cc: Lee Schermerhorn Cc: Andi Kleen Cc: KAMEZAWA Hiroyuki Cc: Wu Fengguang Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/rmap.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'mm/rmap.c') diff --git a/mm/rmap.c b/mm/rmap.c index 1a0ee6e634c..f06cee48eca 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -203,7 +203,7 @@ struct anon_vma *page_lock_anon_vma(struct page *page) rcu_read_lock(); anon_mapping = (unsigned long) page->mapping; - if (!(anon_mapping & PAGE_MAPPING_ANON)) + if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) goto out; if (!page_mapped(page)) goto out; @@ -248,8 +248,7 @@ vma_address(struct page *page, struct vm_area_struct *vma) unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) { if (PageAnon(page)) { - if ((void *)vma->anon_vma != - (void *)page->mapping - PAGE_MAPPING_ANON) + if (vma->anon_vma != page_anon_vma(page)) return -EFAULT; } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { if (!vma->vm_file || @@ -513,7 +512,7 @@ int page_referenced(struct page *page, referenced++; *vm_flags = 0; - if (page_mapped(page) && page->mapping) { + if (page_mapped(page) && page_rmapping(page)) { if (PageAnon(page)) referenced += page_referenced_anon(page, mem_cont, vm_flags); -- cgit v1.2.3-70-g09d2