From 9cbb4cb21b19fff46cf1174d0ed699ef710e641c Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Thu, 13 Jan 2011 15:45:51 -0800 Subject: mm: find_get_pages_contig fixlet Testing ->mapping and ->index without a ref is not stable as the page may have been reused at this point. Signed-off-by: Nick Piggin Reviewed-by: Wu Fengguang Reviewed-by: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'mm') diff --git a/mm/filemap.c b/mm/filemap.c index ca38939..1a3dd59 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -837,9 +837,6 @@ repeat: if (radix_tree_deref_retry(page)) goto restart; - if (page->mapping == NULL || page->index != index) - break; - if (!page_cache_get_speculative(page)) goto repeat; @@ -849,6 +846,16 @@ repeat: goto repeat; } + /* + * must check mapping and index after taking the ref. + * otherwise we can get both false positives and false + * negatives, which is just confusing to the caller. + */ + if (page->mapping == NULL || page->index != index) { + page_cache_release(page); + break; + } + pages[ret] = page; ret++; index++; -- cgit v1.1