From 99a1300e1d84709f419182bb5189760e78234882 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli <aarcange@redhat.com> Date: Fri, 28 Sep 2012 14:35:31 +0200 Subject: [PATCH] thp: avoid VM_BUG_ON page_count(page) false positives in __collapse_huge_page_copy Speculative cache pagecache lookups can elevate the refcount from under us, so avoid the false positive. If the refcount is < 2 we'll be notified by a VM_BUG_ON in put_page_testzero as there are two put_page(src_page) in a row before returning from this function. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Petr Holasek <pholasek@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> --- mm/huge_memory.c | 1 - 1 file changed, 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 57c4b93090151..141dbb695097c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1811,7 +1811,6 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page, src_page = pte_page(pteval); copy_user_highpage(page, src_page, address, vma); VM_BUG_ON(page_mapcount(src_page) != 1); - VM_BUG_ON(page_count(src_page) != 2); release_pte_page(src_page); /* * ptl mostly unnecessary, but preempt has to -- GitLab