linux-kernel - [PATCH v2] rmap: Fix compound check logic in page_remove_file

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Date:	Wed, 10 Aug 2016 15:10:17 +0100
From:	Steve Capper <steve.capper@....com>
To:	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org, shijie.huang@....com,
	will.deacon@....com, catalin.marinas@....com,
	Steve Capper <steve.capper@....com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v2] rmap: Fix compound check logic in page_remove_file_rmap

In page_remove_file_rmap(.) we have the following check:
  VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);

This is meant to check for either HugeTLB pages or THP when a compound
page is passed in.

Unfortunately, if one disables CONFIG_TRANSPARENT_HUGEPAGE, then
PageTransHuge(.) will always return false, provoking BUGs when one runs
the libhugetlbfs test suite.

This patch replaces PageTransHuge(), with PageHead() which will work for
both HugeTLB and THP.

Fixes: dd78fedde4b9 ("rmap: support file thp")
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Steve Capper <steve.capper@....com>

---

v2 - switch to PageHead as suggested by Kirill.
---
 mm/rmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 709bc83..1180340 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1303,7 +1303,7 @@ static void page_remove_file_rmap(struct page *page, bool compound)
 {
 	int i, nr = 1;

-	VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
+	VM_BUG_ON_PAGE(compound && !PageHead(page), page);
 	lock_page_memcg(page);

 	/* Hugepages are not counted in NR_FILE_MAPPED for now. */
-- 
1.8.3.1