PageSlab macro check was added before putting of _mapcount value
to /kpagecount. page->_mapcount is in union with SLAB structure
so for pages controlled by SLAB page_mapcount() returns nonsenses.

Signed-off-by: Petr Holasek <pholasek@redhat.com>
---
 fs/proc/page.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/proc/page.c b/fs/proc/page.c
index 3b8b456..b06c674 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -40,7 +40,7 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf,
 			ppage = pfn_to_page(pfn);
 		else
 			ppage = NULL;
-		if (!ppage)
+		if (!ppage || PageSlab(ppage))
 			pcount = 0;
 		else
 			pcount = page_mapcount(ppage);
--
1.7.2.3

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