kpagecount: add slab page checking because _mapcount is in a union
Petr Holasek [Thu, 13 Jan 2011 01:00:34 +0000 (17:00 -0800)]
Add a PageSlab() check before adding the _mapcount value to /kpagecount.
page->_mapcount is in a union with the SLAB structure so for pages
controlled by SLAB, page_mapcount() returns nonsense.

Signed-off-by: Petr Holasek <pholasek@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/page.c

index 3b8b456..b06c674 100644 (file)
@@ -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);