uprobes/core: Make background page replacement logic account for rss_…

…stat counters

Background page replacement logic adds a new anonymous page
instead of a file backed (while inserting a breakpoint) /
anonymous page (while removing a breakpoint).

Hence the uprobes logic should take care to update the
task->ss_stat counters accordingly.

This bug became apparent courtesy of commit c3f0327
("mm: add rss counters consistency check").

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com>
Cc: Linux-mm <linux-mm@kvack.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120411103516.23245.2700.sendpatchset@srdronam.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/events/uprobes.c

@@ -160,6 +160,11 @@ static int __replace_page(struct vm_area_struct *vma, struct page *page, struct
 	get_page(kpage);
 	page_add_new_anon_rmap(kpage, vma, addr);
 
+	if (!PageAnon(page)) {
+		dec_mm_counter(mm, MM_FILEPAGES);
+		inc_mm_counter(mm, MM_ANONPAGES);
+	}
+
 	flush_cache_page(vma, addr, pte_pfn(*ptep));
 	ptep_clear_flush(vma, addr, ptep);
 	set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));