linux-kernel - [PATCH] rmap: fixup page_referenced() for nommu systems

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Date:	Thu, 18 Jun 2009 20:36:53 -0400
From:	Mike Frysinger <vapier@...too.org>
To:	linux-kernel@...r.kernel.org
Cc:	David Howells <dhowells@...hat.com>,
	David McCullough <davidm@...pgear.com>,
	Greg Ungerer <gerg@...inux.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] rmap: fixup page_referenced() for nommu systems

After the recent changes that went into mm/vmscan.c to overhaul stuff, we
ended up with these warnings on no-mmu systems:
mm/vmscan.c: In function ‘shrink_page_list’:
mm/vmscan.c:580: warning: unused variable ‘vm_flags’
mm/vmscan.c: In function ‘shrink_active_list’:
mm/vmscan.c:1294: warning: ‘vm_flags’ may be used uninitialized in this function
mm/vmscan.c:1242: note: ‘vm_flags’ was declared here

This is because the no-mmu function defines page_referenced() to work on
the first argument only (the page).  It does not clear the vm_flags given
to it because for no-mmu systems, they never actually get utilized.  Since
that is no longer strictly true, we need to set vm_flags to 0 like everyone
else so gcc can do proper dead code elimination without annoying us with
unused warnings.

Signed-off-by: Mike Frysinger <vapier@...too.org>
---
 include/linux/rmap.h |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 216d024..bf116d0 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -118,7 +118,14 @@ int try_to_munlock(struct page *);
 #define anon_vma_prepare(vma)	(0)
 #define anon_vma_link(vma)	do {} while (0)
 
-#define page_referenced(page, locked, cnt, flags) TestClearPageReferenced(page)
+static inline int page_referenced(struct page *page, int is_locked,
+				  struct mem_cgroup *cnt,
+				  unsigned long *vm_flags)
+{
+	*vm_flags = 0;
+	return TestClearPageReferenced(page);
+}
+
 #define try_to_unmap(page, refs) SWAP_FAIL
 
 static inline int page_mkclean(struct page *page)
-- 
1.6.3.1

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