2009-06-19 00:37:14

by Mike Frysinger

[permalink] [raw]
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 <[email protected]>
---
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


2009-06-19 02:27:18

by Paul Mundt

[permalink] [raw]
Subject: Re: [PATCH] rmap: fixup page_referenced() for nommu systems

On Thu, Jun 18, 2009 at 08:36:53PM -0400, Mike Frysinger wrote:
> 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 <[email protected]>

Looks ok to me.

Acked-by: Paul Mundt <[email protected]>

2009-06-19 10:59:33

by David Howells

[permalink] [raw]
Subject: Re: [PATCH] rmap: fixup page_referenced() for nommu systems

Mike Frysinger <[email protected]> wrote:

> 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 <[email protected]>

Acked-by: David Howells <[email protected]>

2009-06-22 07:35:52

by Greg Ungerer

[permalink] [raw]
Subject: Re: [PATCH] rmap: fixup page_referenced() for nommu systems


Mike Frysinger wrote:
> 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 <[email protected]>

Acked-by: Greg Ungerer <[email protected]>



> 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)

--
------------------------------------------------------------------------
Greg Ungerer -- Principal Engineer EMAIL: [email protected]
SnapGear Group, McAfee PHONE: +61 7 3435 2888
825 Stanley St, FAX: +61 7 3891 3630
Woolloongabba, QLD, 4102, Australia WEB: http://www.SnapGear.com