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* [mmotm:master 120/306] fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type?
@ 2014-11-14 11:44 kbuild test robot
  2014-11-17 13:03 ` Kirill A. Shutemov
  0 siblings, 1 reply; 3+ messages in thread
From: kbuild test robot @ 2014-11-14 11:44 UTC (permalink / raw)
  To: kbuild, Kirill A. Shutemov; +Cc: Linux Memory Management List, Dan Carpenter

[ You would have to enable transparent huge page tables on a 32 bit
  system to trigger this bug and I don't think that's possible.

  I don't think Smatch will complain about this if you have the cross
  function database turned on because it knows the value of size in that
  case.  But most people don't build the database so it might be worth
  silencing this bug?  Should I even bother sending these email for
  non-bugs?  Let me know.  -dan ]

tree:   git://git.cmpxchg.org/linux-mmotm.git master
head:   e668fb4c5c5e6de5b9432bd36d83b3a0b4ce78e8
commit: be7c8db9daa43935912bc8c898ecea99b32d805b [120/306] mm: fix huge zero page accounting in smaps report

fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type?

git remote add mmotm git://git.cmpxchg.org/linux-mmotm.git
git remote update mmotm
git checkout be7c8db9daa43935912bc8c898ecea99b32d805b
vim +474 fs/proc/task_mmu.c

be7c8db9 Kirill A. Shutemov 2014-11-13  458  	mss->resident += size;
be7c8db9 Kirill A. Shutemov 2014-11-13  459  	/* Accumulate the size in pages that have been accessed. */
be7c8db9 Kirill A. Shutemov 2014-11-13  460  	if (young || PageReferenced(page))
be7c8db9 Kirill A. Shutemov 2014-11-13  461  		mss->referenced += size;
be7c8db9 Kirill A. Shutemov 2014-11-13  462  	mapcount = page_mapcount(page);
be7c8db9 Kirill A. Shutemov 2014-11-13  463  	if (mapcount >= 2) {
be7c8db9 Kirill A. Shutemov 2014-11-13  464  		if (dirty || PageDirty(page))
be7c8db9 Kirill A. Shutemov 2014-11-13  465  			mss->shared_dirty += size;
be7c8db9 Kirill A. Shutemov 2014-11-13  466  		else
be7c8db9 Kirill A. Shutemov 2014-11-13  467  			mss->shared_clean += size;
be7c8db9 Kirill A. Shutemov 2014-11-13  468  		mss->pss += (size << PSS_SHIFT) / mapcount;
be7c8db9 Kirill A. Shutemov 2014-11-13  469  	} else {
be7c8db9 Kirill A. Shutemov 2014-11-13  470  		if (dirty || PageDirty(page))
be7c8db9 Kirill A. Shutemov 2014-11-13  471  			mss->private_dirty += size;
be7c8db9 Kirill A. Shutemov 2014-11-13  472  		else
be7c8db9 Kirill A. Shutemov 2014-11-13  473  			mss->private_clean += size;
be7c8db9 Kirill A. Shutemov 2014-11-13 @474  		mss->pss += (size << PSS_SHIFT);
be7c8db9 Kirill A. Shutemov 2014-11-13  475  	}
be7c8db9 Kirill A. Shutemov 2014-11-13  476  }
be7c8db9 Kirill A. Shutemov 2014-11-13  477  
be7c8db9 Kirill A. Shutemov 2014-11-13  478  
be7c8db9 Kirill A. Shutemov 2014-11-13  479  static void smaps_pte_entry(pte_t *pte, unsigned long addr,
be7c8db9 Kirill A. Shutemov 2014-11-13  480  		struct mm_walk *walk)
e070ad49 Mauricio Lin       2005-09-03  481  {
2165009b Dave Hansen        2008-06-12  482  	struct mem_size_stats *mss = walk->private;

---
0-DAY kernel test infrastructure                Open Source Technology Center
http://lists.01.org/mailman/listinfo/kbuild                 Intel Corporation

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^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [mmotm:master 120/306] fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type?
  2014-11-14 11:44 [mmotm:master 120/306] fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type? kbuild test robot
@ 2014-11-17 13:03 ` Kirill A. Shutemov
  2014-11-19 23:30   ` Andrew Morton
  0 siblings, 1 reply; 3+ messages in thread
From: Kirill A. Shutemov @ 2014-11-17 13:03 UTC (permalink / raw)
  To: kbuild test robot, akpm
  Cc: kbuild, Linux Memory Management List, Dan Carpenter

On Fri, Nov 14, 2014 at 02:44:15PM +0300, kbuild test robot wrote:
> [ You would have to enable transparent huge page tables on a 32 bit
>   system to trigger this bug and I don't think that's possible.

It is. We have THP on 32-bit x86.

>   I don't think Smatch will complain about this if you have the cross
>   function database turned on because it knows the value of size in that
>   case.  But most people don't build the database so it might be worth
>   silencing this bug?  Should I even bother sending these email for
>   non-bugs?  Let me know.  -dan ]
> 
> tree:   git://git.cmpxchg.org/linux-mmotm.git master
> head:   e668fb4c5c5e6de5b9432bd36d83b3a0b4ce78e8
> commit: be7c8db9daa43935912bc8c898ecea99b32d805b [120/306] mm: fix huge zero page accounting in smaps report
> 
> fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type?

This should fix the issue.

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8fd00743bd4d..de80a887d98e 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -464,17 +464,16 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
                        mss->shared_dirty += size;
                else
                        mss->shared_clean += size;
-               mss->pss += (size << PSS_SHIFT) / mapcount;
+               mss->pss += ((u64)size << PSS_SHIFT) / mapcount;
        } else {
                if (dirty || PageDirty(page))
                        mss->private_dirty += size;
                else
                        mss->private_clean += size;
-               mss->pss += (size << PSS_SHIFT);
+               mss->pss += (u64)size << PSS_SHIFT;
        }
 }
 
-
 static void smaps_pte_entry(pte_t *pte, unsigned long addr,
                struct mm_walk *walk)
 {
-- 
 Kirill A. Shutemov

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^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [mmotm:master 120/306] fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type?
  2014-11-17 13:03 ` Kirill A. Shutemov
@ 2014-11-19 23:30   ` Andrew Morton
  0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2014-11-19 23:30 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: kbuild test robot, kbuild, Linux Memory Management List,
	Dan Carpenter

On Mon, 17 Nov 2014 15:03:28 +0200 "Kirill A. Shutemov" <kirill@shutemov.name> wrote:

> On Fri, Nov 14, 2014 at 02:44:15PM +0300, kbuild test robot wrote:
> > [ You would have to enable transparent huge page tables on a 32 bit
> >   system to trigger this bug and I don't think that's possible.
> 
> It is. We have THP on 32-bit x86.
> 
> >   I don't think Smatch will complain about this if you have the cross
> >   function database turned on because it knows the value of size in that
> >   case.  But most people don't build the database so it might be worth
> >   silencing this bug?  Should I even bother sending these email for
> >   non-bugs?  Let me know.  -dan ]
> > 
> > tree:   git://git.cmpxchg.org/linux-mmotm.git master
> > head:   e668fb4c5c5e6de5b9432bd36d83b3a0b4ce78e8
> > commit: be7c8db9daa43935912bc8c898ecea99b32d805b [120/306] mm: fix huge zero page accounting in smaps report
> > 
> > fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type?
> 
> This should fix the issue.
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 8fd00743bd4d..de80a887d98e 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -464,17 +464,16 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
>                         mss->shared_dirty += size;
>                 else
>                         mss->shared_clean += size;
> -               mss->pss += (size << PSS_SHIFT) / mapcount;
> +               mss->pss += ((u64)size << PSS_SHIFT) / mapcount;
>         } else {
>                 if (dirty || PageDirty(page))
>                         mss->private_dirty += size;
>                 else
>                         mss->private_clean += size;
> -               mss->pss += (size << PSS_SHIFT);
> +               mss->pss += (u64)size << PSS_SHIFT;
>         }
>  }
>  
> -
>  static void smaps_pte_entry(pte_t *pte, unsigned long addr,
>                 struct mm_walk *walk)
>  {

Please check...


From: Andrew Morton <akpm@linux-foundation.org>
Subject: mm-fix-huge-zero-page-accounting-in-smaps-report-fix-2-fix

use do_div to fix 32-bit build

fs/built-in.o: In function `smaps_account':
task_mmu.c:(.text+0x943a3): undefined reference to `__udivdi3'

Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/task_mmu.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff -puN fs/proc/task_mmu.c~mm-fix-huge-zero-page-accounting-in-smaps-report-fix-2-fix fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~mm-fix-huge-zero-page-accounting-in-smaps-report-fix-2-fix
+++ a/fs/proc/task_mmu.c
@@ -461,11 +461,15 @@ static void smaps_account(struct mem_siz
 		mss->referenced += size;
 	mapcount = page_mapcount(page);
 	if (mapcount >= 2) {
+		u64 pss_delta;
+
 		if (dirty || PageDirty(page))
 			mss->shared_dirty += size;
 		else
 			mss->shared_clean += size;
-		mss->pss += ((u64)size << PSS_SHIFT) / mapcount;
+		pss_delta = (u64)size << PSS_SHIFT;
+		do_div(pss_delta, mapcount);
+		mss->pss += pss_delta;
 	} else {
 		if (dirty || PageDirty(page))
 			mss->private_dirty += size;
_

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2014-11-14 11:44 [mmotm:master 120/306] fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type? kbuild test robot
2014-11-17 13:03 ` Kirill A. Shutemov
2014-11-19 23:30   ` Andrew Morton

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