On Mon, 17 Nov 2014 15:03:28 +0200 "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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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