On Tue, 27 Aug 2013 16:02:29 +0800 Wanpeng Li <liw...@linux.vnet.ibm.com> wrote:
> Hi Chen,
> On Tue, Aug 27, 2013 at 03:37:01AM -0400, Chen Gong wrote:
> >> On Tue, Aug 27, 2013 at 11:38:27AM +0800, Wanpeng Li wrote:
> >> > Hi Naoya,
> >> > On Mon, Aug 26, 2013 at 11:28:16PM -0400, Naoya Horiguchi wrote:
> >> > >On Tue, Aug 27, 2013 at 10:39:31AM +0800, Wanpeng Li wrote:
> >> > >> The return value outside for loop is always zero which means
> >> > >> madvise_hwpoison
> >> > >> return success, however, this is not truth for soft_offline_page w/
> >> > >> failure
> >> > >> return value.
> >> > >
> >> > >I don't understand what you want to do for what reason. Could you
> >> > >clarify
> >> > >those?
> >> >
> >> > int ret is defined in two place in madvise_hwpoison. One is out of for
> >> > loop and its value is always zero(zero means success for madvise), the
> >> > other one is in for loop. The soft_offline_page function maybe return
> >> > -EBUSY and break, however, the ret out of for loop is return which means
> >> > madvise_hwpoison success.
> >>
> >> Oh, I see. Thanks.
> >>
> >I don't think such change is a good idea. The original code is obviously
> >easy to confuse people. Why not removing redundant local variable?
> >
>
> I think the trick here is get_user_pages_fast will return the number of
> pages pinned. It is always 1 in madvise_hwpoison, the return value of
> memory_failure is ignored. Therefore we still need to reset ret to 0
> before return madvise_hwpoison.
erk, madvise_hwpoison() has two locals with the same name. Bad.
From: Andrew Morton <a...@linux-foundation.org>
Subject: mm/madvise.c:madvise_hwpoison(): remove local `ret'
madvise_hwpoison() has two locals called "ret". Fix it all up.
Cc: Wanpeng Li <liw...@linux.vnet.ibm.com>
Cc: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
Cc: Andi Kleen <a...@firstfloor.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
---
mm/madvise.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff -puN mm/madvise.c~a mm/madvise.c
--- a/mm/madvise.c~a
+++ a/mm/madvise.c
@@ -343,15 +343,16 @@ static long madvise_remove(struct vm_are
*/
static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
{
- int ret = 0;
-
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
for (; start < end; start += PAGE_SIZE) {
struct page *p;
- int ret = get_user_pages_fast(start, 1, 0, &p);
+ int ret;
+
+ ret = get_user_pages_fast(start, 1, 0, &p);
if (ret != 1)
return ret;
+
if (PageHWPoison(p)) {
put_page(p);
continue;
@@ -369,7 +370,7 @@ static int madvise_hwpoison(int bhv, uns
/* Ignore return value for now */
memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED);
}
- return ret;
+ return 0;
}
#endif
_
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