Re: [PATCH v9 05/10] mm: thp: enable thp migration in generic path
From: Andrew Morton
Date: Wed Jul 19 2017 - 16:59:33 EST
On Wed, 19 Jul 2017 14:39:43 -0400 "Zi Yan" <zi.yan@xxxxxxxxxxxxxx> wrote:
> On 19 Jul 2017, at 4:04, kbuild test robot wrote:
>
> > Hi Zi,
> >
> > [auto build test WARNING on mmotm/master]
> > [also build test WARNING on v4.13-rc1 next-20170718]
> > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> >
> > url: https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2F0day-ci%2Flinux%2Fcommits%2FZi-Yan%2Fmm-page-migration-enhancement-for-thp%2F20170718-095519&data=02%7C01%7Czi.yan%40cs.rutgers.edu%7Ca711ac47d4c0436ef66f08d4ce7cf30c%7Cb92d2b234d35447093ff69aca6632ffe%7C1%7C0%7C636360483431631457&sdata=NpxRpWbxe6o56xDJYpw1K6wgQo11IPCAbG2tE8l%2BU6E%3D&reserved=0
> > base: git://git.cmpxchg.org/linux-mmotm.git master
> > config: xtensa-common_defconfig (attached as .config)
> > compiler: xtensa-linux-gcc (GCC) 4.9.0
> > reproduce:
> > wget https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fraw.githubusercontent.com%2F01org%2Flkp-tests%2Fmaster%2Fsbin%2Fmake.cross&data=02%7C01%7Czi.yan%40cs.rutgers.edu%7Ca711ac47d4c0436ef66f08d4ce7cf30c%7Cb92d2b234d35447093ff69aca6632ffe%7C1%7C0%7C636360483431631457&sdata=rBCfu0xUg3v%2B8r%2Be2tsiqRcqw%2FEZSTa4OtF0hU%2FqMbc%3D&reserved=0 -O ~/bin/make.cross
> > chmod +x ~/bin/make.cross
> > # save the attached .config to linux build tree
> > make.cross ARCH=xtensa
> >
> > All warnings (new ones prefixed by >>):
> >
> > In file included from mm/vmscan.c:55:0:
> > include/linux/swapops.h: In function 'swp_entry_to_pmd':
> >>> include/linux/swapops.h:220:2: warning: missing braces around initializer [-Wmissing-braces]
> > return (pmd_t){ 0 };
> > ^
> > include/linux/swapops.h:220:2: warning: (near initialization for '(anonymous).pud') [-Wmissing-braces]
> >
> > vim +220 include/linux/swapops.h
> >
> > 217
> > 218 static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
> > 219 {
> >> 220 return (pmd_t){ 0 };
> > 221 }
> > 222
>
> It is a GCC 4.9.0 bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
>
> Upgrading GCC can get rid of this warning.
I think there was a workaround for this, but I don't recall what it
was.
This suppressed the warning:
--- a/include/linux/swapops.h~a
+++ a/include/linux/swapops.h
@@ -217,7 +217,7 @@ static inline swp_entry_t pmd_to_swp_ent
static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
{
- return (pmd_t){ 0 };
+ return (pmd_t){};
}
static inline int is_pmd_migration_entry(pmd_t pmd)
But I don't know if this is the approved workaround and I don't know
what it will do at runtime!
But we should fix this. Expecting zillions of people to update their
compiler version isn't nice.