Re: [PATCH v2 05/12] mm: thp: add core routines for thp/pmd migration

From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: kbuild test robot <lkp@intel.com>
Cc: "kbuild-all@01.org" <kbuild-all@01.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Hugh Dickins <hughd@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Michal Hocko <mhocko@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Pavel Emelyanov <xemul@parallels.com>,
	"Zi Yan" <zi.yan@cs.rutgers.edu>,
	Balbir Singh <bsingharora@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Naoya Horiguchi" <nao.horiguchi@gmail.com>
Subject: Re: [PATCH v2 05/12] mm: thp: add core routines for thp/pmd migration
Date: Tue, 8 Nov 2016 06:46:55 +0000	[thread overview]
Message-ID: <20161108064654.GA474@hori1.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <201611081136.ZuJrd6uJ%fengguang.wu@intel.com>

On Tue, Nov 08, 2016 at 11:05:52AM +0800, kbuild test robot wrote:
> Hi Naoya,
> 
> [auto build test ERROR on mmotm/master]
> [also build test ERROR on v4.9-rc4 next-20161028]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Naoya-Horiguchi/mm-x86-move-_PAGE_SWP_SOFT_DIRTY-from-bit-7-to-bit-6/20161108-080615
> base:   git://git.cmpxchg.org/linux-mmotm.git master
> config: arm-at91_dt_defconfig (attached as .config)
> compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
> reproduce:
>         wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         make.cross ARCH=arm 
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from fs/proc/task_mmu.c:14:0:
>    include/linux/swapops.h: In function 'swp_entry_to_pmd':
> >> include/linux/swapops.h:216:14: error: empty scalar initializer
>      pmd_t pmd = {};
>                  ^
>    include/linux/swapops.h:216:14: note: (near initialization for 'pmd')
> 
> vim +216 include/linux/swapops.h
> 
>    210	{
>    211		return swp_entry(0, 0);
>    212	}
>    213	
>    214	static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
>    215	{
>  > 216		pmd_t pmd = {};
>    217	
>    218		return pmd;
>    219	}

Here is an alternative:

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index db8a858cc6ff..748c9233b3a5 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -215,9 +215,7 @@ static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
 
 static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
 {
-	pmd_t pmd = {};
-
-	return pmd;
+	return (pmd_t) { 0 };
 }
 
 static inline int is_pmd_migration_entry(pmd_t pmd)

Thanks,
Naoya Horiguchi

> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
