Hi Stephen,

The warning after removing __pmd() is caused by a gcc bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
so (pmd_t) {0} causes warning in some GCC versions.

__pmd() is defined in alpha, arm, arm64, frv, ia64, m32r, m68k, microblaze, mips, parisc,
powerpc, s390, sh, sparc, tile, um, x86, and asm-generic, according to
http://elixir.free-electrons.com/linux/latest/ident/__pmd

I am not sure about whether arc, blackfin, c6x, cris, h8300, hexagon, metag, mn10300, nios2, score,
xtensa use __pmd() in asm-generic or not.

I am looking for other workarounds for this warning now.


—
Best Regards,
Yan Zi

On 1 Aug 2017, at 6:50, Stephen Rothwell wrote:

> Hi all,
>
> On Tue, 1 Aug 2017 16:39:04 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>
>> After merging the akpm tree, today's linux-next build (sparc defconfig)
>> failed like this:
>>
>> In file included from mm/vmscan.c:55:0:
>> include/linux/swapops.h: In function 'swp_entry_to_pmd':
>> include/linux/swapops.h:226:9: error: implicit declaration of function '__pmd' [-Werror=implicit-function-declaration]
>>   return __pmd(0);
>>          ^
>> include/linux/swapops.h:226:9: error: incompatible types when returning type 'int' but 'pmd_t {aka struct <anonymous>}' was expected
>>
>> Caused by commit
>>
>>   9bb18490758c ("mm-thp-enable-thp-migration-in-generic-path-fix")
>>
>> It looks like sparc 32 bit has no __pmd() ...
>>
>> I have reverted that commit for today.
>
> OK, that is a pain as it causes many build warnings some of which are
> treated as errors :-(  (see e.g.
> https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fkisskb.ellerman.id.au%2Fkisskb%2Fbuildresult%2F13112192%2F&data=02%7C01%7Czi.yan%40cs.rutgers.edu%7Cbf7a7ad57ad04505172f08d4d8cb31c5%7Cb92d2b234d35447093ff69aca6632ffe%7C1%7C0%7C636371814609835949&sdata=diTid245prNY3Jy1pPEaL5q8dSBifFVzliKRq54fXhk%3D&reserved=0).  So maybe
> we need to fix sthe sparc32 build instead?  Are there any other
> architectures/platforms that do not define __pmd() ?
>
> -- 
> Cheers,
> Stephen Rothwell