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Re: linux-next: build failure after merge of the akpm-current tree

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  Re: linux-next: build failure after merge of the akpm-current tree Stephen Rothwell <sfr@canb.auug.org.au> - 2017-09-07 07:30 +0200
    Re: linux-next: build failure after merge of the akpm-current tree Andrew Morton <akpm@linux-foundation.org> - 2017-09-07 09:50 +0200
      Re: linux-next: build failure after merge of the akpm-current tree Stephen Rothwell <sfr@canb.auug.org.au> - 2017-09-08 05:00 +0200
        Re: linux-next: build failure after merge of the akpm-current tree Stephen Rothwell <sfr@canb.auug.org.au> - 2017-09-08 05:50 +0200

#1727915 — Re: linux-next: build failure after merge of the akpm-current tree

Hi all,

On Wed, 2 Aug 2017 16:31:45 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> On Wed, 2 Aug 2017 15:45:54 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > On Tue, 01 Aug 2017 09:08:01 -0400 "Zi Yan" <zi.yan@cs.rutgers.edu> wrote:  
> > >
> > > I found two possible fixes.
> > > 
> > > 1. This uses C++ zero initializer, GCC is OK with it.
> > > I tested with GCC 4.9.3 (has the initialization bug) and GCC 6.4.0.
> > > 
> > > --- 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){};
> > >  }    
> > 
> > I have done that for today ... please decide which is best (or find
> > something better - maybe every platform really needs to have a __pmd()
> > definition) and submit a real fix patch to Andrew.  
> 
> OK, that failed for my compiler (gcc 5.2.0) 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:226:16: error: empty scalar initializer
>   return (pmd_t){};
>                 ^
> include/linux/swapops.h:226:16: note: (near initialization for '(anonymous)')

This has reappeared today :-( (for the arm multi_v7_defconfig build at
least)

> So I used the other idea (on top of Andrew's current tree):

The fix patch now looks like this:

From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Wed, 2 Aug 2017 15:55:02 +1000
Subject: [PATCH] mm-thp-enable-thp-migration-in-generic-path-fix-fix

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
 include/linux/swapops.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 45b092aa6419..61cffa148a79 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -223,7 +223,9 @@ static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
 
 static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
 {
-	return (pmd_t){};
+	pmd_t e;
+	memset(&e, 0, sizeof(pmd_t));
+	return e;
 }
 
 static inline int is_pmd_migration_entry(pmd_t pmd)

-- 
Cheers,
Stephen Rothwell

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#1727984

On Thu, 7 Sep 2017 15:23:55 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:

> Hi all,
> 
> On Wed, 2 Aug 2017 16:31:45 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > On Wed, 2 Aug 2017 15:45:54 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> > >
> > > On Tue, 01 Aug 2017 09:08:01 -0400 "Zi Yan" <zi.yan@cs.rutgers.edu> wrote:  
> > > >
> > > > I found two possible fixes.
> > > > 
> > > > 1. This uses C++ zero initializer, GCC is OK with it.
> > > > I tested with GCC 4.9.3 (has the initialization bug) and GCC 6.4.0.
> > > > 
> > > > --- 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){};
> > > >  }    
> > > 
> > > I have done that for today ... please decide which is best (or find
> > > something better - maybe every platform really needs to have a __pmd()
> > > definition) and submit a real fix patch to Andrew.  
> > 
> > OK, that failed for my compiler (gcc 5.2.0) 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:226:16: error: empty scalar initializer
> >   return (pmd_t){};
> >                 ^
> > include/linux/swapops.h:226:16: note: (near initialization for '(anonymous)')
> 
> This has reappeared today :-( (for the arm multi_v7_defconfig build at
> least)
> 
> > So I used the other idea (on top of Andrew's current tree):
> 
> The fix patch now looks like this:
> 
> From: Stephen Rothwell <sfr@canb.auug.org.au>
> Date: Wed, 2 Aug 2017 15:55:02 +1000
> Subject: [PATCH] mm-thp-enable-thp-migration-in-generic-path-fix-fix
> 
> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> ---
>  include/linux/swapops.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/swapops.h b/include/linux/swapops.h
> index 45b092aa6419..61cffa148a79 100644
> --- a/include/linux/swapops.h
> +++ b/include/linux/swapops.h
> @@ -223,7 +223,9 @@ static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
>  
>  static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
>  {
> -	return (pmd_t){};
> +	pmd_t e;
> +	memset(&e, 0, sizeof(pmd_t));
> +	return e;
>  }

err, yeah.  I didn't want to add that one :(

At the very least we should add a good comment explaining why we had to
resort to this.

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#1728548

Hi all,

On Thu, 07 Sep 2017 06:59:09 -0400 "Zi Yan" <zi.yan@cs.rutgers.edu> wrote:
>
> I think __pmd(0) can be used now. I fixed __pmd() in sparc32 at commit
> 9157259d16a8ee8116a98d32f29b797689327e8d, which is in 4.13 now.
> I should have told you this earlier, sorry about that.
> 
> Just wonder if any other reason prevents us using __pmd().

OK, so today I have applied this instead (which is the same as dropping
mm-thp-enable-thp-migration-in-generic-path-fix-fix-fix):

From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Fri, 8 Sep 2017 12:40:39 +1000
Subject: [PATCH] mm-thp-enable-thp-migration-in-generic-path-fix-fix

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
 include/linux/swapops.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index b88441d284e2..291c4b534658 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -291,7 +291,7 @@ static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
 
 static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
 {
-	return (pmd_t){};
+	return __pmd(0);
 }
 
 static inline int is_pmd_migration_entry(pmd_t pmd)
-- 
2.13.2

-- 
Cheers,
Stephen Rothwell

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#1728577

Hi all,

On Fri, 8 Sep 2017 12:49:59 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> OK, so today I have applied this instead (which is the same as dropping
> mm-thp-enable-thp-migration-in-generic-path-fix-fix-fix):
> 
> From: Stephen Rothwell <sfr@canb.auug.org.au>
> Date: Fri, 8 Sep 2017 12:40:39 +1000
> Subject: [PATCH] mm-thp-enable-thp-migration-in-generic-path-fix-fix
> 
> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> ---
>  include/linux/swapops.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/swapops.h b/include/linux/swapops.h
> index b88441d284e2..291c4b534658 100644
> --- a/include/linux/swapops.h
> +++ b/include/linux/swapops.h
> @@ -291,7 +291,7 @@ static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
>  
>  static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
>  {
> -	return (pmd_t){};
> +	return __pmd(0);
>  }
>  
>  static inline int is_pmd_migration_entry(pmd_t pmd)

That survived my "during the day" builds (including sparc32).  Some one
should just check the overnight build results:
http://kisskb.ellerman.id.au/linux-next
-- 
Cheers,
Stephen Rothwell

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