[PATCH] mm: Make {,set}page_address() static inline if WANT_PAGE_VIRTUAL

[PATCH] mm: Make {,set}page_address() static inline if WANT_PAGE_VIRTUAL

[Geert Uytterhoeven]

{,set}page_address() are macros if WANT_PAGE_VIRTUAL.
If !WANT_PAGE_VIRTUAL, they're plain C functions.

If someone calls them with a void *, this pointer is auto-converted to
struct page * if !WANT_PAGE_VIRTUAL, but causes a build failure on
architectures using WANT_PAGE_VIRTUAL (arc, m68k and sparc):

drivers/md/bcache/bset.c: In function a??__btree_sorta??:
drivers/md/bcache/bset.c:1190: warning: dereferencing a??void *a?? pointer
drivers/md/bcache/bset.c:1190: error: request for member a??virtuala?? in something not a structure or union

Convert them to static inline functions to fix this. There are already
plenty of  users of struct page members inside <linux/mm.h>, so there's no
reason to keep them as macros.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
http://kisskb.ellerman.id.au/kisskb/buildresult/10469287/ (m68k/next)
http://kisskb.ellerman.id.au/kisskb/buildresult/10469488/ (sparc64/next)
https://lkml.org/lkml/2014/1/13/1044 (m68k & sparc/3.10.27-stable)

 include/linux/mm.h |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 35527173cf50..9fac6dd69b11 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -846,11 +846,14 @@ static __always_inline void *lowmem_page_address(const struct page *page)
 #endif
 
 #if defined(WANT_PAGE_VIRTUAL)
-#define page_address(page) ((page)->virtual)
-#define set_page_address(page, address)			\
-	do {						\
-		(page)->virtual = (address);		\
-	} while(0)
+static inline void *page_address(const struct page *page)
+{
+	return page->virtual;
+}
+static inline void set_page_address(struct page *page, void *address)
+{
+	page->virtual = address;
+}
 #define page_address_init()  do { } while(0)
 #endif
 
-- 
1.7.9.5

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Re: [PATCH] mm: Make {,set}page_address() static inline if WANT_PAGE_VIRTUAL

[Michael S. Tsirkin]

On Wed, Jan 15, 2014 at 10:33:46AM +0100, Geert Uytterhoeven wrote:
> {,set}page_address() are macros if WANT_PAGE_VIRTUAL.
> If !WANT_PAGE_VIRTUAL, they're plain C functions.
> 
> If someone calls them with a void *, this pointer is auto-converted to
> struct page * if !WANT_PAGE_VIRTUAL, but causes a build failure on
> architectures using WANT_PAGE_VIRTUAL (arc, m68k and sparc):
> 
> drivers/md/bcache/bset.c: In function a??__btree_sorta??:
> drivers/md/bcache/bset.c:1190: warning: dereferencing a??void *a?? pointer
> drivers/md/bcache/bset.c:1190: error: request for member a??virtuala?? in something not a structure or union
> 
> Convert them to static inline functions to fix this. There are already
> plenty of  users of struct page members inside <linux/mm.h>, so there's no
> reason to keep them as macros.
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

FWIW

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> http://kisskb.ellerman.id.au/kisskb/buildresult/10469287/ (m68k/next)
> http://kisskb.ellerman.id.au/kisskb/buildresult/10469488/ (sparc64/next)
> https://lkml.org/lkml/2014/1/13/1044 (m68k & sparc/3.10.27-stable)
> 
>  include/linux/mm.h |   13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 35527173cf50..9fac6dd69b11 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -846,11 +846,14 @@ static __always_inline void *lowmem_page_address(const struct page *page)
>  #endif
>  
>  #if defined(WANT_PAGE_VIRTUAL)
> -#define page_address(page) ((page)->virtual)
> -#define set_page_address(page, address)			\
> -	do {						\
> -		(page)->virtual = (address);		\
> -	} while(0)
> +static inline void *page_address(const struct page *page)
> +{
> +	return page->virtual;
> +}
> +static inline void set_page_address(struct page *page, void *address)
> +{
> +	page->virtual = address;
> +}
>  #define page_address_init()  do { } while(0)
>  #endif
>  
> -- 
> 1.7.9.5

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Re: [PATCH] mm: Make {,set}page_address() static inline if WANT_PAGE_VIRTUAL

[Guenter Roeck]

On 01/15/2014 01:33 AM, Geert Uytterhoeven wrote:
> {,set}page_address() are macros if WANT_PAGE_VIRTUAL.
> If !WANT_PAGE_VIRTUAL, they're plain C functions.
>
> If someone calls them with a void *, this pointer is auto-converted to
> struct page * if !WANT_PAGE_VIRTUAL, but causes a build failure on
> architectures using WANT_PAGE_VIRTUAL (arc, m68k and sparc):
>
> drivers/md/bcache/bset.c: In function a??__btree_sorta??:
> drivers/md/bcache/bset.c:1190: warning: dereferencing a??void *a?? pointer
> drivers/md/bcache/bset.c:1190: error: request for member a??virtuala?? in something not a structure or union
>
> Convert them to static inline functions to fix this. There are already
> plenty of  users of struct page members inside <linux/mm.h>, so there's no
> reason to keep them as macros.
>
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Tested-by: Guenter Roeck <linux@roeck-us.net>

That also fixes the problem seen in stable-queue for 3.10 and 3.12,
so it may be a better fix for the problem seen there than the patch
provided by Michael.

Guenter

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Re: [PATCH] mm: Make {,set}page_address() static inline if WANT_PAGE_VIRTUAL

[David Rientjes]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1376 bytes --]

On Wed, 15 Jan 2014, Geert Uytterhoeven wrote:

> {,set}page_address() are macros if WANT_PAGE_VIRTUAL.
> If !WANT_PAGE_VIRTUAL, they're plain C functions.
> 
> If someone calls them with a void *, this pointer is auto-converted to
> struct page * if !WANT_PAGE_VIRTUAL, but causes a build failure on
> architectures using WANT_PAGE_VIRTUAL (arc, m68k and sparc):

s/sparc/sparc64/

> 
> drivers/md/bcache/bset.c: In function a??__btree_sorta??:
> drivers/md/bcache/bset.c:1190: warning: dereferencing a??void *a?? pointer
> drivers/md/bcache/bset.c:1190: error: request for member a??virtuala?? in something not a structure or union
> 
> Convert them to static inline functions to fix this. There are already
> plenty of  users of struct page members inside <linux/mm.h>, so there's no
> reason to keep them as macros.
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Tested-by: David Rientjes <rientjes@google.com>

I'm cringing at the page_address(mempool_alloc(..., GFP_NOIO)) in 
drivers/md/bcache/bset.c, though.  It's relying on that fact that 
mempool_alloc() can never return NULL if __GFP_WAIT but I think this could 
have all been avoided with

	struct page *page = mempool_alloc(state->pool, GFP_NOIO);
	out = page_address(page);

instead of burying the mempool_alloc() in page_address() for what I think 
is cleaner code.  Owell, it fixes the issue.

Re: [PATCH] mm: Make {,set}page_address() static inline if WANT_PAGE_VIRTUAL

[Andrew Morton]

On Wed, 15 Jan 2014 14:57:56 -0800 (PST) David Rientjes <rientjes@google.com> wrote:

> On Wed, 15 Jan 2014, Geert Uytterhoeven wrote:
> 
> > {,set}page_address() are macros if WANT_PAGE_VIRTUAL.
> > If !WANT_PAGE_VIRTUAL, they're plain C functions.
> > 
> > If someone calls them with a void *, this pointer is auto-converted to
> > struct page * if !WANT_PAGE_VIRTUAL, but causes a build failure on
> > architectures using WANT_PAGE_VIRTUAL (arc, m68k and sparc):
> 
> s/sparc/sparc64/
> 
> > 
> > drivers/md/bcache/bset.c: In function _____btree_sort___:
> > drivers/md/bcache/bset.c:1190: warning: dereferencing ___void *___ pointer
> > drivers/md/bcache/bset.c:1190: error: request for member ___virtual___ in something not a structure or union
> > 
> > Convert them to static inline functions to fix this. There are already
> > plenty of  users of struct page members inside <linux/mm.h>, so there's no
> > reason to keep them as macros.
> > 
> > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> 
> Tested-by: David Rientjes <rientjes@google.com>
> 
> I'm cringing at the page_address(mempool_alloc(..., GFP_NOIO)) in 
> drivers/md/bcache/bset.c, though.

Yes, I was staring suspiciously at that as well.  Ended up deciding
that I wouldn't have coded it that way, but we should support the
casting.

>  It's relying on that fact that 
> mempool_alloc() can never return NULL if __GFP_WAIT but I think this could 
> have all been avoided with
> 
> 	struct page *page = mempool_alloc(state->pool, GFP_NOIO);
> 	out = page_address(page);
> 
> instead of burying the mempool_alloc() in page_address() for what I think 
> is cleaner code.  Owell, it fixes the issue.

And that would make the later virt_to_page() unnecessary.

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