[PATCH] Cast __page_to_pfn to unsigned long in CONFIG_SPARSEMEM

[Mathieu Desnoyers]

* Dave Hansen (haveblue@xxxxxxxxxx) wrote:
> On Mon, 2007-11-19 at 13:52 -0500, Mathieu Desnoyers wrote:
> > > > So I guess the result is a pointer ? Should this be expected ?
> > > 
> > > Nope.  'pointer - pointer' is an integer.  Just solve this equation for
> > > integer:
> > > 
> > >       'pointer + integer = pointer'
> > > 
> > 
> > Well, using page_to_pfn turns out to be ugly in markers (and in
> > printks) then. Depending on the architecture, it will result in either
> > an unsigned long (x86_64) or an unsigned int (i386), which corresponds
> > to %lu or %u and will print a warning if we don't cast it explicitly. 
> 
> Casting the i386 one to be an unconditional 'unsigned long' shouldn't be
> an issue.  We don't generally expect pfns to fit into ints anyway. 

So would this make sense ?

Cast __page_to_pfn to unsigned long in CONFIG_SPARSEMEM

Make sure the type returned by __page_to_pfn is always unsigned long. If we
don't cast it explicitly, it can be int on i386, but long on x86_64. This is
especially inelegant for printks.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
CC: Dave Hansen <haveblue@xxxxxxxxxx>
CC: linux-mm@xxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx
---
 include/asm-generic/memory_model.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6-lttng/include/asm-generic/memory_model.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-generic/memory_model.h	2007-11-19 14:47:30.000000000 -0500
+++ linux-2.6-lttng/include/asm-generic/memory_model.h	2007-11-19 14:48:30.000000000 -0500
@@ -50,7 +50,7 @@
 
 /* memmap is virtually contigious.  */
 #define __pfn_to_page(pfn)	(vmemmap + (pfn))
-#define __page_to_pfn(page)	((page) - vmemmap)
+#define __page_to_pfn(page)	((unsigned long)((page) - vmemmap))
 
 #elif defined(CONFIG_SPARSEMEM)
 /*

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/