[PATCH] Cast __page_to_pfn to unsigned long in CONFIG_SPARSEMEM

Mathieu Desnoyers
2007-11-19T19:58:19Z

* Dave Hansen (haveblue@us.ibm.com) 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@polymtl.ca>
CC: Dave Hansen <haveblue@us.ibm.com>
CC: linux-mm@kvack.org
CC: linux-kernel@vger.kernel.org
---
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)
/*