* Dave Hansen (haveblue@us.ibm.com) wrote:

On Mon, 2007-11-19 at 13:52 -0500, Mathieu Desnoyers wrote:

quoted

quoted

quoted

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 <redacted>
CC: Dave Hansen <redacted>
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)
 /*

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

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