Re: [PATCH] m68k: Fix virt_addr_valid() W=1 compiler warnings

From: Greg Ungerer
Date: Tue Feb 23 2021 - 08:05:23 EST



On 23/2/21 8:49 pm, Geert Uytterhoeven wrote:
If CONFIG_DEBUG_SG=y, and CONFIG_MMU=y:

include/linux/scatterlist.h: In function ‘sg_set_buf’:
arch/m68k/include/asm/page_mm.h:174:49: warning: ordered comparison of pointer with null pointer [-Wextra]
174 | #define virt_addr_valid(kaddr) ((void *)(kaddr) >= (void *)PAGE_OFFSET && (void *)(kaddr) < high_memory)
| ^~

or CONFIG_MMU=n:

include/linux/scatterlist.h: In function ‘sg_set_buf’:
arch/m68k/include/asm/page_no.h:33:50: warning: ordered comparison of pointer with null pointer [-Wextra]
33 | #define virt_addr_valid(kaddr) (((void *)(kaddr) >= (void *)PAGE_OFFSET) && \
| ^~

Fix this by doing the comparison in the "unsigned long" instead of the
"void *" domain.

Note that for now this is only seen when compiling btrfs, due to commit
e9aa7c285d20a69c ("btrfs: enable W=1 checks for btrfs"), but as people
are doing more W=1 compile testing, it will start to show up elsewhere,
too.

Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>

Acked-by: Greg Ungerer <gerg@xxxxxxxxxxxxxx>


---
Probably we want this as a fix for v5.12, to avoid the build bots
nagging about it all the time?

arch/m68k/include/asm/page_mm.h | 2 +-
arch/m68k/include/asm/page_no.h | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/m68k/include/asm/page_mm.h b/arch/m68k/include/asm/page_mm.h
index 7f5912af2a52ea0a..9b1672f9b2e22cdf 100644
--- a/arch/m68k/include/asm/page_mm.h
+++ b/arch/m68k/include/asm/page_mm.h
@@ -171,7 +171,7 @@ static inline __attribute_const__ int __virt_to_node_shift(void)
#include <asm-generic/memory_model.h>
#endif
-#define virt_addr_valid(kaddr) ((void *)(kaddr) >= (void *)PAGE_OFFSET && (void *)(kaddr) < high_memory)
+#define virt_addr_valid(kaddr) ((unsigned long)(kaddr) >= PAGE_OFFSET && ((unsigned long)kaddr) < (unsigned long)high_memory)
#define pfn_valid(pfn) virt_addr_valid(pfn_to_virt(pfn))
#endif /* __ASSEMBLY__ */
diff --git a/arch/m68k/include/asm/page_no.h b/arch/m68k/include/asm/page_no.h
index 6bbe52025de3c5c6..8d0f862ee9d79532 100644
--- a/arch/m68k/include/asm/page_no.h
+++ b/arch/m68k/include/asm/page_no.h
@@ -30,8 +30,8 @@ extern unsigned long memory_end;
#define page_to_pfn(page) virt_to_pfn(page_to_virt(page))
#define pfn_valid(pfn) ((pfn) < max_mapnr)
-#define virt_addr_valid(kaddr) (((void *)(kaddr) >= (void *)PAGE_OFFSET) && \
- ((void *)(kaddr) < (void *)memory_end))
+#define virt_addr_valid(kaddr) (((unsigned long)(kaddr) >= PAGE_OFFSET) && \
+ ((unsigned long)(kaddr) < memory_end))
#endif /* __ASSEMBLY__ */