Re: [PATCH 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn_valid
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2018-03-04 10:55:22
Also in:
lkml
Mathieu Malaterre [off-list ref] writes:
Rewrite comparison since all values compared are of type `unsigned long`.
Fix a warning (treated as error in W=3D1):
CC arch/powerpc/kernel/irq.o
In file included from ./include/linux/bug.h:5:0,
from ./include/linux/cpumask.h:13,
from ./include/linux/smp.h:13,
from ./include/linux/kernel_stat.h:5,
from arch/powerpc/kernel/irq.c:35:
./include/linux/dma-mapping.h: In function =E2=80=98dma_map_resource=E2==80=99:
./arch/powerpc/include/asm/page.h:129:32: error: comparison of unsigned e=
xpression >=3D 0 is always true [-Werror=3Dtype-limits]
quoted hunk ↗ jump to hunk
#define pfn_valid(pfn) ((pfn) >=3D ARCH_PFN_OFFSET && (pfn) < max_mapnr) ^ Suggested-by: Segher Boessenkool <redacted> Signed-off-by: Mathieu Malaterre <redacted> --- arch/powerpc/include/asm/page.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/p=
age.h
quoted hunk ↗ jump to hunk
index 8da5d4c1cab2..19dea64e7ed2 100644--- a/arch/powerpc/include/asm/page.h +++ b/arch/powerpc/include/asm/page.h@@ -126,7 +126,8 @@ extern long long virt_phys_offset;=20=20 #ifdef CONFIG_FLATMEM #define ARCH_PFN_OFFSET ((unsigned long)(MEMORY_START >> PAGE_SHIFT)) -#define pfn_valid(pfn) ((pfn) >=3D ARCH_PFN_OFFSET && (pfn) < max_mapnr) +#define pfn_valid(pfn) \ + (((pfn) - ARCH_PFN_OFFSET) < (max_mapnr - ARCH_PFN_OFFSET))
I'm not a big fan of this one, because the original code is *far* more obvious as to what it's doing. I'm not sure if we can make this one a static inline, or whether that would help, but it would be worth investigating. cheers