Messages in this thread Patch in this message | | | Subject | Re: [PATCH 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn_valid | From | christophe leroy <> | Date | Sun, 4 Mar 2018 20:46:44 +0100 |
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Le 04/03/2018 à 11:55, Michael Ellerman a écrit : > Mathieu Malaterre <malat@debian.org> writes: > >> Rewrite comparison since all values compared are of type `unsigned long`. >> >> Fix a warning (treated as error in W=1): >> >> 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 ‘dma_map_resource’: >> ./arch/powerpc/include/asm/page.h:129:32: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits] >> #define pfn_valid(pfn) ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr) >> ^ >> Suggested-by: Segher Boessenkool <segher@kernel.crashing.org> >> Signed-off-by: Mathieu Malaterre <malat@debian.org> >> --- >> 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/page.h >> 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; >> >> #ifdef CONFIG_FLATMEM >> #define ARCH_PFN_OFFSET ((unsigned long)(MEMORY_START >> PAGE_SHIFT)) >> -#define pfn_valid(pfn) ((pfn) >= 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. >
The following seems to give a good result:
diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h index 8da5d4c1cab2..6f74938483b7 100644 --- a/arch/powerpc/include/asm/page.h +++ b/arch/powerpc/include/asm/page.h @@ -126,7 +126,15 @@ extern long long virt_phys_offset;
#ifdef CONFIG_FLATMEM #define ARCH_PFN_OFFSET ((unsigned long)(MEMORY_START >> PAGE_SHIFT)) -#define pfn_valid(pfn) ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr) +#ifndef __ASSEMBLY__ +extern unsigned long max_mapnr; +static inline bool pfn_valid(unsigned long pfn) +{ + unsigned long min_pfn = ARCH_PFN_OFFSET; + + return pfn >= min_pfn && pfn < max_mapnr; +} +#endif #endif
#define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT)
Christophe
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