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Subject: Re: [PATCH v2] powerpc: drop page_is_ram() and
 walk_system_ram_range()
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
References: <a14aac5408f98cf8ad8723ffa874764ccb42d4d4.1548978750.git.christophe.leroy@c-s.fr>
 <875ztzonqd.fsf@concordia.ellerman.id.au>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <248f8aa2-10c2-2728-6f94-a56816a989e1@c-s.fr>
Date:   Tue, 5 Feb 2019 07:48:38 +0100
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Le 04/02/2019 à 11:24, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
> 
>> Since commit c40dd2f76644 ("powerpc: Add System RAM to /proc/iomem")
>> it is possible to use the generic walk_system_ram_range() and
>> the generic page_is_ram().
>>
>> To enable the use of walk_system_ram_range() by the IBM EHEA
>> ethernet driver, the generic function has to be exported.
> 
> I'm not sure if we have a policy on that, but I suspect we'd rather not
> add a new export on all arches unless we need to. Especially seeing as
> the only user is the EHEA code which is heavily in maintenance mode.

If you take the exemple of function walk_iomem_res_desc(), that's 
similar. It is only used by x86 it seems and exported for nvdimm/e820 
driver only.

See commit d76401ade0bb6ab0a7 ("libnvdimm, e820: Register all pmem 
resources")

> 
> I'll put the export in powerpc code and make sure that builds.

I thought there was a rule that EXPORT_SYMBOL has to immediately follow 
the function it exports. At least checkpatch checks for that.

Christophe

> 
>> As powerpc was the only (last?) user of CONFIG_ARCH_HAS_WALK_MEMORY,
>> the #ifdef around the generic walk_system_ram_range() has become
>> useless and can be dropped.
> 
> Yes it was the only user:
> 
> a99824f327c7 ("[POWERPC] Add arch-specific walk_memory_remove() for 64-bit powerpc")
> 
> I'll update the changelog.
> 
> cheers
> 
> 
>> Fixes: c40dd2f76644 ("powerpc: Add System RAM to /proc/iomem")
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>>   arch/powerpc/Kconfig            |  3 ---
>>   arch/powerpc/include/asm/page.h |  1 -
>>   arch/powerpc/mm/mem.c           | 33 ---------------------------------
>>   kernel/resource.c               |  5 +----
>>   4 files changed, 1 insertion(+), 41 deletions(-)
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index 2890d36eb531..f92e6754edf1 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -478,9 +478,6 @@ config ARCH_CPU_PROBE_RELEASE
>>   config ARCH_ENABLE_MEMORY_HOTPLUG
>>   	def_bool y
>>   
>> -config ARCH_HAS_WALK_MEMORY
>> -	def_bool y
>> -
>>   config ARCH_ENABLE_MEMORY_HOTREMOVE
>>   	def_bool y
>>   
>> diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
>> index 5c5ea2413413..aa4497175bd3 100644
>> --- a/arch/powerpc/include/asm/page.h
>> +++ b/arch/powerpc/include/asm/page.h
>> @@ -326,7 +326,6 @@ struct page;
>>   extern void clear_user_page(void *page, unsigned long vaddr, struct page *pg);
>>   extern void copy_user_page(void *to, void *from, unsigned long vaddr,
>>   		struct page *p);
>> -extern int page_is_ram(unsigned long pfn);
>>   extern int devmem_is_allowed(unsigned long pfn);
>>   
>>   #ifdef CONFIG_PPC_SMLPAR
>> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
>> index 33cc6f676fa6..fa9916c2c662 100644
>> --- a/arch/powerpc/mm/mem.c
>> +++ b/arch/powerpc/mm/mem.c
>> @@ -80,11 +80,6 @@ static inline pte_t *virt_to_kpte(unsigned long vaddr)
>>   #define TOP_ZONE ZONE_NORMAL
>>   #endif
>>   
>> -int page_is_ram(unsigned long pfn)
>> -{
>> -	return memblock_is_memory(__pfn_to_phys(pfn));
>> -}
>> -
>>   pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>>   			      unsigned long size, pgprot_t vma_prot)
>>   {
>> @@ -176,34 +171,6 @@ int __meminit arch_remove_memory(int nid, u64 start, u64 size,
>>   #endif
>>   #endif /* CONFIG_MEMORY_HOTPLUG */
>>   
>> -/*
>> - * walk_memory_resource() needs to make sure there is no holes in a given
>> - * memory range.  PPC64 does not maintain the memory layout in /proc/iomem.
>> - * Instead it maintains it in memblock.memory structures.  Walk through the
>> - * memory regions, find holes and callback for contiguous regions.
>> - */
>> -int
>> -walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
>> -		void *arg, int (*func)(unsigned long, unsigned long, void *))
>> -{
>> -	struct memblock_region *reg;
>> -	unsigned long end_pfn = start_pfn + nr_pages;
>> -	unsigned long tstart, tend;
>> -	int ret = -1;
>> -
>> -	for_each_memblock(memory, reg) {
>> -		tstart = max(start_pfn, memblock_region_memory_base_pfn(reg));
>> -		tend = min(end_pfn, memblock_region_memory_end_pfn(reg));
>> -		if (tstart >= tend)
>> -			continue;
>> -		ret = (*func)(tstart, tend - tstart, arg);
>> -		if (ret)
>> -			break;
>> -	}
>> -	return ret;
>> -}
>> -EXPORT_SYMBOL_GPL(walk_system_ram_range);
>> -
>>   #ifndef CONFIG_NEED_MULTIPLE_NODES
>>   void __init mem_topology_setup(void)
>>   {
>> diff --git a/kernel/resource.c b/kernel/resource.c
>> index 915c02e8e5dd..2e1636041508 100644
>> --- a/kernel/resource.c
>> +++ b/kernel/resource.c
>> @@ -448,8 +448,6 @@ int walk_mem_res(u64 start, u64 end, void *arg,
>>   				     arg, func);
>>   }
>>   
>> -#if !defined(CONFIG_ARCH_HAS_WALK_MEMORY)
>> -
>>   /*
>>    * This function calls the @func callback against all memory ranges of type
>>    * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
>> @@ -480,8 +478,7 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
>>   	}
>>   	return ret;
>>   }
>> -
>> -#endif
>> +EXPORT_SYMBOL_GPL(walk_system_ram_range);
>>   
>>   static int __is_ram(unsigned long pfn, unsigned long nr_pages, void *arg)
>>   {
>> -- 
>> 2.13.3