On 1/29/21 3:37 PM, David Hildenbrand wrote:
> On 29.01.21 08:39, Anshuman Khandual wrote:
>> There are multiple instances of pfn_to_section_nr() and __pfn_to_section()
>> when CONFIG_SPARSEMEM is enabled. This can be just optimized if the memory
>> section is fetched earlier. Hence bifurcate pfn_valid() into two different
>> definitions depending on whether CONFIG_SPARSEMEM is enabled. Also replace
>> the open coded pfn <--> addr conversion with __[pfn|phys]_to_[phys|pfn]().
>> This does not cause any functional change.
>>
>> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
>> Cc: Will Deacon <will@xxxxxxxxxx>
>> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
>> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>> ---
>> arch/arm64/mm/init.c | 38 +++++++++++++++++++++++++++++++-------
>> 1 file changed, 31 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 1141075e4d53..09adca90c57a 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -217,18 +217,25 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>> free_area_init(max_zone_pfns);
>> }
>> +#ifdef CONFIG_SPARSEMEM
>> int pfn_valid(unsigned long pfn)
>> {
>> - phys_addr_t addr = pfn << PAGE_SHIFT;
>> + struct mem_section *ms = __pfn_to_section(pfn);
>> + phys_addr_t addr = __pfn_to_phys(pfn);
>
> I'd just use PFN_PHYS() here, which is more frequently used in the kernel.
Sure, will replace.
>
>> - if ((addr >> PAGE_SHIFT) != pfn)
>> + /*
>> + * Ensure the upper PAGE_SHIFT bits are clear in the
>> + * pfn. Else it might lead to false positives when
>> + * some of the upper bits are set, but the lower bits
>> + * match a valid pfn.
>> + */
>> + if (__phys_to_pfn(addr) != pfn)
>
> and here PHYS_PFN(). Comment is helpful. :)
Sure, will replace.
>
>> return 0;
>> -#ifdef CONFIG_SPARSEMEM
>> if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
>> return 0;
>> - if (!valid_section(__pfn_to_section(pfn)))
>> + if (!valid_section(ms))
>> return 0;
>> /*
>> @@ -240,11 +247,28 @@ int pfn_valid(unsigned long pfn)
>> * memory sections covering all of hotplug memory including
>> * both normal and ZONE_DEVICE based.
>> */
>> - if (!early_section(__pfn_to_section(pfn)))
>> - return pfn_section_valid(__pfn_to_section(pfn), pfn);
>> -#endif
>> + if (!early_section(ms))
>> + return pfn_section_valid(ms, pfn);
>> +
>> return memblock_is_map_memory(addr);
>> }
>> +#else
>> +int pfn_valid(unsigned long pfn)
>> +{
>> + phys_addr_t addr = __pfn_to_phys(pfn);
>> +
>> + /*
>> + * Ensure the upper PAGE_SHIFT bits are clear in the
>> + * pfn. Else it might lead to false positives when
>> + * some of the upper bits are set, but the lower bits
>> + * match a valid pfn.
>> + */
>> + if (__phys_to_pfn(addr) != pfn)
>> + return 0;
>> +
>> + return memblock_is_map_memory(addr);
>> +}
>
>
> I think you can avoid duplicating the code by doing something like:
Right and also this looks more compact as well. Initially though about
it but then was apprehensive about the style in #ifdef { } #endif code
block inside the function. After this change, the resulting patch also
clears checkpatch.pl test. Will do the change.
>
>
> phys_addr_t addr = PFN_PHYS(pfn);
>
> if (PHYS_PFN(addr) != pfn)
> return 0;
>
> #ifdef CONFIG_SPARSEMEM
> {
> struct mem_section *ms = __pfn_to_section(pfn);
>
> if (!valid_section(ms))
> return 0;
> if (!early_section(ms))
> return pfn_section_valid(ms, pfn);
> }
> #endif
> return memblock_is_map_memory(addr);
>
