Re: [PATCH v2 1/5] mm: page_alloc: remain memblock_next_valid_pfn() when CONFIG_HAVE_ARCH_PFN_VALID is enable

[Jia He <hejianet@gmail.com>]

On 3/28/2018 12:52 AM, Daniel Vacek Wrote:
> On Sat, Mar 24, 2018 at 1:24 PM, Jia He <hejianet@gmail.com> wrote:
>> Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
>> where possible") optimized the loop in memmap_init_zone(). But it causes
>> possible panic bug. So Daniel Vacek reverted it later.
>>
>> But memblock_next_valid_pfn is valid when CONFIG_HAVE_ARCH_PFN_VALID is
>> enabled. And as verified by Eugeniu Rosca, arm can benifit from this
>> commit. So remain the memblock_next_valid_pfn.
> It is not dependent on CONFIG_HAVE_ARCH_PFN_VALID option but on
> arm(64) implementation of pfn_valid() function, IIUC. So it should
> really be moved from generic source file to arm specific location. I'd
> say somewhere close to the pfn_valid() implementation. Such as to
> arch/arm{,64}/mm/ init.c-ish?
>
> --nX
Hi Daniel
I didn't catch the reason why "It is not dependent on 
CONFIG_HAVE_ARCH_PFN_VALID option but
on arm(64) implementation of pfn_valid() function"? Can you explain more 
about it? Thanks

What's your thought if I changed the codes as followed?
in include/linux/memblock.h
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
extern unsigned long memblock_next_valid_pfn(unsigned long pfn);
#else
#define memblock_next_valid_pfn(pfn) (pfn + 1)
#endif

Cheers,
Jia
>
>> Signed-off-by: Jia He <jia.he@hxt-semitech.com>
>> ---
>>   include/linux/memblock.h |  4 ++++
>>   mm/memblock.c            | 29 +++++++++++++++++++++++++++++
>>   mm/page_alloc.c          | 11 ++++++++++-
>>   3 files changed, 43 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>> index 0257aee..efbbe4b 100644
>> --- a/include/linux/memblock.h
>> +++ b/include/linux/memblock.h
>> @@ -203,6 +203,10 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
>>               i >= 0; __next_mem_pfn_range(&i, nid, p_start, p_end, p_nid))
>>   #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
>>
>> +#ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +unsigned long memblock_next_valid_pfn(unsigned long pfn);
>> +#endif
>> +
>>   /**
>>    * for_each_free_mem_range - iterate through free memblock areas
>>    * @i: u64 used as loop variable
>> diff --git a/mm/memblock.c b/mm/memblock.c
>> index ba7c878..bea5a9c 100644
>> --- a/mm/memblock.c
>> +++ b/mm/memblock.c
>> @@ -1102,6 +1102,35 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
>>                  *out_nid = r->nid;
>>   }
>>
>> +#ifdef CONFIG_HAVE_ARCH_PFN_VALID
>> +unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
>> +{
>> +       struct memblock_type *type = &memblock.memory;
>> +       unsigned int right = type->cnt;
>> +       unsigned int mid, left = 0;
>> +       phys_addr_t addr = PFN_PHYS(++pfn);
>> +
>> +       do {
>> +               mid = (right + left) / 2;
>> +
>> +               if (addr < type->regions[mid].base)
>> +                       right = mid;
>> +               else if (addr >= (type->regions[mid].base +
>> +                                 type->regions[mid].size))
>> +                       left = mid + 1;
>> +               else {
>> +                       /* addr is within the region, so pfn is valid */
>> +                       return pfn;
>> +               }
>> +       } while (left < right);
>> +
>> +       if (right == type->cnt)
>> +               return -1UL;
>> +       else
>> +               return PHYS_PFN(type->regions[right].base);
>> +}
>> +#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
>> +
>>   /**
>>    * memblock_set_node - set node ID on memblock regions
>>    * @base: base of area to set node ID for
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index c19f5ac..2a967f7 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5483,8 +5483,17 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>>                  if (context != MEMMAP_EARLY)
>>                          goto not_early;
>>
>> -               if (!early_pfn_valid(pfn))
>> +               if (!early_pfn_valid(pfn)) {
>> +#if (defined CONFIG_HAVE_MEMBLOCK) && (defined CONFIG_HAVE_ARCH_PFN_VALID)
>> +                       /*
>> +                        * Skip to the pfn preceding the next valid one (or
>> +                        * end_pfn), such that we hit a valid pfn (or end_pfn)
>> +                        * on our next iteration of the loop.
>> +                        */
>> +                       pfn = memblock_next_valid_pfn(pfn) - 1;
>> +#endif
>>                          continue;
>> +               }
>>                  if (!early_pfn_in_nid(pfn, nid))
>>                          continue;
>>                  if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
>> --
>> 2.7.4
>>

-- 
Cheers,
Jia