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

[Daniel Vacek <neelx@redhat.com>]

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

> 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
>