Re: [PATCH] Revert "mm/memblock.c: hardcode the end_pfn being -1"

From: Michal Hocko
Date: Fri Mar 16 2018 - 05:06:58 EST


On Thu 15-03-18 19:56:06, Jia He wrote:
> This reverts commit 379b03b7fa05f7db521b7732a52692448a3c34fe.
>
> Commit 864b75f9d6b0 ("mm/page_alloc: fix memmap_init_zone pageblock
> alignment") introduced boot hang issues in arm/arm64 machines, so
> Ard Biesheuvel reverted in commit 3e04040df6d4. But there is a
> preparation patch for commit 864b75f9d6b0. So just revert it for
> the sake of caution.

Why? Is there anything wrong with this one?

>
> Signed-off-by: Jia He <jia.he@xxxxxxxxxxxxxxxx>
> ---
> mm/memblock.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memblock.c b/mm/memblock.c
> index b6ba6b7..5a9ca2a 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1107,7 +1107,7 @@ 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);
> + phys_addr_t addr = PFN_PHYS(pfn + 1);
>
> do {
> mid = (right + left) / 2;
> @@ -1118,15 +1118,15 @@ unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn,
> type->regions[mid].size))
> left = mid + 1;
> else {
> - /* addr is within the region, so pfn is valid */
> - return pfn;
> + /* addr is within the region, so pfn + 1 is valid */
> + return min(pfn + 1, max_pfn);
> }
> } while (left < right);
>
> if (right == type->cnt)
> - return -1UL;
> + return max_pfn;
> else
> - return PHYS_PFN(type->regions[right].base);
> + return min(PHYS_PFN(type->regions[right].base), max_pfn);
> }
>
> /**
> --
> 2.7.4
>

--
Michal Hocko
SUSE Labs