Re: [PATCH v3 1/5] mm: page_alloc: remain memblock_next_valid_pfn() when CONFIG_HAVE_ARCH_PFN_VALID is enable

[Wei Yang]

On Wed, Mar 28, 2018 at 05:49:23PM +0800, Jia He wrote:
>
>
>On 3/28/2018 5:18 PM, Wei Yang Wrote:
>> Oops, I should reply this thread. Forget about the reply on another thread.
>> 
>> On Sun, Mar 25, 2018 at 08:02:15PM -0700, Jia He 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.
>> > 
>> Why this has a bug? Do you have some link about it?
>> 
>> If the audience could know the potential risk, it would be helpful to review
>> the code and decide whether to take it back.
>Hi Wei
>Paul firstly submit a commit b92df1de5 to improve the loop in
>memmap_init_zone.
>And Daniel tried to fix a bug_on panic issue on X86 in commit 864b75f9d6b
>because
>there is evidence that this bug_on was caused by b92df1de5 [1].
>
>But things didn't get better, 864b75f9d6b caused booting hang issue on
>arm{64} [2]
>So maintainer decided to reverted both b92df1de5 and 864b75f9d6b
>
>[1] https://patchwork.kernel.org/patch/10251145/
>[2] https://lkml.org/lkml/2018/3/14/469

I took some time to look into the discussion, while the root cause seems not
clear now?

-- 
Wei Yang
Help you, Help me