Re: [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section

From: Wei Yang
Date: Fri Dec 14 2018 - 19:26:19 EST

On Fri, Dec 14, 2018 at 11:19:59AM +0100, Michal Hocko wrote:
>[Your From address seems to have a typo ( - fixed]
>On Fri 14-12-18 10:33:55, Zaslonko Mikhail wrote:
>> Yes, it might still trigger PF_POISONED_CHECK if the first page
>> of the pageblock is left uninitialized (poisoned).
>> But in order to cover these exceptional cases we would need to
>> adjust memory_hotplug sysfs handler functions with similar
>> checks (as in the for loop of memmap_init_zone()). And I guess
>> that is what we were trying to avoid (adding special cases to
>> memory_hotplug paths).
>is_mem_section_removable should test pfn_valid_within at least.
>But that would require some care because next_active_pageblock expects
>aligned pages. Ble, this code is just horrible. I would just remove it
>altogether. I strongly suspect that nobody is using it for anything
>reasonable anyway. The only reliable way to check whether a block is
>removable is to remove it. Everything else is just racy.

Sounds reasonable.

The result return from removable sysfs is transient. If no user rely on
this, remove this is a better way.

>Michal Hocko
>SUSE Labs

Wei Yang
Help you, Help me