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

From: Michal Hocko
Date: Fri Dec 14 2018 - 05:20:04 EST

[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.

Michal Hocko