Re: [PATCH] mm/memory-failure: Use zone_pcp_disable() for poison handling

[Oscar Salvador <osalvador@suse.de>]

On Thu, May 14, 2026 at 04:57:54PM +0800, Kaitao Cheng wrote:
> From: Kaitao Cheng <chengkaitao@kylinos.cn>
> 
> __page_handle_poison() used drain_all_pages() instead of
> zone_pcp_disable() because dissolve_free_hugetlb_folio() could restore
> HVO vmemmap pages and decrement hugetlb_optimize_vmemmap_key. That static
> key update took cpu_hotplug_lock through static_key_slow_dec(), while
> zone_pcp_disable() holds pcp_batch_high_lock. CPU hotplug takes the locks
> in the opposite order through page_alloc_cpu_online/dead(), so the
> combination could deadlock.
> 
> That dependency no longer exists. Commit da3e2d1ca43d ("mm/hugetlb:
> remove hugetlb_optimize_vmemmap_key static key") removed the HVO static
> key and the static_branch_dec() from hugetlb_vmemmap_restore_folio().
> The dissolve_free_hugetlb_folio() path no longer reaches
> static_key_slow_dec().
> 
> Use zone_pcp_disable() again while dissolving the hugetlb folio and
> taking the target page off the buddy allocator. This prevents the drained
> PCP lists from being refilled before take_page_off_buddy() runs, making
> the page isolation deterministic.
> 
> Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>

Reviewed-by: Oscar Salvador <osalvador@suse.de>

 

-- 
Oscar Salvador
SUSE Labs