From: "David Hildenbrand (Arm)" <david@kernel.org>
To: "Lorenzo Stoakes (Oracle)" <ljs@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-cxl@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>,
Axel Rasmussen <axelrasmussen@google.com>,
Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 09/14] mm/sparse: remove CONFIG_MEMORY_HOTPLUG-specific usemap allocation handling
Date: Fri, 20 Mar 2026 19:58:08 +0100 [thread overview]
Message-ID: <1a05e4c5-01b4-4614-bcc5-43e142fe4b9f@kernel.org> (raw)
In-Reply-To: <306f0fd2-cba1-4f48-af05-248be2bc9506@kernel.org>
>>
>> Anyway I'm also confused by 'given we don't free the pgdat any more', but the
>> comment says a 'pgdat can prevent a section being removed' rather than anything
>> about it being removed?
>
> Well, if a pgdat resides in some memory section, given that it is
> unmovable turns the whole memory section unremovable -> hotunplug fails.
>
> Assuming you could free the pgdat when the node goes offlining, you
> would turn that memory section removable.
>
> And I think that commit somehow assumed that the last memory section
> could be removed if all it contains is the corresponding pgdat (which
> was never the case).
I decided to just drop that whole comment block completely.
--
Cheers,
David
next prev parent reply other threads:[~2026-03-20 18:58 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-17 16:56 [PATCH 00/14] mm: memory hot(un)plug and SPARSEMEM cleanups David Hildenbrand (Arm)
2026-03-17 16:56 ` [PATCH 01/14] mm/memory_hotplug: remove for_each_valid_pfn() usage David Hildenbrand (Arm)
2026-03-17 17:19 ` Lorenzo Stoakes (Oracle)
2026-03-17 20:30 ` David Hildenbrand (Arm)
2026-03-18 7:51 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 02/14] mm/sparse: remove WARN_ONs from (online|offline)_mem_sections() David Hildenbrand (Arm)
2026-03-17 17:21 ` Lorenzo Stoakes (Oracle)
2026-03-18 7:53 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 03/14] mm/Kconfig: make CONFIG_MEMORY_HOTPLUG depend on CONFIG_SPARSEMEM_VMEMMAP David Hildenbrand (Arm)
2026-03-17 17:22 ` Lorenzo Stoakes (Oracle)
2026-03-18 7:55 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 04/14] mm/memory_hotplug: simplify check_pfn_span() David Hildenbrand (Arm)
2026-03-17 17:24 ` Lorenzo Stoakes (Oracle)
2026-03-18 7:56 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 05/14] mm/sparse: remove !CONFIG_SPARSEMEM_VMEMMAP leftovers for CONFIG_MEMORY_HOTPLUG David Hildenbrand (Arm)
2026-03-17 17:54 ` Lorenzo Stoakes (Oracle)
2026-03-18 7:58 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 06/14] mm/bootmem_info: remove handling for !CONFIG_SPARSEMEM_VMEMMAP David Hildenbrand (Arm)
2026-03-17 17:49 ` Lorenzo Stoakes (Oracle)
2026-03-18 8:15 ` Mike Rapoport
2026-03-20 18:37 ` David Hildenbrand (Arm)
2026-03-17 16:56 ` [PATCH 07/14] mm/bootmem_info: avoid using sparse_decode_mem_map() David Hildenbrand (Arm)
2026-03-17 18:02 ` Lorenzo Stoakes (Oracle)
2026-03-18 8:20 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 08/14] mm/sparse: remove sparse_decode_mem_map() David Hildenbrand (Arm)
2026-03-17 19:25 ` Lorenzo Stoakes (Oracle)
2026-03-18 8:20 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 09/14] mm/sparse: remove CONFIG_MEMORY_HOTPLUG-specific usemap allocation handling David Hildenbrand (Arm)
2026-03-17 19:48 ` Lorenzo Stoakes (Oracle)
2026-03-20 18:49 ` David Hildenbrand (Arm)
2026-03-20 18:58 ` David Hildenbrand (Arm) [this message]
2026-03-18 8:34 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 10/14] mm: prepare to move subsection_map_init() to mm/sparse-vmemmap.c David Hildenbrand (Arm)
2026-03-17 19:51 ` Lorenzo Stoakes (Oracle)
2026-03-20 18:59 ` David Hildenbrand (Arm)
2026-03-18 8:46 ` Mike Rapoport
2026-03-20 19:01 ` David Hildenbrand (Arm)
2026-03-17 16:56 ` [PATCH 11/14] mm/sparse: drop set_section_nid() from sparse_add_section() David Hildenbrand (Arm)
2026-03-17 19:55 ` Lorenzo Stoakes (Oracle)
2026-03-18 8:50 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 12/14] mm/sparse: move sparse_init_one_section() to internal.h David Hildenbrand (Arm)
2026-03-17 20:00 ` Lorenzo Stoakes (Oracle)
2026-03-18 8:54 ` Mike Rapoport
2026-03-17 16:56 ` [PATCH 13/14] mm/sparse: move __section_mark_present() " David Hildenbrand (Arm)
2026-03-17 20:01 ` Lorenzo Stoakes (Oracle)
2026-03-18 8:56 ` Mike Rapoport
2026-03-20 19:06 ` David Hildenbrand (Arm)
2026-03-17 16:56 ` [PATCH 14/14] mm/sparse: move memory hotplug bits to sparse-vmemmap.c David Hildenbrand (Arm)
2026-03-17 20:09 ` Lorenzo Stoakes (Oracle)
2026-03-20 19:07 ` David Hildenbrand (Arm)
2026-03-18 8:57 ` Mike Rapoport
2026-03-18 19:51 ` [PATCH 00/14] mm: memory hot(un)plug and SPARSEMEM cleanups Andrew Morton
2026-03-18 19:54 ` David Hildenbrand (Arm)
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