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From: "David Hildenbrand (Arm)" <david@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, linux-cxl@vger.kernel.org,
	"David Hildenbrand (Arm)" <david@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>,
	Lorenzo Stoakes <ljs@kernel.org>,
	"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: [PATCH 02/14] mm/sparse: remove WARN_ONs from (online|offline)_mem_sections()
Date: Tue, 17 Mar 2026 17:56:40 +0100	[thread overview]
Message-ID: <20260317165652.99114-3-david@kernel.org> (raw)
In-Reply-To: <20260317165652.99114-1-david@kernel.org>

We do not allow offlining of memory with memory holes, and always
hotplug memory without holes.

Consequently, we cannot end up onlining or offlining memory sections that
have holes (including invalid sections). That's also why these
WARN_ONs never fired.

Let's remove the WARN_ONs along with the TODO regarding double-checking.

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 mm/sparse.c | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index dfabe554adf8..93252112860e 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -638,13 +638,8 @@ void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
 
 	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
-		struct mem_section *ms;
-
-		/* onlining code should never touch invalid ranges */
-		if (WARN_ON(!valid_section_nr(section_nr)))
-			continue;
+		struct mem_section *ms = __nr_to_section(section_nr);
 
-		ms = __nr_to_section(section_nr);
 		ms->section_mem_map |= SECTION_IS_ONLINE;
 	}
 }
@@ -656,16 +651,8 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn)
 
 	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
-		struct mem_section *ms;
+		struct mem_section *ms = __nr_to_section(section_nr);
 
-		/*
-		 * TODO this needs some double checking. Offlining code makes
-		 * sure to check pfn_valid but those checks might be just bogus
-		 */
-		if (WARN_ON(!valid_section_nr(section_nr)))
-			continue;
-
-		ms = __nr_to_section(section_nr);
 		ms->section_mem_map &= ~SECTION_IS_ONLINE;
 	}
 }
-- 
2.43.0



  parent reply	other threads:[~2026-03-17 16:57 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 ` David Hildenbrand (Arm) [this message]
2026-03-17 17:21   ` [PATCH 02/14] mm/sparse: remove WARN_ONs from (online|offline)_mem_sections() 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)
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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