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Date: Tue, 22 Sep 2026 06:24:12 +0200
From: "Oscar Salvador (SUSE)" <osalvador@kernel.org>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Lorenzo Stoakes <ljs@kernel.org>,
	"Liam R. Howlett" <liam@infradead.org>,
	Vlastimil Babka <vbabka@kernel.org>,
	Mike Rapoport <rppt@kernel.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Michal Hocko <mhocko@suse.com>, Kairui Song <kasong@tencent.com>,
	Qi Zheng <qi.zheng@linux.dev>,
	Shakeel Butt <shakeel.butt@linux.dev>,
	Barry Song <baohua@kernel.org>,
	Axel Rasmussen <axelrasmussen@google.com>,
	Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>,
	Baoquan He <baoquan.he@linux.dev>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	Brendan Jackman <brendan.jackman@linux.dev>,
	Johannes Weiner <hannes@cmpxchg.org>, Zi Yan <ziy@nvidia.com>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	Kieran Bingham <kbingham@kernel.org>,
	Oscar Salvador <osalvador@suse.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Danilo Krummrich <dakr@kernel.org>, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, linux-cxl@vger.kernel.org,
	driver-core@lists.linux.dev, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v2 08/13] mm/sparse: move __highest_used_section_nr
 handling
Message-ID: <arIC7BheTHzBnLoq@localhost.localdomain>
References: <20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org>
 <20260921-b4-sparsemem_cleanups-v2-8-54d81d65e125@kernel.org>
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In-Reply-To: <20260921-b4-sparsemem_cleanups-v2-8-54d81d65e125@kernel.org>

On Mon, Sep 21, 2026 at 09:59:00PM +0200, David Hildenbrand (Arm) wrote:
> In preparation for removing __section_mark_present(), let's move
> __highest_used_section_nr handling into its callers. Verify in
> sparse_init_one_section() that it was properly updated.
> 
> In sparse_sections_init() we can just set it to the last processed
> section_nr.
> 
> No functional change intended.
> 
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

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

> ---
...
> --- a/mm/sparse.h
> +++ b/mm/sparse.h
> @@ -26,6 +26,7 @@ static inline void sparse_init_one_section(struct mem_section *ms,
>  	unsigned long coded_mem_map;
>  
>  	BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT);
> +	VM_WARN_ON_ONCE(section_nr > __highest_used_section_nr);

I wonder, have we seen this in the wild?



-- 
Oscar Salvador
SUSE Labs