linux-kernel - Re: [PATCH v2 4/7] mm: rename mm_struct::map_count to vma

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Message-ID: <c955bff9-b4f5-4b93-b7e0-28473766dd2f@redhat.com>
Date: Wed, 17 Sep 2025 15:41:45 +0200
From: David Hildenbrand <david@...hat.com>
To: Kalesh Singh <kaleshsingh@...gle.com>, akpm@...ux-foundation.org,
 minchan@...nel.org, lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com,
 rppt@...nel.org, pfalcato@...e.de
Cc: kernel-team@...roid.com, android-mm@...gle.com,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
 Kees Cook <kees@...nel.org>, Vlastimil Babka <vbabka@...e.cz>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>, Ben Segall
 <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
 Valentin Schneider <vschneid@...hat.com>, Jann Horn <jannh@...gle.com>,
 Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
 linux-trace-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 4/7] mm: rename mm_struct::map_count to vma_count

On 15.09.25 18:36, Kalesh Singh wrote:
> A mechanical rename of the mm_struct->map_count field to
> vma_count; no functional change is intended.
> 
> The name "map_count" is ambiguous within the memory management subsystem,
> as it can be confused with the folio/page->_mapcount field, which tracks
> PTE references.
> 
> The new name, vma_count, is more precise as this field has always
> counted the number of vm_area_structs associated with an mm_struct.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Cc: Mike Rapoport <rppt@...nel.org>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Pedro Falcato <pfalcato@...e.de>
> Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
> ---


[...]

> +++ b/mm/mmap.c
> @@ -1308,7 +1308,7 @@ void exit_mmap(struct mm_struct *mm)
>   		vma = vma_next(&vmi);
>   	} while (vma && likely(!xa_is_zero(vma)));
>   
> -	BUG_ON(count != mm->map_count);
> +	BUG_ON(count != mm->vma_count);
>   

While at it, best to change that to a WARN_ON_ONCE() or even a 
VM_WARN_ON_ONCE().

[ or remove it -- have we ever seen that firing? ]

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers

David / dhildenb