linux-kernel - Re: [PATCH] mm/huge_memory: refactor after-split (page) cache code.

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Message-ID: <bec0d00b-1284-4d45-bd42-f3089898ff3f@mandelbit.com>
Date: Wed, 16 Jul 2025 21:01:25 +0200
From: Antonio Quartulli <antonio@...delbit.com>
To: Zi Yan <ziy@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins
 <hughd@...gle.com>, linux-mm@...ck.org, David Hildenbrand
 <david@...hat.com>, Kirill Shutemov <k.shutemov@...il.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Dan Carpenter <dan.carpenter@...aro.org>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/huge_memory: refactor after-split (page) cache code.

On 16/07/2025 19:11, Zi Yan wrote:
> Smatch/coverity checkers report NULL mapping referencing issues[1][2][3]
> every time the code is modified, because they do not understand that
> mapping cannot be NULL when a folio is in page cache in the code.
> Refactor the code to make it explicit.
> 
> No functional change is intended.
> 
> [1]https://lore.kernel.org/linux-mm/2afe3d59-aca5-40f7-82a3-a6d976fb0f4f@stanley.mountain/
> [2]https://lore.kernel.org/oe-kbuild/64b54034-f311-4e7d-b935-c16775dbb642@suswa.mountain/
> [3]https://lore.kernel.org/linux-mm/20250716145804.4836-1-antonio@mandelbit.com/
> 
> Suggested-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Zi Yan <ziy@...dia.com>

Much easier to grasp - Thanks a lot!

I am sure Coverity will be happy too at this point, because the 
ambiguity has been fully removed.

In a previous email you asked me how to prevent Coverity from 
complaining about certain code: my thinking is fully aligned with Dan's 
reply. IMHO refactoring the code was the best choice - thanks again.

Regards,

-- 
Antonio Quartulli

CEO and Co-Founder
Mandelbit Srl
https://www.mandelbit.com