linux-kernel - Re: [PATCH] pagemap: Add alert to mapping_set_release_always() for mapping with no release

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Message-ID: <aTnn68vLGxFxO8kv@casper.infradead.org>
Date: Wed, 10 Dec 2025 21:36:43 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Deepakkumar Karn <dkarn@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Liam.Howlett@...cle.com, Vlastimil Babka <vbabka@...e.cz>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>, Jan Kara <jack@...e.cz>,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pagemap: Add alert to mapping_set_release_always() for
 mapping with no release_folio

On Thu, Dec 11, 2025 at 01:31:04AM +0530, Deepakkumar Karn wrote:
>  static inline void mapping_set_release_always(struct address_space *mapping)
>  {
> +	/* Alert while setting the flag with no release_folio callback */

The comment is superfluous.

> +	VM_WARN_ONCE(!mapping->a_ops->release_folio,
> +		     "Setting AS_RELEASE_ALWAYS with no release_folio");

But you haven't said why we need to do this.  Surely the NULL pointer
splat is enough to tell you that you did something stupid?

>  	set_bit(AS_RELEASE_ALWAYS, &mapping->flags);
>  }
>  
> -- 
> 2.52.0
> 
>