linux-kernel - Re: [PATCH v3 2/2] mm: redefine VM

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Message-ID: <98cad9a6-875f-49c2-99b2-389bf4fd9b55@redhat.com>
Date: Wed, 1 Oct 2025 16:04:51 +0200
From: David Hildenbrand <david@...hat.com>
To: Jakub Acs <acsjakub@...zon.de>, linux-mm@...ck.org
Cc: akpm@...ux-foundation.org, xu.xin16@....com.cn, chengming.zhou@...ux.dev,
 peterx@...hat.com, axelrasmussen@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] mm: redefine VM_* flag constants with BIT()

>   
> -#define VM_GROWSDOWN	0x00000100	/* general info on the segment */
> +#define VM_GROWSDOWN	BIT(8)		/* general info on the segment */
>   #ifdef CONFIG_MMU
> -#define VM_UFFD_MISSING	0x00000200	/* missing pages tracking */
> +#define VM_UFFD_MISSING	BIT(9)		/* missing pages tracking */
>   #else /* CONFIG_MMU */
> -#define VM_MAYOVERLAY	0x00000200	/* nommu: R/O MAP_PRIVATE mapping that might overlay a file mapping */
> +#define VM_MAYOVERLAY	BIT(10)		/* nommu: R/O MAP_PRIVATE mapping that might overlay a file mapping */

Careful: VM_UFFD_MISSING and VM_MAYOVERLAY share the same bit, depending 
on CONFIG_MMU (9).

>   #define VM_UFFD_MISSING	0
>   #endif /* CONFIG_MMU */
> -#define VM_PFNMAP	0x00000400	/* Page-ranges managed without "struct page", just pure PFN */
> -#define VM_UFFD_WP	0x00001000	/* wrprotect pages tracking */
> +#define VM_PFNMAP	BIT(11)		/* Page-ranges managed without "struct page", just pure PFN */

-> 10

11 is actually unused IIUC.

> +#define VM_UFFD_WP	BIT(12)		/* wrprotect pages tracking */
>   

This seems to be correct again.


IIRC, Andrew prefers not mixing fixes and cleanups in the same series if 
possible. So you might just want to send out patch #1 separately and, 
send out patch #2 separately with a note under the --- that it depends 
on patch #1.

-- 
Cheers

David / dhildenb