linux-kernel - Re: [PATCH v2 08/16] mm: add ability to take further action in vm_area

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Message-ID: <dce30be7-90d3-4a6a-9b26-44d76c3190a0@intel.com>
Date: Thu, 11 Sep 2025 15:07:21 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Andrew Morton
	<akpm@...ux-foundation.org>
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Subject: Re: [PATCH v2 08/16] mm: add ability to take further action in
 vm_area_desc

Hi Lorenzo,

On 9/10/25 1:22 PM, Lorenzo Stoakes wrote:

...

> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 4a441f78340d..ae6c7a0a18a7 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -770,6 +770,64 @@ struct pfnmap_track_ctx {
>  };
>  #endif
>  
> +/* What action should be taken after an .mmap_prepare call is complete? */
> +enum mmap_action_type {
> +	MMAP_NOTHING,		 /* Mapping is complete, no further action. */
> +	MMAP_REMAP_PFN,		 /* Remap PFN range based on desc->remap. */
> +	MMAP_INSERT_MIXED,	 /* Mixed map based on desc->mixedmap. */
> +	MMAP_INSERT_MIXED_PAGES, /* Mixed map based on desc->mixedmap_pages. */
> +	MMAP_CUSTOM_ACTION,	 /* User-provided hook. */
> +};
> +
> +struct mmap_action {
> +	union {
> +		/* Remap range. */
> +		struct {
> +			unsigned long addr;
> +			unsigned long pfn;
> +			unsigned long size;
> +			pgprot_t pgprot;
> +		} remap;
> +		/* Insert mixed map. */
> +		struct {
> +			unsigned long addr;
> +			unsigned long pfn;
> +			unsigned long num_pages;
> +		} mixedmap;
> +		/* Insert specific mixed map pages. */
> +		struct {
> +			unsigned long addr;
> +			struct page **pages;
> +			unsigned long num_pages;
> +			/* kfree pages on completion? */
> +			bool kfree_pages :1;
> +		} mixedmap_pages;
> +		struct {
> +			int (*action_hook)(struct vm_area_struct *vma);
> +		} custom;
> +	};
> +	enum mmap_action_type type;
> +
> +	/*
> +	 * If specified, this hook is invoked after the selected action has been
> +	 * successfully completed. Not that the VMA write lock still held.

A typo that may trip tired eyes: Not -> Note ? (perhaps also "is still held"?)
(also in the duplicate changes to tools/testing/vma/vma_internal.h)

> +	 *
> +	 * The absolute minimum ought to be done here.
> +	 *
> +	 * Returns 0 on success, or an error code.
> +	 */
> +	int (*success_hook)(struct vm_area_struct *vma);
> +
> +	/*
> +	 * If specified, this hook is invoked when an error occurred when
> +	 * attempting the selection action.
> +	 *
> +	 * The hook can return an error code in order to filter the error, but
> +	 * it is not valid to clear the error here.
> +	 */
> +	int (*error_hook)(int err);
> +};

Reinette