linux-kernel - Re: [RFC V1 01/31] mm/debug_vm_pgtable: Directly use vm_get_page

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Date:   Tue, 25 Jan 2022 23:15:58 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        hch@...radead.org, akpm@...ux-foundation.org
Subject: Re: [RFC V1 01/31] mm/debug_vm_pgtable: Directly use
 vm_get_page_prot()

> +	 *
> +	 * Protection based vm_flags combinatins are always linear
> +	 * and increasing i.e VM_NONE ..[VM_SHARED|READ|WRITE|EXEC].
>  	 */
> -	for (idx = 0; idx < ARRAY_SIZE(protection_map); idx++) {
> +	for (i = VM_NONE; i <= (VM_SHARED | VM_READ | VM_WRITE | VM_EXEC); ix++) {
>  		pte_basic_tests(&args, idx);
>  		pmd_basic_tests(&args, idx);
>  		pud_basic_tests(&args, idx);

This looks rather convoluted.  I'd prefer to add a helper for the body
of this loop, and then explicitly call it for all the valid
combinations.  Right now all are valid, so this dosn't change a thing
except for generating larger code due to the explicit loop unrolling,
but I think it is much easier to follow and maintain.