linux-kernel - Re: [PATCH 2/2] mm: add pageblock

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Message-ID: <e0405abb-d1ea-977b-6d16-859a56bf3027@redhat.com>
Date:   Fri, 2 Sep 2022 10:42:48 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:     Mike Rapoport <rppt@...nel.org>,
        Oscar Salvador <osalvador@...e.de>,
        linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH 2/2] mm: add pageblock_aligned() macro

On 02.09.22 08:47, Kefeng Wang wrote:
> Add pageblock_aligned() and use it to simplify code.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---

[...]

> -	unsigned long nr_pgmask = pageblock_nr_pages - 1;
>  	int nid = zone_to_nid(zone);
>  	unsigned long nr_pages = 0;
>  	int zid = zone_idx(zone);
> @@ -1977,7 +1974,7 @@ static unsigned long  __init deferred_init_pages(struct zone *zone,
>  		if (!deferred_pfn_valid(pfn)) {
>  			page = NULL;
>  			continue;
> -		} else if (!page || !(pfn & nr_pgmask)) {


I didn't sleep too well this night and am tired, please tell me why I'm
wrong :)


"pfn & (pageblock_nr_pages - 1)" is true if the pageblock is not aligned

E.g., pfn = 1, pageblock_nr_pages = 512

pfn & (pageblock_nr_pages - 1)
-> 1 & (512 - 1)
-> 1 & 511
-> true

"!(pfn & (pageblock_nr_pages - 1))" is true if the pageblock is aligned
-> !(true)
-> false


However, "!pageblock_aligned(1)" = true


> +		} else if (!page || !pageblock_aligned(pfn)) {


So shouldn't this be "pageblock_aligned(pfn)"


?

>  			page = pfn_to_page(pfn);
>  		} else {
>  			page++;


-- 
Thanks,

David / dhildenb