Re: [PATCH 2/2] mm: add pageblock_aligned() macro

[Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>]

On 2022/9/2 16:42, David Hildenbrand wrote:

> 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@xxxxxxxxxx>
> > ---
> >       
> [...]
>
> > -	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 :)
>     
    Wish you have a good reset :)
> "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)) {
> >       
>     
pageblock_aligned(pfn) IS_ALIGNED((unsigned long)(pfn), pageblock_nr_pages)

#define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) == 0)

(((pfn) & (pageblock_nr_pages - 1)) == 0)
-> ((1 & 512 -1) == 0)
-> ((1 & 511) == 0)
-> ((511) == 0)
-> false

right ? 
> So shouldn't this be "pageblock_aligned(pfn)"
>
>
> ?
>
> >  			page = pfn_to_page(pfn);
> >  		} else {
> >  			page++;
> >       
>
>