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

[Kefeng Wang]

On 2022/9/2 17:04, David Hildenbrand wrote:
> On 02.09.22 11:02, Kefeng Wang wrote:
> > 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 :)
> Thanks, the headache isn't helping :D
>
> > > "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 ?
> yes ... and inverting that would give you "true", which is not what we want?
oops...  it's my fault, looks like I need to have a reset to save my 
brain...
> Again, sorry if I'm wrong ...