linux-kernel - Re: [PATCH mm-unstable v2 1/3] mm/contig_alloc: support __GFP

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Message-ID: <CAOUHufbq2biYswAfH06_1d=kNfVNvM18jpM5udx=xc4-_KNREQ@mail.gmail.com>
Date: Thu, 22 Aug 2024 11:25:31 -0600
From: Yu Zhao <yuzhao@...gle.com>
To: Yu Liao <liaoyu15@...wei.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Muchun Song <muchun.song@...ux.dev>, 
	"Matthew Wilcox (Oracle)" <willy@...radead.org>, Zi Yan <ziy@...dia.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: Re: [PATCH mm-unstable v2 1/3] mm/contig_alloc: support __GFP_COMP

On Thu, Aug 22, 2024 at 2:21 AM Yu Liao <liaoyu15@...wei.com> wrote:
>
> On 2024/8/14 11:54, Yu Zhao wrote:
> > Support __GFP_COMP in alloc_contig_range(). When the flag is set, upon
> > success the function returns a large folio prepared by
> > prep_new_page(), rather than a range of order-0 pages prepared by
> > split_free_pages() (which is renamed from split_map_pages()).
> >
> > alloc_contig_range() can be used to allocate folios larger than
> > MAX_PAGE_ORDER, e.g., gigantic hugeTLB folios. So on the free path,
> > free_one_page() needs to handle that by split_large_buddy().
> >
> > Signed-off-by: Yu Zhao <yuzhao@...gle.com>
> > ---
> >  include/linux/gfp.h |  23 +++++++++
> >  mm/compaction.c     |  41 ++--------------
> >  mm/page_alloc.c     | 111 +++++++++++++++++++++++++++++++-------------
> >  3 files changed, 108 insertions(+), 67 deletions(-)
> >
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index f53f76e0b17e..59266df56aeb 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -446,4 +446,27 @@ extern struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_
> >  #endif
> >  void free_contig_range(unsigned long pfn, unsigned long nr_pages);
> >
> > +#ifdef CONFIG_CONTIG_ALLOC
> > +static inline struct folio *folio_alloc_gigantic_noprof(int order, gfp_t gfp,
> > +                                                     int nid, nodemask_t *node)
> > +{
> > +     struct page *page;
> > +
> > +     if (WARN_ON(!order || !(gfp | __GFP_COMP)))
>
> It doesn't seem right, it should be !(gfp & __GFP_COMP).

Thanks. I've asked Andrew to patch this up (and another place in mm/cma.c).