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

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Message-ID: <Zsdz-NFl4oqZ37_h@google.com>
Date: Thu, 22 Aug 2024 11:23:04 -0600
From: Yu Zhao <yuzhao@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Muchun Song <muchun.song@...ux.dev>
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Zi Yan <ziy@...dia.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH mm-unstable v2 1/3] mm/contig_alloc: support __GFP_COMP

On Tue, Aug 13, 2024 at 09:54:49PM -0600, 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)))

Andrew, could you patch up the line above? This is what it's supposed
to check:

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 59266df56aeb..03ba9563c6db 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -452,7 +452,7 @@ static inline struct folio *folio_alloc_gigantic_noprof(int order, gfp_t gfp,
 {
 	struct page *page;
 
-	if (WARN_ON(!order || !(gfp | __GFP_COMP)))
+	if (WARN_ON(!order || !(gfp & __GFP_COMP)))
 		return NULL;
 
 	page = alloc_contig_pages_noprof(1 << order, gfp, nid, node);