linux-kernel - Re: [RFC PATCH 1/5] io_uring: allocate folio in io_mem_alloc

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Message-ID: <b37f990b-cb70-489b-849e-202eae190c37@linux.dev>
Date: Sat, 31 Jan 2026 23:30:35 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: Zi Yan <ziy@...dia.com>
Cc: Alistair Popple <apopple@...dia.com>, Balbir Singh <balbirs@...dia.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
 <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Matthew Wilcox <willy@...radead.org>, Suren Baghdasaryan
 <surenb@...gle.com>, Jason Gunthorpe <jgg@...dia.com>,
 Michal Hocko <mhocko@...e.com>, Jens Axboe <axboe@...nel.dk>,
 David Hildenbrand <david@...nel.org>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Muchun Song <muchun.song@...ux.dev>,
 Oscar Salvador <osalvador@...e.de>, Brendan Jackman <jackmanb@...gle.com>,
 Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, io-uring@...r.kernel.org
Subject: Re: [RFC PATCH 1/5] io_uring: allocate folio in
 io_mem_alloc_compound() and function rename

On 2026/1/30 11:48, Zi Yan wrote:
> The page allocated in io_mem_alloc_compound() is actually used as a folio
> later in io_region_mmap(). So allocate a folio instead of a compound page
> and rename io_mem_alloc_compound() to io_mem_alloc_folio().
> 
> This prepares for code separation of compound page and folio in a follow-up
> commit.
> 
> Signed-off-by: Zi Yan <ziy@...dia.com>
> ---
>   io_uring/memmap.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/io_uring/memmap.c b/io_uring/memmap.c
> index 7d3c5eb58480..8ed8a78d71cc 100644
> --- a/io_uring/memmap.c
> +++ b/io_uring/memmap.c
> @@ -15,10 +15,10 @@
>   #include "rsrc.h"
>   #include "zcrx.h"
>   
> -static bool io_mem_alloc_compound(struct page **pages, int nr_pages,
> +static bool io_mem_alloc_folio(struct page **pages, int nr_pages,
>   				  size_t size, gfp_t gfp)
>   {
> -	struct page *page;
> +	struct folio *folio;
>   	int i, order;
>   
>   	order = get_order(size);
> @@ -27,12 +27,12 @@ static bool io_mem_alloc_compound(struct page **pages, int nr_pages,

Nit:

>   	else if (order)
>   		gfp |= __GFP_COMP;

Since we're switching to folio_alloc(), which already adds __GFP_COMP
internally, the "else if (order)" part above can be dropped while at it.

IIUC, for order == 0, __GFP_COMP gets ignored anyway:

  - prep_new_page() won't call prep_compound_page() (since order is zero)
  - page_rmappable_folio() sees a non-compound page and does nothing

So no behavior change there :)

>   
> -	page = alloc_pages(gfp, order);
> -	if (!page)
> +	folio = folio_alloc(gfp, order);
> +	if (!folio)
>   		return false;
>   
>   	for (i = 0; i < nr_pages; i++)
> -		pages[i] = page + i;
> +		pages[i] = folio_page(folio, i);
>   
>   	return true;
>   }
> @@ -162,7 +162,7 @@ static int io_region_allocate_pages(struct io_mapped_region *mr,
>   	if (!pages)
>   		return -ENOMEM;
>   
> -	if (io_mem_alloc_compound(pages, mr->nr_pages, size, gfp)) {
> +	if (io_mem_alloc_folio(pages, mr->nr_pages, size, gfp)) {
>   		mr->flags |= IO_REGION_F_SINGLE_REF;
>   		goto done;
>   	}