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Date: Mon, 29 Jan 2024 11:41:55 +0000
From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev,
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Subject: Re: [PATCH RFC v3 01/35] mm: page_alloc: Add gfp_flags parameter to
 arch_alloc_page()
Message-ID: <ZbePA2dGE6Vs-58t@raptor>
References: <20240125164256.4147-1-alexandru.elisei@arm.com>
 <20240125164256.4147-2-alexandru.elisei@arm.com>
 <de0c74b3-0c7d-4f21-8454-659e8b616ea7@arm.com>
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In-Reply-To: <de0c74b3-0c7d-4f21-8454-659e8b616ea7@arm.com>

Hi,

On Mon, Jan 29, 2024 at 11:18:59AM +0530, Anshuman Khandual wrote:
> 
> On 1/25/24 22:12, Alexandru Elisei wrote:
> > Extend the usefulness of arch_alloc_page() by adding the gfp_flags
> > parameter.
> 
> Although the change here is harmless in itself, it will definitely benefit
> from some additional context explaining the rationale, taking into account
> why-how arch_alloc_page() got added particularly for s390 platform and how
> it's going to be used in the present proposal.

arm64 will use it to reserve tag storage if the caller requested a tagged
page. Right now that means that __GFP_ZEROTAGS is set in the gfp mask, but
I'll rename it to __GFP_TAGGED in patch #18 ("arm64: mte: Rename
__GFP_ZEROTAGS to __GFP_TAGGED") [1].

[1] https://lore.kernel.org/lkml/20240125164256.4147-19-alexandru.elisei@arm.com/

Thanks,
Alex

> 
> > 
> > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> > ---
> > 
> > Changes since rfc v2:
> > 
> > * New patch.
> > 
> >  arch/s390/include/asm/page.h | 2 +-
> >  arch/s390/mm/page-states.c   | 2 +-
> >  include/linux/gfp.h          | 2 +-
> >  mm/page_alloc.c              | 2 +-
> >  4 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
> > index 73b9c3bf377f..859f0958c574 100644
> > --- a/arch/s390/include/asm/page.h
> > +++ b/arch/s390/include/asm/page.h
> > @@ -163,7 +163,7 @@ static inline int page_reset_referenced(unsigned long addr)
> >  
> >  struct page;
> >  void arch_free_page(struct page *page, int order);
> > -void arch_alloc_page(struct page *page, int order);
> > +void arch_alloc_page(struct page *page, int order, gfp_t gfp_flags);
> >  
> >  static inline int devmem_is_allowed(unsigned long pfn)
> >  {
> > diff --git a/arch/s390/mm/page-states.c b/arch/s390/mm/page-states.c
> > index 01f9b39e65f5..b986c8b158e3 100644
> > --- a/arch/s390/mm/page-states.c
> > +++ b/arch/s390/mm/page-states.c
> > @@ -21,7 +21,7 @@ void arch_free_page(struct page *page, int order)
> >  	__set_page_unused(page_to_virt(page), 1UL << order);
> >  }
> >  
> > -void arch_alloc_page(struct page *page, int order)
> > +void arch_alloc_page(struct page *page, int order, gfp_t gfp_flags)
> >  {
> >  	if (!cmma_flag)
> >  		return;
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index de292a007138..9e8aa3d144db 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -172,7 +172,7 @@ static inline struct zonelist *node_zonelist(int nid, gfp_t flags)
> >  static inline void arch_free_page(struct page *page, int order) { }
> >  #endif
> >  #ifndef HAVE_ARCH_ALLOC_PAGE
> > -static inline void arch_alloc_page(struct page *page, int order) { }
> > +static inline void arch_alloc_page(struct page *page, int order, gfp_t gfp_flags) { }
> >  #endif
> >  
> >  struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 150d4f23b010..2c140abe5ee6 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1485,7 +1485,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
> >  	set_page_private(page, 0);
> >  	set_page_refcounted(page);
> >  
> > -	arch_alloc_page(page, order);
> > +	arch_alloc_page(page, order, gfp_flags);
> >  	debug_pagealloc_map_pages(page, 1 << order);
> >  
> >  	/*
> 
> Otherwise LGTM.