linux-kernel - Re: [PATCH v2 2/2] alloc_tag: outline and export free_reserved

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Message-ID: <16286915-1350-4e6b-a0f6-deec02b7fa92@suse.cz>
Date: Wed, 17 Jul 2024 21:35:56 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Suren Baghdasaryan <surenb@...gle.com>, akpm@...ux-foundation.org
Cc: kent.overstreet@...ux.dev, hch@...radead.org, pasha.tatashin@...een.com,
 souravpanda@...gle.com, keescook@...omium.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 2/2] alloc_tag: outline and export free_reserved_page()

On 7/17/24 8:12 PM, Suren Baghdasaryan wrote:
> Outline and export free_reserved_page() because modules use it and it
> in turn uses page_ext_{get|put} which should not be exported. The same
> result could be obtained by outlining {get|put}_page_tag_ref() but that
> would have higher performance impact as these functions are used in
> more performance critical paths.
> 
> Fixes: dcfe378c81f7 ("lib: introduce support for page allocation tagging")
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202407080044.DWMC9N9I-lkp@intel.com/
> Suggested-by: Christoph Hellwig <hch@...radead.org>
> Suggested-by: Vlastimil Babka <vbabka@...e.cz>
> Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

Are these two patches now stable@ material as 6.10 build is broken on ppc64
with alloc taging enabled?

> ---
> Changes since v1 [1]
> - Outlined and exported free_reserved_page() in place of {get|put}_page_tag_ref,
> per Vlastimil Babka
> 
> [1] https://lore.kernel.org/all/20240717011631.2150066-2-surenb@google.com/
> 
>  include/linux/mm.h | 16 +---------------
>  mm/page_alloc.c    | 17 +++++++++++++++++
>  2 files changed, 18 insertions(+), 15 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index eb7c96d24ac0..b58bad248eef 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3177,21 +3177,7 @@ extern void reserve_bootmem_region(phys_addr_t start,
>  				   phys_addr_t end, int nid);
>  
>  /* Free the reserved page into the buddy system, so it gets managed. */
> -static inline void free_reserved_page(struct page *page)
> -{
> -	if (mem_alloc_profiling_enabled()) {
> -		union codetag_ref *ref = get_page_tag_ref(page);
> -
> -		if (ref) {
> -			set_codetag_empty(ref);
> -			put_page_tag_ref(ref);
> -		}
> -	}
> -	ClearPageReserved(page);
> -	init_page_count(page);
> -	__free_page(page);
> -	adjust_managed_page_count(page, 1);
> -}
> +void free_reserved_page(struct page *page);
>  #define free_highmem_page(page) free_reserved_page(page)
>  
>  static inline void mark_page_reserved(struct page *page)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9ecf99190ea2..7d2fa9f5e750 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5805,6 +5805,23 @@ unsigned long free_reserved_area(void *start, void *end, int poison, const char
>  	return pages;
>  }
>  
> +void free_reserved_page(struct page *page)
> +{
> +	if (mem_alloc_profiling_enabled()) {
> +		union codetag_ref *ref = get_page_tag_ref(page);
> +
> +		if (ref) {
> +			set_codetag_empty(ref);
> +			put_page_tag_ref(ref);
> +		}
> +	}
> +	ClearPageReserved(page);
> +	init_page_count(page);
> +	__free_page(page);
> +	adjust_managed_page_count(page, 1);
> +}
> +EXPORT_SYMBOL(free_reserved_page);
> +
>  static int page_alloc_cpu_dead(unsigned int cpu)
>  {
>  	struct zone *zone;