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Subject: Re: [PATCH v14 038/138] mm/memcg: Add folio_memcg() and related
 functions
To:     "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        linux-kernel@vger.kernel.org
Cc:     linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        Christoph Hellwig <hch@lst.de>
References: <20210715033704.692967-1-willy@infradead.org>
 <20210715033704.692967-39-willy@infradead.org>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <1eb08e30-3a84-eaae-e9ee-07d59cbde807@suse.cz>
Date:   Wed, 11 Aug 2021 12:32:45 +0200
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On 7/15/21 5:35 AM, Matthew Wilcox (Oracle) wrote:
> memcg information is only stored in the head page, so the memcg
> subsystem needs to assure that all accesses are to the head page.
> The first step is converting page_memcg() to folio_memcg().
> 
> The callers of page_memcg() and PageMemcgKmem() are not yet ready to be
> converted to use folios, so retain them as wrappers around folio_memcg()
> and folio_memcg_kmem().  They will be converted in a later patch set.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>


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


Nit:

> ---
>  include/linux/memcontrol.h | 109 ++++++++++++++++++++++---------------
>  mm/memcontrol.c            |  21 ++++---
>  2 files changed, 77 insertions(+), 53 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index bfe5c486f4ad..eabae5874161 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -372,6 +372,7 @@ enum page_memcg_data_flags {
>  #define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1)
>  
>  static inline bool PageMemcgKmem(struct page *page);

I think this fwd declaration is no longer needed.

> +static inline bool folio_memcg_kmem(struct folio *folio);
>