linux-kernel - Re: [PATCH v2 02/17] dma-contiguous: simplify cma_early_percent

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Message-ID: <20200805035024.GR10792@MiWiFi-R3L-srv>
Date:   Wed, 5 Aug 2020 11:50:24 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Hellwig <hch@....de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Ingo Molnar <mingo@...hat.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Simek <monstr@...str.eu>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Russell King <linux@...linux.org.uk>,
        Stafford Horne <shorne@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        clang-built-linux@...glegroups.com,
        iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-c6x-dev@...ux-c6x.org,
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Subject: Re: [PATCH v2 02/17] dma-contiguous: simplify
 cma_early_percent_memory()

On 08/02/20 at 07:35pm, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> The memory size calculation in cma_early_percent_memory() traverses
> memblock.memory rather than simply call memblock_phys_mem_size(). The
> comment in that function suggests that at some point there should have been
> call to memblock_analyze() before memblock_phys_mem_size() could be used.
> As of now, there is no memblock_analyze() at all and
> memblock_phys_mem_size() can be used as soon as cold-plug memory is
> registerd with memblock.
> 
> Replace loop over memblock.memory with a call to memblock_phys_mem_size().
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> ---
>  kernel/dma/contiguous.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> index 15bc5026c485..1992afd8ca7b 100644
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -73,16 +73,7 @@ early_param("cma", early_cma);
>  
>  static phys_addr_t __init __maybe_unused cma_early_percent_memory(void)
>  {
> -	struct memblock_region *reg;
> -	unsigned long total_pages = 0;
> -
> -	/*
> -	 * We cannot use memblock_phys_mem_size() here, because
> -	 * memblock_analyze() has not been called yet.
> -	 */
> -	for_each_memblock(memory, reg)
> -		total_pages += memblock_region_memory_end_pfn(reg) -
> -			       memblock_region_memory_base_pfn(reg);
> +	unsigned long total_pages = PHYS_PFN(memblock_phys_mem_size());

Reviewed-by: Baoquan He <bhe@...hat.com>

>  
>  	return (total_pages * CONFIG_CMA_SIZE_PERCENTAGE / 100) << PAGE_SHIFT;
>  }
> -- 
> 2.26.2
>