linux-kernel - Re: [PATCH v2 4/8] powerpc/mm: protect linear mapping modifications by a mutex

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Message-ID: <20201117153750.GD15987@linux>
Date:   Tue, 17 Nov 2020 16:37:50 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Rashmica Gupta <rashmica.g@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>
Subject: Re: [PATCH v2 4/8] powerpc/mm: protect linear mapping modifications
 by a mutex

On Wed, Nov 11, 2020 at 03:53:18PM +0100, David Hildenbrand wrote:
> @@ -144,7 +147,9 @@ void __ref arch_remove_linear_mapping(u64 start, u64 size)
>  	start = (unsigned long)__va(start);
>  	flush_dcache_range_chunked(start, start + size, FLUSH_CHUNK_SIZE);
>  
> +	mutex_lock(&linear_mapping_mutex);
>  	ret = remove_section_mapping(start, start + size);
> +	mutex_unlock(&linear_mapping_mutex);
>  	WARN_ON_ONCE(ret);

My expertise in this area is low, so bear with me.

Why we do not need to protect flush_dcache_range_chunked and
vm_unmap_aliases?

-- 
Oscar Salvador
SUSE L3