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Date: Thu, 7 Jul 2016 16:37:42 +0100
From: Catalin Marinas <catalin.marinas@arm.com>
To: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Will Deacon <will.deacon@arm.com>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Xinwei Hu <huxinwei@huawei.com>, Zefan Li <lizefan@huawei.com>,
        Hanjun Guo <guohanjun@huawei.com>,
        Tianhong Ding <dingtianhong@huawei.com>,
        Steve Capper <Steve.Capper@arm.com>, David Woods <dwoods@ezchip.com>
Subject: Re: [PATCH 1/1] arm64/hugetlb: clear PG_dcache_clean if the page is
 dirty when munmap
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On Thu, Jul 07, 2016 at 08:09:04PM +0800, Zhen Lei wrote:
> At present, PG_dcache_clean is only cleared when the related huge page
> is about to be freed. But sometimes, there maybe a process is in charge
> to copy binary codes into a shared memory, and notifies other processes
> to execute base on that. For the first time, there is no problem, because
> the default value of page->flags is PG_dcache_clean cleared. So the cache
> will be maintained at the time of set_pte_at for other processes. But if
> the content of the shared memory have been updated again, there is no
> cache operations, because the PG_dcache_clean is still set.
> 
> For example:
> Process A
> 	open a hugetlbfs file
> 	mmap it as a shared memory
> 	copy some binary codes into it
> 	munmap
> 
> Process B
> 	open the hugetlbfs file
> 	mmap it as a shared memory, executable
> 	invoke the functions in the shared memory
> 	munmap
> 
> repeat the above steps.

Does this work as you would expect with small pages (and for example
shared file mmap)? I don't want to have a different behaviour between
small and huge pages.

-- 
Catalin