From mboxrd@z Thu Jan  1 00:00:00 1970
From: catalin.marinas@arm.com (Catalin Marinas)
Date: Thu, 25 Aug 2016 10:30:54 +0100
Subject: [PATCH 1/1] arm64/hugetlb: clear PG_dcache_clean if the page is
 dirty when munmap
In-Reply-To: <57BE4D02.1040906@huawei.com>
References: <20160708161347.GC22099@e104818-lin.cambridge.arm.com>
 <57839474.6030203@huawei.com>
 <20160712153535.GH22183@e104818-lin.cambridge.arm.com>
 <578EE603.9020206@huawei.com>
 <20160720091939.GA25890@e104818-lin.cambridge.arm.com>
 <57BA7D38.8030103@huawei.com>
 <20160823172852.GB16213@e104818-lin.cambridge.arm.com>
 <57BD6242.1080801@huawei.com>
 <20160824103044.GA11504@e104818-lin.cambridge.arm.com>
 <57BE4D02.1040906@huawei.com>
Message-ID: <20160825093054.GB20748@e104818-lin.cambridge.arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Thu, Aug 25, 2016 at 09:42:26AM +0800, Leizhen (ThunderTown) wrote:
> On 2016/8/24 18:30, Catalin Marinas wrote:
> >>>>>>>>>> On 2016/7/8 21:54, Catalin Marinas wrote:
> >>>>>>>>>>> ------------8<----------------
> >>>>>>>>>>> diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
> >>>>>>>>>>> index dbd12ea8ce68..c753fa804165 100644
> >>>>>>>>>>> --- a/arch/arm64/mm/flush.c
> >>>>>>>>>>> +++ b/arch/arm64/mm/flush.c
> >>>>>>>>>>> @@ -75,7 +75,8 @@ void __sync_icache_dcache(pte_t pte, unsigned long addr)
> >>>>>>>>>>>  	if (!page_mapping(page))
> >>>>>>>>>>>  		return;
> >>>>>>>>>>>  
> >>>>>>>>>>> -	if (!test_and_set_bit(PG_dcache_clean, &page->flags))
> >>>>>>>>>>> +	if (!test_and_set_bit(PG_dcache_clean, &page->flags) ||
> >>>>>>>>>>> +	    PageDirty(page))
> >>>>>>>>>>>  		sync_icache_aliases(page_address(page),
> >>>>>>>>>>>  				    PAGE_SIZE << compound_order(page));
> >>>>>>>>>>>  	else if (icache_is_aivivt())
> >>>>>>>>>>> ----------------8<---------------------
[...]
> > While we indeed see failures on multiple filesystem types, I wonder
> > whether this test case is actually expected to work. If I modify the
> > test to pass O_TRUNC to open(), I can no longer see failures. So any
> > standard tool that copies/creates executable files (gcc, dpkg, cp, rsync
> > etc.) wouldn't encounter such issues since they truncate the original
> > file and old page cache pages would be removed.
> > 
> > Do you have a real use-case where a task mmap's an executable file,
> > modifies it in place and expects another task to see the new
> > instructions without user-space cache maintenance?
> 
> No, it's just a test case created by testers.

In this case I propose we ignore this patch and you adjust the test to
use O_TRUNC, at least until we find a real scenario where this would
matter.

-- 
Catalin