From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752699AbcHVETe (ORCPT ); Mon, 22 Aug 2016 00:19:34 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:18970 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790AbcHVETd (ORCPT ); Mon, 22 Aug 2016 00:19:33 -0400 Subject: Re: [PATCH 1/1] arm64/hugetlb: clear PG_dcache_clean if the page is dirty when munmap To: Catalin Marinas References: <1467893344-8352-1-git-send-email-thunder.leizhen@huawei.com> <20160707153741.GC27180@e104818-lin.cambridge.arm.com> <577F1FD9.1040205@huawei.com> <20160708135447.GB22099@e104818-lin.cambridge.arm.com> <577FC5AA.5010709@huawei.com> <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> CC: Steve Capper , David Woods , Hanjun Guo , Will Deacon , linux-kernel , Xinwei Hu , Zefan Li , Tianhong Ding , linux-arm-kernel , "fangwei (I)" From: "Leizhen (ThunderTown)" Message-ID: <57BA7D38.8030103@huawei.com> Date: Mon, 22 Aug 2016 12:19:04 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160720091939.GA25890@e104818-lin.cambridge.arm.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.23.164] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020206.57BA7D46.008D,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: db3e58e7860276473dd333901f1acfc7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016/7/20 17:19, Catalin Marinas wrote: > On Wed, Jul 20, 2016 at 10:46:27AM +0800, Leizhen (ThunderTown) 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<--------------------- >> >> Do you plan to send this patch? My colleagues told me that if our >> patches are quite different, it should be Signed-off-by you. > > The reason I'm not sending it is that I don't fully understand how it > solves the problem for a shared file mmap(), not just hugetlbfs. As I > said in an earlier email: after an msync() in user space we > should flush the pages to disk via write_cache_pages(). This function Hi Catalin: I'm so sorry for my fault. The previous small pages test result I actually ran on ramfs. Today, I ran the case on harddisk fs, it worked well without this patch. Summarized as follows: small pages on ramfs: need this patch small pages on harddisk fs: no need this patch hugetlbfs: need this patch > calls clear_page_dirty_for_io() after which PageDirty() is no longer > true. I can't tell how a subsequent mmap() can see the written pages as > dirty. > >> I searched all Linux source code, __sync_icache_dcache is only called >> by set_pte_at, and some check conditions(especially pte_exec) will >> limit its impact. >> >> if (pte_user(pte) && pte_exec(pte) && !pte_special(pte)) >> __sync_icache_dcache(pte, addr); > > Yes, and set_pte_at() would be called as a result of a page fault when > accessing the mmap'ed file. >