From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3FEA4C43331 for ; Wed, 1 Apr 2020 02:31:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19B5020578 for ; Wed, 1 Apr 2020 02:31:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731664AbgDACbJ (ORCPT ); Tue, 31 Mar 2020 22:31:09 -0400 Received: from mga07.intel.com ([134.134.136.100]:36242 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731554AbgDACbI (ORCPT ); Tue, 31 Mar 2020 22:31:08 -0400 IronPort-SDR: 4oOl8ZmwFHBm4g9LriFHcZ1bHkszQo4xyT7KG6Q3oj2VTjYeGVlCn+N0f1wUbWY8d7TC6DwCv0 f3mR160P9J0g== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Mar 2020 19:31:07 -0700 IronPort-SDR: mkxQL4GfjaPiHJkDgxEa8ej+AOXIVcRb79zvXmIGjlpTDcfnWQKS/u2c2Zc07tH0TNGk8wkKX4 s27I35EhfIOQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,330,1580803200"; d="scan'208";a="237910614" Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.23]) by orsmga007.jf.intel.com with ESMTP; 31 Mar 2020 19:31:04 -0700 From: "Huang\, Ying" To: Konstantin Khlebnikov Cc: Andrew Morton , , , Andrea Arcangeli , "Kirill A . Shutemov" , Zi Yan , Vlastimil Babka , Alexey Dobriyan , Michal Hocko , =?utf-8?B?SsOp?= =?utf-8?B?csO0bWU=?= Glisse , Yang Shi Subject: Re: [PATCH] /proc/PID/smaps: Add PMD migration entry parsing References: <20200331085604.1260162-1-ying.huang@intel.com> <49386753-5984-f708-4153-e9c6de632439@yandex-team.ru> Date: Wed, 01 Apr 2020 10:31:03 +0800 In-Reply-To: <49386753-5984-f708-4153-e9c6de632439@yandex-team.ru> (Konstantin Khlebnikov's message of "Tue, 31 Mar 2020 12:51:38 +0300") Message-ID: <87mu7whr88.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Konstantin Khlebnikov writes: > On 31/03/2020 11.56, Huang, Ying wrote: >> From: Huang Ying >> >> Now, when read /proc/PID/smaps, the PMD migration entry in page table is simply >> ignored. To improve the accuracy of /proc/PID/smaps, its parsing and processing >> is added. >> >> Signed-off-by: "Huang, Ying" >> Cc: Andrea Arcangeli >> Cc: Kirill A. Shutemov >> Cc: Zi Yan >> Cc: Vlastimil Babka >> Cc: Alexey Dobriyan >> Cc: Michal Hocko >> Cc: Konstantin Khlebnikov >> Cc: "Jérôme Glisse" >> Cc: Yang Shi >> --- >> fs/proc/task_mmu.c | 16 ++++++++++++---- >> 1 file changed, 12 insertions(+), 4 deletions(-) >> >> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c >> index 8d382d4ec067..b5b3aef8cb3b 100644 >> --- a/fs/proc/task_mmu.c >> +++ b/fs/proc/task_mmu.c >> @@ -548,8 +548,17 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr, >> bool locked = !!(vma->vm_flags & VM_LOCKED); >> struct page *page; > > struct page *page = NULL; Looks good. Will do this in the next version. >> - /* FOLL_DUMP will return -EFAULT on huge zero page */ >> - page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP); >> + if (pmd_present(*pmd)) { >> + /* FOLL_DUMP will return -EFAULT on huge zero page */ >> + page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP); >> + } else if (unlikely(is_swap_pmd(*pmd))) { >> + swp_entry_t entry = pmd_to_swp_entry(*pmd); >> + >> + VM_BUG_ON(!is_migration_entry(entry)); >> + page = migration_entry_to_page(entry); > > if (is_migration_entry(entry)) > page = migration_entry_to_page(entry); > > Seems safer and doesn't add much code. With this, we lose an opportunity to capture some bugs during debugging. Right? Best Regards, Huang, Ying >> + } else { >> + return; >> + } >> if (IS_ERR_OR_NULL(page)) >> return; >> if (PageAnon(page)) >> @@ -578,8 +587,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, >> ptl = pmd_trans_huge_lock(pmd, vma); >> if (ptl) { >> - if (pmd_present(*pmd)) >> - smaps_pmd_entry(pmd, addr, walk); >> + smaps_pmd_entry(pmd, addr, walk); >> spin_unlock(ptl); >> goto out; >> } >>