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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12ECFC00144 for ; Sat, 30 Jul 2022 01:57:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1AC858E0001; Fri, 29 Jul 2022 21:57:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 15CBC6B0072; Fri, 29 Jul 2022 21:57:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0236D8E0001; Fri, 29 Jul 2022 21:57:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id E34BB6B0071 for ; Fri, 29 Jul 2022 21:57:52 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id A8BE0A0EDB for ; Sat, 30 Jul 2022 01:57:52 +0000 (UTC) X-FDA: 79742105184.29.9CC7435 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf17.hostedemail.com (Postfix) with ESMTP id 988A140035 for ; Sat, 30 Jul 2022 01:57:51 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4LvnWZ6FMkz1M8RC; Sat, 30 Jul 2022 09:54:50 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 30 Jul 2022 09:57:46 +0800 Subject: Re: [RFC PATCH v4 8/8] hugetlb: use new vma_lock for pmd sharing synchronization To: Mike Kravetz CC: , , Muchun Song , Michal Hocko , Peter Xu , Naoya Horiguchi , David Hildenbrand , "Aneesh Kumar K . V" , Andrea Arcangeli , "Kirill A . Shutemov" , Davidlohr Bueso , Prakash Sangappa , James Houghton , Mina Almasry , Pasha Tatashin , Axel Rasmussen , Ray Fucillo , Andrew Morton References: <20220706202347.95150-1-mike.kravetz@oracle.com> <20220706202347.95150-9-mike.kravetz@oracle.com> <2adbbbd2-51d2-744d-77b4-374fe651873b@huawei.com> From: Miaohe Lin Message-ID: Date: Sat, 30 Jul 2022 09:57:46 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=none; spf=pass (imf17.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1659146272; a=rsa-sha256; cv=none; b=dePFg8+7UAIdX53AuBcNUfmF5Rs/+RGd6NxgSPwtq5t88xbMfUtsTiS563SVYE7RCBm9vJ K3ye/VxaKtWc+qzMZ0K1A+Y1q0LsS7hckWFEJlWeJso4ST0EO7dL8RF4Yy6EXOHR15vD6B lB6DkMD6PznsWzp39Dmyd62LQCGJskQ= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1659146272; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=LESORQVmyMnLwwM0sjNtSKXDtXiIoOmfRRl6MyqkJmE=; b=xjCRd3lrDlzsNyf30K3KncZAuRq9jbA9+dq1TYsbgkwp73ChviozXHfE/2X7V0TaML5Djp mD10Zva+gWwBfz+2jS0Ll2SvffF3YDbShRpRbqoRSmZLMDeEDdnL6PuF194QeXNWP9Whli L0LNO2SOeTq33I0aZcEXWzvWksf34Jw= X-Rspamd-Server: rspam10 X-Rspam-User: Authentication-Results: imf17.hostedemail.com; dkim=none; spf=pass (imf17.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Stat-Signature: d38henx19y5ffgiead3z8o6gbjyg11wr X-Rspamd-Queue-Id: 988A140035 X-HE-Tag: 1659146271-555071 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/7/30 1:41, Mike Kravetz wrote: > On 07/29/22 09:41, Miaohe Lin wrote: >> On 2022/7/29 1:47, Mike Kravetz wrote: >>> On 07/28/22 14:51, Miaohe Lin wrote: >> snip >>>> >>>> Do we need to check &mm->mm_users == 0 here in case the address_space of corresponding process >>>> has exited? In this case, mmdrop will drop the last reference and free the skipped_mm. So we will >>>> use skipped_mm below after it's freed? >>>> >>> >>> Good point! >>> I think we need to wait to drop since we want to hold the read lock. >>> Will update. >>> >>>>> + vma = find_vma(skipped_mm, skipped_vm_start); >>>>> + if (!vma || vma->vm_file->f_mapping != mapping || >>>> >>>> If skipped_vm_start is unmapped and remapped as a anon vma before we taking the mmap_read_lock, >>>> vma->vm_file will be NULL? >>>> >>> >>> IIUC, vma->vm_file will always be set even for an anon vma. The fault >>> code depends on this. See beginning of hugetlb_fault() where we >>> unconditionally do: >>> >>> mapping = vma->vm_file->f_mapping; >> >> What if vma is non-hugetlb anon vma? >> > > Right. The first check after !vma should be for hugetlb as we do not > care if non-hugetlb vmas and want to quit. Something like, > > vma = find_vma(skipped_mm, skipped_vm_start); > if (!vma || !is_vm_hugetlb_page(vma) || > This looks good to me. Thanks.