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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 8FD5DC433DB for ; Fri, 19 Feb 2021 10:45:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C2FD64EAF for ; Fri, 19 Feb 2021 10:45:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229691AbhBSKpf (ORCPT ); Fri, 19 Feb 2021 05:45:35 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:60625 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229587AbhBSKpf (ORCPT ); Fri, 19 Feb 2021 05:45:35 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613731448; h=from:from: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=/qnTAKaudqj6ibNGsa7QgwKptXTuW5gHmbzgrK/ICxg=; b=AfLxL38byS238BmR8QkdWWQFdnzr+o9b1cT2FR6hWjljtxH8EAOSPiINwRQgE1mo/azwGS f24bEbZV2/9s6QmXUgn+aslZCvqHsbfTGIINoB0WwFHGWy0VGCHgzyC/CKJT2iRy6APs4T smdvCJ1ZVcPjOFRWcN1lLVvOawGvP9w= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-543-CUgcwet2PZq5HCsyQx6W5A-1; Fri, 19 Feb 2021 05:44:06 -0500 X-MC-Unique: CUgcwet2PZq5HCsyQx6W5A-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 78A86106BAA8; Fri, 19 Feb 2021 10:44:02 +0000 (UTC) Received: from [10.36.113.117] (ovpn-113-117.ams2.redhat.com [10.36.113.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id 24E99171FE; Fri, 19 Feb 2021 10:43:50 +0000 (UTC) Subject: Re: [PATCH RFC] mm/madvise: introduce MADV_POPULATE to prefault/prealloc memory To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Arnd Bergmann , Oscar Salvador , Matthew Wilcox , Andrea Arcangeli , Minchan Kim , Jann Horn , Jason Gunthorpe , Dave Hansen , Hugh Dickins , Rik van Riel , "Michael S . Tsirkin" , "Kirill A . Shutemov" , Vlastimil Babka , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Chris Zankel , Max Filippov , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org References: <20210217154844.12392-1-david@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <6e5a5bde-cedb-9d0a-f8c1-22406085b6b9@redhat.com> Date: Fri, 19 Feb 2021 11:43:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On 19.02.21 11:35, Michal Hocko wrote: > On Wed 17-02-21 16:48:44, David Hildenbrand wrote: > [...] > > I only got to the implementation now. > >> +static long madvise_populate(struct vm_area_struct *vma, >> + struct vm_area_struct **prev, >> + unsigned long start, unsigned long end) >> +{ >> + struct mm_struct *mm = vma->vm_mm; >> + unsigned long tmp_end; >> + int locked = 1; >> + long pages; >> + >> + *prev = vma; >> + >> + while (start < end) { >> + /* >> + * We might have temporarily dropped the lock. For example, >> + * our VMA might have been split. >> + */ >> + if (!vma || start >= vma->vm_end) { >> + vma = find_vma(mm, start); >> + if (!vma) >> + return -ENOMEM; >> + } > > Why do you need to find a vma when you already have one. do_madvise will > give you your vma already. I do understand that you want to finish the > vma for some errors but that shouldn't require handling vmas. You should > be in the shope of one here unless I miss anything. See below, we might temporary drop the lock while not having processed all pages > >> + >> + /* Bail out on incompatible VMA types. */ >> + if (vma->vm_flags & (VM_IO | VM_PFNMAP) || >> + !vma_is_accessible(vma)) { >> + return -EINVAL; >> + } >> + >> + /* >> + * Populate pages and take care of VM_LOCKED: simulate user >> + * space access. >> + * >> + * For private, writable mappings, trigger a write fault to >> + * break COW (i.e., shared zeropage). For other mappings (i.e., >> + * read-only, shared), trigger a read fault. >> + */ >> + tmp_end = min_t(unsigned long, end, vma->vm_end); >> + pages = populate_vma_page_range(vma, start, tmp_end, &locked); >> + if (!locked) { >> + mmap_read_lock(mm); >> + *prev = NULL; >> + vma = NULL; ^ here so, the VMA might have been replaced/split/... in the meantime. So to make forward progress, I have to lookup again. (similar. but different to madvise_dontneed_free()). -- Thanks, David / dhildenb From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [PATCH RFC] mm/madvise: introduce MADV_POPULATE to prefault/prealloc memory Date: Fri, 19 Feb 2021 11:43:48 +0100 Message-ID: <6e5a5bde-cedb-9d0a-f8c1-22406085b6b9@redhat.com> References: <20210217154844.12392-1-david@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613731448; h=from:from: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=/qnTAKaudqj6ibNGsa7QgwKptXTuW5gHmbzgrK/ICxg=; b=AfLxL38byS238BmR8QkdWWQFdnzr+o9b1cT2FR6hWjljtxH8EAOSPiINwRQgE1mo/azwGS f24bEbZV2/9s6QmXUgn+aslZCvqHsbfTGIINoB0WwFHGWy0VGCHgzyC/CKJT2iRy6APs4T smdvCJ1ZVcPjOFRWcN1lLVvOawGvP9w= In-Reply-To: Content-Language: en-US List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Arnd Bergmann , Oscar Salvador , Matthew Wilcox , Andrea Arcangeli , Minchan Kim , Jann Horn , Jason Gunthorpe , Dave Hansen , Hugh Dickins , Rik van Riel , "Michael S . Tsirkin" , "Kirill A . Shutemov" , Vlastimil Babka , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , James E.J. Bottomle On 19.02.21 11:35, Michal Hocko wrote: > On Wed 17-02-21 16:48:44, David Hildenbrand wrote: > [...] > > I only got to the implementation now. > >> +static long madvise_populate(struct vm_area_struct *vma, >> + struct vm_area_struct **prev, >> + unsigned long start, unsigned long end) >> +{ >> + struct mm_struct *mm = vma->vm_mm; >> + unsigned long tmp_end; >> + int locked = 1; >> + long pages; >> + >> + *prev = vma; >> + >> + while (start < end) { >> + /* >> + * We might have temporarily dropped the lock. For example, >> + * our VMA might have been split. >> + */ >> + if (!vma || start >= vma->vm_end) { >> + vma = find_vma(mm, start); >> + if (!vma) >> + return -ENOMEM; >> + } > > Why do you need to find a vma when you already have one. do_madvise will > give you your vma already. I do understand that you want to finish the > vma for some errors but that shouldn't require handling vmas. You should > be in the shope of one here unless I miss anything. See below, we might temporary drop the lock while not having processed all pages > >> + >> + /* Bail out on incompatible VMA types. */ >> + if (vma->vm_flags & (VM_IO | VM_PFNMAP) || >> + !vma_is_accessible(vma)) { >> + return -EINVAL; >> + } >> + >> + /* >> + * Populate pages and take care of VM_LOCKED: simulate user >> + * space access. >> + * >> + * For private, writable mappings, trigger a write fault to >> + * break COW (i.e., shared zeropage). For other mappings (i.e., >> + * read-only, shared), trigger a read fault. >> + */ >> + tmp_end = min_t(unsigned long, end, vma->vm_end); >> + pages = populate_vma_page_range(vma, start, tmp_end, &locked); >> + if (!locked) { >> + mmap_read_lock(mm); >> + *prev = NULL; >> + vma = NULL; ^ here so, the VMA might have been replaced/split/... in the meantime. So to make forward progress, I have to lookup again. (similar. but different to madvise_dontneed_free()). -- Thanks, David / dhildenb