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=-7.4 required=3.0 tests=DATE_IN_PAST_06_12, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 7223FC43381 for ; Mon, 25 Mar 2019 16:43:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3996020863 for ; Mon, 25 Mar 2019 16:43:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3996020863 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C30826B0003; Mon, 25 Mar 2019 12:43:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BDFB46B0006; Mon, 25 Mar 2019 12:43:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A80B06B0007; Mon, 25 Mar 2019 12:43:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) by kanga.kvack.org (Postfix) with ESMTP id 63C606B0003 for ; Mon, 25 Mar 2019 12:43:50 -0400 (EDT) Received: by mail-pg1-f200.google.com with SMTP id 73so9834756pga.18 for ; Mon, 25 Mar 2019 09:43:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:date:from:to :cc:subject:message-id:references:mime-version:content-disposition :in-reply-to:user-agent; bh=Pa6nZS3K5nnS9y06L6oLI0n+uD+p/+Diqto8nrQGBog=; b=sU8x3C994NfdrlZFJcedVEh5/QomuT+G1NXz9ggmlqGbJSmqa/zN0iog08Qdw7Gj8n lFoADfi0BDgjYhbLXo6v5qBE1wliLI0GIn3J8Z7y9LjUdepXHHCPyfWTYDQvzqBZoVb+ m6nkcNc+RtSPLrw84PdaXS+bMvLMTeUAzu+amPnEhtDOP3R/Rcto/OSt+Tg3jOKWOIiU G7ZsoerFFn3Z1olQZMV7Ek3xxzXbkT26B1KSDak31/OuP2Zk3qcDRUFYOqP7qQBUEDBp 4t/DdcUdITeXWIX7zeboo5+U09YQITE77N9uweezNaHlRXSeZQPZMuHLnib5Y/WpwgXM xrCw== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Gm-Message-State: APjAAAX17cRhXiVeUvXWsssx6x4Jf0bYvKzjC8RbvCIpNBaKuridGpwM 3zfvbsTvew6SbAVTAT7PWSESS91RvlSlgYP8od+t00gHAS1HmAEObEpbNGEOkAHwKypFejcleo8 01K7Ld7Zki8k+L3VYAU5AGdLjF7FDAxBT6dkrFhG4hPD6SWdR3+OXvUs34I9rD+1h3A== X-Received: by 2002:a17:902:690a:: with SMTP id j10mr26497593plk.103.1553532230032; Mon, 25 Mar 2019 09:43:50 -0700 (PDT) X-Google-Smtp-Source: APXvYqxIBnElVcgwmyd9MfZRmMErdBK6Rm5j6lgVwera0+10uVP/2/VhtuiQsXLw/WGiIqVwvK08 X-Received: by 2002:a17:902:690a:: with SMTP id j10mr26497532plk.103.1553532229235; Mon, 25 Mar 2019 09:43:49 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1553532229; cv=none; d=google.com; s=arc-20160816; b=DEWK+Xh6R/g/dulicPaOxoifo8WhbPCgBxCCAg1bLUjCVZ+eF383QEyWFG0qPx27kW kMq4J0LRPUUIpSUtgv/k1PcjvEs8MqU840MGWVd3G4qtxSDE5Q+m+Y1K8YQHtmPxwwji w30wQympONblbwd0nek1yZwgs2NARM+P1vgjtA4YNLzyKWceW44bDZnkJFhsUoC7OC7M IoBPfOFAHfEHvBtormzr3+/yc3YYzGsxKFflkx9kJtJ1mtmnqnAgTMbjdE5USzTdzCTr vXdMjstSd6A1hXSSGpxPpR/ajAtlkDc/77j/pIufyyJJgG+wTLL3VML+r4HlKH4108hl FUsQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date; bh=Pa6nZS3K5nnS9y06L6oLI0n+uD+p/+Diqto8nrQGBog=; b=yhwgPHqtXzdp07vMuOzRdTrEfclPTh3DET50FNb0NY1ABBQWsA9TeMG5/6qr8Cki3P +vsWMfTJhkdftxdjhpLoYJKNih2skY3S7OKdbUXruUWQSMB6TtTK1MOPmMz5birhrikY xlCBJYz3FyN/T7kNIIhwx8RXuahkxa1o0l+34hL2OvUZkmdTRdgXchmrPpMrtPVLwIv/ xChWNpoyWka1KHaN6lcx8cveHFPwCHrgx5l0swP423QUVSJESClRRwJKjgaNpIXDOsNO jcru5ELc5E+Oah6UL5EPeepJuxcYCRNsiwi6nAmYovFsJ2pjbclbTJw9vMuGuWTDtgIR 7kIA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTPS id r17si9787270pgm.52.2019.03.25.09.43.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 25 Mar 2019 09:43:49 -0700 (PDT) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.88 as permitted sender) client-ip=192.55.52.88; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Mar 2019 09:43:40 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,269,1549958400"; d="scan'208";a="143686285" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by FMSMGA003.fm.intel.com with ESMTP; 25 Mar 2019 09:43:37 -0700 Date: Mon, 25 Mar 2019 01:42:26 -0700 From: Ira Weiny To: Dan Williams Cc: Andrew Morton , John Hubbard , Michal Hocko , "Kirill A. Shutemov" , Peter Zijlstra , Jason Gunthorpe , Benjamin Herrenschmidt , Paul Mackerras , "David S. Miller" , Martin Schwidefsky , Heiko Carstens , Rich Felker , Yoshinori Sato , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Ralf Baechle , James Hogan , linux-mm , Linux Kernel Mailing List , linux-mips@vger.kernel.org, linuxppc-dev , linux-s390 , Linux-sh , sparclinux@vger.kernel.org, linux-rdma@vger.kernel.org, "netdev@vger.kernel.org" Subject: Re: [RESEND 4/7] mm/gup: Add FOLL_LONGTERM capability to GUP fast Message-ID: <20190325084225.GC16366@iweiny-DESK2.sc.intel.com> References: <20190317183438.2057-1-ira.weiny@intel.com> <20190317183438.2057-5-ira.weiny@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1 (2018-12-01) 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 Fri, Mar 22, 2019 at 03:12:55PM -0700, Dan Williams wrote: > On Sun, Mar 17, 2019 at 7:36 PM wrote: > > > > From: Ira Weiny > > > > DAX pages were previously unprotected from longterm pins when users > > called get_user_pages_fast(). > > > > Use the new FOLL_LONGTERM flag to check for DEVMAP pages and fall > > back to regular GUP processing if a DEVMAP page is encountered. > > > > Signed-off-by: Ira Weiny > > --- > > mm/gup.c | 29 +++++++++++++++++++++++++---- > > 1 file changed, 25 insertions(+), 4 deletions(-) > > > > diff --git a/mm/gup.c b/mm/gup.c > > index 0684a9536207..173db0c44678 100644 > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -1600,6 +1600,9 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, > > goto pte_unmap; > > > > if (pte_devmap(pte)) { > > + if (unlikely(flags & FOLL_LONGTERM)) > > + goto pte_unmap; > > + > > pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); > > if (unlikely(!pgmap)) { > > undo_dev_pagemap(nr, nr_start, pages); > > @@ -1739,8 +1742,11 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, > > if (!pmd_access_permitted(orig, flags & FOLL_WRITE)) > > return 0; > > > > - if (pmd_devmap(orig)) > > + if (pmd_devmap(orig)) { > > + if (unlikely(flags & FOLL_LONGTERM)) > > + return 0; > > return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr); > > + } > > > > refs = 0; > > page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > > @@ -1777,8 +1783,11 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, > > if (!pud_access_permitted(orig, flags & FOLL_WRITE)) > > return 0; > > > > - if (pud_devmap(orig)) > > + if (pud_devmap(orig)) { > > + if (unlikely(flags & FOLL_LONGTERM)) > > + return 0; > > return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr); > > + } > > > > refs = 0; > > page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > > @@ -2066,8 +2075,20 @@ int get_user_pages_fast(unsigned long start, int nr_pages, > > start += nr << PAGE_SHIFT; > > pages += nr; > > > > - ret = get_user_pages_unlocked(start, nr_pages - nr, pages, > > - gup_flags); > > + if (gup_flags & FOLL_LONGTERM) { > > + down_read(¤t->mm->mmap_sem); > > + ret = __gup_longterm_locked(current, current->mm, > > + start, nr_pages - nr, > > + pages, NULL, gup_flags); > > + up_read(¤t->mm->mmap_sem); > > + } else { > > + /* > > + * retain FAULT_FOLL_ALLOW_RETRY optimization if > > + * possible > > + */ > > + ret = get_user_pages_unlocked(start, nr_pages - nr, > > + pages, gup_flags); > > I couldn't immediately grok why this path needs to branch on > FOLL_LONGTERM? Won't get_user_pages_unlocked(..., FOLL_LONGTERM) do > the right thing? Unfortunately holding the lock is required to support FOLL_LONGTERM (to check the VMAs) but we don't want to hold the lock to be optimal (specifically allow FAULT_FOLL_ALLOW_RETRY). So I'm maintaining the optimization for *_fast users who do not specify FOLL_LONGTERM. Another way to do this would have been to define __gup_longterm_unlocked with the above logic, but that seemed overkill at this point. Ira