Received: by 2002:a25:1985:0:0:0:0:0 with SMTP id 127csp32354ybz; Tue, 21 Apr 2020 14:35:26 -0700 (PDT) X-Google-Smtp-Source: APiQypIJNuIu2EtpUrI/pt97u9isIygnwHNFLWMwJ240Aq3/Dfr6eszUs8VicIGqPwZKIJmw8Rqa X-Received: by 2002:a17:906:1ec3:: with SMTP id m3mr4592103ejj.88.1587504925875; Tue, 21 Apr 2020 14:35:25 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1587504925; cv=none; d=google.com; s=arc-20160816; b=lyRy8hKbB1AuAWXccVR50Vf0q/s/XHTIeRWjWlLRPfKgMpZaKsWIqMGEPab3ron10W DmE8JnXj4b1u7bHUJYgUIl4HPC0QEIHXW0O2TT3WfbaW8ls8cBcVEHw7MSip2/NTzYIW Y3K5DRJTNw61tT+HTKbKGkrewIGjW/TwBIZgl1p0EG7znY4bMoFYE2kGOxOYRHfVX66y b3sgZQ57EeqSdvdNeTj2bbTJnrZl4Wms2i5M47sDcz7LCmomiskRFa8Zkf/wFOmLmU4Y Xcs+OEgxg5qkPw0jjF0ixfNnFiCRoF+VPpBL9c9zm71KEn0OEfCTaXRPx/rRJ0RExkbA xlRQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding :content-language:in-reply-to:mime-version:user-agent:date :message-id:autocrypt:openpgp:references:cc:to:from:subject :ironport-sdr:ironport-sdr; bh=L7kjnFQU91BRpWxoktrP2BrsUGEj45iHyS4z5P+Hzkk=; b=pJSnP6rYSGdccNWGVjKD6i8SMHEfoTH/54rP1wq2rzmXDUJouMkdgb7z2dfPBX/JZ8 aY6+wCyEWKrnkKecC/FHFlGBXnj9ERP3o4w6hVkEAyIwZtrra7ehvyYYhc0uGQlasJ2c J4/G+cSBZMHwJLnSwPA8MFFQtwPcJrdg3u5z1zdXYAqpRFrlzYxpovubT2u0JFJ6LAlN /h/4TFhdINFktmlWGjjXez0MVSNWt+Bre9p5BfszFhp6SMvnQyA5WGdZGzv3P4ku9cwx Z4NSZThccb4nmJh4sp8RKQUoJ8KQGRMSs11Dxfm4gri5FNDWg7XQtxLE11LssuN54Q4e FNZA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id z14si2434881ejp.19.2020.04.21.14.35.02; Tue, 21 Apr 2020 14:35:25 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726415AbgDUVb3 (ORCPT + 99 others); Tue, 21 Apr 2020 17:31:29 -0400 Received: from mga06.intel.com ([134.134.136.31]:6255 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725850AbgDUVb2 (ORCPT ); Tue, 21 Apr 2020 17:31:28 -0400 IronPort-SDR: yaYxE/S3DvKhjz2VR80Cy2FBsuaKAnsQV95xfv1bh0Pul+L8CFBBcGxUI6vk8+pUcmCYPynZfD TLS7r4NJ6WMA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Apr 2020 14:31:27 -0700 IronPort-SDR: yu9wFQzmjUr5k9T4LttPFzX/986E+PU+0a2JvT1wc9VuuuSsTWryGQrFmD97RqGr6r+sipYwfo +NRT7opDs6tA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,411,1580803200"; d="scan'208";a="258849293" Received: from rpiazzo-mobl.amr.corp.intel.com (HELO [10.254.108.210]) ([10.254.108.210]) by orsmga006.jf.intel.com with ESMTP; 21 Apr 2020 14:31:25 -0700 Subject: Re: [PATCH v4 2/2] mm/gup/writeback: add callbacks for inaccessible pages From: Dave Hansen To: Claudio Imbrenda Cc: Peter Zijlstra , Andy Lutomirski , linux-next@vger.kernel.org, akpm@linux-foundation.org, jack@suse.cz, kirill@shutemov.name, "Edgecombe, Rick P" , Sean Christopherson , borntraeger@de.ibm.com, david@redhat.com, aarcange@redhat.com, linux-mm@kvack.org, frankja@linux.ibm.com, sfr@canb.auug.org.au, jhubbard@nvidia.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Will Deacon , "Williams, Dan J" References: <20200306132537.783769-1-imbrenda@linux.ibm.com> <20200306132537.783769-3-imbrenda@linux.ibm.com> <3ae46945-0c7b-03cd-700a-a6fe8003c6ab@intel.com> <20200415221754.GM2483@worktop.programming.kicks-ass.net> <20200416141547.29be5ea0@p-imbrenda> <20200416165900.68bd4dba@p-imbrenda> <20200416183431.7216e1d1@p-imbrenda> <396a4ece-ec66-d023-2c7e-f09f84b358bc@intel.com> Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; keydata= mQINBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABtEVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT6JAjgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lcuQINBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABiQIfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y Message-ID: Date: Tue, 21 Apr 2020 14:31:28 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <396a4ece-ec66-d023-2c7e-f09f84b358bc@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/16/20 12:02 PM, Dave Hansen wrote: > On 4/16/20 9:34 AM, Claudio Imbrenda wrote: >>> Ahh, so this is *just* intended to precede I/O done on the page, when >>> a non-host entity is touching the memory? >> yep > OK, so we've got to do an action that precedes *all* I/O to a page. > That's not too bad. > > I still don't understand how this could work generally, though There > are lots of places where I/O is done to a page without either going > through __test_set_page_writeback() or gup() with FOLL_PIN set. > > sendfile() is probably the best example of this: > > fd = open("/normal/ext4/file", O_RDONLY); > sendfile(socket_fd, fd, &off, count); > > There's no gup in sight since the file doesn't have an address and it's > not being written to so there's no writeback. > > How does sendfile work? Did you manage to see if sendfile works (or any other operation that DMAs file-backed data without being preceded by a gup)? I suspect it's actually not that hard to fix. As long as you have a dma_ops for the devices in question either via dev->dma_ops or you add an s390 get_arch_vm_ops(), you can fix *all* the DMA sites, sendfile() included. BTW, device drivers do need to know how to use the DMA mapping API. If s390 has drivers that need to be updated, I think that's vastly preferable to incomplete hooks in core mm code.