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 7CDD7C00140 for ; Wed, 10 Aug 2022 09:30:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DF2998E0002; Wed, 10 Aug 2022 05:30:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D544A8E0001; Wed, 10 Aug 2022 05:30:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BCD9A8E0002; Wed, 10 Aug 2022 05:30:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id ADCA08E0001 for ; Wed, 10 Aug 2022 05:30:32 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 8910116130F for ; Wed, 10 Aug 2022 09:30:32 +0000 (UTC) X-FDA: 79783162704.01.995C1F1 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by imf12.hostedemail.com (Postfix) with ESMTP id 8327A40185 for ; Wed, 10 Aug 2022 09:30:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1660123831; x=1691659831; h=date:from:to:cc:subject:message-id:reply-to:references: mime-version:in-reply-to; bh=zHygXbTWCyPOJ+4aJpksT5a9YTzKkpyV1mfD/3Fs2Cg=; b=hXTJ1/cRcbwtT4VowGnYl/0GeJsO6cwkz/ZZck6L0EddxhjOELruANSn Mk7UXBsmKPnxeqRSkfwa2h9s1JcvgJ+5bkxUfcKo3vqPJgfJ4sz7l1Gy8 CXRJ0LgUgvA5Tp1XZae3atx24F+Fai47cZ0Oz7LrRbjbvQX6UxitG0cjx VqAcaw93t+0XsnXM1bH9OLUr8kkD3gefFawXQxTEy4TGYVzeJxoEIE7/J Xk+gR6YgiIQI+k9Bz1Gn1CXexWo/oZSg33YoQTgLQWQMeIvMejEasOrLY PVWyNxvPEAkNHMR67eF0LQRhXzx2YYwKj69Z9OhHqDDeEdSk6w8ecbjNQ g==; X-IronPort-AV: E=McAfee;i="6400,9594,10434"; a="316987584" X-IronPort-AV: E=Sophos;i="5.93,227,1654585200"; d="scan'208";a="316987584" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2022 02:30:29 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.93,227,1654585200"; d="scan'208";a="664821304" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.193.75]) by fmsmga008.fm.intel.com with ESMTP; 10 Aug 2022 02:30:18 -0700 Date: Wed, 10 Aug 2022 17:25:32 +0800 From: Chao Peng To: David Hildenbrand Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, linux-kselftest@vger.kernel.org, Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , Michael Roth , mhocko@suse.com, Muchun Song Subject: Re: [PATCH v7 04/14] mm/shmem: Support memfile_notifier Message-ID: <20220810092532.GD862421@chaop.bj.intel.com> Reply-To: Chao Peng References: <20220706082016.2603916-1-chao.p.peng@linux.intel.com> <20220706082016.2603916-5-chao.p.peng@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660123832; h=from:from:sender:reply-to: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UiFYGladr01Gf00GrRFlWk7AOFz8ih9is3vYJiMEWNA=; b=PKMXfBx8dxk9x/gAhNI/W5tZqSwv71QelZDQbgIgCbYjfjLyRK44uFNLMvVE7NTIqBcuQe 0w9EkUvOjJlNmJqg7RAH8wkL1VYnp6eTZpSx6RQDrao66Xsap6PYg2o26yOq2+h9PAcpkq w1Idv0TZPFuq4mp9Rg2FYJpRXd/Z6Ek= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b="hXTJ1/cR"; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none); spf=none (imf12.hostedemail.com: domain of chao.p.peng@linux.intel.com has no SPF policy when checking 192.55.52.88) smtp.mailfrom=chao.p.peng@linux.intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660123832; a=rsa-sha256; cv=none; b=IkKDgVW/GMQd76zAo8XqZwx5UriNuPyyDhpC5YdlhoJ++N014ddV2Tp472x0R+T4DFHiUr vXRU99pxypY6zF5ufx4dx+5HsEsHXFN3k3VAEXlxrb0V8Gp+urBg7W4Ge5b0ZwslbhPb5x LdRge0r0RJR1BtwAz3/59xdJ89CTl7w= X-Rspamd-Queue-Id: 8327A40185 X-Rspamd-Server: rspam03 X-Rspam-User: Authentication-Results: imf12.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b="hXTJ1/cR"; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none); spf=none (imf12.hostedemail.com: domain of chao.p.peng@linux.intel.com has no SPF policy when checking 192.55.52.88) smtp.mailfrom=chao.p.peng@linux.intel.com X-Stat-Signature: gigaa47zbum9xx7wpgedpy5tthz9k8nw X-HE-Tag: 1660123831-467474 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, Aug 05, 2022 at 03:26:02PM +0200, David Hildenbrand wrote: > On 06.07.22 10:20, Chao Peng wrote: > > From: "Kirill A. Shutemov" > > > > Implement shmem as a memfile_notifier backing store. Essentially it > > interacts with the memfile_notifier feature flags for userspace > > access/page migration/page reclaiming and implements the necessary > > memfile_backing_store callbacks. > > > > Signed-off-by: Kirill A. Shutemov > > Signed-off-by: Chao Peng > > --- > > [...] > > > +#ifdef CONFIG_MEMFILE_NOTIFIER > > +static struct memfile_node *shmem_lookup_memfile_node(struct file *file) > > +{ > > + struct inode *inode = file_inode(file); > > + > > + if (!shmem_mapping(inode->i_mapping)) > > + return NULL; > > + > > + return &SHMEM_I(inode)->memfile_node; > > +} > > + > > + > > +static int shmem_get_pfn(struct file *file, pgoff_t offset, pfn_t *pfn, > > + int *order) > > +{ > > + struct page *page; > > + int ret; > > + > > + ret = shmem_getpage(file_inode(file), offset, &page, SGP_WRITE); > > + if (ret) > > + return ret; > > + > > + unlock_page(page); > > + *pfn = page_to_pfn_t(page); > > + *order = thp_order(compound_head(page)); > > + return 0; > > +} > > + > > +static void shmem_put_pfn(pfn_t pfn) > > +{ > > + struct page *page = pfn_t_to_page(pfn); > > + > > + if (!page) > > + return; > > + > > + put_page(page); > > > Why do we export shmem_get_pfn/shmem_put_pfn and not simply > > get_folio() > > and let the caller deal with putting the folio? What's the reason to > > a) Operate on PFNs and not folios > b) Have these get/put semantics? We have a design assumption that somedays this can even support non-page based backing stores. There are some discussions: https://lkml.org/lkml/2022/3/28/1440 I should add document for this two callbacks. > > > +} > > + > > +static struct memfile_backing_store shmem_backing_store = { > > + .lookup_memfile_node = shmem_lookup_memfile_node, > > + .get_pfn = shmem_get_pfn, > > + .put_pfn = shmem_put_pfn, > > +}; > > +#endif /* CONFIG_MEMFILE_NOTIFIER */ > > + > > void __init shmem_init(void) > > { > > int error; > > @@ -3956,6 +4059,10 @@ void __init shmem_init(void) > > else > > shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */ > > #endif > > + > > +#ifdef CONFIG_MEMFILE_NOTIFIER > > + memfile_register_backing_store(&shmem_backing_store); > > Can we instead prove a dummy function that does nothing without > CONFIG_MEMFILE_NOTIFIER? Sounds good. Chao > > > +#endif > > return; > > > > out1: > > > -- > Thanks, > > David / dhildenb >