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 32A41C433EF for ; Thu, 17 Feb 2022 13:23:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9EF0C6B0074; Thu, 17 Feb 2022 08:23:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 977646B0075; Thu, 17 Feb 2022 08:23:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 81B726B0078; Thu, 17 Feb 2022 08:23:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0080.hostedemail.com [216.40.44.80]) by kanga.kvack.org (Postfix) with ESMTP id 6E51B6B0074 for ; Thu, 17 Feb 2022 08:23:56 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 18F081808E68F for ; Thu, 17 Feb 2022 13:23:56 +0000 (UTC) X-FDA: 79152339672.10.0BC7A90 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by imf07.hostedemail.com (Postfix) with ESMTP id 2547E40004 for ; Thu, 17 Feb 2022 13:23:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1645104235; x=1676640235; h=date:from:to:cc:subject:message-id:reply-to:references: mime-version:in-reply-to; bh=7ROqYA+WyEzn2lj20W8JxFtIkCz3sbVl7IBm5h9FArM=; b=MoOop8v/bXA6BgNHHeAiAZFObqeyH7uFMIxYajWump+w5BEZztdhNzAU u3m/igMV2uytdcTaNrPZYkZv6tEpVnvA4kO4m+CNoAdvcjwTIdyq3G3Nt Ghc2Ko0XkSmoKWqXSK/686B6cGZekmHgzFY7TAn5smlKyNoIqyK8DKP1V jPnu9LfFLpC0lmcQHP3Bqo6pXMZJKjDbFaKhedahDHp8kQPvt77oOo1/y 1WYrWXTxfaTRlPXxR5q/hK58FQBtuQyRTEyoq7AjpFLbEDi/UiylYEbEw XtGe3eU68dQtcF1TS8RSGTkG1euSPWyDHozK0c2ue1eh9ZM4ph/mNWELF A==; X-IronPort-AV: E=McAfee;i="6200,9189,10260"; a="234401750" X-IronPort-AV: E=Sophos;i="5.88,375,1635231600"; d="scan'208";a="234401750" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Feb 2022 05:23:53 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,375,1635231600"; d="scan'208";a="681959596" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.192.101]) by fmsmga001.fm.intel.com with ESMTP; 17 Feb 2022 05:23:47 -0800 Date: Thu, 17 Feb 2022 21:23:25 +0800 From: Chao Peng To: Andy Lutomirski Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, qemu-devel@nongnu.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 , Yu Zhang , "Kirill A . Shutemov" , jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com Subject: Re: [PATCH v4 04/12] mm/shmem: Support memfile_notifier Message-ID: <20220217132325.GD32679@chaop.bj.intel.com> Reply-To: Chao Peng References: <20220118132121.31388-1-chao.p.peng@linux.intel.com> <20220118132121.31388-5-chao.p.peng@linux.intel.com> <314affa4-fbcb-2cb9-deb7-f61a2ac99260@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <314affa4-fbcb-2cb9-deb7-f61a2ac99260@kernel.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2547E40004 X-Stat-Signature: fx5udb8s496dtwrt4aj4q8j3pa4creof Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b="MoOop8v/"; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf07.hostedemail.com: domain of chao.p.peng@linux.intel.com has no SPF policy when checking 134.134.136.126) smtp.mailfrom=chao.p.peng@linux.intel.com X-HE-Tag: 1645104234-85006 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, Feb 11, 2022 at 03:40:09PM -0800, Andy Lutomirski wrote: > On 1/18/22 05:21, Chao Peng wrote: > > It maintains a memfile_notifier list in shmem_inode_info structure and > > implements memfile_pfn_ops callbacks defined by memfile_notifier. It > > then exposes them to memfile_notifier via > > shmem_get_memfile_notifier_info. > > > > We use SGP_NOALLOC in shmem_get_lock_pfn since the pages should be > > allocated by userspace for private memory. If there is no pages > > allocated at the offset then error should be returned so KVM knows that > > the memory is not private memory. > > > > Signed-off-by: Kirill A. Shutemov > > Signed-off-by: Chao Peng > > > static int memfile_get_notifier_info(struct inode *inode, > > struct memfile_notifier_list **list, > > struct memfile_pfn_ops **ops) > > { > > - return -EOPNOTSUPP; > > + int ret = -EOPNOTSUPP; > > +#ifdef CONFIG_SHMEM > > + ret = shmem_get_memfile_notifier_info(inode, list, ops); > > +#endif > > + return ret; > > } > > > +int shmem_get_memfile_notifier_info(struct inode *inode, > > + struct memfile_notifier_list **list, > > + struct memfile_pfn_ops **ops) > > +{ > > + struct shmem_inode_info *info; > > + > > + if (!shmem_mapping(inode->i_mapping)) > > + return -EINVAL; > > + > > + info = SHMEM_I(inode); > > + *list = &info->memfile_notifiers; > > + if (ops) > > + *ops = &shmem_pfn_ops; > > + > > + return 0; > > I can't wrap my head around exactly who is supposed to call these functions > and when, but there appears to be a missing check that the inode is actually > a shmem inode. > > What is this code trying to do? It's very abstract. This is to be called by memfile_(un)register_notifier in patch-03 to allow shmem to be connected to memfile_notifer. But as Mike pointed out, probably introducing a memfile_notifier_register_backing_store() sounds better so backing store (e.g. shmem) can register itself to memfile_notifier. Chao