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 0FCBEC433EF for ; Tue, 21 Dec 2021 09:06:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A0DFA6B0073; Tue, 21 Dec 2021 04:06:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9BD376B0074; Tue, 21 Dec 2021 04:06:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 885D96B0075; Tue, 21 Dec 2021 04:06:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0165.hostedemail.com [216.40.44.165]) by kanga.kvack.org (Postfix) with ESMTP id 791526B0073 for ; Tue, 21 Dec 2021 04:06:52 -0500 (EST) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 38C3E180EB6FE for ; Tue, 21 Dec 2021 09:06:52 +0000 (UTC) X-FDA: 78941221464.12.EBD53F0 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf24.hostedemail.com (Postfix) with ESMTP id 642CE180022 for ; Tue, 21 Dec 2021 09:06:47 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id C06A968B05; Tue, 21 Dec 2021 10:06:48 +0100 (CET) Date: Tue, 21 Dec 2021 10:06:48 +0100 From: Christoph Hellwig To: Logan Gunthorpe Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , Christian =?iso-8859-1?Q?K=F6nig?= , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy , Martin Oliveira , Chaitanya Kulkarni Subject: Re: [PATCH v4 21/23] mm: use custom page_free for P2PDMA pages Message-ID: <20211221090648.GE7949@lst.de> References: <20211117215410.3695-1-logang@deltatee.com> <20211117215410.3695-22-logang@deltatee.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211117215410.3695-22-logang@deltatee.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Queue-Id: 642CE180022 X-Stat-Signature: 4pqfu547wpstwwpsthexzziiktt5y9ei Authentication-Results: imf24.hostedemail.com; dkim=none; dmarc=none; spf=none (imf24.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de X-Rspamd-Server: rspam11 X-HE-Tag: 1640077607-245552 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 Wed, Nov 17, 2021 at 02:54:08PM -0700, Logan Gunthorpe wrote: > When P2PDMA pages are passed to userspace, they will need to be > reference counted properly and returned to their genalloc after their > reference count returns to 1. This is accomplished with the existing > DEV_PAGEMAP_OPS and the .page_free() operation. > > Change CONFIG_P2PDMA to select CONFIG_DEV_PAGEMAP_OPS and add > MEMORY_DEVICE_PCI_P2PDMA to page_is_devmap_managed(), > devmap_managed_enable_[put|get]() and free_devmap_managed_page(). Uuuh. We are trying hard to kill off this magic free at refcount 1 behavior in the amdgpu device coherent series. We really should not add more of this.