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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0F3E6C433EF for ; Tue, 21 Dec 2021 09:06:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ayt0gCpnryUyYdi0W2WvbFVrUVVILAQTSVQnFdJyV9c=; b=PSpxhNQ/CwKk6JSvKjJ7LWZ/yj qOwetgV4IynHl1TvAxwJChDnkd09OkznuQ7i0BoV3Fqs42BRm+tHmM+8OkmyhuMAYtve8JegRRPYd xk1dvmE+DJj6CnFas74PpwoMXMgvo1i0XOUWJ3Y7+Nnak7+lUHd2l7ozkpOroe5ZYK8TZOqsAV+Z2 +eUqfB6OAYHJg4U0c03Xqq9KCZhhWqle/TcRAG7AItTZQJK2hQNf97UrvuX8X/7PWJvFqhfrn2UEq CJfWP8KhORKXfBLdjVJzXLv4gR+YrlxKQnEDIArXO/Zb7C8jJCJ8jM5aFxfhVwFYAyAMM//WYDXYv PlU26CeQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mzb6k-006226-MN; Tue, 21 Dec 2021 09:06:54 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mzb6h-006205-OJ for linux-nvme@lists.infradead.org; Tue, 21 Dec 2021 09:06:53 +0000 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211221_010651_978168_4914B91B X-CRM114-Status: GOOD ( 13.05 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org 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.