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 X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0712EC2D0DB for ; Fri, 31 Jan 2020 15:25:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD24C206D5 for ; Fri, 31 Jan 2020 15:25:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729089AbgAaPZP convert rfc822-to-8bit (ORCPT ); Fri, 31 Jan 2020 10:25:15 -0500 Received: from mail.fireflyinternet.com ([77.68.26.236]:61171 "EHLO fireflyinternet.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1728839AbgAaPZO (ORCPT ); Fri, 31 Jan 2020 10:25:14 -0500 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 20074443-1500050 for multiple; Fri, 31 Jan 2020 15:24:14 +0000 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT To: "Kirill A. Shutemov" , Andrea Arcangeli , Andrew Morton , Hugh Dickins From: Chris Wilson In-Reply-To: <1426784902-125149-10-git-send-email-kirill.shutemov@linux.intel.com> Cc: Dave Hansen , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , Jerome Marchand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kirill A. Shutemov" References: <1426784902-125149-1-git-send-email-kirill.shutemov@linux.intel.com> <1426784902-125149-10-git-send-email-kirill.shutemov@linux.intel.com> Message-ID: <158048425224.2430.4905670949721797624@skylake-alporthouse-com> User-Agent: alot/0.6 Subject: Re: [PATCH 09/16] page-flags: define PG_reserved behavior on compound pages Date: Fri, 31 Jan 2020 15:24:12 +0000 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Kirill A. Shutemov (2015-03-19 17:08:15) > As far as I can see there's no users of PG_reserved on compound pages. > Let's use NO_COMPOUND here. Much later than you would ever expect, but we just had a user update an ancient device and trip over this. https://gitlab.freedesktop.org/drm/intel/issues/1027 In drm_pci_alloc() we allocate a high-order page (for it to be physically contiguous) and mark each page as Reserved. dmah->vaddr = dma_alloc_coherent(&dev->pdev->dev, size, &dmah->busaddr, GFP_KERNEL | __GFP_COMP); /* XXX - Is virt_to_page() legal for consistent mem? */ /* Reserve */ for (addr = (unsigned long)dmah->vaddr, sz = size; sz > 0; addr += PAGE_SIZE, sz -= PAGE_SIZE) { SetPageReserved(virt_to_page((void *)addr)); } It's been doing that since commit ddf19b973be5a96d77c8467f657fe5bd7d126e0f Author: Dave Airlie Date: Sun Mar 19 18:56:12 2006 +1100 drm: fixup PCI DMA support I haven't found anything to say if we are meant to be reserving the pages or not. So I bring it to your attention, asking for help. Thanks, -Chris