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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 C78FBC04AAF for ; Mon, 20 May 2019 09:22:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A839420675 for ; Mon, 20 May 2019 09:22:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731132AbfETJWZ (ORCPT ); Mon, 20 May 2019 05:22:25 -0400 Received: from mx2.suse.de ([195.135.220.15]:38788 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729598AbfETJWZ (ORCPT ); Mon, 20 May 2019 05:22:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 07D5DAF5F; Mon, 20 May 2019 09:22:24 +0000 (UTC) Message-ID: <1558343365.12672.2.camel@suse.com> Subject: Re: [RFC PATCH] usb: host: xhci: allow __GFP_FS in dma allocation From: Oliver Neukum To: Christoph Hellwig , Jaewon Kim Cc: linux-mm@kvack.org, gregkh@linuxfoundation.org, Jaewon Kim , m.szyprowski@samsung.com, ytk.lee@samsung.com, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Date: Mon, 20 May 2019 11:09:25 +0200 In-Reply-To: <20190520055657.GA31866@infradead.org> References: <20190520055657.GA31866@infradead.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On So, 2019-05-19 at 22:56 -0700, Christoph Hellwig wrote: > Folks, you can't just pass arbitary GFP_ flags to dma allocation > routines, beause very often they are not just wrappers around > the page allocator. > > So no, you can't just fine grained control the flags, but the > existing code is just as buggy. > > Please switch to use memalloc_noio_save() instead. > Hi, we actually do. It is just higher up in the calling path: int usb_reset_device(struct usb_device *udev) { int ret; int i; unsigned int noio_flag; struct usb_port *port_dev; struct usb_host_config *config = udev->actconfig; struct usb_hub *hub = usb_hub_to_struct_hub(udev->parent); if (udev->state == USB_STATE_NOTATTACHED || udev->state == USB_STATE_SUSPENDED) { dev_dbg(&udev->dev, "device reset not allowed in state %d\n", udev->state); return -EINVAL; } if (!udev->parent) { /* this requires hcd-specific logic; see ohci_restart() */ dev_dbg(&udev->dev, "%s for root hub!\n", __func__); return -EISDIR; } port_dev = hub->ports[udev->portnum - 1]; /* * Don't allocate memory with GFP_KERNEL in current * context to avoid possible deadlock if usb mass * storage interface or usbnet interface(iSCSI case) * is included in current configuration. The easist * approach is to do it for every device reset, * because the device 'memalloc_noio' flag may have * not been set before reseting the usb device. */ noio_flag = memalloc_noio_save(); So, do we need to audit the mem_flags again? What are we supposed to use? GFP_KERNEL? Regards Oliver