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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F12F6C7EE2A for ; Wed, 10 May 2023 14:38:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237423AbjEJOiw (ORCPT ); Wed, 10 May 2023 10:38:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42768 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237117AbjEJOiu (ORCPT ); Wed, 10 May 2023 10:38:50 -0400 Received: from netrider.rowland.org (netrider.rowland.org [192.131.102.5]) by lindbergh.monkeyblade.net (Postfix) with SMTP id 2EE0A268E for ; Wed, 10 May 2023 07:38:49 -0700 (PDT) Received: (qmail 623646 invoked by uid 1000); 10 May 2023 10:38:48 -0400 Date: Wed, 10 May 2023 10:38:48 -0400 From: Alan Stern To: Ruihan Li Cc: linux-mm@kvack.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Pasha Tatashin , David Hildenbrand , Matthew Wilcox , Andrew Morton , Christoph Hellwig , Greg Kroah-Hartman , stable@vger.kernel.org Subject: Re: [PATCH 2/4] usb: usbfs: Use consistent mmap functions Message-ID: References: <20230510085527.57953-1-lrh2000@pku.edu.cn> <20230510085527.57953-3-lrh2000@pku.edu.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230510085527.57953-3-lrh2000@pku.edu.cn> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 10, 2023 at 04:55:25PM +0800, Ruihan Li wrote: > When hcd->localmem_pool is non-null, it is used to allocate DMA memory. > In this case, the dma address will be properly returned (in dma_handle), > and dma_mmap_coherent should be used to map this memory into the user > space. However, the current implementation uses pfn_remap_range, which > is supposed to map normal pages (instead of DMA pages). > > Instead of repeating the logic in the memory allocation function, this > patch introduces a more robust solution. To address the previous issue, > this patch checks the type of allocated memory by testing whether > dma_handle is properly set. If dma_handle is properly returned, it means > some DMA pages are allocated and dma_mmap_coherent should be used to map > them. Otherwise, normal pages are allocated and pfn_remap_range should > be called. This ensures that the correct mmap functions are used > consistently, independently with logic details that determine which type > of memory gets allocated. > > Fixes: a0e710a7def4 ("USB: usbfs: fix mmap dma mismatch") > Cc: stable@vger.kernel.org > Signed-off-by: Ruihan Li > --- > drivers/usb/core/devio.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c > index b4cf9e860..5067030b7 100644 > --- a/drivers/usb/core/devio.c > +++ b/drivers/usb/core/devio.c > @@ -235,7 +235,7 @@ static int usbdev_mmap(struct file *file, struct vm_area_struct *vma) > size_t size = vma->vm_end - vma->vm_start; > void *mem; > unsigned long flags; > - dma_addr_t dma_handle; > + dma_addr_t dma_handle = DMA_MAPPING_ERROR; > int ret; > > ret = usbfs_increase_memory_usage(size + sizeof(struct usb_memory)); > @@ -265,7 +265,13 @@ static int usbdev_mmap(struct file *file, struct vm_area_struct *vma) > usbm->vma_use_count = 1; > INIT_LIST_HEAD(&usbm->memlist); > > - if (hcd->localmem_pool || !hcd_uses_dma(hcd)) { > + /* In DMA-unavailable cases, hcd_buffer_alloc_pages allocates > + * normal pages and assigns DMA_MAPPING_ERROR to dma_handle. Check > + * whether we are in such cases, and then use remap_pfn_range (or > + * dma_mmap_coherent) to map normal (or DMA) pages into the user > + * space, respectively. > + */ Another stylistic issue. For multi-line comments, the format we use is: /* * Blah, blah, blah * Blah, blah, blah */ Alan Stern