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s=arc-20220608; d=hostedemail.com; t=1683729529; a=rsa-sha256; cv=none; b=F/hfERhj6d8B1pSNGfCjAVrGmV1pbEQbu80EBrSlqruhO+XZUtpMEcVS0h+gPqtuNVAOqz u7yCG1cXjDxQGl8TVVe2eiy6RENF0VjEuN4v+XKiHUuq3tyF5VImrOnUcx4WmY0ha0m6sT Gu9o2rIGaS0avjMCBDLbnnJrsXtfNNU= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=none; spf=pass (imf25.hostedemail.com: domain of stern+6456d096@netrider.rowland.org designates 192.131.102.5 as permitted sender) smtp.mailfrom=stern+6456d096@netrider.rowland.org; dmarc=none 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> X-Rspamd-Queue-Id: 78C3AA000C X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: aker9jbrg4up58d8ss33o9h4aj9ng7zt X-HE-Tag: 1683729529-186153 X-HE-Meta: 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 4B+BYAdD vLaa2ZfsDz0a7DOi8KxWwSRSAWttEV1pA2kTzDpl8uYxsLPyk3JikyVLRNx1nNJL5iaDOAXsTSc7W4ZOm8vSMGUvF3Fe7nDbLvfYbzGVXCiEMqgFbnG7GcoxY4ziVS9mhtyVSH4PT8MdL7Eo9+ekUduDX8qMQRjwfnjJLzc+NtGv175cQRCqlyX1PWjfcSsS1OSqzSjy9MFODVAGqVJ4K6beU8nS1RCN0RJvJImFR2GNmUbO6m0+m4w3Z7rkTufPQ0uzlD7X5Nn9v+7e6dvdHcWPMuw== 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, 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