Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934388AbdDFRZn (ORCPT ); Thu, 6 Apr 2017 13:25:43 -0400 Received: from mail-io0-f172.google.com ([209.85.223.172]:32868 "EHLO mail-io0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934333AbdDFRZf (ORCPT ); Thu, 6 Apr 2017 13:25:35 -0400 Subject: Re: [PATCH] staging: android: ashmem: lseek failed due to no FMODE_LSEEK. To: Greg KH References: <1491489029-11052-1-git-send-email-zhangshuxiaomi@gmail.com> <94155867-d589-6451-2f3b-a960df559702@google.com> <20170406170813.GA29139@kroah.com> Cc: zhangshuxiaomi@gmail.com, arve@android.com, riandrews@android.com, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, zhangshuxiao From: Greg Hackmann Message-ID: <580f0656-7420-ef29-a4ac-bd376d3faf5a@google.com> Date: Thu, 6 Apr 2017 10:25:32 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170406170813.GA29139@kroah.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1732 Lines: 49 On 04/06/2017 10:08 AM, Greg KH wrote: > On Thu, Apr 06, 2017 at 08:30:40AM -0700, Greg Hackmann wrote: >> On 04/06/2017 07:30 AM, zhangshuxiaomi@gmail.com wrote: >>> From: zhangshuxiao >>> >>> vfs_llseek will check whether the file mode has >>> FMODE_LSEEK, no return failure. But ashmem can be >>> lseek, so add FMODE_LSEEK to ashmem file. >>> >>> Signed-off-by: Shuxiao Zhang >>> Tested-by: Greg Hackmann >>> --- >>> drivers/staging/android/ashmem.c | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c >>> index 3f11332..e4530ac 100644 >>> --- a/drivers/staging/android/ashmem.c >>> +++ b/drivers/staging/android/ashmem.c >>> @@ -392,6 +392,7 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) >>> ret = PTR_ERR(vmfile); >>> goto out; >>> } >>> + vmfile->f_mode |= FMODE_LSEEK; >>> asma->file = vmfile; >>> } >>> get_file(asma->file); >>> >> >> This commit message is missing some important context. >> >> ashmem_llseek() passes the llseek() call through to the backing shmem file. >> 91360b02ab48 ("ashmem: use vfs_llseek()") changed this from directly calling >> the file's llseek() op into a VFS layer call. This also adds a check for >> the FMODE_LSEEK bit, so without that bit ashmem_llseek() now always fails >> with -ESPIPE. >> >> I've tested that this patch fixes the regression on both hikey running AOSP >> and User Mode Linux running Debian. > > Thanks for letting me know, I'll update the changelog a bit. How far > back does this patch need to go in stable kernel releases? > > thanks, > > greg k-h > 3.18 and later.