From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757928Ab1COOBo (ORCPT ); Tue, 15 Mar 2011 10:01:44 -0400 Received: from moutng.kundenserver.de ([212.227.17.10]:55285 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757888Ab1COOBn (ORCPT ); Tue, 15 Mar 2011 10:01:43 -0400 From: Arnd Bergmann To: Alexey Mikhailov Subject: Re: lseek() on debugfs entries in 2.6.37 Date: Tue, 15 Mar 2011 15:01:41 +0100 User-Agent: KMail/1.12.2 (Linux/2.6.37; KDE/4.3.2; x86_64; ; ) Cc: linux-kernel@vger.kernel.org References: <874o74ilxl.wl%karma@galois.botik.ru> In-Reply-To: <874o74ilxl.wl%karma@galois.botik.ru> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201103151501.42105.arnd@arndb.de> X-Provags-ID: V02:K0:s3/iMRjoahync6wp2I6Dtj31iX3xGtzZXkwGI/3JR1J xcWpYQ0f2BDLzstN48jON97io+CzROKPRcC5mo0tsGtkyLHPZE O81yYCzLByZ0GR+bEfoKISXgmE44RAeyYp2YARtzPsiKNVr+s3 nglOz2Jh+ySQohvwDqLFQKZsXXR7tW44T+eVUuNDv6oJMHAsg7 /t5si+y7CaJeLhH9MlYgA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 15 March 2011, Alexey Mikhailov wrote: > I use simple debugfs entries for user-space <-> kernel-space > interaction. Basically I read unsigned integers from debugfs > files like this: > > ... > char buf[64]; > lseek(timesync_fd, 0, SEEK_SET); > read(timesync_fd, buf, sizeof(buf)); > ... > > It works perfectly with 2.6.32 kernel. But with 2.6.37 kernel, > lseek() fails with errno=29(Illegal seek). So second read() > call just fails or returns garbage. Can someone please shed > some light on it? This is probably a result of the changes I made as part of the BKL removal. Which file specifically are you talking about? In older kernels, having no .llseek function meant that you implicitly get default_llseek. New kernels now require that the driver explicitly chooses one llseek variant. I did a patch to automatically convert all drivers, but this patch may have missed some that got moved around while I was patching them. Arnd