Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754821Ab0BAVVs (ORCPT ); Mon, 1 Feb 2010 16:21:48 -0500 Received: from mail-px0-f182.google.com ([209.85.216.182]:33849 "EHLO mail-px0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753894Ab0BAVVr (ORCPT ); Mon, 1 Feb 2010 16:21:47 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:content-transfer-encoding :in-reply-to:user-agent; b=SkS1M9Nz4qzlrKO/OqCb/ZYlVd8CTu7peO/jgzTxzYc7S136jgNqu+lJxQx69wV7Fn mCzoxBBido+PaOWUQ+A6C6kmdZ+z+ZtK78QgeYkYksmMnw7o/7vHl6zXE0oV1Rvv9UXK Fg/G3oPEKY7oTKpuSqOcFHhGGwssnzVmZ72F8= Date: Mon, 1 Feb 2010 13:21:33 -0800 From: Dmitry Torokhov To: John Kacur Cc: Arnd Bergmann , Thadeu Lima de Souza Cascardo , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] input: remove BKL from uinput open function Message-ID: <20100201212132.GA7380@core.coreip.homeip.net> References: <1264800197-29523-1-git-send-email-cascardo@holoscopio.com> <201001302257.09354.arnd@arndb.de> <520f0cf11001301507k20e3cf8dqa73026e12f3a1767@mail.gmail.com> <201001310520.55813.arnd@arndb.de> <20100131052942.GA12320@core.coreip.homeip.net> <520f0cf11002011222h134dbf06rf1db612da9a9728@mail.gmail.com> <520f0cf11002011227s74e57673j3922941f7ee87989@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <520f0cf11002011227s74e57673j3922941f7ee87989@mail.gmail.com> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4134 Lines: 111 On Mon, Feb 01, 2010 at 09:27:22PM +0100, John Kacur wrote: > On Mon, Feb 1, 2010 at 9:22 PM, John Kacur wrote: > > On Sun, Jan 31, 2010 at 6:29 AM, Dmitry Torokhov > > wrote: > >> On Sun, Jan 31, 2010 at 05:20:55AM +0100, Arnd Bergmann wrote: > >>> On Sunday 31 January 2010, John Kacur wrote: > >>> > > Sorry, I should have been clearer, but not implementing llseek > >>> > > is the problem I was referring to: When a driver has no explicit > >>> > > .llseek operation in its file operations and does not call > >>> > > nonseekable_open from its open operation, the VFS layer will > >>> > > implicitly use default_llseek, which takes the BKL. We're > >>> > > in the process of changing drivers not to do this, one by one > >>> > > so we can kill the BKL in the end. > >>> > > > >>> > > >>> > I know we've discussed this before, but why wouldn't the following > >>> > make more sense? > >>> > ?.llseek ? ? ? ? = no_llseek, > >>> > >>> That's one of the possible solutions. Assigning it to generic_file_llseek > >>> also gets rid of the BKL but keeps the current behaviour (calling seek > >>> returns success without having an effect, no_llseek returns -ESPIPE), > >>> while calling nonseekable_open has the other side-effect of making > >>> pread/pwrite fail with -ESPIPE, which is more consistent than > >>> only failing seek. > >>> > >> > >> OK, so how about the patch below (on top of Thadeu's patch)? > >> > >> -- > >> Dmitry > >> > >> Input: uinput - use nonseekable_open > >> > >> Seeking does not make sense for uinput so let's use nonseekable_open > >> to mark the device non-seekable. > >> > >> Signed-off-by: Dmitry Torokhov > >> --- > >> > >> ?drivers/input/misc/uinput.c | ? ?7 +++++++ > >> ?1 files changed, 7 insertions(+), 0 deletions(-) > >> > >> > >> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c > >> index 18206e1..7089151 100644 > >> --- a/drivers/input/misc/uinput.c > >> +++ b/drivers/input/misc/uinput.c > >> @@ -278,6 +278,7 @@ static int uinput_create_device(struct uinput_device *udev) > >> ?static int uinput_open(struct inode *inode, struct file *file) > >> ?{ > >> ? ? ? ?struct uinput_device *newdev; > >> + ? ? ? int error; > >> > >> ? ? ? ?newdev = kzalloc(sizeof(struct uinput_device), GFP_KERNEL); > >> ? ? ? ?if (!newdev) > >> @@ -291,6 +292,12 @@ static int uinput_open(struct inode *inode, struct file *file) > >> > >> ? ? ? ?file->private_data = newdev; > >> > >> + ? ? ? error = nonseekable_open(inode, file); > >> + ? ? ? if (error) { > >> + ? ? ? ? ? ? ? kfree(newdev); > >> + ? ? ? ? ? ? ? return error; > >> + ? ? ? } > >> + > >> ? ? ? ?return 0; > >> ?} > >> > >> > > > > Hmnn, if you look at nonseekable_open() it will always return 0. I > > think you can just do the following. It always returns 0 _now_ but I do not see any guarantees that it will never ever return anything but 0. If somebody would provide such garantee then we certainly would not need to handle errors. > > > > diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c > > index 18206e1..697c0a6 100644 > > --- a/drivers/input/misc/uinput.c > > +++ b/drivers/input/misc/uinput.c > > @@ -291,7 +291,7 @@ static int uinput_open(struct inode *inode, struct file *fil > > > > ? ? ? ?file->private_data = newdev; > > > > - ? ? ? return 0; > > + ? ? ? return nonseekable_open(inode, file); > > ?} > > > > Signed-off-by: John Kacur > > > > Btw, Thadeu Lima de Souza Cascardo should just combine that all into > one patch, no point really in making two patches out of that. I think these are 2 separate changes (the fact that nonseekable_open also gets rid of BKL invocation is a side-effect), that is not considering the fact that I already applied Thadeu's change and don't want to rewind my public branch unless really necessary. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/