From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Kacur Subject: Re: [PATCH] input: remove BKL from uinput open function Date: Mon, 1 Feb 2010 21:27:22 +0100 Message-ID: <520f0cf11002011227s74e57673j3922941f7ee87989@mail.gmail.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <520f0cf11002011222h134dbf06rf1db612da9a9728@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Dmitry Torokhov Cc: Arnd Bergmann , Thadeu Lima de Souza Cascardo , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-input@vger.kernel.org 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 explici= t >>> > > .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 followin= g >>> > make more sense? >>> > =A0.llseek =A0 =A0 =A0 =A0 =3D 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 s= eek >>> 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 >> --- >> >> =A0drivers/input/misc/uinput.c | =A0 =A07 +++++++ >> =A01 files changed, 7 insertions(+), 0 deletions(-) >> >> >> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput= =2Ec >> 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_de= vice *udev) >> =A0static int uinput_open(struct inode *inode, struct file *file) >> =A0{ >> =A0 =A0 =A0 =A0struct uinput_device *newdev; >> + =A0 =A0 =A0 int error; >> >> =A0 =A0 =A0 =A0newdev =3D kzalloc(sizeof(struct uinput_device), GFP_= KERNEL); >> =A0 =A0 =A0 =A0if (!newdev) >> @@ -291,6 +292,12 @@ static int uinput_open(struct inode *inode, str= uct file *file) >> >> =A0 =A0 =A0 =A0file->private_data =3D newdev; >> >> + =A0 =A0 =A0 error =3D nonseekable_open(inode, file); >> + =A0 =A0 =A0 if (error) { >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 kfree(newdev); >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 return error; >> + =A0 =A0 =A0 } >> + >> =A0 =A0 =A0 =A0return 0; >> =A0} >> >> > > Hmnn, if you look at nonseekable_open() it will always return 0. I > think you can just do the following. > > 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, struc= t file *fil > > =A0 =A0 =A0 =A0file->private_data =3D newdev; > > - =A0 =A0 =A0 return 0; > + =A0 =A0 =A0 return nonseekable_open(inode, file); > =A0} > > 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.