On Sun, Jan 31, 2010 at 6:29 AM, Dmitry Torokhov
[off-list ref] wrote:

quoted

On Sun, Jan 31, 2010 at 05:20:55AM +0100, Arnd Bergmann wrote:

quoted

On Sunday 31 January 2010, John Kacur wrote:

quoted

quoted

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 <redacted>
---

 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.

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 <jkacur@redhat.com>