[PATCH] virtio_console: correct error message on failure of debugfs_create_dir

[PATCH] virtio_console: correct error message on failure of debugfs_create_dir

[Sasha Levin]

debugfs_create_dir() returns NULL if it fails, there's little point in
calling PTR_ERR on it.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
---
 drivers/char/virtio_console.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index c594cb1..490b70e 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -2212,10 +2212,9 @@ static int __init init(void)
 	}
 
 	pdrvdata.debugfs_dir = debugfs_create_dir("virtio-ports", NULL);
-	if (!pdrvdata.debugfs_dir) {
-		pr_warning("Error %ld creating debugfs dir for virtio-ports\n",
-			   PTR_ERR(pdrvdata.debugfs_dir));
-	}
+	if (!pdrvdata.debugfs_dir)
+		pr_warn("Error creating debugfs dir for virtio-ports\n");
+
 	INIT_LIST_HEAD(&pdrvdata.consoles);
 	INIT_LIST_HEAD(&pdrvdata.portdevs);
 
-- 
1.8.0

Re: [PATCH] virtio_console: correct error message on failure of debugfs_create_dir

[Amit Shah]

On (Thu) 20 Dec 2012 [14:11:21], Sasha Levin wrote:
> debugfs_create_dir() returns NULL if it fails, there's little point in
> calling PTR_ERR on it.
> 
> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
> ---
>  drivers/char/virtio_console.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index c594cb1..490b70e 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -2212,10 +2212,9 @@ static int __init init(void)
>  	}
>  
>  	pdrvdata.debugfs_dir = debugfs_create_dir("virtio-ports", NULL);
> -	if (!pdrvdata.debugfs_dir) {
> -		pr_warning("Error %ld creating debugfs dir for virtio-ports\n",
> -			   PTR_ERR(pdrvdata.debugfs_dir));
> -	}
> +	if (!pdrvdata.debugfs_dir)
> +		pr_warn("Error creating debugfs dir for virtio-ports\n");

debugfs_create_dir() does return an error value if debugfs is not
enabled.

This check for !pdrvdata.debugfs_dir should infact use
IS_ERR_OR_NULL().  Care to submit a patch for that?

		Amit

Re: [PATCH] virtio_console: correct error message on failure of debugfs_create_dir

[Arnd Bergmann]

On Friday 21 December 2012, Amit Shah wrote:
> On (Thu) 20 Dec 2012 [14:11:21], Sasha Levin wrote:
> > debugfs_create_dir() returns NULL if it fails, there's little point in
> > calling PTR_ERR on it.
>
> debugfs_create_dir() does return an error value if debugfs is not
> enabled.
> 
> This check for !pdrvdata.debugfs_dir should infact use
> IS_ERR_OR_NULL().  Care to submit a patch for that?

How about we fix the stub instead to return NULL when debugfs is disabled?

	Arnd

Re: [PATCH] virtio_console: correct error message on failure of debugfs_create_dir

[Greg Kroah-Hartman]

On Mon, Dec 24, 2012 at 11:55:46AM +0000, Arnd Bergmann wrote:
> On Friday 21 December 2012, Amit Shah wrote:
> > On (Thu) 20 Dec 2012 [14:11:21], Sasha Levin wrote:
> > > debugfs_create_dir() returns NULL if it fails, there's little point in
> > > calling PTR_ERR on it.
> >
> > debugfs_create_dir() does return an error value if debugfs is not
> > enabled.
> > 
> > This check for !pdrvdata.debugfs_dir should infact use
> > IS_ERR_OR_NULL().  Care to submit a patch for that?
> 
> How about we fix the stub instead to return NULL when debugfs is disabled?

No, please read debugfs.h for why I decided to not do this (i.e. we try
to learn from our mistakes...)

thanks,

greg k-h

Re: [PATCH] virtio_console: correct error message on failure of debugfs_create_dir

[Sasha Levin]

On Mon, Dec 24, 2012 at 12:39 PM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Mon, Dec 24, 2012 at 11:55:46AM +0000, Arnd Bergmann wrote:
>> On Friday 21 December 2012, Amit Shah wrote:
>> > On (Thu) 20 Dec 2012 [14:11:21], Sasha Levin wrote:
>> > > debugfs_create_dir() returns NULL if it fails, there's little point in
>> > > calling PTR_ERR on it.
>> >
>> > debugfs_create_dir() does return an error value if debugfs is not
>> > enabled.
>> >
>> > This check for !pdrvdata.debugfs_dir should infact use
>> > IS_ERR_OR_NULL().  Care to submit a patch for that?
>>
>> How about we fix the stub instead to return NULL when debugfs is disabled?
>
> No, please read debugfs.h for why I decided to not do this (i.e. we try
> to learn from our mistakes...)

Why won't we fix it the other way around and return an actual error
code instead of a NULL on failure?


Thanks,
Sasha

Re: [PATCH] virtio_console: correct error message on failure of debugfs_create_dir

[Greg Kroah-Hartman]

On Mon, Dec 24, 2012 at 01:24:52PM -0500, Sasha Levin wrote:
> On Mon, Dec 24, 2012 at 12:39 PM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Mon, Dec 24, 2012 at 11:55:46AM +0000, Arnd Bergmann wrote:
> >> On Friday 21 December 2012, Amit Shah wrote:
> >> > On (Thu) 20 Dec 2012 [14:11:21], Sasha Levin wrote:
> >> > > debugfs_create_dir() returns NULL if it fails, there's little point in
> >> > > calling PTR_ERR on it.
> >> >
> >> > debugfs_create_dir() does return an error value if debugfs is not
> >> > enabled.
> >> >
> >> > This check for !pdrvdata.debugfs_dir should infact use
> >> > IS_ERR_OR_NULL().  Care to submit a patch for that?
> >>
> >> How about we fix the stub instead to return NULL when debugfs is disabled?
> >
> > No, please read debugfs.h for why I decided to not do this (i.e. we try
> > to learn from our mistakes...)
> 
> Why won't we fix it the other way around and return an actual error
> code instead of a NULL on failure?

Again, no, that doesn't make your code simpler/faster.  You really don't
need to check the return value of debugfs, just handle it as if it
always works, and look, the code handles it all properly, no matter if
debugfs is enabled or not.  It's only debugging code, you shouldn't
really care if it is present or not, right?

If you do, perhaps you shouldn't be using debugfs?

greg k-h