| Message ID | 20190612121258.19535-3-gregkh@linuxfoundation.org (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Andy Shevchenko |
| Headers | show |
| Series | [1/8] platform: x86: acer-wmi: no need to check return value of debugfs_create functions | expand |
On Wednesday 12 June 2019 14:12:53 Greg Kroah-Hartman wrote: > When calling debugfs functions, there is no need to ever check the > return value. The function can work or not, but the code logic should > never do something different based on this. > > Cc: Matthew Garrett <mjg59@srcf.ucam.org> > Cc: "Pali Rohár" <pali.rohar@gmail.com> > Cc: Darren Hart <dvhart@infradead.org> > Cc: Andy Shevchenko <andy@infradead.org> > Cc: platform-driver-x86@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > --- > drivers/platform/x86/dell-laptop.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c > index a561f653cf13..94a2f259031c 100644 > --- a/drivers/platform/x86/dell-laptop.c > +++ b/drivers/platform/x86/dell-laptop.c > @@ -2176,9 +2176,8 @@ static int __init dell_init(void) > kbd_led_init(&platform_device->dev); > > dell_laptop_dir = debugfs_create_dir("dell_laptop", NULL); > - if (dell_laptop_dir != NULL) > - debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, > - &dell_debugfs_fops); > + debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, > + &dell_debugfs_fops); Hi! So... debugfs_create_dir() can return NULL, right? And it is then OK to call debugfs_create_file("rfkill", 0444, dell_laptop_dir, ...) with dell_laptop_dir = NULL? Where would be that "rfkill" file created? > > dell_laptop_register_notifier(&dell_laptop_notifier); >
On Wed, Jun 12, 2019 at 02:21:05PM +0200, Pali Rohár wrote: > On Wednesday 12 June 2019 14:12:53 Greg Kroah-Hartman wrote: > > When calling debugfs functions, there is no need to ever check the > > return value. The function can work or not, but the code logic should > > never do something different based on this. > > > > Cc: Matthew Garrett <mjg59@srcf.ucam.org> > > Cc: "Pali Rohár" <pali.rohar@gmail.com> > > Cc: Darren Hart <dvhart@infradead.org> > > Cc: Andy Shevchenko <andy@infradead.org> > > Cc: platform-driver-x86@vger.kernel.org > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > --- > > drivers/platform/x86/dell-laptop.c | 5 ++--- > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c > > index a561f653cf13..94a2f259031c 100644 > > --- a/drivers/platform/x86/dell-laptop.c > > +++ b/drivers/platform/x86/dell-laptop.c > > @@ -2176,9 +2176,8 @@ static int __init dell_init(void) > > kbd_led_init(&platform_device->dev); > > > > dell_laptop_dir = debugfs_create_dir("dell_laptop", NULL); > > - if (dell_laptop_dir != NULL) > > - debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, > > - &dell_debugfs_fops); > > + debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, > > + &dell_debugfs_fops); > > Hi! > > So... debugfs_create_dir() can return NULL, right? Nope. > And it is then OK to call > debugfs_create_file("rfkill", 0444, dell_laptop_dir, ...) with > dell_laptop_dir = NULL? Yes. > Where would be that "rfkill" file created? The root of debugfs. But, if debugfs_create_dir() return an error, and you pass that value into debugfs_create_file() it will happily just return an error back again, and move on. So it is always safe to pass the return value of one debugfs call into another, no need to check anything. If the system is so messed up that debugfs_create_dir() fails (i.e. you are out of memory), failing to create a debugfs file is the least of your worries :) And even then, no need to change your code logic, the functionality of your code should never depend on if debugfs is working properly at the moment or not. thanks, greg k-h
On Wednesday 12 June 2019 14:36:04 Greg Kroah-Hartman wrote: > On Wed, Jun 12, 2019 at 02:21:05PM +0200, Pali Rohár wrote: > > On Wednesday 12 June 2019 14:12:53 Greg Kroah-Hartman wrote: > > > When calling debugfs functions, there is no need to ever check the > > > return value. The function can work or not, but the code logic should > > > never do something different based on this. > > > > > > Cc: Matthew Garrett <mjg59@srcf.ucam.org> > > > Cc: "Pali Rohár" <pali.rohar@gmail.com> > > > Cc: Darren Hart <dvhart@infradead.org> > > > Cc: Andy Shevchenko <andy@infradead.org> > > > Cc: platform-driver-x86@vger.kernel.org > > > Cc: linux-kernel@vger.kernel.org > > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > --- > > > drivers/platform/x86/dell-laptop.c | 5 ++--- > > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c > > > index a561f653cf13..94a2f259031c 100644 > > > --- a/drivers/platform/x86/dell-laptop.c > > > +++ b/drivers/platform/x86/dell-laptop.c > > > @@ -2176,9 +2176,8 @@ static int __init dell_init(void) > > > kbd_led_init(&platform_device->dev); > > > > > > dell_laptop_dir = debugfs_create_dir("dell_laptop", NULL); > > > - if (dell_laptop_dir != NULL) > > > - debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, > > > - &dell_debugfs_fops); > > > + debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, > > > + &dell_debugfs_fops); > > > > Hi! > > > > So... debugfs_create_dir() can return NULL, right? > > Nope. Yea, now I see implementation. It does not return NULL on error, but rather ERR_PTR. So dell_laptop_dir is always not-NULL. And that check was wrong. You can add my Reviewed-by: Pali Rohár <pali.rohar@gmail.com> > > And it is then OK to call > > debugfs_create_file("rfkill", 0444, dell_laptop_dir, ...) with > > dell_laptop_dir = NULL? > > Yes. > > > Where would be that "rfkill" file created? > > The root of debugfs. > > But, if debugfs_create_dir() return an error, and you pass that value > into debugfs_create_file() it will happily just return an error back > again, and move on. > > So it is always safe to pass the return value of one debugfs call into > another, no need to check anything. If the system is so messed up that > debugfs_create_dir() fails (i.e. you are out of memory), failing to > create a debugfs file is the least of your worries :) > > And even then, no need to change your code logic, the functionality of > your code should never depend on if debugfs is working properly at the > moment or not. > > thanks, > > greg k-h
On Wed, Jun 12, 2019 at 02:44:11PM +0200, Pali Rohár wrote: > On Wednesday 12 June 2019 14:36:04 Greg Kroah-Hartman wrote: > > On Wed, Jun 12, 2019 at 02:21:05PM +0200, Pali Rohár wrote: > > > On Wednesday 12 June 2019 14:12:53 Greg Kroah-Hartman wrote: > > > > When calling debugfs functions, there is no need to ever check the > > > > return value. The function can work or not, but the code logic should > > > > never do something different based on this. > > > > > > > > Cc: Matthew Garrett <mjg59@srcf.ucam.org> > > > > Cc: "Pali Rohár" <pali.rohar@gmail.com> > > > > Cc: Darren Hart <dvhart@infradead.org> > > > > Cc: Andy Shevchenko <andy@infradead.org> > > > > Cc: platform-driver-x86@vger.kernel.org > > > > Cc: linux-kernel@vger.kernel.org > > > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > > --- > > > > drivers/platform/x86/dell-laptop.c | 5 ++--- > > > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c > > > > index a561f653cf13..94a2f259031c 100644 > > > > --- a/drivers/platform/x86/dell-laptop.c > > > > +++ b/drivers/platform/x86/dell-laptop.c > > > > @@ -2176,9 +2176,8 @@ static int __init dell_init(void) > > > > kbd_led_init(&platform_device->dev); > > > > > > > > dell_laptop_dir = debugfs_create_dir("dell_laptop", NULL); > > > > - if (dell_laptop_dir != NULL) > > > > - debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, > > > > - &dell_debugfs_fops); > > > > + debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, > > > > + &dell_debugfs_fops); > > > > > > Hi! > > > > > > So... debugfs_create_dir() can return NULL, right? > > > > Nope. > > Yea, now I see implementation. It does not return NULL on error, but > rather ERR_PTR. > > So dell_laptop_dir is always not-NULL. And that check was wrong. > > You can add my > Reviewed-by: Pali Rohár <pali.rohar@gmail.com> Thanks! greg k-h
diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c index a561f653cf13..94a2f259031c 100644 --- a/drivers/platform/x86/dell-laptop.c +++ b/drivers/platform/x86/dell-laptop.c @@ -2176,9 +2176,8 @@ static int __init dell_init(void) kbd_led_init(&platform_device->dev); dell_laptop_dir = debugfs_create_dir("dell_laptop", NULL); - if (dell_laptop_dir != NULL) - debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, - &dell_debugfs_fops); + debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL, + &dell_debugfs_fops); dell_laptop_register_notifier(&dell_laptop_notifier);
When calling debugfs functions, there is no need to ever check the return value. The function can work or not, but the code logic should never do something different based on this. Cc: Matthew Garrett <mjg59@srcf.ucam.org> Cc: "Pali Rohár" <pali.rohar@gmail.com> Cc: Darren Hart <dvhart@infradead.org> Cc: Andy Shevchenko <andy@infradead.org> Cc: platform-driver-x86@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/platform/x86/dell-laptop.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)