linux-kernel - Re: [PATCH] HID: usbhid: Use GFP_KERNEL instead of GFP

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Date:   Thu, 1 Aug 2019 15:47:33 +0200
From:   Greg KH <greg@...ah.com>
To:     walter harms <wharms@....de>
Cc:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        jikos@...nel.org, benjamin.tissoires@...hat.com,
        linux-usb@...r.kernel.org, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] HID: usbhid: Use GFP_KERNEL instead of GFP_ATOMIC when
 applicable

On Thu, Aug 01, 2019 at 12:06:03PM +0200, walter harms wrote:
> 
> 
> Am 01.08.2019 09:47, schrieb Christophe JAILLET:
> > There is no need to use GFP_ATOMIC when calling 'usb_alloc_coherent()'
> > here. These calls are done from probe functions and using GFP_KERNEL should
> > be safe.
> > The memory itself is used within some interrupts, but it is not a
> > problem, once it has been allocated.
> > 
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> > ---
> >  drivers/hid/usbhid/usbkbd.c   | 4 ++--
> >  drivers/hid/usbhid/usbmouse.c | 2 +-
> >  2 files changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/hid/usbhid/usbkbd.c b/drivers/hid/usbhid/usbkbd.c
> > index d5b7a696a68c..63e8ef8beb45 100644
> > --- a/drivers/hid/usbhid/usbkbd.c
> > +++ b/drivers/hid/usbhid/usbkbd.c
> > @@ -239,11 +239,11 @@ static int usb_kbd_alloc_mem(struct usb_device *dev, struct usb_kbd *kbd)
> >  		return -1;
> >  	if (!(kbd->led = usb_alloc_urb(0, GFP_KERNEL)))
> >  		return -1;
> > -	if (!(kbd->new = usb_alloc_coherent(dev, 8, GFP_ATOMIC, &kbd->new_dma)))
> > +	if (!(kbd->new = usb_alloc_coherent(dev, 8, GFP_KERNEL, &kbd->new_dma)))
> >  		return -1;
> >  	if (!(kbd->cr = kmalloc(sizeof(struct usb_ctrlrequest), GFP_KERNEL)))
> >  		return -1;
> > -	if (!(kbd->leds = usb_alloc_coherent(dev, 1, GFP_ATOMIC, &kbd->leds_dma)))
> > +	if (!(kbd->leds = usb_alloc_coherent(dev, 1, GFP_KERNEL, &kbd->leds_dma)))
> >  		return -1;
> >  
> 
> the kernel style is usually:
>  kbd->new = usb_alloc_coherent(dev, 8, GFP_ATOMIC, &kbd->new_dma);
>  if (!kbd->new)
> 	return -1;
> 
> 
> in usbmouse.c this is done, any reason for the change here ?

If you want to be extra-correct, don't return -1, return -ENOMEM.

thanks,

greg k-h