Re: [PATCH net-next] liquidio: Remove unneeded cast from memory allocation

[wanghai (M)]

å 2020/7/28 17:11, Joe Perches åé:
> On Tue, 2020-07-28 at 16:42 +0800, wanghai (M) wrote:
> > å 2020/7/25 5:29, Joe Perches åé:
> > > On Fri, 2020-07-24 at 21:00 +0800, Wang Hai wrote:
> > > > Remove casting the values returned by memory allocation function.
> > > >
> > > > Coccinelle emits WARNING:
> > > >
> > > > ./drivers/net/ethernet/cavium/liquidio/octeon_device.c:1155:14-36: WARNING:
> > > >    casting value returned by memory allocation function to (struct octeon_dispatch *) is useless.
> > > []
> > > > diff --git a/drivers/net/ethernet/cavium/liquidio/octeon_device.c b/drivers/net/ethernet/cavium/liquidio/octeon_device.c
> > > []
> > > > @@ -1152,8 +1152,7 @@ octeon_register_dispatch_fn(struct octeon_device *oct,
> > > >    
> > > >    		dev_dbg(&oct->pci_dev->dev,
> > > >    			"Adding opcode to dispatch list linked list\n");
> > > > -		dispatch = (struct octeon_dispatch *)
> > > > -			   vmalloc(sizeof(struct octeon_dispatch));
> > > > +		dispatch = vmalloc(sizeof(struct octeon_dispatch));
> > > More the question is why this is vmalloc at all
> > > as the structure size is very small.
> > >
> > > Likely this should just be kmalloc.
> > Thanks for your advice.  It is indeed best to use kmalloc here.
> > > >    		if (!dispatch) {
> > > >    			dev_err(&oct->pci_dev->dev,
> > > >    				"No memory to add dispatch function\n");
> > > And this dev_err is unnecessary.
> > I don't understand why dev_err is not needed here. We can easily know
> > that an error has occurred here through dev_err
> Memory allocation failures without __GFP_NOWARN. already
> do a dump_stack to show the location of the code that
> could not successfully allocate memory.
Thanks for your explanation. I got it.

Can it be modified like this?

--- a/drivers/net/ethernet/cavium/liquidio/octeon_device.c
+++ b/drivers/net/ethernet/cavium/liquidio/octeon_device.c
@@ -1152,11 +1152,8 @@ octeon_register_dispatch_fn(struct octeon_device 
*oct,

ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dev_dbg(&oct->pci_dev->dev,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ "Adding opcode to dispatch list linked list\n");
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dispatch = (struct octeon_dispatch *)
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vmalloc(sizeof(struct octeon_dispatch));
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dispatch = kmalloc(sizeof(struct octeon_dispatch), 
GFP_KERNEL);
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (!dispatch) {
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dev_err(&oct->pci_dev->dev,
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ "No memory to add dispatch function\n");
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return 1;
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ }
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dispatch->opcode = combined_opcode;

> .