[PATCH] USB: optimise devio.c::usbdev_read

this is a small optimisation. It is ridiculous to do a kmalloc for
18 bytes. This puts it onto the stack.

Signed-off-by: Oliver Neukum <oliver@neukum.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 13 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 2b68998fe4b3..d01bd77e7b14 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -134,26 +134,21 @@ static ssize_t usbdev_read(struct file *file, char __user *buf, size_t nbytes, l
         }
 
         if (pos < sizeof(struct usb_device_descriptor)) {
-                struct usb_device_descriptor *desc = kmalloc(sizeof(*desc), GFP_KERNEL);
-                if (!desc) {
-                        ret = -ENOMEM;
-                        goto err;
-                }
-                memcpy(desc, &dev->descriptor, sizeof(dev->descriptor));
-                le16_to_cpus(&desc->bcdUSB);
-                le16_to_cpus(&desc->idVendor);
-                le16_to_cpus(&desc->idProduct);
-                le16_to_cpus(&desc->bcdDevice);
+                struct usb_device_descriptor temp_desc ; /* 18 bytes - fits on the stack */
+
+                memcpy(&temp_desc, &dev->descriptor, sizeof(dev->descriptor));
+                le16_to_cpus(&temp_desc->bcdUSB);
+                le16_to_cpus(&temp_desc->idVendor);
+                le16_to_cpus(&temp_desc->idProduct);
+                le16_to_cpus(&temp_desc->bcdDevice);
 
                 len = sizeof(struct usb_device_descriptor) - pos;
                 if (len > nbytes)
                         len = nbytes;
-                if (copy_to_user(buf, ((char *)desc) + pos, len)) {
-                        kfree(desc);
+                if (copy_to_user(buf, ((char *)&temp_desc) + pos, len)) {
                         ret = -EFAULT;
                         goto err;
                 }
-                kfree(desc);
 
                 *ppos += len;
                 buf += len;