[PATCH 4/4] USB: serial: wwan: replace __get_free_page() with kmalloc()

[Mike Rapoport (Microsoft)]

usb_wwan_port_probe() allocates the transfer buffers for the read URBs.

These buffers can be allocated with kmalloc() as there's nothing special
about them to go directly to the page allocator.

kmalloc() provides a better API that does not require ugly casts and
kfree() does not need to know the size of the freed object.

Performance difference between kmalloc() and __get_free_pages() is not
measurable as both allocators take an object/page from a per-CPU list for
fast path allocations.

For the slow path the performance is anyway determined by the amount of
reclaim involved rather than by what allocator is used.

While on it, allocate IN_BUFLEN bytes rather than a full page. IN_BUFLEN
is the transfer_buffer_length of the read URBs, the page allocator was
only used because IN_BUFLEN happens to equal PAGE_SIZE on x86.

Replace use of __get_free_page() with kmalloc() and free_page() with
kfree().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@xxxxxxxxxx
Assisted-by: copilot:claude-opus
Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
---
 drivers/usb/serial/usb_wwan.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c
index a183cc4515ed..a3929d3a3ec1 100644
--- a/drivers/usb/serial/usb_wwan.c
+++ b/drivers/usb/serial/usb_wwan.c
@@ -455,7 +455,7 @@ int usb_wwan_port_probe(struct usb_serial_port *port)
 	init_usb_anchor(&portdata->delayed);
 
 	for (i = 0; i < N_IN_URB; i++) {
-		buffer = (u8 *)__get_free_page(GFP_KERNEL);
+		buffer = kmalloc(IN_BUFLEN, GFP_KERNEL);
 		if (!buffer)
 			goto bail_out_error;
 		portdata->in_buffer[i] = buffer;
@@ -492,7 +492,7 @@ int usb_wwan_port_probe(struct usb_serial_port *port)
 bail_out_error:
 	for (i = 0; i < N_IN_URB; i++) {
 		usb_free_urb(portdata->in_urbs[i]);
-		free_page((unsigned long)portdata->in_buffer[i]);
+		kfree(portdata->in_buffer[i]);
 	}
 	kfree(portdata);
 
@@ -510,7 +510,7 @@ void usb_wwan_port_remove(struct usb_serial_port *port)
 
 	for (i = 0; i < N_IN_URB; i++) {
 		usb_free_urb(portdata->in_urbs[i]);
-		free_page((unsigned long)portdata->in_buffer[i]);
+		kfree(portdata->in_buffer[i]);
 	}
 	for (i = 0; i < N_OUT_URB; i++) {
 		usb_free_urb(portdata->out_urbs[i]);

-- 
2.53.0