s390/hvc_iucv: Replace get_zeroed_page() with kzalloc()

hvc_iucv_alloc() allocates a send staging buffer for accumulating
outbound terminal characters before they are copied into a separate
IUCV message buffer for transmission to the hypervisor. The staging
buffer itself is never passed to any IUCV function.

This buffer can be allocated with kmalloc() as there's nothing special
about it 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.

Replace use of get_zeroed_page() with kzalloc() and free_page() with
kfree().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

diff --git a/drivers/tty/hvc/hvc_iucv.c b/drivers/tty/hvc/hvc_iucv.c
index 37db8a3e5158e6a57404d0af3d359c94b12d8db1..d29a86d161f61a33a82a873dd9a24f675d2a3175 100644 (file)
--- a/drivers/tty/hvc/hvc_iucv.c
+++ b/drivers/tty/hvc/hvc_iucv.c
@@ -1060,7 +1060,7 @@ static int __init hvc_iucv_alloc(int id, unsigned int is_console)
        INIT_DELAYED_WORK(&priv->sndbuf_work, hvc_iucv_sndbuf_work);
        init_waitqueue_head(&priv->sndbuf_waitq);
 
-       priv->sndbuf = (void *) get_zeroed_page(GFP_KERNEL);
+       priv->sndbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
        if (!priv->sndbuf) {
                kfree(priv);
                return -ENOMEM;
@@ -1103,7 +1103,7 @@ static int __init hvc_iucv_alloc(int id, unsigned int is_console)
 out_error_dev:
        hvc_remove(priv->hvc);
 out_error_hvc:
-       free_page((unsigned long) priv->sndbuf);
+       kfree(priv->sndbuf);
        kfree(priv);
 
        return rc;
@@ -1116,7 +1116,7 @@ static void __init hvc_iucv_destroy(struct hvc_iucv_private *priv)
 {
        hvc_remove(priv->hvc);
        device_unregister(priv->dev);
-       free_page((unsigned long) priv->sndbuf);
+       kfree(priv->sndbuf);
        kfree(priv);
 }