[PATCH v4 1/2] xor: use kmalloc() in calibrate_xor_blocks()

The xor benchmark allocates 4 pages for a scratch buffer that is used
purely as a CPU-only XOR working area.

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 than ancient __get_free_pages().
kmalloc() does not require ugly casts and kfree() does not need to know the
size of the freed object.

There is no performance difference because kmalloc() redirects allocations
of such size to the page allocator.

Replace __get_free_pages() call with kmalloc().

Link: https://lore.kernel.org/all/[email protected]
Signed-off-by: Mike Rapoport (Microsoft) <[email protected]>
---
 lib/raid/xor/xor-core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/raid/xor/xor-core.c b/lib/raid/xor/xor-core.c
index bd4e6e434418..50931fbf0324 100644
--- a/lib/raid/xor/xor-core.c
+++ b/lib/raid/xor/xor-core.c
@@ -8,6 +8,7 @@
 
 #include <linux/module.h>
 #include <linux/gfp.h>
+#include <linux/slab.h>
 #include <linux/raid/xor.h>
 #include <linux/jiffies.h>
 #include <linux/preempt.h>
@@ -114,7 +115,7 @@ static int __init calibrate_xor_blocks(void)
 	if (forced_template)
 		return 0;
 
-	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
+	b1 = kmalloc(PAGE_SIZE * 4, GFP_KERNEL);
 	if (!b1) {
 		pr_warn("xor: Yikes!  No memory available.\n");
 		return -ENOMEM;
@@ -132,7 +133,7 @@ static int __init calibrate_xor_blocks(void)
 	pr_info("xor: using function: %s (%d MB/sec)\n",
 	       fastest->name, fastest->speed);
 
-	free_pages((unsigned long)b1, 2);
+	kfree(b1);
 	return 0;
 }
 

-- 
2.53.0