[PATCH 1/5] s390/zcore: Replace __get_free_page() with kmalloc()

["Mike Rapoport (Microsoft)" <rppt@kernel.org>]

zcore_reipl_init() allocates buffers that keep a copy of the IPL block
and of the OS info structure of the crashed system.

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.

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

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 drivers/s390/char/zcore.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/s390/char/zcore.c b/drivers/s390/char/zcore.c
index 1ab7400a3c10f..92e31a8a7f242 100644
--- a/drivers/s390/char/zcore.c
+++ b/drivers/s390/char/zcore.c
@@ -224,7 +224,7 @@ static int __init zcore_reipl_init(void)
 		return rc;
 	if (ipib_info.ipib == 0)
 		return 0;
-	zcore_ipl_block = (void *) __get_free_page(GFP_KERNEL);
+	zcore_ipl_block = kmalloc(PAGE_SIZE, GFP_KERNEL);
 	if (!zcore_ipl_block)
 		return -ENOMEM;
 	if (ipib_info.ipib < sclp.hsa_size)
@@ -235,7 +235,7 @@ static int __init zcore_reipl_init(void)
 	if (rc || (__force u32)csum_partial(zcore_ipl_block, zcore_ipl_block->hdr.len, 0) !=
 	    ipib_info.checksum) {
 		TRACE("Checksum does not match\n");
-		free_page((unsigned long) zcore_ipl_block);
+		kfree(zcore_ipl_block);
 		zcore_ipl_block = NULL;
 	}
 	/*
@@ -244,7 +244,7 @@ static int __init zcore_reipl_init(void)
 	 * to continue dump processing, considering that os_info could be
 	 * corrupted on the panicked system.
 	 */
-	os_info = (void *)__get_free_page(GFP_KERNEL);
+	os_info = kmalloc(PAGE_SIZE, GFP_KERNEL);
 	if (!os_info)
 		return -ENOMEM;
 	rc = memcpy_hsa_kernel(&os_info_addr, __LC_OS_INFO, sizeof(os_info_addr));
@@ -266,7 +266,7 @@ static int __init zcore_reipl_init(void)
 			os_info_flags = 0;
 	}
 out:
-	free_page((unsigned long)os_info);
+	kfree(os_info);
 	return 0;
 }
 

-- 
2.53.0