[PATCH 13/14] s390/sclp_mem: Replace page allocator calls with k[mz]alloc()

[Mike Rapoport (Microsoft)]

do_assign_storage(), sclp_attach_storage() and sclp_setup_memory()
allocate the SCCBs used to assign, attach and query standby memory.

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_zeroed_page() with kzalloc(), __get_free_page() with
kmalloc() and free_page() with kfree().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@xxxxxxxxxx
Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
---
 drivers/s390/char/sclp_mem.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c
index 6df1926d4c62a..c28460598d385 100644
--- a/drivers/s390/char/sclp_mem.c
+++ b/drivers/s390/char/sclp_mem.c
@@ -84,7 +84,7 @@ static int do_assign_storage(sclp_cmdw_t cmd, u16 rn)
 	struct assign_storage_sccb *sccb;
 	int rc;
 
-	sccb = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+	sccb = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
 	if (!sccb)
 		return -ENOMEM;
 	sccb->header.length = PAGE_SIZE;
@@ -103,7 +103,7 @@ static int do_assign_storage(sclp_cmdw_t cmd, u16 rn)
 		break;
 	}
 out:
-	free_page((unsigned long)sccb);
+	kfree(sccb);
 	return rc;
 }
 
@@ -130,7 +130,7 @@ static int sclp_attach_storage(u8 id)
 	struct attach_storage_sccb *sccb;
 	int rc, i;
 
-	sccb = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+	sccb = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
 	if (!sccb)
 		return -ENOMEM;
 	sccb->header.length = PAGE_SIZE;
@@ -152,7 +152,7 @@ static int sclp_attach_storage(u8 id)
 		break;
 	}
 out:
-	free_page((unsigned long)sccb);
+	kfree(sccb);
 	return rc;
 }
 
@@ -487,7 +487,7 @@ static int __init sclp_setup_memory(void)
 	if ((sclp.facilities & 0xe00000000000UL) != 0xe00000000000UL)
 		return 0;
 	rc = -ENOMEM;
-	sccb = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
+	sccb = kmalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
 	if (!sccb)
 		goto out;
 	assigned = 0;
@@ -530,7 +530,7 @@ static int __init sclp_setup_memory(void)
 		insert_increment(0, 1, 0);
 	rc = sclp_init_mem();
 out:
-	free_page((unsigned long)sccb);
+	kfree(sccb);
 	return rc;
 }
 __initcall(sclp_setup_memory);

-- 
2.53.0