[PATCH 09/14] s390/sclp_sd: Replace __get_free_page() with kmalloc()

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

sclp_sd_store_data() allocates the SCCB used for the SCLP store data
requests.

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.

While on it, pass the SCCB to sclp_sd_sync() as a typed pointer instead
of an unsigned long.

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/sclp_sd.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/s390/char/sclp_sd.c b/drivers/s390/char/sclp_sd.c
index c62b2eacdc131..cc0b4481e2bed 100644
--- a/drivers/s390/char/sclp_sd.c
+++ b/drivers/s390/char/sclp_sd.c
@@ -173,7 +173,7 @@ static struct sclp_register sclp_sd_register = {
 
 /**
  * sclp_sd_sync() - Perform Store Data request synchronously
- * @page: Address of work page - must be below 2GB
+ * @sccb: Address of work SCCB - must be below 2GB
  * @eq: Input EQ value
  * @di: Input DI value
  * @sat: Input SAT value
@@ -186,10 +186,9 @@ static struct sclp_register sclp_sd_register = {
  * Return %0 on success and store resulting DSIZE and ESIZE values in
  * @dsize_ptr and @esize_ptr (if provided). Return non-zero on error.
  */
-static int sclp_sd_sync(unsigned long page, u8 eq, u8 di, u64 sat, u64 sa,
+static int sclp_sd_sync(struct sclp_sd_sccb *sccb, u8 eq, u8 di, u64 sat, u64 sa,
 			u32 *dsize_ptr, u32 *esize_ptr)
 {
-	struct sclp_sd_sccb *sccb = (void *) page;
 	struct sclp_sd_listener listener;
 	struct sclp_sd_evbuf *evbuf;
 	int rc;
@@ -291,17 +290,18 @@ static int sclp_sd_sync(unsigned long page, u8 eq, u8 di, u64 sat, u64 sa,
  */
 static int sclp_sd_store_data(struct sclp_sd_data *result, u8 di)
 {
+	struct sclp_sd_sccb *sccb;
 	u32 dsize = 0, esize = 0;
-	unsigned long page, asce = 0;
+	unsigned long asce = 0;
 	void *data = NULL;
 	int rc;
 
-	page = __get_free_page(GFP_KERNEL | GFP_DMA);
-	if (!page)
+	sccb = kmalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
+	if (!sccb)
 		return -ENOMEM;
 
 	/* Get size */
-	rc = sclp_sd_sync(page, SD_EQ_SIZE, di, 0, 0, &dsize, &esize);
+	rc = sclp_sd_sync(sccb, SD_EQ_SIZE, di, 0, 0, &dsize, &esize);
 	if (rc)
 		goto out;
 	if (dsize == 0)
@@ -323,12 +323,12 @@ static int sclp_sd_store_data(struct sclp_sd_data *result, u8 di)
 	}
 
 	/* Get data */
-	rc = sclp_sd_sync(page, SD_EQ_STORE_DATA, di, asce, (u64) data, &dsize,
+	rc = sclp_sd_sync(sccb, SD_EQ_STORE_DATA, di, asce, (u64) data, &dsize,
 			  &esize);
 	if (rc) {
 		/* Cancel running request if interrupted or timed out */
 		if (rc == -ERESTARTSYS || rc == -ETIME) {
-			if (sclp_sd_sync(page, SD_EQ_HALT, di, 0, 0, NULL, NULL)) {
+			if (sclp_sd_sync(sccb, SD_EQ_HALT, di, 0, 0, NULL, NULL)) {
 				pr_warn("Could not stop Store Data request - leaking at least %zu bytes\n",
 					(size_t)dsize * PAGE_SIZE);
 				data = NULL;
@@ -346,7 +346,7 @@ static int sclp_sd_store_data(struct sclp_sd_data *result, u8 di)
 
 out:
 	base_asce_free(asce);
-	free_page(page);
+	kfree(sccb);
 
 	return rc;
 }

-- 
2.53.0