[PATCH 2/5] RDMA/mlx5: replace __get_free_page() with kmalloc()

[Mike Rapoport (Microsoft)]

mlx5_ib_mr_wqe_pfault_handler() allocates a scratch buffer for
parsing work queue entries during page fault handling.

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_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/infiniband/hw/mlx5/odp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index 1badec9bf527..90706ff7102a 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -38,6 +38,7 @@
 #include <linux/hmm-dma.h>
 #include <linux/pci-p2pdma.h>
 
+#include <linux/slab.h>
 #include "mlx5_ib.h"
 #include "cmd.h"
 #include "umr.h"
@@ -1414,7 +1415,7 @@ static void mlx5_ib_mr_wqe_pfault_handler(struct mlx5_ib_dev *dev,
 		goto resolve_page_fault;
 	}
 
-	wqe_start = (void *)__get_free_page(GFP_KERNEL);
+	wqe_start = kmalloc(PAGE_SIZE, GFP_KERNEL);
 	if (!wqe_start) {
 		mlx5_ib_err(dev, "Error allocating memory for IO page fault handling.\n");
 		goto resolve_page_fault;
@@ -1475,7 +1476,7 @@ static void mlx5_ib_mr_wqe_pfault_handler(struct mlx5_ib_dev *dev,
 		    pfault->wqe.wq_num, resume_with_error,
 		    pfault->type);
 	mlx5_core_res_put(res);
-	free_page((unsigned long)wqe_start);
+	kfree(wqe_start);
 }
 
 static void mlx5_ib_mr_rdma_pfault_handler(struct mlx5_ib_dev *dev,

-- 
2.53.0