[PATCH 5.13 298/300] RDMA/mlx5: Fix number of allocated XLT entries

[Greg Kroah-Hartman]

From: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>

commit 9660dcbe0d9186976917c94bce4e69dbd8d7a974 upstream.

In commit 8010d74b9965b ("RDMA/mlx5: Split the WR setup out of
mlx5_ib_update_xlt()") the allocation logic was split out of
mlx5_ib_update_xlt() and the logic was changed to enable better OOM
handling. Sadly this change introduced a miscalculation of the number of
entries that were actually allocated when under memory pressure where it
can actually become 0 which on s390 lets dma_map_single() fail.

It can also lead to corruption of the free pages list when the wrong
number of entries is used in the calculation of sg->length which is used
as argument for free_pages().

Fix this by using the allocation size instead of misusing get_order(size).

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 8010d74b9965 ("RDMA/mlx5: Split the WR setup out of mlx5_ib_update_xlt()")
Link: https://lore.kernel.org/r/20210908081849.7948-1-schnelle@xxxxxxxxxxxxx
Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/infiniband/hw/mlx5/mr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1022,7 +1022,7 @@ static void *mlx5_ib_alloc_xlt(size_t *n
 
 	if (size > MLX5_SPARE_UMR_CHUNK) {
 		size = MLX5_SPARE_UMR_CHUNK;
-		*nents = get_order(size) / ent_size;
+		*nents = size / ent_size;
 		res = (void *)__get_free_pages(gfp_mask | __GFP_NOWARN,
 					       get_order(size));
 		if (res)