RDMA/mlx5: Fix number of allocated XLT entries

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@vger.kernel.org
Fixes: 8010d74b9965 ("RDMA/mlx5: Split the WR setup out of mlx5_ib_update_xlt()")
Link: https://lore.kernel.org/r/20210908081849.7948-1-schnelle@linux.ibm.com
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index a520ac8..b2dd117 100644 (file)
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1024,7 +1024,7 @@ static void *mlx5_ib_alloc_xlt(size_t *nents, size_t ent_size, gfp_t gfp_mask)
 
        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)