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    Subject[PATCH 5.14 330/334] RDMA/mlx5: Fix number of allocated XLT entries
    Date
    From: Niklas Schnelle <schnelle@linux.ibm.com>

    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@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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    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
    @@ -1024,7 +1024,7 @@ 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)

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