[PATCH net-next] mlxsw: spectrum_router: Use struct_size() in kzalloc()

[Gustavo A. R. Silva]

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = kzalloc(size, GFP_KERNEL)

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL)

Notice that, in this case, variable alloc_size is not necessary, hence
it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com>
---
 .../net/ethernet/mellanox/mlxsw/spectrum_router.c    | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c 
b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
index 230e1f6e192b..e3a3535f9f23 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -3813,13 +3813,11 @@ mlxsw_sp_nexthop4_group_create(struct mlxsw_sp 
*mlxsw_sp, struct fib_info *fi)
        struct mlxsw_sp_nexthop_group *nh_grp;
        struct mlxsw_sp_nexthop *nh;
        struct fib_nh *fib_nh;
-       size_t alloc_size;
        int i;
        int err;
 
-       alloc_size = sizeof(*nh_grp) +
-                    fi->fib_nhs * sizeof(struct mlxsw_sp_nexthop);
-       nh_grp = kzalloc(alloc_size, GFP_KERNEL);
+       nh_grp = kzalloc(struct_size(nh_grp, nexthops, fi->fib_nhs),
+                        GFP_KERNEL);
        if (!nh_grp)
                return ERR_PTR(-ENOMEM);
        nh_grp->priv = fi;
@@ -5045,13 +5043,11 @@ mlxsw_sp_nexthop6_group_create(struct mlxsw_sp 
*mlxsw_sp,
        struct mlxsw_sp_nexthop_group *nh_grp;
        struct mlxsw_sp_rt6 *mlxsw_sp_rt6;
        struct mlxsw_sp_nexthop *nh;
-       size_t alloc_size;
        int i = 0;
        int err;
 
-       alloc_size = sizeof(*nh_grp) +
-                    fib6_entry->nrt6 * sizeof(struct mlxsw_sp_nexthop);
-       nh_grp = kzalloc(alloc_size, GFP_KERNEL);
+       nh_grp = kzalloc(struct_size(nh_grp, nexthops, fib6_entry->nrt6),
+                        GFP_KERNEL);
        if (!nh_grp)
                return ERR_PTR(-ENOMEM);
        INIT_LIST_HEAD(&nh_grp->fib_list);
-- 
2.20.1