net/sched: cls_u32: Replace one-element array with flexible-array member
There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. Refactor the code according to the use of a flexible-array member in struct tc_u_hnode and use the struct_size() helper to calculate the size for the allocations. Commit 5778d39d ("net_sched: fix struct tc_u_hnode layout in u32") makes it clear that the code is expected to dynamically allocate divisor + 1 entries for ->ht[] in tc_uhnode. Also, based on other observations, as the piece of code below: 1232 for (h = 0; h <= ht->divisor; h++) { 1233 for (n = rtnl_dereference(ht->ht[h]); 1234 n; 1235 n = rtnl_dereference(n->next)) { 1236 if (tc_skip_hw(n->flags)) 1237 continue; 1238 1239 err = u32_reoffload_knode(tp, n, add, cb, 1240 cb_priv, extack); 1241 if (err) 1242 return err; 1243 } 1244 } we can assume that, in general, the code is actually expecting to allocate that extra space for the one-element array in tc_uhnode, everytime it allocates memory for instances of tc_uhnode or tc_u_common structures. That's the reason for passing '1' as the last argument for struct_size() in the allocation for _root_ht_ and _tp_c_, and 'divisor + 1' in the allocation code for _ht_. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays Tested-by:kernel test robot <lkp@intel.com> Link: https://lore.kernel.org/lkml/5f7062af.z3T9tn9yIPv6h5Ny%25lkp@intel.com/ Signed-off-by: