Issue with hash_for_each_possible() in Kernel Hashtable Implementation

I'm developing a Linux kernel feature that tracks per-process network 
bandwidth usage using a hashtable (DEFINE_HASHTABLE()). My function logs 
network activity per PID using the struct sock structure and associates 
it with incoming and outgoing packet statistics.

The macro hash_for_each_possible has an error: expression must have a 
constant valueC/C++(28)

"pointer type mismatch in container_of()"); ((typeof(*(entry)) *)(__mptr 
-__builtin_offsetof(typeof(*(entry)), hlist))); }) :((void*)0); }))


#include<linux/net_bandwidth.h>
DEFINE_HASHTABLE(pid_bw_table, 8);
DEFINE_SPINLOCK(pid_bw_lock);
voidpid_bw_entry(structsock*sk, u64rx, u64tx)
{
if(!sk->sk_socket||!sk->sk_socket->file)
return;
structpid_bw_entry*entry;
pid_tsk_pid=sk->sk_socket->file->f_owner.pid;
spin_lock(&pid_bw_lock);
hash_for_each_possible(pid_bw_table, entry, hlist, sk_pid) {
if(entry->pid==sk_pid) {
entry->rx_bytes+=rx;
entry->tx_bytes+=tx;
spin_unlock(&pid_bw_lock);
return;
}
}
entry=kmalloc(sizeof(structpid_bw_entry), GFP_KERNEL);
if(!entry) {
spin_unlock(&pid_bw_lock);
return;
}
entry->pid=sk_pid;
strncpy(entry->comm, current->comm, sizeof(entry->comm));
entry->rx_bytes=rx;
entry->tx_bytes=tx;
hash_add(pid_bw_table, &entry->hlist, (unsignedlong)sk_pid);
spin_unlock(&pid_bw_lock);
}
This is my header file:
#ifndef_LINUX_NET_BANDWIDTH_H
#define_LINUX_NET_BANDWIDTH_H
#include<linux/types.h>
#include<linux/spinlock.h>
#include<linux/hashtable.h>
#include<linux/slab.h>
#include<linux/file.h>
#include<linux/skbuff.h>
#include<net/sock.h>
structpid_bw_entry{
pid_tpid;
charcomm[16];
u64rx_bytes;
u64tx_bytes;
structhlist_nodehlist;
};
externstructhlist_headpid_bw_table[1<<8];
externspinlock_tpid_bw_lock;
voidpid_bw_entry(structsock*sk, u64rx, u64tx);
#endif/* _LINUX_NET_BANDWIDTH_H */