fib: fib_result_assign() should not change fib refcounts

After commit ebc0ffae (RCU conversion of fib_lookup()),
fib_result_assign()  should not change fib refcounts anymore.

Thanks to Michael who did the bisection and bug report.
Reported-by: NMichael Ellerman <michael@ellerman.id.au>
Tested-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/fib_lookup.h

@@ -47,11 +47,8 @@ extern int fib_detect_death(struct fib_info *fi, int order,
 static inline void fib_result_assign(struct fib_result *res,
 				     struct fib_info *fi)
 {
-	if (res->fi != NULL)
-		fib_info_put(res->fi);
+	/* we used to play games with refcounts, but we now use RCU */
 	res->fi = fi;
-	if (fi != NULL)
-		atomic_inc(&fi->fib_clntref);
 }
 
 #endif /* _FIB_LOOKUP_H */