NFSD: Initialize struct nfsd4_copy earlier

Ensure the refcount and async_copies fields are initialized early.
cleanup_async_copy() will reference these fields if an error occurs
in nfsd4_copy(). If they are not correctly initialized, at the very
least, a refcount underflow occurs.

Reported-by: Olga Kornievskaia <okorniev@redhat.com>
Fixes: aadc3bb ("NFSD: Limit the number of concurrent async COPY operations")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Olga Kornievskaia <okorniev@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4proc.c

@@ -1841,14 +1841,14 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		if (!async_copy)
 			goto out_err;
 		async_copy->cp_nn = nn;
+		INIT_LIST_HEAD(&async_copy->copies);
+		refcount_set(&async_copy->refcount, 1);
 		/* Arbitrary cap on number of pending async copy operations */
 		if (atomic_inc_return(&nn->pending_async_copies) >
 				(int)rqstp->rq_pool->sp_nrthreads) {
 			atomic_dec(&nn->pending_async_copies);
 			goto out_err;
 		}
-		INIT_LIST_HEAD(&async_copy->copies);
-		refcount_set(&async_copy->refcount, 1);
 		async_copy->cp_src = kmalloc(sizeof(*async_copy->cp_src), GFP_KERNEL);
 		if (!async_copy->cp_src)
 			goto out_err;