NFSv4.2 copy do not allocate memory under the lock

Bruce pointed out that we shouldn't allocate memory while holding
a lock in the nfs4_callback_offload() and handle_async_copy()
that deal with a racing CB_OFFLOAD and reply to COPY case.
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/callback_proc.c

@@ -686,20 +686,24 @@ __be32 nfs4_callback_offload(void *data, void *dummy,
 {
 	struct cb_offloadargs *args = data;
 	struct nfs_server *server;
-	struct nfs4_copy_state *copy;
+	struct nfs4_copy_state *copy, *tmp_copy;
 	bool found = false;
 
+	copy = kzalloc(sizeof(struct nfs4_copy_state), GFP_NOFS);
+	if (!copy)
+		return htonl(NFS4ERR_SERVERFAULT);
+
 	spin_lock(&cps->clp->cl_lock);
 	rcu_read_lock();
 	list_for_each_entry_rcu(server, &cps->clp->cl_superblocks,
 				client_link) {
-		list_for_each_entry(copy, &server->ss_copies, copies) {
+		list_for_each_entry(tmp_copy, &server->ss_copies, copies) {
 			if (memcmp(args->coa_stateid.other,
-					copy->stateid.other,
+					tmp_copy->stateid.other,
 					sizeof(args->coa_stateid.other)))
 				continue;
-			nfs4_copy_cb_args(copy, args);
-			complete(&copy->completion);
+			nfs4_copy_cb_args(tmp_copy, args);
+			complete(&tmp_copy->completion);
 			found = true;
 			goto out;
 		}
@@ -707,15 +711,11 @@ __be32 nfs4_callback_offload(void *data, void *dummy,
 out:
 	rcu_read_unlock();
 	if (!found) {
-		copy = kzalloc(sizeof(struct nfs4_copy_state), GFP_NOFS);
-		if (!copy) {
-			spin_unlock(&cps->clp->cl_lock);
-			return htonl(NFS4ERR_SERVERFAULT);
-		}
 		memcpy(&copy->stateid, &args->coa_stateid, NFS4_STATEID_SIZE);
 		nfs4_copy_cb_args(copy, args);
 		list_add_tail(&copy->copies, &cps->clp->pending_cb_stateids);
-	}
+	} else
+		kfree(copy);
 	spin_unlock(&cps->clp->cl_lock);
 
 	return 0;

fs/nfs/nfs42proc.c

@@ -137,31 +137,32 @@ static int handle_async_copy(struct nfs42_copy_res *res,
 			     struct file *dst,
 			     nfs4_stateid *src_stateid)
 {
-	struct nfs4_copy_state *copy;
+	struct nfs4_copy_state *copy, *tmp_copy;
 	int status = NFS4_OK;
 	bool found_pending = false;
 	struct nfs_open_context *ctx = nfs_file_open_context(dst);
 
+	copy = kzalloc(sizeof(struct nfs4_copy_state), GFP_NOFS);
+	if (!copy)
+		return -ENOMEM;
+
 	spin_lock(&server->nfs_client->cl_lock);
-	list_for_each_entry(copy, &server->nfs_client->pending_cb_stateids,
+	list_for_each_entry(tmp_copy, &server->nfs_client->pending_cb_stateids,
 				copies) {
-		if (memcmp(&res->write_res.stateid, &copy->stateid,
+		if (memcmp(&res->write_res.stateid, &tmp_copy->stateid,
 				NFS4_STATEID_SIZE))
 			continue;
 		found_pending = true;
-		list_del(&copy->copies);
+		list_del(&tmp_copy->copies);
 		break;
 	}
 	if (found_pending) {
 		spin_unlock(&server->nfs_client->cl_lock);
+		kfree(copy);
+		copy = tmp_copy;
 		goto out;
 	}
 
-	copy = kzalloc(sizeof(struct nfs4_copy_state), GFP_NOFS);
-	if (!copy) {
-		spin_unlock(&server->nfs_client->cl_lock);
-		return -ENOMEM;
-	}
 	memcpy(&copy->stateid, &res->write_res.stateid, NFS4_STATEID_SIZE);
 	init_completion(&copy->completion);
 	copy->parent_state = ctx->state;