NFSv4: Fixup smatch warning for ambiguous return

BugLink: https://bugs.launchpad.net/bugs/2073603

[ Upstream commit 37ffe06537af3e3ec212e7cbe941046fce0a822f ]

Dan Carpenter reports smatch warning for nfs4_try_migration() when a memory
allocation failure results in a zero return value.  In this case, a
transient allocation failure error will likely be retried the next time the
server responds with NFS4ERR_MOVED.

We can fixup the smatch warning with a small refactor: attempt all three
allocations before testing and returning on a failure.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Fixes: c3ed222 ("NFSv4: Fix free of uninitialized nfs4_label on referral lookup.")
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Portia Stephens <portia.stephens@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>

Author: bcodding-rh

fs/nfs/nfs4state.c

@@ -2117,6 +2117,7 @@ static int nfs4_try_migration(struct nfs_server *server, const struct cred *cred
 {
 	struct nfs_client *clp = server->nfs_client;
 	struct nfs4_fs_locations *locations = NULL;
+	struct nfs_fattr *fattr;
 	struct inode *inode;
 	struct page *page;
 	int status, result;
@@ -2126,19 +2127,16 @@ static int nfs4_try_migration(struct nfs_server *server, const struct cred *cred
 			(unsigned long long)server->fsid.minor,
 			clp->cl_hostname);
 
-	result = 0;
 	page = alloc_page(GFP_KERNEL);
 	locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
-	if (page == NULL || locations == NULL) {
-		dprintk("<-- %s: no memory\n", __func__);
-		goto out;
-	}
-	locations->fattr = nfs_alloc_fattr();
-	if (locations->fattr == NULL) {
+	fattr = nfs_alloc_fattr();
+	if (page == NULL || locations == NULL || fattr == NULL) {
 		dprintk("<-- %s: no memory\n", __func__);
+		result = 0;
 		goto out;
 	}
 
+	locations->fattr = fattr;
 	inode = d_inode(server->super->s_root);
 	result = nfs4_proc_get_locations(server, NFS_FH(inode), locations,
 					 page, cred);