NFSv4: change nfs4_select_rw_stateid to take a lock_context inplace of lock_owner

The only time that a lock_context is not immediately available is in
setattr, and now that it has an open_context, it can easily find one
with nfs_get_lock_context.
This removes the need for the on-stack nfs_lockowner.

This change is preparation for correctly support flock stateids.

Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 3ab4dd5..1c629f5 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2945,12 +2945,13 @@ static int _nfs4_do_setattr(struct inode *inode,
 	if (nfs4_copy_delegation_stateid(inode, fmode, &arg->stateid, &delegation_cred)) {
 		/* Use that stateid */
 	} else if (truncate && ctx != NULL) {
-		struct nfs_lockowner lockowner = {
-			.l_owner = current->files,
-		};
+		struct nfs_lock_context *l_ctx;
 		if (!nfs4_valid_open_stateid(ctx->state))
 			return -EBADF;
-		if (nfs4_select_rw_stateid(ctx->state, FMODE_WRITE, &lockowner,
+		l_ctx = nfs_get_lock_context(ctx);
+		if (IS_ERR(l_ctx))
+			return PTR_ERR(l_ctx);
+		if (nfs4_select_rw_stateid(ctx->state, FMODE_WRITE, l_ctx,
 				&arg->stateid, &delegation_cred) == -EIO)
 			return -EBADF;
 	} else
@@ -4576,11 +4577,7 @@ int nfs4_set_rw_stateid(nfs4_stateid *stateid,
 		const struct nfs_lock_context *l_ctx,
 		fmode_t fmode)
 {
-	const struct nfs_lockowner *lockowner = NULL;
-
-	if (l_ctx != NULL)
-		lockowner = &l_ctx->lockowner;
-	return nfs4_select_rw_stateid(ctx->state, fmode, lockowner, stateid, NULL);
+	return nfs4_select_rw_stateid(ctx->state, fmode, l_ctx, stateid, NULL);
 }
 EXPORT_SYMBOL_GPL(nfs4_set_rw_stateid);