wrappers for ->i_mutex access

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
index 6e81749..bd25dc7 100644
--- a/fs/nfs/nfs42proc.c
+++ b/fs/nfs/nfs42proc.c
@@ -101,13 +101,13 @@
 	if (!nfs_server_capable(inode, NFS_CAP_ALLOCATE))
 		return -EOPNOTSUPP;
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 
 	err = nfs42_proc_fallocate(&msg, filep, offset, len);
 	if (err == -EOPNOTSUPP)
 		NFS_SERVER(inode)->caps &= ~NFS_CAP_ALLOCATE;
 
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 	return err;
 }
 
@@ -123,7 +123,7 @@
 		return -EOPNOTSUPP;
 
 	nfs_wb_all(inode);
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 
 	err = nfs42_proc_fallocate(&msg, filep, offset, len);
 	if (err == 0)
@@ -131,7 +131,7 @@
 	if (err == -EOPNOTSUPP)
 		NFS_SERVER(inode)->caps &= ~NFS_CAP_DEALLOCATE;
 
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 	return err;
 }