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/inode.c b/fs/nfs/inode.c
index 8e24d88..86faecf 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -661,9 +661,9 @@
 	trace_nfs_getattr_enter(inode);
 	/* Flush out writes to the server in order to update c/mtime.  */
 	if (S_ISREG(inode->i_mode)) {
-		mutex_lock(&inode->i_mutex);
+		inode_lock(inode);
 		err = nfs_sync_inode(inode);
-		mutex_unlock(&inode->i_mutex);
+		inode_unlock(inode);
 		if (err)
 			goto out;
 	}
@@ -1178,9 +1178,9 @@
 	spin_unlock(&inode->i_lock);
 	trace_nfs_invalidate_mapping_enter(inode);
 	if (may_lock) {
-		mutex_lock(&inode->i_mutex);
+		inode_lock(inode);
 		ret = nfs_invalidate_mapping(inode, mapping);
-		mutex_unlock(&inode->i_mutex);
+		inode_unlock(inode);
 	} else
 		ret = nfs_invalidate_mapping(inode, mapping);
 	trace_nfs_invalidate_mapping_exit(inode, ret);