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/exec.c b/fs/exec.c
index 828ec5f..dcd4ac7 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1307,13 +1307,13 @@
 		return;
 
 	/* Be careful if suid/sgid is set */
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 
 	/* reload atomically mode/uid/gid now that lock held */
 	mode = inode->i_mode;
 	uid = inode->i_uid;
 	gid = inode->i_gid;
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 
 	/* We ignore suid/sgid if there are no mappings for them in the ns */
 	if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||