From 5221b55bb3b78d6dafcc33a609513b594fb62dbf Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Fri, 19 May 2023 14:22:14 +0200 Subject: [PATCH] switch-root: sync() before MNT_DETACH unmounting all old mounts As discussed here: https://github.com/systemd/systemd/pull/27670#discussion_r1196716794 --- src/shared/switch-root.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/shared/switch-root.c b/src/shared/switch-root.c index 2431facba00..d5b3d169bf8 100644 --- a/src/shared/switch-root.c +++ b/src/shared/switch-root.c @@ -63,6 +63,13 @@ int switch_root(const char *new_root, (void) mkdir_p_label(resolved_old_root_after, 0755); } + /* We are about to unmount various file systems with MNT_DETACH (either explicitly via umount() or + * indirectly via pivot_root()), and thus do not synchronously wait for them to be fully sync'ed — + * all while making them invisible/inaccessible in the file system tree for later code. That makes + * sync'ing them then difficult. Let's hence issue a manual sync() here, so that we at least can + * guarantee all file systems are an a good state before entering this state. */ + sync(); + /* Work-around for kernel design: the kernel refuses MS_MOVE if any file systems are mounted * MS_SHARED. Hence remount them MS_PRIVATE here as a work-around. * -- 2.47.3