remounting overlayfs fails #2528
Description
I found this digging in to https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/2037417 where I thought something a bit deeper around an overlayfs that was using paths no longer available from the current mount namespace was going on, but no:
mwhudson@orcrist:~/tmp/lp-2037417$ cat repro2.sh
#!/bin/bash
set -eux
mkdir -p lower work upper mountpoint
mount -o ro,lowerdir=lower,upperdir=upper,workdir=work -t overlay overlay mountpoint
mount -o remount,rw mountpoint
mwhudson@orcrist:~/tmp/lp-2037417$ sudo bash repro2.sh
+ mkdir -p lower work upper mountpoint
+ mount -o ro,lowerdir=lower,upperdir=upper,workdir=work -t overlay overlay mountpoint
+ mount -o remount,rw mountpoint
mount: /home/mwhudson/tmp/lp-2037417/mountpoint: mount point not mounted or bad option.
dmesg(1) may have more information after failed mount system call.The failure seems to be this syscall:
mwhudson@orcrist:~/tmp/lp-2037417$ sudo strace -e fsconfig mount -o remount,rw mountpoint
fsconfig(4, FSCONFIG_SET_STRING, "lowerdir", "lower", 0) = -1 EINVAL (Invalid argument)
mount: /home/mwhudson/tmp/lp-2037417/mountpoint: mount point not mounted or bad option.
dmesg(1) may have more information after failed mount system call.
+++ exited with 32 +++