Deal with dmsg warning/errors

[ezrizhu]

[  +0.002145] overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.000003] overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.

(nested mounts)

[ +0.013092] overlayfs: failed to clone lowerpath we're catching this so it's fine with nested mounts

[  +0.000687] overlayfs: failed to set xattr on upper
[  +0.000001] overlayfs: try mounting with 'userxattr' option

fixable with -o userxattr

[angelhof]

Let's figure out if we want to fix the issue above before or after 0.2 (I would propose only leaving it for after 0.2 if it takes a lot of time).

[mgree]

I'm open either way, but would be good to to 0.2 so we can think about other things for a bit.

More generally, it'd be good to detect failures that we can diagnose, e.g., the need to run sudo sysctl -w kernel.unprivileged_userns_clone=1, and give appropriate guidance.

[mgree]

Was the core issue here resolved by #106? (There's a separate issue of "we're very noisy and don't give good feedback on errors".)

[ezrizhu]

We fixed the

[  +0.000687] overlayfs: failed to set xattr on upper
[  +0.000001] overlayfs: try mounting with 'userxattr' option

issue

We have not fixed the [ +0.002145] overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior. issue yet, although the solution should be quite easy, I just have to write it.

[ezrizhu]

On ubuntu (5.15.0-87-generic)(root backed by ext4 via LVM), we get

[ +15.794541] overlayfs: fs on '//bin' does not support file handles, falling back to xino=off.
[  +0.002284] overlayfs: fs on '//boot' does not support file handles, falling back to xino=off.
[  +0.002380] overlayfs: fs on '//etc' does not support file handles, falling back to xino=off.
[  +0.002473] overlayfs: fs on '//home' does not support file handles, falling back to xino=off.
[  +0.002800] overlayfs: fs on '//lib' does not support file handles, falling back to xino=off.
[  +0.002307] overlayfs: fs on '//lib32' does not support file handles, falling back to xino=off.
[  +0.002307] overlayfs: fs on '//lib64' does not support file handles, falling back to xino=off.
[  +0.002439] overlayfs: fs on '//libx32' does not support file handles, falling back to xino=off.
[  +0.002441] overlayfs: fs on '//lost+found' does not support file handles, falling back to xino=off.
[  +0.002398] overlayfs: fs on '//media' does not support file handles, falling back to xino=off.
[  +0.002544] overlayfs: fs on '//mnt' does not support file handles, falling back to xino=off.
[  +0.002355] overlayfs: fs on '//opt' does not support file handles, falling back to xino=off.
[  +0.002592] overlayfs: fs on '//root' does not support file handles, falling back to xino=off.
[  +0.002425] overlayfs: fs on '//run' does not support file handles, falling back to xino=off.
[  +0.000007] overlayfs: failed to clone lowerpath
[  +0.009018] overlayfs: fs on '/tmp/tmp.VYf3HlXIPk' does not support file handles, falling back to xino=off.
[  +0.002741] overlayfs: fs on '//sbin' does not support file handles, falling back to xino=off.
[  +0.002880] overlayfs: fs on '//snap' does not support file handles, falling back to xino=off.
[  +0.000008] overlayfs: failed to clone lowerpath
[  +0.008570] overlayfs: fs on '/tmp/tmp.Y6OeXDcKZa' does not support file handles, falling back to xino=off.
[  +0.003769] overlayfs: fs on '//snap/core20/1974' does not support file handles, falling back to xino=off.
[  +0.000012] overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.000003] overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.003800] overlayfs: fs on '//snap/core20/2015' does not support file handles, falling back to xino=off.
[  +0.000016] overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.000004] overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.003706] overlayfs: fs on '//snap/lxd/24322' does not support file handles, falling back to xino=off.
[  +0.000016] overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.000003] overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.003724] overlayfs: fs on '//snap/snapd/20092' does not support file handles, falling back to xino=off.
[  +0.000028] overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.000004] overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.004519] overlayfs: fs on '//snap/snapd/20290' does not support file handles, falling back to xino=off.
[  +0.000021] overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.000004] overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
[  +0.003022] overlayfs: fs on '//srv' does not support file handles, falling back to xino=off.
[  +0.002669] overlayfs: fs on '//sys' does not support file handles, falling back to xino=off.
[  +0.000007] overlayfs: failed to clone lowerpath
[  +0.009198] overlayfs: fs on '/tmp/tmp.CGDV1VEGJ5' does not support file handles, falling back to xino=off.
[  +0.002734] overlayfs: fs on '//tmp' does not support file handles, falling back to xino=off.
[  +0.002645] overlayfs: fs on '//tmp.2' does not support file handles, falling back to xino=off.
[  +0.002907] overlayfs: fs on '//usr' does not support file handles, falling back to xino=off.
[  +0.002688] overlayfs: fs on '//var' does not support file handles, falling back to xino=off.

On debian(6.4.0-1-amd64)(root based by ext4), we have

[Nov29 13:31] overlayfs: failed to clone lowerpath
[  +0.026867] overlayfs: failed to clone lowerpath
[  +0.022979] overlayfs: failed to clone lowerpath

[ +0.000003] overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior. could be due to LVM, will have to do test on that next.