Re: generic/699 fails on ext4 due to using ext4 mount options w/ overlayfs

["Theodore Ts'o" <tytso@mit.edu>]

On Tue, Mar 18, 2025 at 07:58:05PM -0500, Eric Sandeen wrote:
> 
> I shouldn't have said "failed" - you're seeing what I'm seeing, it's 
> skipped (not failed) because it tries to test overlayfs idmapped layers
> using the ext4 default options, and acl mounts fail, skipping the test.

Ah, OK.

Hmm... I think the fundamental problem is that _overlay_mount_dirs()
shouldn't be using _common_dev_mount_options().  Depending on the file
system configuration that we might be testing, MOUNT_OPTIONS might
include any number of things which overlayfs might not understand,
including things like: "nfsvers=4", "data=journal", "dax",
"test_dummy_encryption", "trans=virtio" ,"version=9p2000.L"
,"posixacl", "prjquota", and probably quite a few others.

After all, we'd want to test overlayfs on top of (for exaple) 9pfs
with generic/699, and in that case, MOUNT_OPTIONS will be set from
PLAN9_MOUNT_OPTIONS, and will contain options like "version=9p2000.L"
that overalyfs has no hope of handling.

What I'm wondering is what mount options _overlay_mount_dirs() needs
from _common_dev_mount_options()?  Why is it there in the first place?
If there are some specific mount options that we need to pass on to
overlatyfs, maybe _overlay_mount_dirs() should be grepping out
whatever mount options. it needs, instead of just blindly pulling all
of the mount options?  Or, maybe _overlay_mount_dirs() sould avoid
calling _common_dev_mount_options if FSTYP != overlay?

				     	      - Ted