===== DF-3217: ext4-extents image mounts but all I/O is EINVAL stubs =====
MOUNT-OK (incompat EXTENTS accepted)
cat: /mnt/hello: Invalid argument
cat exit=0 (nonzero == read path broken)
dd: /mnt/hello: Invalid argument
/mnt
--- free-blocks before/after unlink (leak check) ---
/dev/vn1       29940 4111 24191    15%    /mnt
rm: /mnt/hello: Invalid argument
/dev/vn1       29940 4111 24191    15%    /mnt