path-lookup inconsistency ?

[Badhri Jagan Sridharan]

Hi,

I mounted overlayfs at /

My cat /proc/mounts looks like the following.
# cat /proc/mounts
/dev/root / squashfs ro,seclabel,relatime 0 0
..
overlayfs / overlay
rw,relatime,lowerdir=/,upperdir=/cache/upper,workdir=/cache/working 0
0

The original blockdevice at fs root is squashfs formatted so doesnt
support write operations. I mounted overlayfs on fs root to cache the
writes made.

While in /, the filesystem does not allow me to create files/directories,
if I dont prefix it with ".." directive.

hikey:/ # mkdir test
mkdir: 'testt12': Read-only file system
hikey:/ # mkdir ../test

"mkdir ../test" command succeeds.

I traced through the fs/namei.c code to notice that __follow_mount_rcu
does not get called when I execute "mkdir test" whereas, it gets called from
the follow_dotdot_rcu when I execute "mkdir ../test"

What is the expected behavior ? Should "mkdir test" and "mkdir ../test"
both succeed ?

Similar inconsistency is found with "ls" and "ls .." as well while in fs root.

Thanks,
Badhri