linux-2.6.25: 'mkdir -p' does not work with rootdir as mount point inside a read only filesystem

From: Lothar Waßmann
Date: Wed Apr 30 2008 - 11:23:20 EST


Hi,

when trying to create a directory path with 'mkdir -p' with the root
being a mount point of a writeable filesystem that exists inside a
read-only file system, mkdir return -EROFS.

This was tested with the latest git-tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

The last kernel I know of this has been working was 2.6.22.

E.g.:
|root@triton1:/# mount
|rootfs on / type rootfs (rw)
|/dev/root on / type jffs2 (ro)
|proc on /proc type proc (rw)
|sysfs on /sys type sysfs (rw)
|/dev/root on /dev/.static/dev type jffs2 (ro)
|tmpfs on /dev type tmpfs (rw,size=10240k,mode=755)
|tmpfs on /var type tmpfs (rw)
|tmpfs on /tmp type tmpfs (rw)
|devpts on /dev/pts type devpts (rw,gid=5,mode=620)
|tmpfs on /dev/shm type tmpfs (rw)
|root@triton1:/# mkdir -p /dev/.udev/db
|mkdir: Cannot create directory `/dev/': Read-only file system

While:
|root@triton1:/# cd /dev
|root@triton1:/# mkdir -p .udev/db
works as expected...

Has anyone else encountered this problem already?
I've searched the archives but could not find anything related to this
problem.



Lothar Waßmann
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