Linux kernel warnings when trying to remount a shared folder

[Eugene]

When I try to remount a shared folder on a Linux guest, it fails and the guest kernel issues several warnings that may indicate that some problem has occured. The steps to reproduce are as follows:

First I mount a shared folder "vbshare" to /mnt/shared:

#> mount -t vboxsf vbshare /mnt/shared

So far so good. Now I try to remount it read only:

#> mount -t vboxsf -o remount,ro vbshare /mnt/shared 
/sbin/mount.vboxsf: mounting failed with the error: Invalid argument

In the system log on the guest there are several warnings triggered in the kernel during the execution of sf_read_super_26() (see the attached system.log file for details):

• WARNING: at /build/buildd/linux-2.6.38/fs/sysfs/dir.c:455 sysfs_add_one+0xc8/0xf0()

Hardware name: VirtualBox sysfs: cannot create duplicate filename '/devices/virtual/bdi/vboxsf-vbshare'

• kobject_add_internal failed for vboxsf-vbshare with -EEXIST, don't try to register things with the same name in the same directory.

• And 3 more.

At the end, the log shows that sf_read_super_aux() returned -EINVAL (-22) and mounting failed indeed.

Guest: Ubuntu 11.04 x64, kernel 2.6.38-8-generic, this problem showed up on other systems too.
Host: Windows XP SP3

[Eugene]

Output of dmesg

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.