xfs tries to write on readonly device on unmount

[Christoph Hellwig]

On Tue, Jul 21, 2009 at 12:51:20PM +0200, Michael Prokop wrote:
> Hi,
> 
> This issue might be related to
> http://oss.sgi.com/bugzilla/show_bug.cgi?id=413
> 
> A XFS partition is set to read-only mode (using 'blockdev --setro')
> and mounted. As soon as I *un*mount the filesystem there seem to
> happen write requests.
> 
> I've a Tableau Forensic Bridge? which avoids the write requests and
> attached it to a Linux live-system running kernel 2.6.28 inside
> VMware and Virtualbox. I can easily reproduce the problem.


Block 0 is the superblock, so it appears like there is a superblock
write somewhere not guarded by an read-only check.  Can you still
reproduce this with a current kernel?  We now do have a testcase in
xfsqa (test 200) that checks exactly that scenario, but it doesn't
show issues on recent kernels.