Re: [PATCH] SGI 882960: Busy inodes after unmount, oops

[Olaf Kirch <okir@suse.de>]

Hi Greg,

I've been looking at your analysis a little closer, and am
trying to understand how the bug was triggered. Here's what
I think happened:

 -	the unlink code keeps a reference to the dentry of
 	the parent directory, but not to the vfsmount
 -	this allows the umount to proceed, because there
 	don't seem to be any more references to the mount
 -	rpc_shutdown_client calls rpc_killall_tasks, which
 	terminates the async unlink task.
 -	rpciod is woken up and schedules the async task,
 	calling __rpc_execute
 -	__rpc_execute notices the task is dead (no tk_action),
 	leaves the loop and invokes task->tk_exit == nfs_async_unlink_done
 -	nfs_async_unlink_done calls dput() on the parent dentry,
 	but the dentry is not unhashed.

Now looking at kill_super(), the sequence of calls there looks
like this:

	shrink_dcache_parent(root);
	...
	sop->put_super(sb);
	...
	if (invalidate_inodes(sb)) {
		printk(KERN_ERR "VFS: Busy inodes after unmount. "
			"Self-destruct in 5 seconds.  Have a nice day...\n");
	}

So the real problem is that the dentry isn't unhashed. The other
part of the patch isn't required because the tk_exit() function
is called always, even when rpc_killall_tasks triggers the demise
of an async task.

Do you agree with this analysis?

Olaf
-- 
Olaf Kirch     |  Stop wasting entropy - start using predictable
okir@suse.de   |  tempfile names today!
---------------+ 


-------------------------------------------------------
The SF.Net email is sponsored by EclipseCon 2004
Premiere Conference on Open Tools Development and Integration
See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
http://www.eclipsecon.org/osdn
_______________________________________________
NFS maillist  -  NFS@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/nfs