Re: [PATCH 25/20] sysfs: Only support removing emtpy sysfs directories.

[Alan Stern]

On Wed, 27 May 2009, Eric W. Biederman wrote:

> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> 
> >
> > As fas as I know, they can't.  Instead, they can cause the SCSI layer 
> > to unregister a sysfs directory containing a child directory.  :-)
> >
> > Basically, a user program can delay removal of the child (i.e., the
> > target) directory indefinitely, because currently the target isn't
> > unregistered when all its children are removed -- it's unregistered
> > when all its children are _released_.
> 
> Ok.  Is this opens of /dev/sda1 and the like that are being held open by
> userspace that are potentially causing problems?

Yes, plus any other mechanism for preventing a struct device's refcount 
from going to 0.

> I think I have the fix to that...

The fix is to delete the target when its children are deleted, and not
wait until the children are released.

Alan Stern

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