Re: [PATCH} fix defect with kobject memory leaks during del_gendisk

[Steven Dake <sdake@mvista.com>]

On Thu, 2003-09-25 at 10:26, Patrick Mochel wrote:
> > Attached is a patch which fixes a few memory leaks in 2.6.0-test5. 
> > Comments are welcome as to whether or not this patch is the right
> > solution.
> > 
> > I added the ability to linux MD to generate add and remove hotplug calls
> > on RAID START and STOPs.  To achieve this, I use the del_gendisk call
> > which deletes the gendisk, delete the children kobjects, and delete the
> > parent (in this case, mdX) kobject.
> > 
> > Unfortunately it appears that del_gendisk uses kobject_del to delete the
> > kobject.  If the kobject has a ktype release function, it is not called
> > in the kobject_del call path, but only in kobject_unregister.
> > 
> > This patch changes the functionality so the release function (in this
> > case the block device release function in drivers/block/genhd.c) is
> > called by changing the kobject_del to kobject_unregister.
> 
> It is not the right thing to do, as Christoph pointed out. Gendisks have a 
> lifetime longer than the time between add_disk() and del_gendisk(). They 
> are created before they are added, and the objects may persist longer 
> after they have been removed from view. 
> 
> To delete the last reference, the MD layer should be calling put_disk(), 
> which will trigger release to happen. 
> 
> Your patch will actually cause other bugs, since the final put_disk() of 
> other block drivers will now be called on already freed memory.
> 
> 
> 	Pat
> 
> 
Thanks good call..  Didn't see the put_disk call but it makes sense now.

-steve