Re: SLUB sysfs support

[Al Viro <viro@ZenIV.linux.org.uk>]

On Thu, Dec 27, 2007 at 03:22:28PM -0800, Christoph Lameter wrote:
> > a) remove symlink when slab goes away
> 
> Ok. Need to think about how to code that.

Huh?  Just call it from kmem_cache_destroy(); what business does that symlink
have being around after that point?

> > b) instead of kfree() in slab removal do kobject_put() if you have sysfs stuff
> 
> Hmmmm.... Okay. Patch follows but its strange to do a kobject_put after a 
> kobject_del().

kobject_del() undoes the effect of kobject_add().  And then you are left
with the refcount you had before kobject_add(), i.e. from kobject_init().

Think of it that way: kobject refcount controls the lifetime of structure
the sucker's embedded into.  Depending on kobject methods, you might
be unable to do cleanup of non-kobject parts of that animal until after
kobject_del().  IOW, you _can't_ have kobject_del() dropping the (hopefully)
final reference to kobject - only the caller knows what might have to be
done in between.