Re: kern/29360: vfs.generic.usermount and mount(8) general questions

[Antti Kantee <pooka%cs.hut.fi@localhost>]

On Sun Sep 06 2009 at 17:24:56 +0200, Manuel Bouyer wrote:
> > As I recall, it was
> > added because mounting enough file systems (I used kernfs for testing back
> > then) would cause the kernel to run out of memory and the system to panic.
> 
> I think the discussion about this also refereced the above SA (which had been
> fixed at this time, but showed how fragile usermounts are), but I may
> be wrong.

Apparently you can still make the system panic by just mounting a zillion
kernfs's (which is just one way to make the kernel run out of memory).
I think the problem is that somewhere along the line kmem_alloc(KM_SLEEP)
returns NULL.  I remember there being discussions that the caller of
kmem_alloc() should always check against NULL return, but that of course
makes calling it slightly inconvenient.