Re: Proposal: kmem_valloc [was: Re: raspberry pi panic 7.0_BETA after install fs resize]

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Sun, Nov 09, 2014 at 09:06:40AM +0100, Maxime Villard wrote:
> Le 08/11/2014 23:28, Jean-Yves Migeon a ??crit :
> 
> Yes, but still, what's the point of giving a size then? If the kernel
> knows the size, we can remove kmem_free's size argument, otherwise it
> is inconsistent.
> 
> And then, as I said, we lose the memory optimisation: one more kmem page
> is allocated to hold the size.

I'm not in favor of that.

Also, my experience porting a great deal of code from a very old 4.4BSD kernel
to NetBSD several years ago was that in converting the code from malloc to
kmem_alloc, I found a _lot_ of bugs -- use after frees, double frees, etc. --
because you had to keep much more careful track of what exactly you were
freeing, and when, in order to know its size.  I don't think we should give
that up (though I think the pool allocators are even better in this regard
and that perhaps it is use of any variable-size allocator that should be
discouraged).

Thor