Re: [Xen-devel] netfront leaking two pages on unload?

[Andy Grover <andy.grover@xxxxxxxxxx>]

On Thu, 2008-01-17 at 15:48 +0000, Keir Fraser wrote:
> On 16/1/08 21:16, "Andy Grover" <andy.grover@xxxxxxxxxx> wrote:

> > Otherwise the pages cannot be freed properly in the guest, right?
> 
> Well, I think you've chosen slightly the wrong place, so I've just committed
> a change that makes the close-down logic more like in blkback. Possibly the
> reason we didn't follow that same logic before is that netif_disconnect()
> also makes the network device in dom0 also go away, which might cause
> unwanted chnages to routing and firewall rules, execution of hotplug
> scripts, etc. But we can separate the concepts of relinquishing frontend
> resources and destroying the backend netdev later if it turns out to be
> necessary.

Thanks for taking a look.

I was going to put together a patch to properly free the 2 pages in
netfront, but it looks like this is already handled inside
gnttab_end_foreign_access().

It seems a little non-intuitive that gnttab_end_foreign_access doesn't
just end foreign access, it frees the page too. This leads to what
confused me -- a driver allocating a page but (seemingly) never freeing
it.

I think it might be clearer to make callers explicitly free the page
after checking gnttab_end_foreign_access's return val for success. Would
you accept a patch doing this, or are there other reasons for the
current code?

Thanks -- Regards -- Andy



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