Re: [PATCH 10 of 20] ipath - support for userspace apps using core driver

["Bryan O'Sullivan" <bos@pathscale.com>]

On Wed, 2006-03-15 at 21:38 -0800, Andrew Morton wrote:

> You need to decide who "owns" these pages.  Once that's decided, it tells
> you who should release them.

OK, I've made some interesting progress here.

The driver is now doing all of its allocations of DMAable memory using
dma_alloc_coherent.  We do a get_page right after the allocation in
every case, and a put_page right before the free.  In the cases where
I'm allocating memory that I know or think might be greater than a page
in size, I'm using __GFP_COMP.

The nopage handler always does a get_page.

We now have a rational-looking set of VM_* flags, instead of a random
heap of whatever seemed to work.  And we're not touching PG_reserved.

And now everything works.  I have yet to examine /proc/meminfo in
microscopic detail after 100,000 runs to be sure we don't have a leak of
some kind, but I no longer get oopses or crashes after 20 repeated runs,
where before I didn't survive even one.

Whew!  What a relief.

Hugh, Andrew, Linus and Roland: thanks very much.  This has been a
tremendous help.

	<b

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