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

[Hugh Dickins <hugh@veritas.com>]

On Thu, 16 Mar 2006, Bryan O'Sullivan wrote:
> 
> This is more or less what we're doing now.  Except we're not doing a
> get_page after dma_alloc_coherent, and vmops->nopage is doing a
> get_page.  Reading between the lines, I guess the driver should be doing
> a get_page right after the allocation, and a put_page before it does the
> free?  This matches my mental model at least, but it seems that my model
> is a bit mental.

There's no need to do a get_page after the allocation and a put_page
before the free (though you could, it's just extra unnecessary work):
the allocation comes with a reference count of 1, the free frees up
that last remaining reference count of 1 (as Andrew explained more
lucidly elsewhere in his mail).

Hugh
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