Messages in this thread | | | Date | Thu, 16 Mar 2006 17:27:41 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: [PATCH 10 of 20] ipath - support for userspace apps using core driver |
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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).
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