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Re: [Xen-devel] [patch 6/6] netif_release_rx_bufs

To: Gerd Hoffmann <kraxel@xxxxxxx>
Subject: Re: [Xen-devel] [patch 6/6] netif_release_rx_bufs
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 18 Aug 2006 09:54:19 +0100
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On 18/8/06 7:43 am, "Gerd Hoffmann" <kraxel@xxxxxxx> wrote:

>>> How can I do that?  gnttab_end_foreign_transfer_ref() doesn't cut it, it
>>> will not succeed unconditionally ...
>> The function will not spin unboundedly and, when it returns, the grant is
>> definitely no longer active. If any page was transferred via the grant, it
>> is returned to the caller (else zero is returned). It does just what you
>> need.
> Oh, ok.  I assumed zero return means it failed.  Guess I just have to
> keep track of the original mfns so I can map them back into the address
> space in case no page was transfered, right?

You've given up the original mfns at this point, to ensure you have enough
reservation headroom for the transfer. You'll be wanting to give the 'empty
mfn' to the balloon driver, which can simply stick the page on its
ballooned-out list. You might need to add a new API function to balloon
driver to do this.

 -- Keir

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