Re: [Xen-devel] SetPageForeign in netback

To:	"Zang Hongyong" <zanghongyong@xxxxxxxxxx>
Subject:	Re: [Xen-devel] SetPageForeign in netback
From:	"Grzegorz Miłoś" <gm281@xxxxxxxxx>
Date:	Wed, 18 Jun 2008 11:52:27 +0100
Cc:	xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date:	Wed, 18 Jun 2008 03:52:51 -0700
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> hi,
>  in netback init mmap_pages,
>                SetPageForeign(page, netif_page_release);
>  that is, page->index = netif_page_release
>  while netif_page_release is a function.

netif_page_release is a function, and therefore:
page->index = netif_page_release
will store netif_page_release function pointer in 'index'

>  so what's the meaning of SetPageForeign?

Setting a page foreign means that the page is owned by another domain,
and that some care needs to be taken when freeing it.

>  And when the function  netif_page_release() will be called?

Whenever PageForeignDestructor is called (as it calls the destructor
function stored in the 'index' field).
PageForeignDestructor is called from:
__free_pages_ok
and
free_hot_cold_page

Hope this helps.

Cheers
Gr(z)egor(z)

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Re: [Xen-devel] SetPageForeign in netback