Re: Re: [Xen-devel] SetPageForeign in netback

["Zang Hongyong" <zanghongyong@xxxxxxxxxx>]

Many thanks!
And that is, when tx, after the data page is sent by native Nic driver in dom0, 
the data page will be freed, then netif_page_release() called which indicates 
netback to unmap the page offered by domU, and moves on its tx response.

Is that so?
If so, how about a bad NIC driver which doen't call free_page() after sending 
data out of machine ?

and Why mmap_pages is allocated by 
alloc_empty_pages_and_pagevec(MAX_PENDING_REQS)?
can  mmap_pages be allocated by alloc_vm_area() and vmalloc_to_page() ??

Forgive my silly questions above please.
        

======= 2008-06-18 18:52:27 您在来信中写道：=======

>> 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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>
>

= = = = = = = = = = = = = = = = = = = =
Zang Hongyong
zanghongyong@xxxxxxxxxx
2008-06-18

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