Re: [Xen-devel] [PATCH v4] xen/grant-table: Avoid m2p_override duringmapping

From: David Vrabel
Date: Wed Jan 22 2014 - 05:58:16 EST

On 21/01/14 20:22, Zoltan Kiss wrote:
> The grant mapping API does m2p_override unnecessarily: only gntdev needs it,
> for blkback and future netback patches it just cause a lock contention, as
> those pages never go to userspace. Therefore this series does the following:
> - the original functions were renamed to __gnttab_[un]map_refs, with a new
> parameter m2p_override
> - based on m2p_override either they follow the original behaviour, or just set
> the private flag and call set_phys_to_machine
> - gnttab_[un]map_refs are now a wrapper to call __gnttab_[un]map_refs with
> m2p_override false
> - a new function gnttab_[un]map_refs_userspace provides the old behaviour
> v2:
> - move the storing of the old mfn in page->index to gnttab_map_refs
> - move the function header update to a separate patch
> v3:
> - a new approach to retain old behaviour where it needed
> - squash the patches into one
> v4:
> - move out the common bits from m2p* functions, and pass pfn/mfn as parameter
> - clear page->private before doing anything with the page, so m2p_find_override
> won't race with this

I would prune this version information out of the commit message.

> Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
> Suggested-by: David Vrabel <david.vrabel@xxxxxxxxxx>

Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

But I think this needs Stefano's ack.

It would be useful to get this into 3.14 if possible.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at