linux-kernel - Re: [Xen-devel] [PATCH v4] xen/grant-table: Avoid m2p

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Message-ID: <52DFA438.6050103@citrix.com>
Date:	Wed, 22 Jan 2014 10:58:00 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Zoltan Kiss <zoltan.kiss@...rix.com>
CC:	<ian.campbell@...rix.com>, <wei.liu2@...rix.com>,
	<xen-devel@...ts.xenproject.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <jonathan.davies@...rix.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: Re: [Xen-devel] [PATCH v4] xen/grant-table: Avoid m2p_override during
 mapping

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@...rix.com>
> Suggested-by: David Vrabel <david.vrabel@...rix.com>

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

But I think this needs Stefano's ack.

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

David
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