Re: [Xen-devel] [PATCH v2] xen/mm.h: add helper function to test-and-clear _PGC_allocated

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 15/07/2019 10:17, Paul Durrant wrote:
> The _PGC_allocated flag is set on a page when it is assigned to a domain
> along with an initial reference count of at least 1. To clear this
> 'allocation' reference it is necessary to test-and-clear _PGC_allocated and
> then only drop the reference if the test-and-clear succeeds. This is open-
> coded in many places. It is also unsafe to test-and-clear _PGC_allocated
> unless the caller holds an additional reference.
>
> This patch adds a helper function, put_page_alloc_ref(), to replace all the
> open-coded test-and-clear/put_page occurrences and incorporates in that a
> BUG_ON() an additional page reference not being held.
>
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
For the Arm bits:

Acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,

--
Julien Grall

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