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Re: [Xen-devel] [PATCH v2] xen/mm.h: add helper function to test-and-clear _PGC_allocated
- To: Paul Durrant <paul.durrant@xxxxxxxxxx>
- From: Jan Beulich <JBeulich@xxxxxxxx>
- Date: Mon, 15 Jul 2019 09:24:04 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Ian Jackson <ian.jackson@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, Tamas K Lengyel <tamas@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, VolodymyrBabchuk <Volodymyr_Babchuk@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Mon, 15 Jul 2019 09:44:45 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHVOu5JruoXiXL6K0+SvpwJHZPvbabLaDGA
- Thread-topic: [PATCH v2] xen/mm.h: add helper function to test-and-clear _PGC_allocated
On 15.07.2019 11:17, 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.
This last sentence reads somewhat strange to me - are there words
missing and/or mis-ordered?
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
With the commit message aspect clarified
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Jan
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