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Re: [Qemu-devel] [PATCH v9 3/5] mm: function to offer a page block on th

From: Wei Wang
Subject: Re: [Qemu-devel] [PATCH v9 3/5] mm: function to offer a page block on the free list
Date: Fri, 14 Apr 2017 10:30:27 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 04/14/2017 04:02 AM, Andrew Morton wrote:
On Thu, 13 Apr 2017 17:35:06 +0800 Wei Wang <address@hidden> wrote:

Add a function to find a page block on the free list specified by the
caller. Pages from the page block may be used immediately after the
function returns. The caller is responsible for detecting or preventing
the use of such pages.


--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4498,6 +4498,93 @@ void show_free_areas(unsigned int filter)
+ * Heuristically get a page block in the system that is unused.
+ * It is possible that pages from the page block are used immediately after
+ * inquire_unused_page_block() returns. It is the caller's responsibility
+ * to either detect or prevent the use of such pages.
+ *
+ * The free list to check: zone->free_area[order].free_list[migratetype].
+ *
+ * If the caller supplied page block (i.e. **page) is on the free list, offer
+ * the next page block on the list to the caller. Otherwise, offer the first
+ * page block on the list.
+ *
+ * Return 0 when a page block is found on the caller specified free list.
+ */
+int inquire_unused_page_block(struct zone *zone, unsigned int order,
+                             unsigned int migratetype, struct page **page)
Perhaps we can wrap this in the appropriate ifdef so the kernels which
won't be using virtio-balloon don't carry the added overhead.

OK. What do you think if we add this:



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