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Subject[PATCH v16 3/9] mm: Add function __putback_isolated_page
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From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

There are cases where we would benefit from avoiding having to go through
the allocation and free cycle to return an isolated page.

Examples for this might include page poisoning in which we isolate a page
and then put it back in the free list without ever having actually
allocated it.

This will enable us to also avoid notifiers for the future free page
reporting which will need to avoid retriggering page reporting when
returning pages that have been reported on.

Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
mm/internal.h | 2 ++
mm/page_alloc.c | 19 +++++++++++++++++++
mm/page_isolation.c | 6 ++----
3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 3cf20ab3ca01..7b108222e5f4 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -157,6 +157,8 @@ static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn,
}

extern int __isolate_free_page(struct page *page, unsigned int order);
+extern void __putback_isolated_page(struct page *page, unsigned int order,
+ int mt);
extern void memblock_free_pages(struct page *page, unsigned long pfn,
unsigned int order);
extern void __free_pages_core(struct page *page, unsigned int order);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 459c6b2109bd..9dce69fce9e0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3228,6 +3228,25 @@ int __isolate_free_page(struct page *page, unsigned int order)
return 1UL << order;
}

+/**
+ * __putback_isolated_page - Return a now-isolated page back where we got it
+ * @page: Page that was isolated
+ * @order: Order of the isolated page
+ *
+ * This function is meant to return a page pulled from the free lists via
+ * __isolate_free_page back to the free lists they were pulled from.
+ */
+void __putback_isolated_page(struct page *page, unsigned int order, int mt)
+{
+ struct zone *zone = page_zone(page);
+
+ /* zone lock should be held when this function is called */
+ lockdep_assert_held(&zone->lock);
+
+ /* Return isolated page to tail of freelist. */
+ __free_one_page(page, page_to_pfn(page), zone, order, mt);
+}
+
/*
* Update NUMA hit/miss statistics
*
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 04ee1663cdbe..cb26aea9b9fd 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -134,13 +134,11 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
__mod_zone_freepage_state(zone, nr_pages, migratetype);
}
set_pageblock_migratetype(page, migratetype);
+ if (isolated_page)
+ __putback_isolated_page(page, order, migratetype);
zone->nr_isolate_pageblock--;
out:
spin_unlock_irqrestore(&zone->lock, flags);
- if (isolated_page) {
- post_alloc_hook(page, order, __GFP_MOVABLE);
- __free_pages(page, order);
- }
}

static inline struct page *
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