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Subject[PATCH 2/9] mm: alloc_contig_freed_pages() added
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

This commit introduces alloc_contig_freed_pages() function
which allocates (ie. removes from buddy system) free pages
in range. Caller has to guarantee that all pages in range
are in buddy system.

Along with this function, a free_contig_pages() function is
provided which frees all (or a subset of) pages allocated
with alloc_contig_free_pages().

Michal Nazarewicz has modified the function to make it easier
to allocate not MAX_ORDER_NR_PAGES aligned pages by making it
return pfn of one-past-the-last allocated page.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
[m.nazarewicz: added checks if all allocated pages comes from the
same memory zone]
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
[m.szyprowski: fixed wrong condition in VM_BUG_ON assert]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
---
include/linux/mmzone.h | 16 +++++++++
include/linux/page-isolation.h | 5 +++
mm/page_alloc.c | 67 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 88 insertions(+), 0 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a2760bb..862a834 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1168,6 +1168,22 @@ static inline int memmap_valid_within(unsigned long pfn,
}
#endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */

+#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
+/*
+ * Both PFNs must be from the same zone! If this function returns
+ * true, pfn_to_page(pfn1) + (pfn2 - pfn1) == pfn_to_page(pfn2).
+ */
+static inline bool zone_pfn_same_memmap(unsigned long pfn1, unsigned long pfn2)
+{
+ return pfn_to_section_nr(pfn1) == pfn_to_section_nr(pfn2);
+}
+
+#else
+
+#define zone_pfn_same_memmap(pfn1, pfn2) (true)
+
+#endif
+
#endif /* !__GENERATING_BOUNDS.H */
#endif /* !__ASSEMBLY__ */
#endif /* _LINUX_MMZONE_H */
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 58cdbac..b9fc428 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -33,6 +33,11 @@ test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn);
extern int set_migratetype_isolate(struct page *page);
extern void unset_migratetype_isolate(struct page *page);

+/* The below functions must be run on a range from a single zone. */
+extern unsigned long alloc_contig_freed_pages(unsigned long start,
+ unsigned long end, gfp_t flag);
+extern void free_contig_pages(unsigned long pfn, unsigned nr_pages);
+
/*
* For migration.
*/
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bf4399a..fbfb920 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5706,6 +5706,73 @@ out:
spin_unlock_irqrestore(&zone->lock, flags);
}

+unsigned long alloc_contig_freed_pages(unsigned long start, unsigned long end,
+ gfp_t flag)
+{
+ unsigned long pfn = start, count;
+ struct page *page;
+ struct zone *zone;
+ int order;
+
+ VM_BUG_ON(!pfn_valid(start));
+ page = pfn_to_page(start);
+ zone = page_zone(page);
+
+ spin_lock_irq(&zone->lock);
+
+ for (;;) {
+ VM_BUG_ON(page_count(page) || !PageBuddy(page) ||
+ page_zone(page) != zone);
+
+ list_del(&page->lru);
+ order = page_order(page);
+ count = 1UL << order;
+ zone->free_area[order].nr_free--;
+ rmv_page_order(page);
+ __mod_zone_page_state(zone, NR_FREE_PAGES, -(long)count);
+
+ pfn += count;
+ if (pfn >= end)
+ break;
+ VM_BUG_ON(!pfn_valid(pfn));
+
+ if (zone_pfn_same_memmap(pfn - count, pfn))
+ page += count;
+ else
+ page = pfn_to_page(pfn);
+ }
+
+ spin_unlock_irq(&zone->lock);
+
+ /* After this, pages in the range can be freed one be one */
+ count = pfn - start;
+ pfn = start;
+ for (page = pfn_to_page(pfn); count; --count) {
+ prep_new_page(page, 0, flag);
+ ++pfn;
+ if (likely(zone_pfn_same_memmap(pfn - 1, pfn)))
+ ++page;
+ else
+ page = pfn_to_page(pfn);
+ }
+
+ return pfn;
+}
+
+void free_contig_pages(unsigned long pfn, unsigned nr_pages)
+{
+ struct page *page = pfn_to_page(pfn);
+
+ while (nr_pages--) {
+ __free_page(page);
+ ++pfn;
+ if (likely(zone_pfn_same_memmap(pfn - 1, pfn)))
+ ++page;
+ else
+ page = pfn_to_page(pfn);
+ }
+}
+
#ifdef CONFIG_MEMORY_HOTREMOVE
/*
* All pages in the range must be isolated before calling this.
--
1.7.1.569.g6f426


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