[PATCH v2 5/6] mm/balloon_compaction: use common page ballooning

From: Konstantin Khlebnikov
Date: Sat Aug 30 2014 - 12:42:42 EST

From: Konstantin Khlebnikov <k.khlebnikov@xxxxxxxxxxx>

This patch replaces checking AS_BALLOON_MAP in page->mapping->flags
with PageBalloon which is stored directly in the struct page.
All code of balloon_compaction now under CONFIG_MEMORY_BALLOON.

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@xxxxxxxxxxx>
---
drivers/virtio/Kconfig | 1
include/linux/balloon_compaction.h | 135 ++++++------------------------------
mm/Kconfig | 2 -
mm/Makefile | 3 +
mm/balloon_compaction.c | 7 +-
mm/compaction.c | 9 +-
mm/migrate.c | 6 +-
mm/vmscan.c | 2 -
8 files changed, 39 insertions(+), 126 deletions(-)

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index c6683f2..00b2286 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -25,6 +25,7 @@ config VIRTIO_PCI
config VIRTIO_BALLOON
tristate "Virtio balloon driver"
depends on VIRTIO
+ select MEMORY_BALLOON
---help---
This driver supports increasing and decreasing the amount
of memory within a KVM guest.
diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
index 284fc1d..09f8c5a 100644
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h
@@ -46,6 +46,8 @@
#include <linux/gfp.h>
#include <linux/err.h>

+#ifdef CONFIG_MEMORY_BALLOON
+
/*
* Balloon device information descriptor.
* This struct is used to allow the common balloon compaction interface
@@ -93,91 +95,6 @@ static inline void balloon_page_free(struct page *page)
__free_page(page);
}

-#ifdef CONFIG_BALLOON_COMPACTION
-extern bool balloon_page_isolate(struct page *page);
-extern void balloon_page_putback(struct page *page);
-extern int balloon_page_migrate(struct page *newpage,
- struct page *page, enum migrate_mode mode);
-extern struct address_space
-*balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
- const struct address_space_operations *a_ops);
-
-static inline void balloon_mapping_free(struct address_space *balloon_mapping)
-{
- kfree(balloon_mapping);
-}
-
-/*
- * page_flags_cleared - helper to perform balloon @page ->flags tests.
- *
- * As balloon pages are obtained from buddy and we do not play with page->flags
- * at driver level (exception made when we get the page lock for compaction),
- * we can safely identify a ballooned page by checking if the
- * PAGE_FLAGS_CHECK_AT_PREP page->flags are all cleared. This approach also
- * helps us skip ballooned pages that are locked for compaction or release, thus
- * mitigating their racy check at balloon_page_movable()
- */
-static inline bool page_flags_cleared(struct page *page)
-{
- return !(page->flags & PAGE_FLAGS_CHECK_AT_PREP);
-}
-
-/*
- * __is_movable_balloon_page - helper to perform @page mapping->flags tests
- */
-static inline bool __is_movable_balloon_page(struct page *page)
-{
- struct address_space *mapping = page->mapping;
- return !PageAnon(page) && mapping_balloon(mapping);
-}
-
-/*
- * balloon_page_movable - test page->mapping->flags to identify balloon pages
- * that can be moved by compaction/migration.
- *
- * This function is used at core compaction's page isolation scheme, therefore
- * most pages exposed to it are not enlisted as balloon pages and so, to avoid
- * undesired side effects like racing against __free_pages(), we cannot afford
- * holding the page locked while testing page->mapping->flags here.
- *
- * As we might return false positives in the case of a balloon page being just
- * released under us, the page->mapping->flags need to be re-tested later,
- * under the proper page lock, at the functions that will be coping with the
- * balloon page case.
- */
-static inline bool balloon_page_movable(struct page *page)
-{
- /*
- * Before dereferencing and testing mapping->flags, let's make sure
- * this is not a page that uses ->mapping in a different way
- */
- if (page_flags_cleared(page) && !page_mapped(page) &&
- page_count(page) == 1)
- return __is_movable_balloon_page(page);
-
- return false;
-}
-
-/*
- * isolated_balloon_page - identify an isolated balloon page on private
- * compaction/migration page lists.
- *
- * After a compaction thread isolates a balloon page for migration, it raises
- * the page refcount to prevent concurrent compaction threads from re-isolating
- * the same page. For that reason putback_movable_pages(), or other routines
- * that need to identify isolated balloon pages on private pagelists, cannot
- * rely on balloon_page_movable() to accomplish the task.
- */
-static inline bool isolated_balloon_page(struct page *page)
-{
- /* Already isolated balloon pages, by default, have a raised refcount */
- if (page_flags_cleared(page) && !page_mapped(page) &&
- page_count(page) >= 2)
- return __is_movable_balloon_page(page);
-
- return false;
-}
-
/*
* balloon_page_insert - insert a page into the balloon's page list and make
* the page->mapping assignment accordingly.
@@ -192,6 +109,8 @@ static inline void balloon_page_insert(struct page *page,
struct address_space *mapping,
struct list_head *head)
{
+ __SetPageBalloon(page);
+ inc_zone_page_state(page, NR_BALLOON_PAGES);
page->mapping = mapping;
list_add(&page->lru, head);
}
@@ -206,10 +125,29 @@ static inline void balloon_page_insert(struct page *page,
*/
static inline void balloon_page_delete(struct page *page)
{
+ __ClearPageBalloon(page);
+ dec_zone_page_state(page, NR_BALLOON_PAGES);
page->mapping = NULL;
list_del(&page->lru);
}

+#endif /* CONFIG_MEMORY_BALLOON */
+
+#ifdef CONFIG_BALLOON_COMPACTION
+
+extern bool balloon_page_isolate(struct page *page);
+extern void balloon_page_putback(struct page *page);
+extern int balloon_page_migrate(struct page *newpage,
+ struct page *page, enum migrate_mode mode);
+extern struct address_space
+*balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
+ const struct address_space_operations *a_ops);
+
+static inline void balloon_mapping_free(struct address_space *balloon_mapping)
+{
+ kfree(balloon_mapping);
+}
+
/*
* balloon_page_device - get the b_dev_info descriptor for the balloon device
* that enqueues the given page.
@@ -246,33 +184,6 @@ static inline void balloon_mapping_free(struct address_space *balloon_mapping)
return;
}

-static inline void balloon_page_insert(struct page *page,
- struct address_space *mapping,
- struct list_head *head)
-{
- list_add(&page->lru, head);
-}
-
-static inline void balloon_page_delete(struct page *page)
-{
- list_del(&page->lru);
-}
-
-static inline bool __is_movable_balloon_page(struct page *page)
-{
- return false;
-}
-
-static inline bool balloon_page_movable(struct page *page)
-{
- return false;
-}
-
-static inline bool isolated_balloon_page(struct page *page)
-{
- return false;
-}
-
static inline bool balloon_page_isolate(struct page *page)
{
return false;
diff --git a/mm/Kconfig b/mm/Kconfig
index 72e0db0..e09cf0a 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -237,7 +237,7 @@ config MEMORY_BALLOON
config BALLOON_COMPACTION
bool "Allow for balloon memory compaction/migration"
def_bool y
- depends on COMPACTION && VIRTIO_BALLOON
+ depends on COMPACTION && MEMORY_BALLOON
help
Memory fragmentation introduced by ballooning might reduce
significantly the number of 2MB contiguous memory blocks that can be
diff --git a/mm/Makefile b/mm/Makefile
index a96e3a1..b2f18dc 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -16,7 +16,7 @@ obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
readahead.o swap.o truncate.o vmscan.o shmem.o \
util.o mmzone.o vmstat.o backing-dev.o \
mm_init.o mmu_context.o percpu.o slab_common.o \
- compaction.o balloon_compaction.o vmacache.o \
+ compaction.o vmacache.o \
interval_tree.o list_lru.o workingset.o \
iov_iter.o $(mmu-y)

@@ -64,3 +64,4 @@ obj-$(CONFIG_ZBUD) += zbud.o
obj-$(CONFIG_ZSMALLOC) += zsmalloc.o
obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
obj-$(CONFIG_CMA) += cma.o
+obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index 6e45a50..a942081 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -239,8 +239,7 @@ bool balloon_page_isolate(struct page *page)
* Prevent concurrent compaction threads from isolating
* an already isolated balloon page by refcount check.
*/
- if (__is_movable_balloon_page(page) &&
- page_count(page) == 2) {
+ if (PageBalloon(page) && page_count(page) == 2) {
__isolate_balloon_page(page);
unlock_page(page);
return true;
@@ -261,7 +260,7 @@ void balloon_page_putback(struct page *page)
*/
lock_page(page);

- if (__is_movable_balloon_page(page)) {
+ if (PageBalloon(page)) {
__putback_balloon_page(page);
/* drop the extra ref count taken for page isolation */
put_page(page);
@@ -286,7 +285,7 @@ int balloon_page_migrate(struct page *newpage,
*/
BUG_ON(!trylock_page(newpage));

- if (WARN_ON(!__is_movable_balloon_page(page))) {
+ if (WARN_ON(!PageBalloon(page))) {
dump_page(page, "not movable balloon page");
unlock_page(newpage);
return rc;
diff --git a/mm/compaction.c b/mm/compaction.c
index ad58f73..7d9d92e 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -642,11 +642,10 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
* Skip any other type of page
*/
if (!PageLRU(page)) {
- if (unlikely(balloon_page_movable(page))) {
- if (balloon_page_isolate(page)) {
- /* Successfully isolated */
- goto isolate_success;
- }
+ if (unlikely(PageBalloon(page)) &&
+ balloon_page_isolate(page)) {
+ /* Successfully isolated */
+ goto isolate_success;
}
continue;
}
diff --git a/mm/migrate.c b/mm/migrate.c
index 57c94f9..a4939b1 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -92,7 +92,7 @@ void putback_movable_pages(struct list_head *l)
list_del(&page->lru);
dec_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
- if (unlikely(isolated_balloon_page(page)))
+ if (unlikely(PageBalloon(page)))
balloon_page_putback(page);
else
putback_lru_page(page);
@@ -873,7 +873,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
}
}

- if (unlikely(__is_movable_balloon_page(page))) {
+ if (unlikely(PageBalloon(page))) {
/*
* A ballooned page does not need any special attention from
* physical to virtual reverse mapping procedures.
@@ -952,6 +952,7 @@ static int unmap_and_move(new_page_t get_new_page, free_page_t put_new_page,

rc = __unmap_and_move(page, newpage, force, mode);

+#ifdef CONFIG_MEMORY_BALLOON
if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) {
/*
* A ballooned page has been migrated already.
@@ -963,6 +964,7 @@ static int unmap_and_move(new_page_t get_new_page, free_page_t put_new_page,
balloon_page_free(page);
return MIGRATEPAGE_SUCCESS;
}
+#endif
out:
if (rc != -EAGAIN) {
/*
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1a71b8b..88dd901 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1160,7 +1160,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,

list_for_each_entry_safe(page, next, page_list, lru) {
if (page_is_file_cache(page) && !PageDirty(page) &&
- !isolated_balloon_page(page)) {
+ !PageBalloon(page)) {
ClearPageActive(page);
list_move(&page->lru, &clean_pages);
}

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