[PATCH 3/4] mm/balloon: apply mobile page migratable into balloon

From: Gioh Kim
Date: Mon Jul 13 2015 - 04:34:40 EST

From: Gioh Kim <gurugio@xxxxxxxxxxx>

Apply mobile page migration into balloon driver.
The balloong driver has an anonymous inode that manages
address_space_operation for page migration.
Compaction calls interfaces of mobile page migration
instead of calling balloon migration directly.

Signed-off-by: Gioh Kim <gioh.kim@xxxxxxx>
Acked-by: Rafael Aquini <aquini@xxxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 3 ++
include/linux/balloon_compaction.h | 15 ++++++--
mm/balloon_compaction.c | 72 ++++++++++++--------------------------
mm/compaction.c | 8 ++---
mm/migrate.c | 21 ++++++-----
5 files changed, 54 insertions(+), 65 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 82e80e0..ef5b9b5 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -30,6 +30,7 @@
#include <linux/balloon_compaction.h>
#include <linux/oom.h>
#include <linux/wait.h>
+#include <linux/anon_inodes.h>

/*
* Balloon device works in 4K page units. So each page is pointed to by
@@ -505,6 +506,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
balloon_devinfo_init(&vb->vb_dev_info);
#ifdef CONFIG_BALLOON_COMPACTION
vb->vb_dev_info.migratepage = virtballoon_migratepage;
+ vb->vb_dev_info.inode = anon_inode_new();
+ vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
#endif

err = init_vqs(vb);
diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
index 9b0a15d..a9e0bde 100644
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h
@@ -48,6 +48,7 @@
#include <linux/migrate.h>
#include <linux/gfp.h>
#include <linux/err.h>
+#include <linux/fs.h>

/*
* Balloon device information descriptor.
@@ -62,6 +63,7 @@ struct balloon_dev_info {
struct list_head pages; /* Pages enqueued & handled to Host */
int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
struct page *page, enum migrate_mode mode);
+ struct inode *inode;
};

extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
@@ -73,12 +75,16 @@ static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
spin_lock_init(&balloon->pages_lock);
INIT_LIST_HEAD(&balloon->pages);
balloon->migratepage = NULL;
+ balloon->inode = NULL;
}

#ifdef CONFIG_BALLOON_COMPACTION
-extern bool balloon_page_isolate(struct page *page);
+extern const struct address_space_operations balloon_aops;
+extern bool balloon_page_isolate(struct page *page,
+ isolate_mode_t mode);
extern void balloon_page_putback(struct page *page);
-extern int balloon_page_migrate(struct page *newpage,
+extern int balloon_page_migrate(struct address_space *mapping,
+ struct page *newpage,
struct page *page, enum migrate_mode mode);

/*
@@ -124,6 +130,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
struct page *page)
{
__SetPageBalloon(page);
+ page->mapping = balloon->inode->i_mapping;
SetPagePrivate(page);
set_page_private(page, (unsigned long)balloon);
list_add(&page->lru, &balloon->pages);
@@ -140,6 +147,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
static inline void balloon_page_delete(struct page *page)
{
__ClearPageBalloon(page);
+ page->mapping = NULL;
set_page_private(page, 0);
if (PagePrivate(page)) {
ClearPagePrivate(page);
@@ -191,7 +199,8 @@ static inline bool isolated_balloon_page(struct page *page)
return false;
}

-static inline bool balloon_page_isolate(struct page *page)
+static inline bool balloon_page_isolate(struct page *page,
+ isolate_mode_t mode)
{
return false;
}
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index fcad832..8fbcf9c 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -131,43 +131,16 @@ static inline void __putback_balloon_page(struct page *page)
}

/* __isolate_lru_page() counterpart for a ballooned page */
-bool balloon_page_isolate(struct page *page)
+bool balloon_page_isolate(struct page *page, isolate_mode_t mode)
{
/*
- * Avoid burning cycles with pages that are yet under __free_pages(),
- * or just got freed under us.
- *
- * In case we 'win' a race for a balloon page being freed under us and
- * raise its refcount preventing __free_pages() from doing its job
- * the put_page() at the end of this block will take care of
- * release this page, thus avoiding a nasty leakage.
+ * A ballooned page, by default, has PagePrivate set.
+ * Prevent concurrent compaction threads from isolating
+ * an already isolated balloon page by clearing it.
*/
- if (likely(get_page_unless_zero(page))) {
- /*
- * As balloon pages are not isolated from LRU lists, concurrent
- * compaction threads can race against page migration functions
- * as well as race against the balloon driver releasing a page.
- *
- * In order to avoid having an already isolated balloon page
- * being (wrongly) re-isolated while it is under migration,
- * or to avoid attempting to isolate pages being released by
- * the balloon driver, lets be sure we have the page lock
- * before proceeding with the balloon page isolation steps.
- */
- if (likely(trylock_page(page))) {
- /*
- * A ballooned page, by default, has PagePrivate set.
- * Prevent concurrent compaction threads from isolating
- * an already isolated balloon page by clearing it.
- */
- if (balloon_page_movable(page)) {
- __isolate_balloon_page(page);
- unlock_page(page);
- return true;
- }
- unlock_page(page);
- }
- put_page(page);
+ if (balloon_page_movable(page)) {
+ __isolate_balloon_page(page);
+ return true;
}
return false;
}
@@ -175,37 +148,31 @@ bool balloon_page_isolate(struct page *page)
/* putback_lru_page() counterpart for a ballooned page */
void balloon_page_putback(struct page *page)
{
- /*
- * 'lock_page()' stabilizes the page and prevents races against
- * concurrent isolation threads attempting to re-isolate it.
- */
- lock_page(page);
+ if (!isolated_balloon_page(page))
+ return;

if (__is_movable_balloon_page(page)) {
__putback_balloon_page(page);
- /* drop the extra ref count taken for page isolation */
- put_page(page);
} else {
WARN_ON(1);
dump_page(page, "not movable balloon page");
}
- unlock_page(page);
}

/* move_to_new_page() counterpart for a ballooned page */
-int balloon_page_migrate(struct page *newpage,
+int balloon_page_migrate(struct address_space *mapping,
+ struct page *newpage,
struct page *page, enum migrate_mode mode)
{
struct balloon_dev_info *balloon = balloon_page_device(page);
int rc = -EAGAIN;

+ if (!isolated_balloon_page(page))
+ return rc;
+
/*
- * Block others from accessing the 'newpage' when we get around to
- * establishing additional references. We should be the only one
- * holding a reference to the 'newpage' at this point.
+ * newpage and page should be already locked.
*/
- BUG_ON(!trylock_page(newpage));
-
if (WARN_ON(!__is_movable_balloon_page(page))) {
dump_page(page, "not movable balloon page");
unlock_page(newpage);
@@ -215,7 +182,14 @@ int balloon_page_migrate(struct page *newpage,
if (balloon && balloon->migratepage)
rc = balloon->migratepage(balloon, newpage, page, mode);

- unlock_page(newpage);
return rc;
}
+
+/* define the balloon_mapping->a_ops callback to allow balloon page migration */
+const struct address_space_operations balloon_aops = {
+ .migratepage = balloon_page_migrate,
+ .isolatepage = balloon_page_isolate,
+ .putbackpage = balloon_page_putback,
+};
+EXPORT_SYMBOL_GPL(balloon_aops);
#endif /* CONFIG_BALLOON_COMPACTION */
diff --git a/mm/compaction.c b/mm/compaction.c
index 018f08d..60e4cbb 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -14,7 +14,7 @@
#include <linux/backing-dev.h>
#include <linux/sysctl.h>
#include <linux/sysfs.h>
-#include <linux/balloon_compaction.h>
+#include <linux/compaction.h>
#include <linux/page-isolation.h>
#include <linux/kasan.h>
#include "internal.h"
@@ -714,12 +714,12 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,

/*
* Check may be lockless but that's ok as we recheck later.
- * It's possible to migrate LRU pages and balloon pages
+ * It's possible to migrate LRU pages and mobile pages
* Skip any other type of page
*/
if (!PageLRU(page)) {
- if (unlikely(balloon_page_movable(page))) {
- if (balloon_page_isolate(page)) {
+ if (unlikely(mobile_page(page))) {
+ if (isolate_mobilepage(page, isolate_mode)) {
/* Successfully isolated */
goto isolate_success;
}
diff --git a/mm/migrate.c b/mm/migrate.c
index ee401e4..53f0081d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -35,7 +35,7 @@
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
#include <linux/gfp.h>
-#include <linux/balloon_compaction.h>
+#include <linux/compaction.h>
#include <linux/mmu_notifier.h>

#include <asm/tlbflush.h>
@@ -76,7 +76,7 @@ int migrate_prep_local(void)
* from where they were once taken off for compaction/migration.
*
* This function shall be used whenever the isolated pageset has been
- * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
+ * built from lru, mobile, hugetlbfs page. See isolate_migratepages_range()
* and isolate_huge_page().
*/
void putback_movable_pages(struct list_head *l)
@@ -92,8 +92,8 @@ 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)))
- balloon_page_putback(page);
+ if (unlikely(mobile_page(page)))
+ putback_mobilepage(page);
else
putback_lru_page(page);
}
@@ -844,15 +844,18 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
}
}

- if (unlikely(isolated_balloon_page(page))) {
+ if (unlikely(mobile_page(page))) {
/*
- * A ballooned page does not need any special attention from
+ * A mobile page does not need any special attention from
* physical to virtual reverse mapping procedures.
* Skip any attempt to unmap PTEs or to remap swap cache,
* in order to avoid burning cycles at rmap level, and perform
* the page migration right away (proteced by page lock).
*/
- rc = balloon_page_migrate(newpage, page, mode);
+ lock_page(newpage);
+ rc = page->mapping->a_ops->migratepage(page->mapping,
+ newpage, page, mode);
+ unlock_page(newpage);
goto out_unlock;
}

@@ -962,8 +965,8 @@ out:
if (rc != MIGRATEPAGE_SUCCESS && put_new_page) {
ClearPageSwapBacked(newpage);
put_new_page(newpage, private);
- } else if (unlikely(__is_movable_balloon_page(newpage))) {
- /* drop our reference, page already in the balloon */
+ } else if (unlikely(mobile_page(newpage))) {
+ /* drop our reference */
put_page(newpage);
} else
putback_lru_page(newpage);
--
2.1.4

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