mm/balloon_compaction: ignore anonymous pages

Proper testing shows yet another problem in balloon migration: it works only once for each page. balloon_page_movable() check page flags and page_count. In __unmap_and_move page is locked, reference counter is elevated, so balloon_page_movable() _always_ fails here. As result in __unmap_and_move() migration goes to the normal migration path.

Balloon ->migratepage() is so special, it returns MIGRATEPAGE_BALLOON_SUCCESS instead of MIGRATEPAGE_SUCCESS. After that in move_to_new_page() successfully migrated page got NULL into its mapping pointer and loses connectivity with balloon and ability for further migration.

It's safe to use __is_movable_balloon_page here: page is isolated and pinned.

Signed-off-by Konstantin Khlebnikov <[email protected]>

Cc stable <[email protected]> # v3.8

---
 mm/migrate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

mm/migrate.c +0 -0

index f78ec9b..161d044 100644

LRU-lock isn't required for balloon page isolation. This check makes migration of some ballooned pages mostly impossible because isolate_migratepages_range() drops LRU lock periodically.

Signed-off-by Konstantin Khlebnikov <[email protected]>

Cc stable <[email protected]> # v3.8

---
 mm/compaction.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

mm/compaction.c +0 -0

index 21bf292..0653f5f 100644

This patch adds page state PageBallon() and functions __Set/ClearPageBalloon. Like PageBuddy() PageBalloon() looks like page-flag but actually this is special state of page->_mapcount counter. There is no conflict because ballooned pages cannot be mapped and cannot be in buddy allocator.

Ballooned pages are counted in vmstat counter NR_BALLOON_PAGES, it's shown them in /proc/meminfo and /proc/meminfo. Also this patch it exports PageBallon into userspace via /proc/kpageflags as KPF_BALLOON.

All this code including mm/balloon_compaction.o is under CONFIG_MEMORY_BALLOON, it should be selected by ballooning driver which want use this feature.

Signed-off-by Konstantin Khlebnikov <[email protected]>

---
 Documentation/filesystems/proc.txt     |    2 ++
 drivers/base/node.c                    |   16 ++++++++++------
 drivers/virtio/Kconfig                 |    1 +
 fs/proc/meminfo.c                      |    6 ++++++
 fs/proc/page.c                         |    3 +++
 include/linux/mm.h                     |   10 ++++++++++
 include/linux/mmzone.h                 |    3 +++
 include/uapi/linux/kernel-page-flags.h |    1 +
 mm/Kconfig                             |    5 +++++
 mm/Makefile                            |    3 ++-
 mm/balloon_compaction.c                |   14 ++++++++++++++
 mm/vmstat.c                            |    8 +++++++-
 tools/vm/page-types.c                  |    1 +
 13 files changed, 65 insertions(+), 8 deletions(-)

Documentation/filesystems/proc.txt +2 -0

index eb8a10e..154a345 100644
@@ -796,6 +796,7 @@ VmallocTotal:   112216 kB
 VmallocUsed:       428 kB
 VmallocChunk:   111088 kB
 AnonHugePages:   49152 kB
+BalloonPages:        0 kB
 
     MemTotal: Total usable ram (i.e. physical ram minus a few reserved
               bits and the kernel binary code)

@@ -838,6 +839,7 @@ MemAvailable: An estimate of how much memory is available for starting new
    Writeback: Memory which is actively being written back to the disk
    AnonPages: Non-file backed pages mapped into userspace page tables
 AnonHugePages: Non-file backed huge pages mapped into userspace page tables
+BalloonPages: Memory which was ballooned, not included into MemTotal
       Mapped: files which have been mmaped, such as libraries
         Slab: in-kernel data structures cache
 SReclaimable: Part of Slab, that might be reclaimed, such as caches

drivers/base/node.c +10 -6

index c6d3ae0..59e565c 100644
@@ -120,6 +120,9 @@ static ssize_t node_read_meminfo(struct device *dev,
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 		       "Node %d AnonHugePages:  %8lu kB\n"
 #endif
+#ifdef CONFIG_MEMORY_BALLOON
+		       "Node %d BalloonPages:   %8lu kB\n"
+#endif
 			,
 		       nid, K(node_page_state(nid, NR_FILE_DIRTY)),
 		       nid, K(node_page_state(nid, NR_WRITEBACK)),

@@ -136,14 +139,15 @@ static ssize_t node_read_meminfo(struct device *dev,
 		       nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE) +
 				node_page_state(nid, NR_SLAB_UNRECLAIMABLE)),
 		       nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE)),
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 		       nid, K(node_page_state(nid, NR_SLAB_UNRECLAIMABLE))
-			, nid,
-			K(node_page_state(nid, NR_ANON_TRANSPARENT_HUGEPAGES) *
-			HPAGE_PMD_NR));
-#else
-		       nid, K(node_page_state(nid, NR_SLAB_UNRECLAIMABLE)));
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+		       ,nid, K(node_page_state(nid,
+				NR_ANON_TRANSPARENT_HUGEPAGES) * HPAGE_PMD_NR)
+#endif
+#ifdef CONFIG_MEMORY_BALLOON
+		       ,nid, K(node_page_state(nid, NR_BALLOON_PAGES))
 #endif
+		       );
 	n += hugetlb_report_node_meminfo(nid, buf + n);
 	return n;
 }

drivers/virtio/Kconfig +1 -0

index c6683f2..00b2286 100644
@@ -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.

fs/proc/meminfo.c +6 -0

index aa1eee0..f897fbf 100644
@@ -138,6 +138,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 		"AnonHugePages:  %8lu kB\n"
 #endif
+#ifdef CONFIG_MEMORY_BALLOON
+		"BalloonPages:   %8lu kB\n"
+#endif
 		,
 		K(i.totalram),
 		K(i.freeram),

@@ -193,6 +196,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 		,K(global_page_state(NR_ANON_TRANSPARENT_HUGEPAGES) *
 		   HPAGE_PMD_NR)
 #endif
+#ifdef CONFIG_MEMORY_BALLOON
+		,K(global_page_state(NR_BALLOON_PAGES))
+#endif
 		);
 
 	hugetlb_report_meminfo(m);

fs/proc/page.c +3 -0

index e647c55..1e3187d 100644
@@ -133,6 +133,9 @@ u64 stable_page_flags(struct page *page)
 	if (PageBuddy(page))
 		u |= 1 << KPF_BUDDY;
 
+	if (PageBalloon(page))
+		u |= 1 << KPF_BALLOON;
+
 	u |= kpf_copy_bit(k, KPF_LOCKED,	PG_locked);
 
 	u |= kpf_copy_bit(k, KPF_SLAB,		PG_slab);

include/linux/mm.h +0 -0

index 8981cc8..d2dd497 100644
@@ -553,6 +553,16 @@ static inline void __ClearPageBuddy(struct page *page)
 	atomic_set(&page->_mapcount, -1);
 }
 

include/linux/mm.h +0 -0

 void put_page(struct page *page);
 void put_pages_list(struct list_head *pages);
 

include/linux/mmzone.h +3 -0

index 318df70..d88fd01 100644
@@ -157,6 +157,9 @@ enum zone_stat_item {
 	WORKINGSET_NODERECLAIM,
 	NR_ANON_TRANSPARENT_HUGEPAGES,
 	NR_FREE_CMA_PAGES,
+#ifdef CONFIG_MEMORY_BALLOON
+	NR_BALLOON_PAGES,
+#endif
 	NR_VM_ZONE_STAT_ITEMS };
 
 /*

include/uapi/linux/kernel-page-flags.h +1 -0

index 5116a0e..2f96d23 100644
@@ -31,6 +31,7 @@
 
 #define KPF_KSM			21
 #define KPF_THP			22
+#define KPF_BALLOON		23
 
 
 #endif /* _UAPILINUX_KERNEL_PAGE_FLAGS_H */

mm/Kconfig +5 -0

index 886db21..72e0db0 100644
@@ -228,6 +228,11 @@ config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 	boolean
 
 #
+# support for memory ballooning
+config MEMORY_BALLOON
+	boolean
+
+#
 # support for memory balloon compaction
 config BALLOON_COMPACTION
 	bool "Allow for balloon memory compaction/migration"

mm/Makefile +2 -1

index 632ae77..2d33d7f 100644
@@ -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

mm/balloon_compaction.c +4 -0

index 6e45a50..533c567 100644
@@ -10,6 +10,20 @@
 #include <linux/export.h>
 #include <linux/balloon_compaction.h>
 
+void __SetPageBalloon(struct page *page)
+{
+	VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
+	atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE);

mm/balloon_compaction.c +0 -0

 /*
  * balloon_devinfo_alloc - allocates a balloon device information descriptor.
  * @balloon_dev_descriptor: pointer to reference the balloon device which

mm/vmstat.c +7 -1

index e9ab104..6e704cc 100644
@@ -735,7 +735,7 @@ static void walk_zones_in_node(struct seq_file *m, pg_data_t *pgdat,
 					TEXT_FOR_HIGHMEM(xx) xx "_movable",
 
 const char * const vmstat_text[] = {
-	/* Zoned VM counters */
+	/* enum zone_stat_item countes */
 	"nr_free_pages",
 	"nr_alloc_batch",
 	"nr_inactive_anon",

@@ -778,10 +778,16 @@ const char * const vmstat_text[] = {
 	"workingset_nodereclaim",
 	"nr_anon_transparent_hugepages",
 	"nr_free_cma",
+#ifdef CONFIG_MEMORY_BALLOON
+	"nr_balloon_pages",
+#endif
+
+	/* enum writeback_stat_item counters */
 	"nr_dirty_threshold",
 	"nr_dirty_background_threshold",
 
 #ifdef CONFIG_VM_EVENT_COUNTERS
+	/* enum vm_event_item counters */
 	"pgpgin",
 	"pgpgout",
 	"pswpin",

tools/vm/page-types.c +0 -0

index c4d6d2e..264fbc2 100644

This patch replaces checking AS_BALLOON_MAP in page->mapping->flags with PageBalloon which is stored directly in the struct page.

Signed-off-by Konstantin Khlebnikov <[email protected]>

---
 include/linux/balloon_compaction.h |   85 ++----------------------------------
 mm/Kconfig                         |    2 -
 mm/balloon_compaction.c            |    7 +--
 mm/compaction.c                    |    9 ++--
 mm/migrate.c                       |    4 +-
 mm/vmscan.c                        |    2 -
 6 files changed, 15 insertions(+), 94 deletions(-)

include/linux/balloon_compaction.h +4 -81

index 53d482e..f5fda8b 100644
@@ -108,77 +108,6 @@ static inline void balloon_mapping_free(struct address_space *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.
  * @page    : page to be assigned as a 'balloon page'

@@ -192,6 +121,7 @@ static inline void balloon_page_insert(struct page *page,
 				       struct address_space *mapping,
 				       struct list_head *head)
 {
+	__SetPageBalloon(page);
 	page->mapping = mapping;
 	list_add(&page->lru, head);
 }

@@ -206,6 +136,7 @@ static inline void balloon_page_insert(struct page *page,
  */
 static inline void balloon_page_delete(struct page *page)
 {
+	__ClearPageBalloon(page);
 	page->mapping = NULL;
 	list_del(&page->lru);
 }

@@ -250,24 +181,16 @@ static inline void balloon_page_insert(struct page *page,
 				       struct address_space *mapping,
 				       struct list_head *head)
 {
+	__SetPageBalloon(page);
 	list_add(&page->lru, head);
 }
 
 static inline void balloon_page_delete(struct page *page)
 {
+	__ClearPageBalloon(page);
 	list_del(&page->lru);
 }
 
-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;

mm/Kconfig +1 -1

index 72e0db0..e09cf0a 100644
@@ -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

mm/balloon_compaction.c +3 -4

index 533c567..22c8e03 100644
@@ -253,8 +253,7 @@ 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;

@@ -275,7 +274,7 @@ 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);

@@ -300,7 +299,7 @@ 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;

mm/compaction.c +4 -5

index 0653f5f..e9aeed2 100644
@@ -596,11 +596,10 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
 		 * 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;
 		}

mm/migrate.c +2 -2

index 161d044..c35e6f2 100644
@@ -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.

mm/vmscan.c +0 -0

index 2836b53..f90f93e 100644

* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

Signed-off-by Konstantin Khlebnikov <[email protected]>

---
 drivers/virtio/virtio_balloon.c    |   77 ++++---------
 include/linux/balloon_compaction.h |  107 ++++++------------
 include/linux/migrate.h            |   11 --
 include/linux/pagemap.h            |   18 ---
 mm/balloon_compaction.c            |  214 ++++++++++++------------------------
 mm/migrate.c                       |   27 +----
 6 files changed, 130 insertions(+), 324 deletions(-)

Quoted 6 lines · Konstantin Khlebnikov

* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

Signed-off-by Konstantin Khlebnikov <[email protected]>

Quoted 9 lines

---
 drivers/virtio/virtio_balloon.c    |   77 ++++---------
 include/linux/balloon_compaction.h |  107 ++++++------------
 include/linux/migrate.h            |   11 --
 include/linux/pagemap.h            |   18 ---
 mm/balloon_compaction.c            |  214 ++++++++++++------------------------
 mm/migrate.c                       |   27 +----
 6 files changed, 130 insertions(+), 324 deletions(-)

Very nice clean-up, just as all other patches in this set. Please, just consider amending the following changes to this patch of yours

Rafael
---

include/linux/balloon_compaction.h +41 -62

index dc7073b..569cf96 100644
@@ -75,41 +75,6 @@ extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
 #ifdef CONFIG_BALLOON_COMPACTION
 extern bool balloon_page_isolate(struct page *page);
 extern void balloon_page_putback(struct page *page);
-
-/*
- * balloon_page_insert - insert a page into the balloon's page list and make
- *                      the page->mapping assignment accordingly.
- * @page    : page to be assigned as a 'balloon page'
- * @mapping : allocated special 'balloon_mapping'
- * @head    : balloon's device page list head
- *
- * Caller must ensure the page is locked and the spin_lock protecting balloon
- * pages list is held before inserting a page into the balloon device.
- */
-static inline void
-balloon_page_insert(struct balloon_dev_info *balloon, struct page *page)
-{
-       __SetPageBalloon(page);
-       set_page_private(page, (unsigned long)balloon);
-       list_add(&page->lru, &balloon->pages);
-}
-
-/*
- * balloon_page_delete - delete a page from balloon's page list and clear
- *                      the page->mapping assignement accordingly.
- * @page    : page to be released from balloon's page list
- *
- * Caller must ensure the page is locked and the spin_lock protecting balloon
- * pages list is held before deleting a page from the balloon device.
- */
-static inline void balloon_page_delete(struct page *page, bool isolated)
-{
-       __ClearPageBalloon(page);
-       set_page_private(page, 0);
-       if (!isolated)
-               list_del(&page->lru);
-}
-
 int balloon_page_migrate(new_page_t get_new_page, free_page_t put_new_page,
                unsigned long private, struct page *page,
                int force, enum migrate_mode mode);

@@ -130,31 +95,6 @@ static inline gfp_t balloon_mapping_gfp_mask(void)
 
 #else /* !CONFIG_BALLOON_COMPACTION */
 
-static inline void *balloon_mapping_alloc(void *balloon_device,
-                               const struct address_space_operations *a_ops)
-{
-       return ERR_PTR(-EOPNOTSUPP);
-}
-
-static inline void balloon_mapping_free(struct address_space *balloon_mapping)
-{
-       return;
-}
-
-static inline void
-balloon_page_insert(struct balloon_dev_info *balloon, struct page *page)
-{
-       __SetPageBalloon(page);
-       list_add(&page->lru, head);
-}
-
-static inline void balloon_page_delete(struct page *page, bool isolated)
-{
-       __ClearPageBalloon(page);
-       if (!isolated)
-               list_del(&page->lru);
-}
-
 static inline int balloon_page_migrate(new_page_t get_new_page,
                free_page_t put_new_page, unsigned long private,
                struct page *page, int force, enum migrate_mode mode)

@@ -176,6 +116,46 @@ static inline gfp_t balloon_mapping_gfp_mask(void)
 {
        return GFP_HIGHUSER;
 }
-
 #endif /* CONFIG_BALLOON_COMPACTION */
+
+/*
+ * balloon_page_insert - insert a page into the balloon's page list and make
+ *                      the page->mapping assignment accordingly.
+ * @page    : page to be assigned as a 'balloon page'
+ * @mapping : allocated special 'balloon_mapping'
+ * @head    : balloon's device page list head
+ *
+ * Caller must ensure the page is locked and the spin_lock protecting balloon
+ * pages list is held before inserting a page into the balloon device.
+ */
+static inline void
+balloon_page_insert(struct balloon_dev_info *balloon, struct page *page)
+{
+#ifdef CONFIG_MEMORY_BALLOON
+       __SetPageBalloon(page);
+       set_page_private(page, (unsigned long)balloon);
+       list_add(&page->lru, &balloon->pages);
+       inc_zone_page_state(page, NR_BALLOON_PAGES);
+#endif
+}
+
+/*
+ * balloon_page_delete - delete a page from balloon's page list and clear
+ *                      the page->mapping assignement accordingly.
+ * @page    : page to be released from balloon's page list
+ *
+ * Caller must ensure the page is locked and the spin_lock protecting balloon
+ * pages list is held before deleting a page from the balloon device.
+ */
+static inline void balloon_page_delete(struct page *page, bool isolated)
+{
+#ifdef CONFIG_MEMORY_BALLOON
+       __ClearPageBalloon(page);
+       set_page_private(page, 0);
+       if (!isolated)
+               list_del(&page->lru);
+       dec_zone_page_state(page, NR_BALLOON_PAGES);
+#endif
+}
+
 #endif /* _LINUX_BALLOON_COMPACTION_H */
--

1.9.3

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Quoted 16 lines · Rafael Aquini

Quoted 15 lines · Konstantin Khlebnikov

* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

Signed-off-by Konstantin Khlebnikov <[email protected]>

---
 drivers/virtio/virtio_balloon.c    |   77 ++++---------
 include/linux/balloon_compaction.h |  107 ++++++------------
 include/linux/migrate.h            |   11 --
 include/linux/pagemap.h            |   18 ---
 mm/balloon_compaction.c            |  214 ++++++++++++------------------------
 mm/migrate.c                       |   27 +----
 6 files changed, 130 insertions(+), 324 deletions(-)

Quoted 2 lines

Very nice clean-up, just as all other patches in this set. Please, just consider amending the following changes to this patch of yours

Well. Probably it's better to hide __Set/Clear inside mm/balloon_compaction.c it very unlikely that they might be used by somebody else.
mm.h contains too many obscure static inlines and other barely used stuff.

And it's worth to rename balloon_compaction.c/h into just balloon.c or memory_balloon because
it provides generic balloon wtihout compaction too. Any objections?

Quoted 133 lines

Rafael
---

include/linux/balloon_compaction.h +41 -62

index dc7073b..569cf96 100644
@@ -75,41 +75,6 @@ extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
 #ifdef CONFIG_BALLOON_COMPACTION
 extern bool balloon_page_isolate(struct page *page);
 extern void balloon_page_putback(struct page *page);
-
-/*
- * balloon_page_insert - insert a page into the balloon's page list and make
- *                      the page->mapping assignment accordingly.
- * @page    : page to be assigned as a 'balloon page'
- * @mapping : allocated special 'balloon_mapping'
- * @head    : balloon's device page list head
- *
- * Caller must ensure the page is locked and the spin_lock protecting balloon
- * pages list is held before inserting a page into the balloon device.
- */
-static inline void
-balloon_page_insert(struct balloon_dev_info *balloon, struct page *page)
-{
-       __SetPageBalloon(page);
-       set_page_private(page, (unsigned long)balloon);
-       list_add(&page->lru, &balloon->pages);
-}
-
-/*
- * balloon_page_delete - delete a page from balloon's page list and clear
- *                      the page->mapping assignement accordingly.
- * @page    : page to be released from balloon's page list
- *
- * Caller must ensure the page is locked and the spin_lock protecting balloon
- * pages list is held before deleting a page from the balloon device.
- */
-static inline void balloon_page_delete(struct page *page, bool isolated)
-{
-       __ClearPageBalloon(page);
-       set_page_private(page, 0);
-       if (!isolated)
-               list_del(&page->lru);
-}
-
 int balloon_page_migrate(new_page_t get_new_page, free_page_t put_new_page,
                unsigned long private, struct page *page,
                int force, enum migrate_mode mode);

@@ -130,31 +95,6 @@ static inline gfp_t balloon_mapping_gfp_mask(void)
 
 #else /* !CONFIG_BALLOON_COMPACTION */
 
-static inline void *balloon_mapping_alloc(void *balloon_device,
-                               const struct address_space_operations *a_ops)
-{
-       return ERR_PTR(-EOPNOTSUPP);
-}
-
-static inline void balloon_mapping_free(struct address_space *balloon_mapping)
-{
-       return;
-}
-
-static inline void
-balloon_page_insert(struct balloon_dev_info *balloon, struct page *page)
-{
-       __SetPageBalloon(page);
-       list_add(&page->lru, head);
-}
-
-static inline void balloon_page_delete(struct page *page, bool isolated)
-{
-       __ClearPageBalloon(page);
-       if (!isolated)
-               list_del(&page->lru);
-}
-
 static inline int balloon_page_migrate(new_page_t get_new_page,
                free_page_t put_new_page, unsigned long private,
                struct page *page, int force, enum migrate_mode mode)

@@ -176,6 +116,46 @@ static inline gfp_t balloon_mapping_gfp_mask(void)
 {
        return GFP_HIGHUSER;
 }
-
 #endif /* CONFIG_BALLOON_COMPACTION */
+
+/*
+ * balloon_page_insert - insert a page into the balloon's page list and make
+ *                      the page->mapping assignment accordingly.
+ * @page    : page to be assigned as a 'balloon page'
+ * @mapping : allocated special 'balloon_mapping'
+ * @head    : balloon's device page list head
+ *
+ * Caller must ensure the page is locked and the spin_lock protecting balloon
+ * pages list is held before inserting a page into the balloon device.
+ */
+static inline void
+balloon_page_insert(struct balloon_dev_info *balloon, struct page *page)
+{
+#ifdef CONFIG_MEMORY_BALLOON
+       __SetPageBalloon(page);
+       set_page_private(page, (unsigned long)balloon);
+       list_add(&page->lru, &balloon->pages);
+       inc_zone_page_state(page, NR_BALLOON_PAGES);
+#endif
+}
+
+/*
+ * balloon_page_delete - delete a page from balloon's page list and clear
+ *                      the page->mapping assignement accordingly.
+ * @page    : page to be released from balloon's page list
+ *
+ * Caller must ensure the page is locked and the spin_lock protecting balloon
+ * pages list is held before deleting a page from the balloon device.
+ */
+static inline void balloon_page_delete(struct page *page, bool isolated)
+{
+#ifdef CONFIG_MEMORY_BALLOON
+       __ClearPageBalloon(page);
+       set_page_private(page, 0);
+       if (!isolated)
+               list_del(&page->lru);
+       dec_zone_page_state(page, NR_BALLOON_PAGES);
+#endif
+}
+
 #endif /* _LINUX_BALLOON_COMPACTION_H */
--

1.9.3

Quoted 5 lines

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* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

Quoted 5 lines · On Wed, 20 Aug 2014 19:05:09 +0400 Konstantin Khlebnikov…

* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

grump.

diff -puN include/linux/balloon_compaction.h~mm-balloon_compaction-general-cleanup-fix include/linux/balloon_compaction.h

include/linux/balloon_compaction.h renamed from include/linux/balloon_compaction.h~mm-balloon_compaction-general-cleanup-fix +1 -1

@@ -145,7 +145,7 @@ static inline void
 balloon_page_insert(struct balloon_dev_info *balloon, struct page *page)
 {
 	__SetPageBalloon(page);
-	list_add(&page->lru, head);
+	list_add(&page->lru, &balloon->pages);
 }
 
 static inline void balloon_page_delete(struct page *page, bool isolated)

This obviously wasn't tested with CONFIG_BALLOON_COMPACTION=n. Please complete the testing of this patchset and let us know the result?

Quoted 21 lines · Andrew Morton

Quoted 5 lines · On Wed, 20 Aug 2014 19:05:09 +0400 Konstantin Khlebnikov…

* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

grump.

diff -puN include/linux/balloon_compaction.h~mm-balloon_compaction-general-cleanup-fix include/linux/balloon_compaction.h

include/linux/balloon_compaction.h renamed from include/linux/balloon_compaction.h~mm-balloon_compaction-general-cleanup-fix +1 -1

@@ -145,7 +145,7 @@ static inline void
 balloon_page_insert(struct balloon_dev_info *balloon, struct page *page)
 {
 	__SetPageBalloon(page);
-	list_add(&page->lru, head);
+	list_add(&page->lru, &balloon->pages);
 }
 

Quoted 6 lines

include/linux/balloon_compaction.h renamed from include/linux/balloon_compaction.h~mm-balloon_compaction-general-cleanup-fix +0 -0

 static inline void balloon_page_delete(struct page *page, bool isolated)

This obviously wasn't tested with CONFIG_BALLOON_COMPACTION=n. Please complete the testing of this patchset and let us know the result?

That also reminds me why I suggested moving those as static inlines into mm.h, instead of getting them hidden in mm/balloon_compaction.c

Cheers,
-- Rafael

* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

include/linux/balloon_compaction.h +0 -0

@@ -54,58 +54,27 @@
  * balloon driver as a page book-keeper for its registered balloon devices.

Quoted 4 lines · On Wed, 20 Aug 2014 19:05:09 +0400 Konstantin Khlebnikov…

* move special branch for balloon migraion into migrate_pages
* remove special mapping for balloon and its flag AS_BALLOON_MAP
* embed struct balloon_dev_info into struct virtio_balloon
* cleanup balloon_page_dequeue, kill balloon_page_free

Another testing failure. Guys, allnoconfig is really fast.

Quoted 10 lines

include/linux/balloon_compaction.h +0 -2

@@ -54,58 +54,27 @@
  * balloon driver as a page book-keeper for its registered balloon devices.
  */
 struct balloon_dev_info {
-     void *balloon_device;           /* balloon device descriptor */
-     struct address_space *mapping;  /* balloon special page->mapping */
      unsigned long isolated_pages;   /* # of isolated pages for migration */

include/linux/balloon_compaction.h line 62

Quoted 5 lines

include/linux/balloon_compaction.h +2 -0

      spinlock_t pages_lock;          /* Protection to pages list */
      struct list_head pages;         /* Pages enqueued & handled to Host */
+     int (* migrate_page)(struct balloon_dev_info *, struct page *newpage,
+                     struct page *page, enum migrate_mode mode);
 };

If CONFIG_MIGRATION=n this gets turned into "NULL" and chaos ensues. I think I'll just nuke that #define:

include/linux/migrate.h renamed from include/linux/migrate.h~include-linux-migrateh-remove-migratepage-define +0 -3

@@ -82,9 +82,6 @@ static inline int migrate_huge_page_move
        return -ENOSYS;
 }
 
-/* Possible settings for the migrate_page() method in address_operations */
-#define migrate_page NULL
-
 #endif /* CONFIG_MIGRATION */
 
 #ifdef CONFIG_NUMA_BALANCING

mm/swap_state.c renamed from mm/swap_state.c~include-linux-migrateh-remove-migratepage-define +2 -0

@@ -28,7 +28,9 @@
 static const struct address_space_operations swap_aops = {
        .writepage      = swap_writepage,
        .set_page_dirty = swap_set_page_dirty,
+#ifdef CONFIG_MIGRATION
        .migratepage    = migrate_page,
+#endif
 };
 
 static struct backing_dev_info swap_backing_dev_info = {

mm/shmem.c renamed from mm/shmem.c~include-linux-migrateh-remove-migratepage-define +2 -0

@@ -3075,7 +3075,9 @@ static const struct address_space_operat
        .write_begin    = shmem_write_begin,
        .write_end      = shmem_write_end,
 #endif
+#ifdef CONFIG_MIGRATION
        .migratepage    = migrate_page,
+#endif
        .error_remove_page = generic_error_remove_page,
 };
 

Our mixture of "migratepage" and "migrate_page" is maddening.

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Sasha Levin reported KASAN splash inside isolate_migratepages_range(). Problem is in function __is_movable_balloon_page() which tests AS_BALLOON_MAP in page->mapping->flags. This function has no protection against anonymous pages. As result it tried to check address space flags in inside anon-vma.

Signed-off-by Konstantin Khlebnikov <[email protected]>

Reported-by Sasha Levin <[email protected]>

Link http://lkml.kernel.org/p/[email protected] open here

Cc stable <[email protected]> # v3.8

---
 include/linux/balloon_compaction.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

include/linux/balloon_compaction.h +0 -0

index 089743a..53d482e 100644