[PATCH v2 4/6] mm: introduce common page state for ballooned memory

[Konstantin Khlebnikov <koct9i@gmail.com>]

From: Konstantin Khlebnikov <k.khlebnikov@samsung.com>

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 new code is under CONFIG_MEMORY_BALLOON, it should be selected by
ballooning driver which wants use this feature.

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
---
 Documentation/filesystems/proc.txt     |    2 ++
 drivers/base/node.c                    |   16 ++++++++++------
 fs/proc/meminfo.c                      |    6 ++++++
 fs/proc/page.c                         |    3 +++
 include/linux/mm.h                     |   20 ++++++++++++++++++++
 include/linux/mmzone.h                 |    3 +++
 include/uapi/linux/kernel-page-flags.h |    1 +
 mm/Kconfig                             |    5 +++++
 mm/vmstat.c                            |    8 +++++++-
 tools/vm/page-types.c                  |    1 +
 10 files changed, 58 insertions(+), 7 deletions(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index eb8a10e..154a345 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -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
diff --git a/drivers/base/node.c b/drivers/base/node.c
index c6d3ae0..59e565c 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -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;
 }
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index aa1eee0..f897fbf 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -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);
diff --git a/fs/proc/page.c b/fs/proc/page.c
index e647c55..1e3187d 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -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);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index da79328..a9a27ea 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -554,6 +554,26 @@ static inline void __ClearPageBuddy(struct page *page)
 	atomic_set(&page->_mapcount, -1);
 }
 
+#define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
+
+static inline int PageBalloon(struct page *page)
+{
+	return IS_ENABLED(CONFIG_MEMORY_BALLOON) &&
+		atomic_read(&page->_mapcount) == PAGE_BALLOON_MAPCOUNT_VALUE;
+}
+
+static inline void __SetPageBalloon(struct page *page)
+{
+	VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
+	atomic_set(&page->_mapcount, PAGE_BALLOON_MAPCOUNT_VALUE);
+}
+
+static inline void __ClearPageBalloon(struct page *page)
+{
+	VM_BUG_ON_PAGE(!PageBalloon(page), page);
+	atomic_set(&page->_mapcount, -1);
+}
+
 void put_page(struct page *page);
 void put_pages_list(struct list_head *pages);
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 318df70..d88fd01 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -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 };
 
 /*
diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h
index 5116a0e..2f96d23 100644
--- a/include/uapi/linux/kernel-page-flags.h
+++ b/include/uapi/linux/kernel-page-flags.h
@@ -31,6 +31,7 @@
 
 #define KPF_KSM			21
 #define KPF_THP			22
+#define KPF_BALLOON		23
 
 
 #endif /* _UAPILINUX_KERNEL_PAGE_FLAGS_H */
diff --git a/mm/Kconfig b/mm/Kconfig
index 886db21..72e0db0 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -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"
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 84c688d..ff7bd29 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -751,7 +751,7 @@ 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",
@@ -794,10 +794,16 @@ 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",
diff --git a/tools/vm/page-types.c b/tools/vm/page-types.c
index c4d6d2e..264fbc2 100644
--- a/tools/vm/page-types.c
+++ b/tools/vm/page-types.c
@@ -132,6 +132,7 @@ static const char * const page_flag_names[] = {
 	[KPF_NOPAGE]		= "n:nopage",
 	[KPF_KSM]		= "x:ksm",
 	[KPF_THP]		= "t:thp",
+	[KPF_BALLOON]		= "o:balloon",
 
 	[KPF_RESERVED]		= "r:reserved",
 	[KPF_MLOCKED]		= "m:mlocked",