[PATCH v4] memcg: add per-memcg vmalloc stat

[Shakeel Butt <shakeelb@google.com>]

The kvmalloc* allocation functions can fallback to vmalloc allocations
and more often on long running machines. In addition the kernel does
have __GFP_ACCOUNT kvmalloc* calls. So, often on long running machines,
the memory.stat does not tell the complete picture which type of memory
is charged to the memcg. So add a per-memcg vmalloc stat.

Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <guro@fb.com>

---
Changes since v3:
- Removed area->page[0] checks and moved to page by page accounting as
  suggested by Michal

Changes since v2:
- remove cast, per Muchun
- add area->page[0] check, per Michal

Changes since v1:
- page_memcg() within rcu lock as suggested by Muchun.

 Documentation/admin-guide/cgroup-v2.rst |  3 +++
 include/linux/memcontrol.h              | 21 +++++++++++++++++++++
 mm/memcontrol.c                         |  1 +
 mm/vmalloc.c                            | 13 +++++++++++--
 4 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 82c8dc91b2be..5aa368d165da 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1314,6 +1314,9 @@ PAGE_SIZE multiple when read back.
 	  sock (npn)
 		Amount of memory used in network transmission buffers
 
+	  vmalloc (npn)
+		Amount of memory used for vmap backed memory.
+
 	  shmem
 		Amount of cached filesystem data that is swap-backed,
 		such as tmpfs, shm segments, shared anonymous mmap()s
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d76dad703580..b72d75141e12 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -33,6 +33,7 @@ enum memcg_stat_item {
 	MEMCG_SWAP = NR_VM_NODE_STAT_ITEMS,
 	MEMCG_SOCK,
 	MEMCG_PERCPU_B,
+	MEMCG_VMALLOC,
 	MEMCG_NR_STAT,
 };
 
@@ -944,6 +945,21 @@ static inline void mod_memcg_state(struct mem_cgroup *memcg,
 	local_irq_restore(flags);
 }
 
+static inline void mod_memcg_page_state(struct page *page,
+					int idx, int val)
+{
+	struct mem_cgroup *memcg;
+
+	if (mem_cgroup_disabled())
+		return;
+
+	rcu_read_lock();
+	memcg = page_memcg(page);
+	if (memcg)
+		mod_memcg_state(memcg, idx, val);
+	rcu_read_unlock();
+}
+
 static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
 {
 	return READ_ONCE(memcg->vmstats.state[idx]);
@@ -1399,6 +1415,11 @@ static inline void mod_memcg_state(struct mem_cgroup *memcg,
 {
 }
 
+static inline void mod_memcg_page_state(struct page *page,
+					int idx, int val)
+{
+}
+
 static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
 {
 	return 0;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 101b22a23096..56ed6b5dd328 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1375,6 +1375,7 @@ static const struct memory_stat memory_stats[] = {
 	{ "pagetables",			NR_PAGETABLE			},
 	{ "percpu",			MEMCG_PERCPU_B			},
 	{ "sock",			MEMCG_SOCK			},
+	{ "vmalloc",			MEMCG_VMALLOC			},
 	{ "shmem",			NR_SHMEM			},
 	{ "file_mapped",		NR_FILE_MAPPED			},
 	{ "file_dirty",			NR_FILE_DIRTY			},
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index eb6e527a6b77..bdc7222f87d4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -31,6 +31,7 @@
 #include <linux/kmemleak.h>
 #include <linux/atomic.h>
 #include <linux/compiler.h>
+#include <linux/memcontrol.h>
 #include <linux/llist.h>
 #include <linux/bitops.h>
 #include <linux/rbtree_augmented.h>
@@ -2624,12 +2625,13 @@ static void __vunmap(const void *addr, int deallocate_pages)
 
 	if (deallocate_pages) {
 		unsigned int page_order = vm_area_page_order(area);
-		int i;
+		int i, step = 1U << page_order;
 
-		for (i = 0; i < area->nr_pages; i += 1U << page_order) {
+		for (i = 0; i < area->nr_pages; i += step) {
 			struct page *page = area->pages[i];
 
 			BUG_ON(!page);
+			mod_memcg_page_state(page, MEMCG_VMALLOC, -step);
 			__free_pages(page, page_order);
 			cond_resched();
 		}
@@ -2964,6 +2966,13 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 		page_order, nr_small_pages, area->pages);
 
 	atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
+	if (gfp_mask & __GFP_ACCOUNT) {
+		int i, step = 1U << page_order;
+
+		for (i = 0; i < area->nr_pages; i += step)
+			mod_memcg_page_state(area->pages[i], MEMCG_VMALLOC,
+					     step);
+	}
 
 	/*
 	 * If not enough pages were obtained to accomplish an
-- 
2.34.1.448.ga2b2bfdf31-goog