Message-Id: <1267699215-4101-4-git-send-email-arighi@develer.com>
Date:	Thu,  4 Mar 2010 11:40:14 +0100
From:	Andrea Righi <arighi@...eler.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Trond Myklebust <trond.myklebust@....uio.no>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Andrew Morton <akpm@...ux-foundation.org>,
	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrea Righi <arighi@...eler.com>
Subject: [PATCH -mmotm 3/4] memcg: dirty pages accounting and limiting infrastructure

Infrastructure to account dirty pages per cgroup and add dirty limit
interfaces in the cgroupfs:

 - Direct write-out: memory.dirty_ratio, memory.dirty_bytes

 - Background write-out: memory.dirty_background_ratio, memory.dirty_background_bytes

Signed-off-by: Andrea Righi <arighi@...eler.com>
---
 include/linux/memcontrol.h |   80 ++++++++-
 mm/memcontrol.c            |  420 +++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 450 insertions(+), 50 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 1f9b119..cc3421b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -19,12 +19,66 @@
 
 #ifndef _LINUX_MEMCONTROL_H
 #define _LINUX_MEMCONTROL_H
+
+#include <linux/writeback.h>
 #include <linux/cgroup.h>
+
 struct mem_cgroup;
 struct page_cgroup;
 struct page;
 struct mm_struct;
 
+/* Cgroup memory statistics items exported to the kernel */
+enum mem_cgroup_page_stat_item {
+	MEMCG_NR_DIRTYABLE_PAGES,
+	MEMCG_NR_RECLAIM_PAGES,
+	MEMCG_NR_WRITEBACK,
+	MEMCG_NR_DIRTY_WRITEBACK_PAGES,
+};
+
+/* Dirty memory parameters */
+struct dirty_param {
+	int dirty_ratio;
+	unsigned long dirty_bytes;
+	int dirty_background_ratio;
+	unsigned long dirty_background_bytes;
+};
+
+/*
+ * Statistics for memory cgroup.
+ */
+enum mem_cgroup_stat_index {
+	/*
+	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
+	 */
+	MEM_CGROUP_STAT_CACHE,	   /* # of pages charged as cache */
+	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
+	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
+	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
+	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
+	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
+	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
+	MEM_CGROUP_STAT_FILE_DIRTY,   /* # of dirty pages in page cache */
+	MEM_CGROUP_STAT_WRITEBACK,   /* # of pages under writeback */
+	MEM_CGROUP_STAT_WRITEBACK_TEMP,   /* # of pages under writeback using
+						temporary buffers */
+	MEM_CGROUP_STAT_UNSTABLE_NFS,   /* # of NFS unstable pages */
+
+	MEM_CGROUP_STAT_NSTATS,
+};
+
+/*
+ * TODO: provide a validation check routine. And retry if validation
+ * fails.
+ */
+static inline void get_global_dirty_param(struct dirty_param *param)
+{
+	param->dirty_ratio = vm_dirty_ratio;
+	param->dirty_bytes = vm_dirty_bytes;
+	param->dirty_background_ratio = dirty_background_ratio;
+	param->dirty_background_bytes = dirty_background_bytes;
+}
+
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
 /*
  * All "charge" functions with gfp_mask should use GFP_KERNEL or
@@ -117,6 +171,10 @@ extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
 extern int do_swap_account;
 #endif
 
+extern bool mem_cgroup_has_dirty_limit(void);
+extern void get_dirty_param(struct dirty_param *param);
+extern s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item);
+
 static inline bool mem_cgroup_disabled(void)
 {
 	if (mem_cgroup_subsys.disabled)
@@ -125,7 +183,8 @@ static inline bool mem_cgroup_disabled(void)
 }
 
 extern bool mem_cgroup_oom_called(struct task_struct *task);
-void mem_cgroup_update_file_mapped(struct page *page, int val);
+void mem_cgroup_update_stat(struct page *page,
+			enum mem_cgroup_stat_index idx, int val);
 unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 						gfp_t gfp_mask, int nid,
 						int zid);
@@ -300,8 +359,8 @@ mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 {
 }
 
-static inline void mem_cgroup_update_file_mapped(struct page *page,
-							int val)
+static inline void mem_cgroup_update_stat(struct page *page,
+			enum mem_cgroup_stat_index idx, int val)
 {
 }
 
@@ -312,6 +371,21 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 	return 0;
 }
 
+static inline bool mem_cgroup_has_dirty_limit(void)
+{
+	return false;
+}
+
+static inline void get_dirty_param(struct dirty_param *param)
+{
+	get_global_dirty_param(param);
+}
+
+static inline s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item)
+{
+	return -ENOSYS;
+}
+
 #endif /* CONFIG_CGROUP_MEM_CONT */
 
 #endif /* _LINUX_MEMCONTROL_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 497b6f7..9842e7b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -73,28 +73,23 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
 #define THRESHOLDS_EVENTS_THRESH (7) /* once in 128 */
 #define SOFTLIMIT_EVENTS_THRESH (10) /* once in 1024 */
 
-/*
- * Statistics for memory cgroup.
- */
-enum mem_cgroup_stat_index {
-	/*
-	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
-	 */
-	MEM_CGROUP_STAT_CACHE, 	   /* # of pages charged as cache */
-	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
-	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
-	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
-	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
-	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
-	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
-
-	MEM_CGROUP_STAT_NSTATS,
-};
-
 struct mem_cgroup_stat_cpu {
 	s64 count[MEM_CGROUP_STAT_NSTATS];
 };
 
+/* Per cgroup page statistics */
+struct mem_cgroup_page_stat {
+	enum mem_cgroup_page_stat_item item;
+	s64 value;
+};
+
+enum {
+	MEM_CGROUP_DIRTY_RATIO,
+	MEM_CGROUP_DIRTY_BYTES,
+	MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
+	MEM_CGROUP_DIRTY_BACKGROUND_BYTES,
+};
+
 /*
  * per-zone information in memory controller.
  */
@@ -208,6 +203,9 @@ struct mem_cgroup {
 
 	unsigned int	swappiness;
 
+	/* control memory cgroup dirty pages */
+	struct dirty_param dirty_param;
+
 	/* set when res.limit == memsw.limit */
 	bool		memsw_is_minimum;
 
@@ -1033,6 +1031,156 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
 	return swappiness;
 }
 
+static bool dirty_param_is_valid(struct dirty_param *param)
+{
+	if (param->dirty_ratio && param->dirty_bytes)
+		return false;
+	if (param->dirty_background_ratio && param->dirty_background_bytes)
+		return false;
+	return true;
+}
+
+static void
+__mem_cgroup_get_dirty_param(struct dirty_param *param, struct mem_cgroup *mem)
+{
+	param->dirty_ratio = mem->dirty_param.dirty_ratio;
+	param->dirty_bytes = mem->dirty_param.dirty_bytes;
+	param->dirty_background_ratio = mem->dirty_param.dirty_background_ratio;
+	param->dirty_background_bytes = mem->dirty_param.dirty_background_bytes;
+}
+
+/*
+ * get_dirty_param() - get dirty memory parameters of the current memcg
+ * @param:	a structure is filled with the dirty memory settings
+ *
+ * The function fills @param with the current memcg dirty memory settings. If
+ * memory cgroup is disabled or in case of error the structure is filled with
+ * the global dirty memory settings.
+ */
+void get_dirty_param(struct dirty_param *param)
+{
+	struct mem_cgroup *memcg;
+
+	if (mem_cgroup_disabled()) {
+		get_global_dirty_param(param);
+		return;
+	}
+	/*
+	 * It's possible that "current" may be moved to other cgroup while we
+	 * access cgroup. But precise check is meaningless because the task can
+	 * be moved after our access and writeback tends to take long time.
+	 * At least, "memcg" will not be freed under rcu_read_lock().
+	 */
+	while (1) {
+		rcu_read_lock();
+		memcg = mem_cgroup_from_task(current);
+		if (likely(memcg))
+			__mem_cgroup_get_dirty_param(param, memcg);
+		else
+			get_global_dirty_param(param);
+		rcu_read_unlock();
+		/*
+		 * Since global and memcg dirty_param are not protected we try
+		 * to speculatively read them and retry if we get inconsistent
+		 * values.
+		 */
+		if (likely(dirty_param_is_valid(param)))
+			break;
+	}
+}
+
+static inline bool mem_cgroup_can_swap(struct mem_cgroup *memcg)
+{
+	if (!do_swap_account)
+		return nr_swap_pages > 0;
+	return !memcg->memsw_is_minimum &&
+		(res_counter_read_u64(&memcg->memsw, RES_LIMIT) > 0);
+}
+
+static s64 mem_cgroup_get_local_page_stat(struct mem_cgroup *memcg,
+				enum mem_cgroup_page_stat_item item)
+{
+	s64 ret;
+
+	switch (item) {
+	case MEMCG_NR_DIRTYABLE_PAGES:
+		ret = res_counter_read_u64(&memcg->res, RES_LIMIT) -
+			res_counter_read_u64(&memcg->res, RES_USAGE);
+		/* Translate free memory in pages */
+		ret >>= PAGE_SHIFT;
+		ret += mem_cgroup_read_stat(memcg, LRU_ACTIVE_FILE) +
+			mem_cgroup_read_stat(memcg, LRU_INACTIVE_FILE);
+		if (mem_cgroup_can_swap(memcg))
+			ret += mem_cgroup_read_stat(memcg, LRU_ACTIVE_ANON) +
+				mem_cgroup_read_stat(memcg, LRU_INACTIVE_ANON);
+		break;
+	case MEMCG_NR_RECLAIM_PAGES:
+		ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_FILE_DIRTY) +
+			mem_cgroup_read_stat(memcg,
+					MEM_CGROUP_STAT_UNSTABLE_NFS);
+		break;
+	case MEMCG_NR_WRITEBACK:
+		ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_WRITEBACK);
+		break;
+	case MEMCG_NR_DIRTY_WRITEBACK_PAGES:
+		ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_WRITEBACK) +
+			mem_cgroup_read_stat(memcg,
+				MEM_CGROUP_STAT_UNSTABLE_NFS);
+		break;
+	default:
+		BUG_ON(1);
+	}
+	return ret;
+}
+
+static int mem_cgroup_page_stat_cb(struct mem_cgroup *mem, void *data)
+{
+	struct mem_cgroup_page_stat *stat = (struct mem_cgroup_page_stat *)data;
+
+	stat->value += mem_cgroup_get_local_page_stat(mem, stat->item);
+	return 0;
+}
+
+/*
+ * mem_cgroup_has_dirty_limit() - check if current memcg has local dirty limits
+ *
+ * Return true if the current memory cgroup has local dirty memory settings,
+ * false otherwise.
+ */
+bool mem_cgroup_has_dirty_limit(void)
+{
+	if (mem_cgroup_disabled())
+		return false;
+	return mem_cgroup_from_task(current) != NULL;
+}
+
+/*
+ * mem_cgroup_page_stat() - get memory cgroup file cache statistics
+ * @item:	memory statistic item exported to the kernel
+ *
+ * Return the accounted statistic value, or a negative value in case of error.
+ */
+s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item)
+{
+	struct mem_cgroup_page_stat stat = {};
+	struct mem_cgroup *memcg;
+
+	rcu_read_lock();
+	memcg = mem_cgroup_from_task(current);
+	if (memcg) {
+		/*
+		 * Recursively evaulate page statistics against all cgroup
+		 * under hierarchy tree
+		 */
+		stat.item = item;
+		mem_cgroup_walk_tree(memcg, &stat, mem_cgroup_page_stat_cb);
+	} else
+		stat.value = -EINVAL;
+	rcu_read_unlock();
+
+	return stat.value;
+}
+
 static int mem_cgroup_count_children_cb(struct mem_cgroup *mem, void *data)
 {
 	int *val = data;
@@ -1275,34 +1423,70 @@ static void record_last_oom(struct mem_cgroup *mem)
 }
 
 /*
- * Currently used to update mapped file statistics, but the routine can be
- * generalized to update other statistics as well.
+ * Generalized routine to update file cache's status for memcg.
+ *
+ * Before calling this, mapping->tree_lock should be held and preemption is
+ * disabled.  Then, it's guarnteed that the page is not uncharged while we
+ * access page_cgroup. We can make use of that.
  */
-void mem_cgroup_update_file_mapped(struct page *page, int val)
+void mem_cgroup_update_stat(struct page *page,
+			enum mem_cgroup_stat_index idx, int val)
 {
 	struct mem_cgroup *mem;
 	struct page_cgroup *pc;
 
+	if (mem_cgroup_disabled())
+		return;
 	pc = lookup_page_cgroup(page);
-	if (unlikely(!pc))
+	if (unlikely(!pc) || !PageCgroupUsed(pc))
 		return;
 
-	lock_page_cgroup(pc);
-	mem = pc->mem_cgroup;
-	if (!mem)
-		goto done;
-
-	if (!PageCgroupUsed(pc))
-		goto done;
-
+	lock_page_cgroup_migrate(pc);
 	/*
-	 * Preemption is already disabled. We can use __this_cpu_xxx
-	 */
-	__this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED], val);
-
-done:
-	unlock_page_cgroup(pc);
+	* It's guarnteed that this page is never uncharged.
+	* The only racy problem is moving account among memcgs.
+	*/
+	switch (idx) {
+	case MEM_CGROUP_STAT_FILE_MAPPED:
+		if (val > 0)
+			SetPageCgroupFileMapped(pc);
+		else
+			ClearPageCgroupFileMapped(pc);
+		break;
+	case MEM_CGROUP_STAT_FILE_DIRTY:
+		if (val > 0)
+			SetPageCgroupDirty(pc);
+		else
+			ClearPageCgroupDirty(pc);
+		break;
+	case MEM_CGROUP_STAT_WRITEBACK:
+		if (val > 0)
+			SetPageCgroupWriteback(pc);
+		else
+			ClearPageCgroupWriteback(pc);
+		break;
+	case MEM_CGROUP_STAT_WRITEBACK_TEMP:
+		if (val > 0)
+			SetPageCgroupWritebackTemp(pc);
+		else
+			ClearPageCgroupWritebackTemp(pc);
+		break;
+	case MEM_CGROUP_STAT_UNSTABLE_NFS:
+		if (val > 0)
+			SetPageCgroupUnstableNFS(pc);
+		else
+			ClearPageCgroupUnstableNFS(pc);
+		break;
+	default:
+		BUG();
+		break;
+	}
+	mem = pc->mem_cgroup;
+	if (likely(mem))
+		__this_cpu_add(mem->stat->count[idx], val);
+	unlock_page_cgroup_migrate(pc);
 }
+EXPORT_SYMBOL_GPL(mem_cgroup_update_stat);
 
 /*
  * size of first charge trial. "32" comes from vmscan.c's magic value.
@@ -1701,6 +1885,45 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
 	memcg_check_events(mem, pc->page);
 }
 
+/*
+ * Update file cache accounted statistics on task migration.
+ *
+ * TODO: We don't move charges of file (including shmem/tmpfs) pages for now.
+ * So, at the moment this function simply returns without updating accounted
+ * statistics, because we deal only with anonymous pages here.
+ */
+static void __mem_cgroup_update_file_stat(struct page_cgroup *pc,
+	struct mem_cgroup *from, struct mem_cgroup *to)
+{
+	struct page *page = pc->page;
+
+	if (!page_mapped(page) || PageAnon(page))
+		return;
+
+	if (PageCgroupFileMapped(pc)) {
+		__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
+	}
+	if (PageCgroupDirty(pc)) {
+		__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_DIRTY]);
+		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_DIRTY]);
+	}
+	if (PageCgroupWriteback(pc)) {
+		__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_WRITEBACK]);
+		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_WRITEBACK]);
+	}
+	if (PageCgroupWritebackTemp(pc)) {
+		__this_cpu_dec(
+			from->stat->count[MEM_CGROUP_STAT_WRITEBACK_TEMP]);
+		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_WRITEBACK_TEMP]);
+	}
+	if (PageCgroupUnstableNFS(pc)) {
+		__this_cpu_dec(
+			from->stat->count[MEM_CGROUP_STAT_UNSTABLE_NFS]);
+		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_UNSTABLE_NFS]);
+	}
+}
+
 /**
  * __mem_cgroup_move_account - move account of the page
  * @pc:	page_cgroup of the page.
@@ -1721,22 +1944,16 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
 static void __mem_cgroup_move_account(struct page_cgroup *pc,
 	struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
 {
-	struct page *page;
-
 	VM_BUG_ON(from == to);
 	VM_BUG_ON(PageLRU(pc->page));
 	VM_BUG_ON(!PageCgroupLocked(pc));
 	VM_BUG_ON(!PageCgroupUsed(pc));
 	VM_BUG_ON(pc->mem_cgroup != from);
 
-	page = pc->page;
-	if (page_mapped(page) && !PageAnon(page)) {
-		/* Update mapped_file data for mem_cgroup */
-		preempt_disable();
-		__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		preempt_enable();
-	}
+	preempt_disable();
+	lock_page_cgroup_migrate(pc);
+	__mem_cgroup_update_file_stat(pc, from, to);
+
 	mem_cgroup_charge_statistics(from, pc, false);
 	if (uncharge)
 		/* This is not "cancel", but cancel_charge does all we need. */
@@ -1745,6 +1962,8 @@ static void __mem_cgroup_move_account(struct page_cgroup *pc,
 	/* caller should have done css_get */
 	pc->mem_cgroup = to;
 	mem_cgroup_charge_statistics(to, pc, true);
+	unlock_page_cgroup_migrate(pc);
+	preempt_enable();
 	/*
 	 * We charges against "to" which may not have any tasks. Then, "to"
 	 * can be under rmdir(). But in current implementation, caller of
@@ -3042,6 +3261,10 @@ enum {
 	MCS_PGPGIN,
 	MCS_PGPGOUT,
 	MCS_SWAP,
+	MCS_FILE_DIRTY,
+	MCS_WRITEBACK,
+	MCS_WRITEBACK_TEMP,
+	MCS_UNSTABLE_NFS,
 	MCS_INACTIVE_ANON,
 	MCS_ACTIVE_ANON,
 	MCS_INACTIVE_FILE,
@@ -3064,6 +3287,10 @@ struct {
 	{"pgpgin", "total_pgpgin"},
 	{"pgpgout", "total_pgpgout"},
 	{"swap", "total_swap"},
+	{"filedirty", "dirty_pages"},
+	{"writeback", "writeback_pages"},
+	{"writeback_tmp", "writeback_temp_pages"},
+	{"nfs", "nfs_unstable"},
 	{"inactive_anon", "total_inactive_anon"},
 	{"active_anon", "total_active_anon"},
 	{"inactive_file", "total_inactive_file"},
@@ -3092,6 +3319,14 @@ static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
 		val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
 		s->stat[MCS_SWAP] += val * PAGE_SIZE;
 	}
+	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_DIRTY);
+	s->stat[MCS_FILE_DIRTY] += val;
+	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_WRITEBACK);
+	s->stat[MCS_WRITEBACK] += val;
+	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_WRITEBACK_TEMP);
+	s->stat[MCS_WRITEBACK_TEMP] += val;
+	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_UNSTABLE_NFS);
+	s->stat[MCS_UNSTABLE_NFS] += val;
 
 	/* per zone stat */
 	val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON);
@@ -3453,6 +3688,60 @@ unlock:
 	return ret;
 }
 
+static u64 mem_cgroup_dirty_read(struct cgroup *cgrp, struct cftype *cft)
+{
+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+
+	switch (cft->private) {
+	case MEM_CGROUP_DIRTY_RATIO:
+		return memcg->dirty_param.dirty_ratio;
+	case MEM_CGROUP_DIRTY_BYTES:
+		return memcg->dirty_param.dirty_bytes;
+	case MEM_CGROUP_DIRTY_BACKGROUND_RATIO:
+		return memcg->dirty_param.dirty_background_ratio;
+	case MEM_CGROUP_DIRTY_BACKGROUND_BYTES:
+		return memcg->dirty_param.dirty_background_bytes;
+	default:
+		BUG();
+	}
+}
+
+static int
+mem_cgroup_dirty_write(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+	int type = cft->private;
+
+	if (cgrp->parent == NULL)
+		return -EINVAL;
+	if ((type == MEM_CGROUP_DIRTY_RATIO ||
+		type == MEM_CGROUP_DIRTY_BACKGROUND_RATIO) && val > 100)
+		return -EINVAL;
+	/*
+	 * TODO: provide a validation check routine. And retry if validation
+	 * fails.
+	 */
+	switch (type) {
+	case MEM_CGROUP_DIRTY_RATIO:
+		memcg->dirty_param.dirty_ratio = val;
+		memcg->dirty_param.dirty_bytes = 0;
+		break;
+	case MEM_CGROUP_DIRTY_BYTES:
+		memcg->dirty_param.dirty_ratio  = 0;
+		memcg->dirty_param.dirty_bytes = val;
+		break;
+	case MEM_CGROUP_DIRTY_BACKGROUND_RATIO:
+		memcg->dirty_param.dirty_background_ratio = val;
+		memcg->dirty_param.dirty_background_bytes = 0;
+		break;
+	case MEM_CGROUP_DIRTY_BACKGROUND_BYTES:
+		memcg->dirty_param.dirty_background_ratio = 0;
+		memcg->dirty_param.dirty_background_bytes = val;
+		break;
+	}
+	return 0;
+}
+
 static struct cftype mem_cgroup_files[] = {
 	{
 		.name = "usage_in_bytes",
@@ -3504,6 +3793,30 @@ static struct cftype mem_cgroup_files[] = {
 		.write_u64 = mem_cgroup_swappiness_write,
 	},
 	{
+		.name = "dirty_ratio",
+		.read_u64 = mem_cgroup_dirty_read,
+		.write_u64 = mem_cgroup_dirty_write,
+		.private = MEM_CGROUP_DIRTY_RATIO,
+	},
+	{
+		.name = "dirty_bytes",
+		.read_u64 = mem_cgroup_dirty_read,
+		.write_u64 = mem_cgroup_dirty_write,
+		.private = MEM_CGROUP_DIRTY_BYTES,
+	},
+	{
+		.name = "dirty_background_ratio",
+		.read_u64 = mem_cgroup_dirty_read,
+		.write_u64 = mem_cgroup_dirty_write,
+		.private = MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
+	},
+	{
+		.name = "dirty_background_bytes",
+		.read_u64 = mem_cgroup_dirty_read,
+		.write_u64 = mem_cgroup_dirty_write,
+		.private = MEM_CGROUP_DIRTY_BACKGROUND_BYTES,
+	},
+	{
 		.name = "move_charge_at_immigrate",
 		.read_u64 = mem_cgroup_move_charge_read,
 		.write_u64 = mem_cgroup_move_charge_write,
@@ -3762,8 +4075,21 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 	mem->last_scanned_child = 0;
 	spin_lock_init(&mem->reclaim_param_lock);
 
-	if (parent)
+	if (parent) {
 		mem->swappiness = get_swappiness(parent);
+		mem->dirty_param = parent->dirty_param;
+	} else {
+		while (1) {
+			get_global_dirty_param(&mem->dirty_param);
+			/*
+			 * Since global dirty parameters are not protected we
+			 * try to speculatively read them and retry if we get
+			 * inconsistent values.
+			 */
+			if (likely(dirty_param_is_valid(&mem->dirty_param)))
+				break;
+		}
+	}
 	atomic_set(&mem->refcnt, 1);
 	mem->move_charge_at_immigrate = 0;
 	mutex_init(&mem->thresholds_lock);
-- 
1.6.3.3

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