[RFC][PATCHv3 6/7] zsmalloc/zram: move `num_migrated' to zs_pool

[Sergey Senozhatsky]

Remove the number of migrated objects from `zs_compact_control'
and move it to `zs_pool'. `zs_compact_control' has a limited
lifespan, we lose it when zs_compaction() returns back to zram.

To keep track of objects migrated during auto-compaction (issued
by the shrinker) we need to store this number in zs_pool.

Introduce zs_get_num_migrated() to export zs_pool's ->num_migrated
counter and use it in zram, so we can also drop a zram's copy of
`num_migrated'.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
 drivers/block/zram/zram_drv.c | 12 ++++++------
 drivers/block/zram/zram_drv.h |  1 -
 include/linux/zsmalloc.h      |  1 +
 mm/zsmalloc.c                 | 41 +++++++++++++++++++----------------------
 4 files changed, 26 insertions(+), 29 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index fb655e8..28ad3f8 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -388,7 +388,6 @@ static ssize_t comp_algorithm_store(struct device *dev,
 static ssize_t compact_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
-	unsigned long nr_migrated;
 	struct zram *zram = dev_to_zram(dev);
 	struct zram_meta *meta;
 
@@ -399,8 +398,7 @@ static ssize_t compact_store(struct device *dev,
 	}
 
 	meta = zram->meta;
-	nr_migrated = zs_compact(meta->mem_pool);
-	atomic64_add(nr_migrated, &zram->stats.num_migrated);
+	zs_compact(meta->mem_pool);
 	up_read(&zram->init_lock);
 
 	return len;
@@ -428,13 +426,15 @@ static ssize_t mm_stat_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
 	struct zram *zram = dev_to_zram(dev);
-	u64 orig_size, mem_used = 0;
+	u64 orig_size, mem_used = 0, num_migrated = 0;
 	long max_used;
 	ssize_t ret;
 
 	down_read(&zram->init_lock);
-	if (init_done(zram))
+	if (init_done(zram)) {
 		mem_used = zs_get_total_pages(zram->meta->mem_pool);
+		num_migrated = zs_get_num_migrated(zram->meta->mem_pool);
+	}
 
 	orig_size = atomic64_read(&zram->stats.pages_stored);
 	max_used = atomic_long_read(&zram->stats.max_used_pages);
@@ -447,7 +447,7 @@ static ssize_t mm_stat_show(struct device *dev,
 			zram->limit_pages << PAGE_SHIFT,
 			max_used << PAGE_SHIFT,
 			(u64)atomic64_read(&zram->stats.zero_pages),
-			(u64)atomic64_read(&zram->stats.num_migrated));
+			num_migrated);
 	up_read(&zram->init_lock);
 
 	return ret;
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 6dbe2df..8e92339 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -78,7 +78,6 @@ struct zram_stats {
 	atomic64_t compr_data_size;	/* compressed size of pages stored */
 	atomic64_t num_reads;	/* failed + successful */
 	atomic64_t num_writes;	/* --do-- */
-	atomic64_t num_migrated;	/* no. of migrated object */
 	atomic64_t failed_reads;	/* can happen when memory is too low */
 	atomic64_t failed_writes;	/* can happen when memory is too low */
 	atomic64_t invalid_io;	/* non-page-aligned I/O requests */
diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
index 1338190..e878875 100644
--- a/include/linux/zsmalloc.h
+++ b/include/linux/zsmalloc.h
@@ -47,6 +47,7 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
 void zs_unmap_object(struct zs_pool *pool, unsigned long handle);
 
 unsigned long zs_get_total_pages(struct zs_pool *pool);
+unsigned long zs_get_num_migrated(struct zs_pool *pool);
 unsigned long zs_compact(struct zs_pool *pool);
 
 #endif
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 5fa96ae..c9aea0a 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -237,16 +237,19 @@ struct link_free {
 };
 
 struct zs_pool {
-	char *name;
+	char			*name;
 
-	struct size_class **size_class;
-	struct kmem_cache *handle_cachep;
+	struct size_class	**size_class;
+	struct kmem_cache	*handle_cachep;
 
-	gfp_t flags;	/* allocation flags used when growing pool */
-	atomic_long_t pages_allocated;
+	/* Allocation flags used when growing pool */
+	gfp_t			flags;
+	atomic_long_t		pages_allocated;
+	/* How many objects were migrated */
+	unsigned long		num_migrated;
 
 #ifdef CONFIG_ZSMALLOC_STAT
-	struct dentry *stat_dentry;
+	struct dentry		*stat_dentry;
 #endif
 };
 
@@ -1220,6 +1223,12 @@ unsigned long zs_get_total_pages(struct zs_pool *pool)
 }
 EXPORT_SYMBOL_GPL(zs_get_total_pages);
 
+unsigned long zs_get_num_migrated(struct zs_pool *pool)
+{
+	return pool->num_migrated;
+}
+EXPORT_SYMBOL_GPL(zs_get_num_migrated);
+
 /**
  * zs_map_object - get address of allocated object from handle.
  * @pool: pool from which the object was allocated
@@ -1586,8 +1595,6 @@ struct zs_compact_control {
 	 /* Starting object index within @s_page which used for live object
 	  * in the subpage. */
 	int index;
-	/* how many of objects are migrated */
-	int nr_migrated;
 };
 
 static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
@@ -1598,7 +1605,6 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
 	struct page *s_page = cc->s_page;
 	struct page *d_page = cc->d_page;
 	unsigned long index = cc->index;
-	int nr_migrated = 0;
 	int ret = 0;
 
 	while (1) {
@@ -1625,13 +1631,12 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
 		record_obj(handle, free_obj);
 		unpin_tag(handle);
 		obj_free(pool, class, used_obj);
-		nr_migrated++;
+		pool->num_migrated++;
 	}
 
 	/* Remember last position in this iteration */
 	cc->s_page = s_page;
 	cc->index = index;
-	cc->nr_migrated = nr_migrated;
 
 	return ret;
 }
@@ -1706,13 +1711,11 @@ static unsigned long zs_can_compact(struct size_class *class)
 	return obj_wasted;
 }
 
-static unsigned long __zs_compact(struct zs_pool *pool,
-				struct size_class *class)
+static void __zs_compact(struct zs_pool *pool, struct size_class *class)
 {
 	struct zs_compact_control cc;
 	struct page *src_page;
 	struct page *dst_page = NULL;
-	unsigned long nr_total_migrated = 0;
 
 	spin_lock(&class->lock);
 	while ((src_page = isolate_source_page(class))) {
@@ -1735,7 +1738,6 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 				break;
 
 			putback_zspage(pool, class, dst_page);
-			nr_total_migrated += cc.nr_migrated;
 		}
 
 		/* Stop if we couldn't find slot */
@@ -1745,7 +1747,6 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 		putback_zspage(pool, class, dst_page);
 		putback_zspage(pool, class, src_page);
 		spin_unlock(&class->lock);
-		nr_total_migrated += cc.nr_migrated;
 		cond_resched();
 		spin_lock(&class->lock);
 	}
@@ -1754,14 +1755,11 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 		putback_zspage(pool, class, src_page);
 
 	spin_unlock(&class->lock);
-
-	return nr_total_migrated;
 }
 
 unsigned long zs_compact(struct zs_pool *pool)
 {
 	int i;
-	unsigned long nr_migrated = 0;
 	struct size_class *class;
 
 	for (i = zs_size_classes - 1; i >= 0; i--) {
@@ -1770,10 +1768,9 @@ unsigned long zs_compact(struct zs_pool *pool)
 			continue;
 		if (class->index != i)
 			continue;
-		nr_migrated += __zs_compact(pool, class);
+		__zs_compact(pool, class);
 	}
-
-	return nr_migrated;
+	return pool->num_migrated;
 }
 EXPORT_SYMBOL_GPL(zs_compact);
 
-- 
2.4.4

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