zram: make deduplication feature optional

Benefit of deduplication is dependent on the workload so it's not
preferable to always enable. Therefore, make it optional in Kconfig
and device param. Default is 'off'. This option will be beneficial
for users who use the zram as blockdev and stores build output to it.

Change-Id: If282bb8aa15c5749859a87cf36db7eb9edb3b1ed
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Link: https://lore.kernel.org/patchwork/patch/787164/
Patch-mainline: linux-kernel@ Thu, 11 May 2017 22:30:52
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
[swatsrid@codeaurora.org: Fix trivial merge conflicts]
Signed-off-by: Swathi Sridhar <swatsrid@codeaurora.org>

Documentation/ABI/testing/sysfs-block-zram

@@ -137,3 +137,13 @@ Description:
 		The writeback_limit file is read-write and specifies the maximum
 		amount of writeback ZRAM can do. The limit could be changed
 		in run time.
+
+What:		/sys/block/zram<id>/use_dedup
+Date:		March 2017
+Contact:	Joonsoo Kim <iamjoonsoo.kim@lge.com>
+Description:
+		The use_dedup file is read-write and specifies deduplication
+		feature is used or not. If enabled, duplicated data is
+		managed by reference count and will not be stored in memory
+		twice. Benefit of this feature largely depends on the workload
+		so keep attention when use.

Documentation/blockdev/zram.txt

@@ -173,7 +173,7 @@ compact           	WO	trigger memory compaction
 debug_stat        	RO	this file is used for zram debugging purposes
 backing_dev	  	RW	set up backend storage for zram to write out
 idle		  	WO	mark allocated slot as idle
-
+use_dedup		RW	show and set deduplication feature
 
 User space is advised to use the following files to read the device statistics.
 

drivers/block/zram/Kconfig

@@ -15,6 +15,20 @@ config ZRAM
 
 	  See Documentation/blockdev/zram.txt for more information.
 
+config ZRAM_DEDUP
+	bool "Deduplication support for ZRAM data"
+	depends on ZRAM
+	default n
+	help
+	  Deduplicate ZRAM data to reduce amount of memory consumption.
+	  Advantage largely depends on the workload. In some cases, this
+          option reduces memory usage to the half. However, if there is no
+	  duplicated data, the amount of memory consumption would be
+	  increased due to additional metadata usage. And, there is
+	  computation time trade-off. Please check the benefit before
+	  enabling this option. Experiment shows the positive effect when
+	  the zram is used as blockdev and is used to store build output.
+
 config ZRAM_WRITEBACK
        bool "Write back incompressible or idle page to backing device"
        depends on ZRAM

drivers/block/zram/Makefile

@@ -1,3 +1,4 @@
-zram-y	:=	zcomp.o zram_drv.o zram_dedup.o
+zram-y				:=	zcomp.o zram_drv.o
+zram-$(CONFIG_ZRAM_DEDUP)	+=	zram_dedup.o
 
 obj-$(CONFIG_ZRAM)	+=	zram.o

drivers/block/zram/zram_dedup.c

@@ -41,6 +41,9 @@ void zram_dedup_insert(struct zram *zram, struct zram_entry *new,
 	struct rb_node **rb_node, *parent = NULL;
 	struct zram_entry *entry;
 
+	if (!zram_dedup_enabled(zram))
+		return;
+
 	new->checksum = checksum;
 	hash = &zram->hash[checksum % zram->hash_size];
 	rb_root = &hash->rb_root;
@@ -148,6 +151,9 @@ struct zram_entry *zram_dedup_find(struct zram *zram, struct page *page,
 	void *mem;
 	struct zram_entry *entry;
 
+	if (!zram_dedup_enabled(zram))
+		return NULL;
+
 	mem = kmap_atomic(page);
 	*checksum = zram_dedup_checksum(mem);
 
@@ -160,6 +166,9 @@ struct zram_entry *zram_dedup_find(struct zram *zram, struct page *page,
 void zram_dedup_init_entry(struct zram *zram, struct zram_entry *entry,
 				unsigned long handle, unsigned int len)
 {
+	if (!zram_dedup_enabled(zram))
+		return;
+
 	entry->handle = handle;
 	entry->refcount = 1;
 	entry->len = len;
@@ -167,6 +176,9 @@ void zram_dedup_init_entry(struct zram *zram, struct zram_entry *entry,
 
 bool zram_dedup_put_entry(struct zram *zram, struct zram_entry *entry)
 {
+	if (!zram_dedup_enabled(zram))
+		return true;
+
 	if (zram_dedup_put(zram, entry))
 		return false;
 
@@ -178,6 +190,9 @@ int zram_dedup_init(struct zram *zram, size_t num_pages)
 	int i;
 	struct zram_hash *hash;
 
+	if (!zram_dedup_enabled(zram))
+		return 0;
+
 	zram->hash_size = num_pages >> ZRAM_HASH_SHIFT;
 	zram->hash_size = min_t(size_t, ZRAM_HASH_SIZE_MAX, zram->hash_size);
 	zram->hash_size = max_t(size_t, ZRAM_HASH_SIZE_MIN, zram->hash_size);

drivers/block/zram/zram_dedup.h

@@ -4,6 +4,8 @@
 struct zram;
 struct zram_entry;
 
+#ifdef CONFIG_ZRAM_DEDUP
+
 u64 zram_dedup_dup_size(struct zram *zram);
 u64 zram_dedup_meta_size(struct zram *zram);
 
@@ -18,5 +20,26 @@ bool zram_dedup_put_entry(struct zram *zram, struct zram_entry *entry);
 
 int zram_dedup_init(struct zram *zram, size_t num_pages);
 void zram_dedup_fini(struct zram *zram);
+#else
+
+static inline u64 zram_dedup_dup_size(struct zram *zram) { return 0; }
+static inline u64 zram_dedup_meta_size(struct zram *zram) { return 0; }
+
+static inline void zram_dedup_insert(struct zram *zram, struct zram_entry *new,
+			u32 checksum) { }
+static inline struct zram_entry *zram_dedup_find(struct zram *zram,
+			struct page *page, u32 *checksum) { return NULL; }
+
+static inline void zram_dedup_init_entry(struct zram *zram,
+			struct zram_entry *entry, unsigned long handle,
+			unsigned int len) { }
+static inline bool zram_dedup_put_entry(struct zram *zram,
+			struct zram_entry *entry) { return true; }
+
+static inline int zram_dedup_init(struct zram *zram,
+			size_t num_pages) { return 0; }
+static inline void zram_dedup_fini(struct zram *zram) { }
+
+#endif
 
 #endif /* _ZRAM_DEDUP_H_ */

drivers/block/zram/zram_drv.c

@@ -1030,6 +1030,41 @@ static ssize_t comp_algorithm_store(struct device *dev,
 	return len;
 }
 
+static ssize_t use_dedup_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	bool val;
+	struct zram *zram = dev_to_zram(dev);
+
+	down_read(&zram->init_lock);
+	val = zram->use_dedup;
+	up_read(&zram->init_lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", (int)val);
+}
+
+#ifdef CONFIG_ZRAM_DEDUP
+static ssize_t use_dedup_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	int val;
+	struct zram *zram = dev_to_zram(dev);
+
+	if (kstrtoint(buf, 10, &val) || (val != 0 && val != 1))
+		return -EINVAL;
+
+	down_write(&zram->init_lock);
+	if (init_done(zram)) {
+		up_write(&zram->init_lock);
+		pr_info("Can't change dedup usage for initialized device\n");
+		return -EBUSY;
+	}
+	zram->use_dedup = val;
+	up_write(&zram->init_lock);
+	return len;
+}
+#endif
+
 static ssize_t compact_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
@@ -1147,20 +1182,32 @@ static DEVICE_ATTR_RO(bd_stat);
 #endif
 static DEVICE_ATTR_RO(debug_stat);
 
+static unsigned long zram_entry_handle(struct zram *zram,
+		struct zram_entry *entry)
+{
+	if (zram_dedup_enabled(zram))
+		return entry->handle;
+	else
+		return (unsigned long)entry;
+}
+
 static struct zram_entry *zram_entry_alloc(struct zram *zram,
 					   unsigned int len, gfp_t flags)
 {
 	struct zram_entry *entry;
 	unsigned long handle;
 
-	entry = kzalloc(sizeof(*entry),
-			flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE|__GFP_CMA));
-	if (!entry)
+	handle = zs_malloc(zram->mem_pool, len, flags);
+	if (!handle)
 		return NULL;
 
-	handle = zs_malloc(zram->mem_pool, len, flags);
-	if (!handle) {
-		kfree(entry);
+	if (!zram_dedup_enabled(zram))
+		return (struct zram_entry *)handle;
+
+	entry = kzalloc(sizeof(*entry),
+			flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE|__GFP_CMA));
+	if (!entry) {
+		zs_free(zram->mem_pool, handle);
 		return NULL;
 	}
 
@@ -1175,7 +1222,11 @@ void zram_entry_free(struct zram *zram, struct zram_entry *entry)
 	if (!zram_dedup_put_entry(zram, entry))
 		return;
 
-	zs_free(zram->mem_pool, entry->handle);
+	zs_free(zram->mem_pool, zram_entry_handle(zram, entry));
+
+	if (!zram_dedup_enabled(zram))
+		return;
+
 	kfree(entry);
 
 	atomic64_sub(sizeof(*entry), &zram->stats.meta_data_size);
@@ -1311,7 +1362,8 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
 
 	size = zram_get_obj_size(zram, index);
 
-	src = zs_map_object(zram->mem_pool, entry->handle, ZS_MM_RO);
+	src = zs_map_object(zram->mem_pool,
+			    zram_entry_handle(zram, entry), ZS_MM_RO);
 	if (size == PAGE_SIZE) {
 		dst = kmap_atomic(page);
 		memcpy(dst, src, PAGE_SIZE);
@@ -1325,7 +1377,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
 		kunmap_atomic(dst);
 		zcomp_stream_put(zram->comp);
 	}
-	zs_unmap_object(zram->mem_pool, entry->handle);
+	zs_unmap_object(zram->mem_pool, zram_entry_handle(zram, entry));
 	zram_slot_unlock(zram, index);
 
 	/* Should NEVER happen. Return bio error if it does. */
@@ -1454,7 +1506,8 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 		return -ENOMEM;
 	}
 
-	dst = zs_map_object(zram->mem_pool, entry->handle, ZS_MM_WO);
+	dst = zs_map_object(zram->mem_pool,
+			    zram_entry_handle(zram, entry), ZS_MM_WO);
 
 	src = zstrm->buffer;
 	if (comp_len == PAGE_SIZE)
@@ -1464,7 +1517,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 		kunmap_atomic(src);
 
 	zcomp_stream_put(zram->comp);
-	zs_unmap_object(zram->mem_pool, entry->handle);
+	zs_unmap_object(zram->mem_pool, zram_entry_handle(zram, entry));
 	atomic64_add(comp_len, &zram->stats.compr_data_size);
 	zram_dedup_insert(zram, entry, checksum);
 out:
@@ -1908,6 +1961,11 @@ static DEVICE_ATTR_WO(writeback);
 static DEVICE_ATTR_RW(writeback_limit);
 static DEVICE_ATTR_RW(writeback_limit_enable);
 #endif
+#ifdef CONFIG_ZRAM_DEDUP
+static DEVICE_ATTR_RW(use_dedup);
+#else
+static DEVICE_ATTR_RO(use_dedup);
+#endif
 
 static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_disksize.attr,
@@ -1925,6 +1983,7 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_writeback_limit.attr,
 	&dev_attr_writeback_limit_enable.attr,
 #endif
+	&dev_attr_use_dedup.attr,
 	&dev_attr_io_stat.attr,
 	&dev_attr_mm_stat.attr,
 #ifdef CONFIG_ZRAM_WRITEBACK

drivers/block/zram/zram_drv.h

@@ -134,6 +134,7 @@ struct zram {
 	 * zram is claimed so open request will be failed
 	 */
 	bool claim; /* Protected by bdev->bd_mutex */
+	bool use_dedup;
 	struct file *backing_dev;
 #ifdef CONFIG_ZRAM_WRITEBACK
 	spinlock_t wb_limit_lock;
@@ -149,5 +150,14 @@ struct zram {
 #endif
 };
 
+static inline bool zram_dedup_enabled(struct zram *zram)
+{
+#ifdef CONFIG_ZRAM_DEDUP
+	return zram->use_dedup;
+#else
+	return false;
+#endif
+}
+
 void zram_entry_free(struct zram *zram, struct zram_entry *entry);
 #endif