[PATCH 4/4] zram: make deduplication feature optional

[js1304]

From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

Benefit of deduplication is dependent on the workload so it's not
preferable to always enable. Therefore, make it optional.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
 drivers/block/zram/zram_drv.c | 80 ++++++++++++++++++++++++++++++++++++++-----
 drivers/block/zram/zram_drv.h |  1 +
 2 files changed, 73 insertions(+), 8 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 012425f..e45aa9f 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -328,6 +328,39 @@ 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)
+{
+	int 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", val);
+}
+
+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;
+}
+
 static ssize_t compact_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
@@ -422,11 +455,23 @@ static ssize_t debug_stat_show(struct device *dev,
 static DEVICE_ATTR_RO(mm_stat);
 static DEVICE_ATTR_RO(debug_stat);
 
-static u32 zram_calc_checksum(unsigned char *mem)
+static u32 zram_calc_checksum(struct zram *zram, unsigned char *mem)
 {
+	if (!zram->use_dedup)
+		return 0;
+
 	return jhash(mem, PAGE_SIZE, 0);
 }
 
+static unsigned long zram_entry_handle(struct zram *zram,
+				struct zram_entry *entry)
+{
+	if (!zram->use_dedup)
+		return (unsigned long)entry;
+
+	return entry->handle;
+}
+
 static struct zram_entry *zram_entry_alloc(struct zram *zram,
 					unsigned int len, gfp_t flags)
 {
@@ -438,6 +483,9 @@ static struct zram_entry *zram_entry_alloc(struct zram *zram,
 	if (!handle)
 		return NULL;
 
+	if (!zram->use_dedup)
+		return (struct zram_entry *)handle;
+
 	entry = kzalloc(sizeof(*entry), flags);
 	if (!entry) {
 		zs_free(meta->mem_pool, handle);
@@ -462,6 +510,9 @@ static void zram_entry_insert(struct zram *zram, struct zram_entry *new,
 	struct rb_node **rb_node, *parent = NULL;
 	struct zram_entry *entry;
 
+	if (!zram->use_dedup)
+		return;
+
 	new->checksum = checksum;
 	hash = &meta->hash[checksum % meta->hash_size];
 	rb_root = &hash->rb_root;
@@ -492,7 +543,8 @@ static bool zram_entry_match(struct zram *zram, struct zram_entry *entry,
 	struct zram_meta *meta = zram->meta;
 	struct zcomp_strm *zstrm;
 
-	cmem = zs_map_object(meta->mem_pool, entry->handle, ZS_MM_RO);
+	cmem = zs_map_object(meta->mem_pool,
+			zram_entry_handle(zram, entry), ZS_MM_RO);
 	if (entry->len == PAGE_SIZE) {
 		match = !memcmp(mem, cmem, PAGE_SIZE);
 	} else {
@@ -501,7 +553,7 @@ static bool zram_entry_match(struct zram *zram, struct zram_entry *entry,
 			match = !memcmp(mem, zstrm->buffer, PAGE_SIZE);
 		zcomp_stream_put(zram->comp);
 	}
-	zs_unmap_object(meta->mem_pool, entry->handle);
+	zs_unmap_object(meta->mem_pool, zram_entry_handle(zram, entry));
 
 	return match;
 }
@@ -521,6 +573,11 @@ static bool zram_entry_put(struct zram *zram, struct zram_meta *meta,
 	struct zram_hash *hash;
 	u32 checksum;
 
+	if (!zram->use_dedup) {
+		zs_free(meta->mem_pool, zram_entry_handle(zram, entry));
+		return false;
+	}
+
 	if (!populated)
 		goto free;
 
@@ -551,6 +608,9 @@ static struct zram_entry *zram_entry_get(struct zram *zram,
 	struct zram_entry *entry;
 	struct rb_node *rb_node;
 
+	if (!zram->use_dedup)
+		return NULL;
+
 	hash = &meta->hash[checksum % meta->hash_size];
 
 	spin_lock(&hash->lock);
@@ -713,7 +773,8 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 		return 0;
 	}
 
-	cmem = zs_map_object(meta->mem_pool, entry->handle, ZS_MM_RO);
+	cmem = zs_map_object(meta->mem_pool,
+			zram_entry_handle(zram, entry), ZS_MM_RO);
 	if (size == PAGE_SIZE) {
 		copy_page(mem, cmem);
 	} else {
@@ -722,7 +783,7 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 		ret = zcomp_decompress(zstrm, cmem, size, mem);
 		zcomp_stream_put(zram->comp);
 	}
-	zs_unmap_object(meta->mem_pool, entry->handle);
+	zs_unmap_object(meta->mem_pool, zram_entry_handle(zram, entry));
 	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 
 	/* Should NEVER happen. Return bio error if it does. */
@@ -840,7 +901,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 		goto out;
 	}
 
-	checksum = zram_calc_checksum(uncmem);
+	checksum = zram_calc_checksum(zram, uncmem);
 	if (!entry) {
 		entry = zram_entry_get(zram, uncmem, checksum);
 		if (entry) {
@@ -915,7 +976,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 		goto out;
 	}
 
-	cmem = zs_map_object(meta->mem_pool, entry->handle, ZS_MM_WO);
+	cmem = zs_map_object(meta->mem_pool,
+			zram_entry_handle(zram, entry), ZS_MM_WO);
 
 	if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
 		src = kmap_atomic(page);
@@ -927,7 +989,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 	zcomp_stream_put(zram->comp);
 	zstrm = NULL;
-	zs_unmap_object(meta->mem_pool, entry->handle);
+	zs_unmap_object(meta->mem_pool, zram_entry_handle(zram, entry));
 	zram_entry_insert(zram, entry, checksum);
 
 found_duplication:
@@ -1310,6 +1372,7 @@ static int zram_open(struct block_device *bdev, fmode_t mode)
 static DEVICE_ATTR_WO(mem_used_max);
 static DEVICE_ATTR_RW(max_comp_streams);
 static DEVICE_ATTR_RW(comp_algorithm);
+static DEVICE_ATTR_RW(use_dedup);
 
 static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_disksize.attr,
@@ -1320,6 +1383,7 @@ static int zram_open(struct block_device *bdev, fmode_t mode)
 	&dev_attr_mem_used_max.attr,
 	&dev_attr_max_comp_streams.attr,
 	&dev_attr_comp_algorithm.attr,
+	&dev_attr_use_dedup.attr,
 	&dev_attr_io_stat.attr,
 	&dev_attr_mm_stat.attr,
 	&dev_attr_debug_stat.attr,
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 07d1f8d..b823555 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -141,5 +141,6 @@ struct zram {
 	 * zram is claimed so open request will be failed
 	 */
 	bool claim; /* Protected by bdev->bd_mutex */
+	int use_dedup;
 };
 #endif
-- 
1.9.1