[RFC PATCH v1 4/5] zram: add fold sysfs knob

[Alexey Romanov <avromanov@sberdevices.ru>]

Allow zram to fold identical zsmalloc objects into single one:

echo 1 > /sys/block/zramX/fold

Signed-off-by: Alexey Romanov <avromanov@sberdevices.ru>
---
 drivers/block/zram/zram_drv.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index e290d6d97047..06a614d1643d 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1184,6 +1184,25 @@ static ssize_t compact_store(struct device *dev,
 	return len;
 }
 
+#ifdef CONFIG_ZSMALLOC_FOLD
+static ssize_t fold_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct zram *zram = dev_to_zram(dev);
+
+	down_read(&zram->init_lock);
+	if (!init_done(zram)) {
+		up_read(&zram->init_lock);
+		return -EINVAL;
+	}
+
+	zs_fold(zram->mem_pool);
+	up_read(&zram->init_lock);
+
+	return len;
+}
+#endif
+
 static ssize_t io_stat_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
@@ -2313,6 +2332,9 @@ static DEVICE_ATTR_RW(writeback_limit_enable);
 static DEVICE_ATTR_RW(recomp_algorithm);
 static DEVICE_ATTR_WO(recompress);
 #endif
+#ifdef CONFIG_ZSMALLOC_FOLD
+static DEVICE_ATTR_WO(fold);
+#endif
 
 static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_disksize.attr,
@@ -2339,6 +2361,9 @@ static struct attribute *zram_disk_attrs[] = {
 #ifdef CONFIG_ZRAM_MULTI_COMP
 	&dev_attr_recomp_algorithm.attr,
 	&dev_attr_recompress.attr,
+#endif
+#ifdef CONFIG_ZSMALLOC_FOLD
+	&dev_attr_fold.attr,
 #endif
 	NULL,
 };
-- 
2.38.1