linux-kernel - [RFC PATCH v1 2/4] zram: add merge sysfs knob

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Date:   Mon, 21 Nov 2022 22:00:18 +0300
From:   Alexey Romanov <avromanov@...rdevices.ru>
To:     <minchan@...nel.org>, <senozhatsky@...omium.org>,
        <ngupta@...are.org>, <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <kernel@...rdevices.ru>, <ddrokosov@...rdevices.ru>,
        Alexey Romanov <avromanov@...rdevices.ru>
Subject: [RFC PATCH v1 2/4] zram: add merge sysfs knob

Allow zram to merge identical pages into signle one:

echo 1 > /sys/block/zramX/merge

Signed-off-by: Alexey Romanov <avromanov@...rdevices.ru>
---
 drivers/block/zram/zram_drv.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 716c2f72805e..1dae3564cabd 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1197,6 +1197,30 @@ static ssize_t compact_store(struct device *dev,
 	return len;
 }
 
+static int zram_do_scan(struct zram *zram);
+
+static ssize_t merge_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct zram *zram = dev_to_zram(dev);
+	int ret;
+
+	down_read(&zram->init_lock);
+	if (!init_done(zram)) {
+		up_read(&zram->init_lock);
+		return -EINVAL;
+	}
+
+	ret = zram_do_scan(zram);
+	if (ret != 0) {
+		up_read(&zram->init_lock);
+		return -ENOMEM;
+	}
+
+	up_read(&zram->init_lock);
+	return len;
+}
+
 static ssize_t io_stat_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
@@ -2569,6 +2593,7 @@ static const struct block_device_operations zram_devops = {
 };
 
 static DEVICE_ATTR_WO(compact);
+static DEVICE_ATTR_WO(merge);
 static DEVICE_ATTR_RW(disksize);
 static DEVICE_ATTR_RO(initstate);
 static DEVICE_ATTR_WO(reset);
@@ -2609,6 +2634,7 @@ static struct attribute *zram_disk_attrs[] = {
 #ifdef CONFIG_ZRAM_WRITEBACK
 	&dev_attr_bd_stat.attr,
 #endif
+	&dev_attr_merge.attr,
 	&dev_attr_debug_stat.attr,
 #ifdef CONFIG_ZRAM_MULTI_COMP
 	&dev_attr_recomp_algorithm.attr,
-- 
2.25.1