[PATCH] zram: limit memory size for zram

[Minchan Kim]

I have received a request several time from zram users.
They want to limit memory size for zram because zram can consume
lot of memory on system without limit so it makes memory management
control hard.

This patch adds new knob to limit memory of zram.

Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 Documentation/blockdev/zram.txt |  1 +
 drivers/block/zram/zram_drv.c   | 39 +++++++++++++++++++++++++++++++++++++--
 include/linux/zsmalloc.h        |  2 ++
 mm/zsmalloc.c                   | 24 ++++++++++++++++++++++++
 4 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index d24534bee763..fcb0561dfe2e 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -96,6 +96,7 @@ size of the disk when not in use so a huge zram is wasteful.
 		compr_data_size
 		mem_used_total
 		mem_used_max
+		mem_limit
 
 7) Deactivate:
 	swapoff /dev/zram0
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index a4d637b4db7d..069e81ef0c17 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -137,6 +137,41 @@ static ssize_t max_comp_streams_show(struct device *dev,
 	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
 }
 
+static ssize_t mem_limit_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	u64 val = 0;
+	struct zram *zram = dev_to_zram(dev);
+	struct zram_meta *meta = zram->meta;
+
+	down_read(&zram->init_lock);
+	if (init_done(zram))
+		val = zs_get_limit_size_bytes(meta->mem_pool);
+	up_read(&zram->init_lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
+}
+
+static ssize_t mem_limit_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	int ret;
+	u64 limit;
+	struct zram *zram = dev_to_zram(dev);
+	struct zram_meta *meta = zram->meta;
+
+	ret = kstrtoull(buf, 0, &limit);
+	if (ret < 0)
+		return ret;
+
+	down_write(&zram->init_lock);
+	if (init_done(zram))
+		zs_set_limit_size_bytes(meta->mem_pool, limit);
+	up_write(&zram->init_lock);
+	ret = len;
+	return ret;
+}
+
 static ssize_t max_comp_streams_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
@@ -506,8 +541,6 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 	handle = zs_malloc(meta->mem_pool, clen);
 	if (!handle) {
-		pr_info("Error allocating memory for compressed page: %u, size=%zu\n",
-			index, clen);
 		ret = -ENOMEM;
 		goto out;
 	}
@@ -854,6 +887,7 @@ static DEVICE_ATTR(reset, S_IWUSR, NULL, reset_store);
 static DEVICE_ATTR(orig_data_size, S_IRUGO, orig_data_size_show, NULL);
 static DEVICE_ATTR(mem_used_total, S_IRUGO, mem_used_total_show, NULL);
 static DEVICE_ATTR(mem_used_max, S_IRUGO, mem_used_max_show, NULL);
+static DEVICE_ATTR(mem_limit, S_IRUGO, mem_limit_show, mem_limit_store);
 static DEVICE_ATTR(max_comp_streams, S_IRUGO | S_IWUSR,
 		max_comp_streams_show, max_comp_streams_store);
 static DEVICE_ATTR(comp_algorithm, S_IRUGO | S_IWUSR,
@@ -883,6 +917,7 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_compr_data_size.attr,
 	&dev_attr_mem_used_total.attr,
 	&dev_attr_mem_used_max.attr,
+	&dev_attr_mem_limit.attr,
 	&dev_attr_max_comp_streams.attr,
 	&dev_attr_comp_algorithm.attr,
 	NULL,
diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
index fb087ca06a88..41122251a2d0 100644
--- a/include/linux/zsmalloc.h
+++ b/include/linux/zsmalloc.h
@@ -49,4 +49,6 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle);
 u64 zs_get_total_size_bytes(struct zs_pool *pool);
 u64 zs_get_max_size_bytes(struct zs_pool *pool);
 
+u64 zs_get_limit_size_bytes(struct zs_pool *pool);
+void zs_set_limit_size_bytes(struct zs_pool *pool, u64 limit);
 #endif
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 3b5be076268a..8ca51118cf2b 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -220,6 +220,7 @@ struct zs_pool {
 	gfp_t flags;	/* allocation flags used when growing pool */
 	unsigned long pages_allocated;
 	unsigned long max_pages_allocated;
+	unsigned long pages_limited;
 };
 
 /*
@@ -940,6 +941,11 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
 
 	if (!first_page) {
 		spin_unlock(&class->lock);
+
+		if (pool->pages_limited && (pool->pages_limited <
+			pool->pages_allocated + class->pages_per_zspage))
+			return 0;
+
 		first_page = alloc_zspage(class, pool->flags);
 		if (unlikely(!first_page))
 			return 0;
@@ -1132,6 +1138,24 @@ u64 zs_get_max_size_bytes(struct zs_pool *pool)
 }
 EXPORT_SYMBOL_GPL(zs_get_max_size_bytes);
 
+void zs_set_limit_size_bytes(struct zs_pool *pool, u64 limit)
+{
+	pool->pages_limited = round_down(limit, PAGE_SIZE) >> PAGE_SHIFT;
+}
+EXPORT_SYMBOL_GPL(zs_set_limit_size_bytes);
+
+u64 zs_get_limit_size_bytes(struct zs_pool *pool)
+{
+	u64 npages;
+
+	spin_lock(&pool->stat_lock);
+	npages = pool->pages_limited;
+	spin_unlock(&pool->stat_lock);
+	return npages << PAGE_SHIFT;
+
+}
+EXPORT_SYMBOL_GPL(zs_get_limit_size_bytes);
+
 module_init(zs_init);
 module_exit(zs_exit);
 
-- 
2.0.0

-- 
Kind regards,
Minchan Kim
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