4 files changed, 79 insertions, 4 deletions

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 70ec992514d0..ea67fa3f3cff 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -119,3 +119,12 @@ Description:
                 efficiency can be calculated using compr_data_size and this
                 statistic.
                 Unit: bytes
+
+What:           /sys/block/zram<id>/mem_limit
+Date:           August 2014
+Contact:        Minchan Kim <minchan@kernel.org>
+Description:
+                The mem_limit file is read/write and specifies the maximum
+                amount of memory ZRAM can use to store the compressed data.  The
+                limit could be changed in run time and "0" means disable the
+                limit.  No limit is the initial state.  Unit: bytes
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 0595c3f56ccf..82c6a41116db 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -74,14 +74,30 @@ There is little point creating a zram of greater than twice the size of memory
 since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the
 size of the disk when not in use so a huge zram is wasteful.
 
-5) Activate:
+5) Set memory limit: Optional
+        Set memory limit by writing the value to sysfs node 'mem_limit'.
+        The value can be either in bytes or you can use mem suffixes.
+        In addition, you could change the value in runtime.
+        Examples:
+            # limit /dev/zram0 with 50MB memory
+            echo $((50*1024*1024)) > /sys/block/zram0/mem_limit
+
+            # Using mem suffixes
+            echo 256K > /sys/block/zram0/mem_limit
+            echo 512M > /sys/block/zram0/mem_limit
+            echo 1G > /sys/block/zram0/mem_limit
+
+            # To disable memory limit
+            echo 0 > /sys/block/zram0/mem_limit
+
+6) Activate:
         mkswap /dev/zram0
         swapon /dev/zram0
 
         mkfs.ext4 /dev/zram1
         mount /dev/zram1 /tmp
 
-6) Stats:
+7) Stats:
         Per-device statistics are exported as various nodes under
         /sys/block/zram<id>/
                 disksize
@@ -96,11 +112,11 @@ size of the disk when not in use so a huge zram is wasteful.
                 compr_data_size
                 mem_used_total
 
-7) Deactivate:
+8) Deactivate:
         swapoff /dev/zram0
         umount /dev/zram1
 
-8) Reset:
+9) Reset:
         Write any positive value to 'reset' sysfs node
         echo 1 > /sys/block/zram0/reset
         echo 1 > /sys/block/zram1/reset
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index f0b8b30a7128..64b27cf9a583 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -122,6 +122,37 @@ 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;
+        struct zram *zram = dev_to_zram(dev);
+
+        down_read(&zram->init_lock);
+        val = zram->limit_pages;
+        up_read(&zram->init_lock);
+
+        return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
+}
+
+static ssize_t mem_limit_store(struct device *dev,
+                struct device_attribute *attr, const char *buf, size_t len)
+{
+        u64 limit;
+        char *tmp;
+        struct zram *zram = dev_to_zram(dev);
+
+        limit = memparse(buf, &tmp);
+        if (buf == tmp) /* no chars parsed, invalid input */
+                return -EINVAL;
+
+        down_write(&zram->init_lock);
+        zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT;
+        up_write(&zram->init_lock);
+
+        return len;
+}
+
 static ssize_t max_comp_streams_store(struct device *dev,
                 struct device_attribute *attr, const char *buf, size_t len)
 {
@@ -513,6 +544,14 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
                 ret = -ENOMEM;
                 goto out;
         }
+
+        if (zram->limit_pages &&
+                zs_get_total_pages(meta->mem_pool) > zram->limit_pages) {
+                zs_free(meta->mem_pool, handle);
+                ret = -ENOMEM;
+                goto out;
+        }
+
         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
 
         if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
@@ -617,6 +656,9 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
         struct zram_meta *meta;
 
         down_write(&zram->init_lock);
+
+        zram->limit_pages = 0;
+
         if (!init_done(zram)) {
                 up_write(&zram->init_lock);
                 return;
@@ -857,6 +899,8 @@ static DEVICE_ATTR(initstate, S_IRUGO, initstate_show, NULL);
 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_limit, S_IRUGO | S_IWUSR, 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,
@@ -885,6 +929,7 @@ static struct attribute *zram_disk_attrs[] = {
         &dev_attr_orig_data_size.attr,
         &dev_attr_compr_data_size.attr,
         &dev_attr_mem_used_total.attr,
+        &dev_attr_mem_limit.attr,
         &dev_attr_max_comp_streams.attr,
         &dev_attr_comp_algorithm.attr,
         NULL,
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index e0f725c87cc6..b7aa9c21553f 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -112,6 +112,11 @@ struct zram {
         u64 disksize;   /* bytes */
         int max_comp_streams;
         struct zram_stats stats;
+        /*
+         * the number of pages zram can consume for storing compressed data
+         */
+        unsigned long limit_pages;
+
         char compressor[10];
 };
 #endif