3 files changed, 41 insertions, 3 deletions

diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index c06f75f54718..ac276f79f21c 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -136,6 +136,29 @@ static void zcomp_strm_multi_release(struct zcomp *comp, struct zcomp_strm *zstr
 	zcomp_strm_free(comp, zstrm);
 }
 
+/* change max_strm limit */
+static int zcomp_strm_multi_set_max_streams(struct zcomp *comp, int num_strm)
+{
+	struct zcomp_strm_multi *zs = comp->stream;
+	struct zcomp_strm *zstrm;
+
+	spin_lock(&zs->strm_lock);
+	zs->max_strm = num_strm;
+	/*
+	 * if user has lowered the limit and there are idle streams,
+	 * immediately free as much streams (and memory) as we can.
+	 */
+	while (zs->avail_strm > num_strm && !list_empty(&zs->idle_strm)) {
+		zstrm = list_entry(zs->idle_strm.next,
+				struct zcomp_strm, list);
+		list_del(&zstrm->list);
+		zcomp_strm_free(comp, zstrm);
+		zs->avail_strm--;
+	}
+	spin_unlock(&zs->strm_lock);
+	return 0;
+}
+
 static void zcomp_strm_multi_destroy(struct zcomp *comp)
 {
 	struct zcomp_strm_multi *zs = comp->stream;
@@ -158,6 +181,7 @@ static int zcomp_strm_multi_create(struct zcomp *comp, int max_strm)
 	comp->destroy = zcomp_strm_multi_destroy;
 	comp->strm_find = zcomp_strm_multi_find;
 	comp->strm_release = zcomp_strm_multi_release;
+	comp->set_max_streams = zcomp_strm_multi_set_max_streams;
 	zs = kmalloc(sizeof(struct zcomp_strm_multi), GFP_KERNEL);
 	if (!zs)
 		return -ENOMEM;
@@ -192,6 +216,12 @@ static void zcomp_strm_single_release(struct zcomp *comp,
 	mutex_unlock(&zs->strm_lock);
 }
 
+static int zcomp_strm_single_set_max_streams(struct zcomp *comp, int num_strm)
+{
+	/* zcomp_strm_single support only max_comp_streams == 1 */
+	return -ENOTSUPP;
+}
+
 static void zcomp_strm_single_destroy(struct zcomp *comp)
 {
 	struct zcomp_strm_single *zs = comp->stream;
@@ -206,6 +236,7 @@ static int zcomp_strm_single_create(struct zcomp *comp)
 	comp->destroy = zcomp_strm_single_destroy;
 	comp->strm_find = zcomp_strm_single_find;
 	comp->strm_release = zcomp_strm_single_release;
+	comp->set_max_streams = zcomp_strm_single_set_max_streams;
 	zs = kmalloc(sizeof(struct zcomp_strm_single), GFP_KERNEL);
 	if (!zs)
 		return -ENOMEM;
@@ -220,6 +251,11 @@ static int zcomp_strm_single_create(struct zcomp *comp)
 	return 0;
 }
 
+int zcomp_set_max_streams(struct zcomp *comp, int num_strm)
+{
+	return comp->set_max_streams(comp, num_strm);
+}
+
 struct zcomp_strm *zcomp_strm_find(struct zcomp *comp)
 {
 	return comp->strm_find(comp);
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index 2a3684446160..bd11d59c5dd1 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -46,6 +46,7 @@ struct zcomp {
 
 	struct zcomp_strm *(*strm_find)(struct zcomp *comp);
 	void (*strm_release)(struct zcomp *comp, struct zcomp_strm *zstrm);
+	int (*set_max_streams)(struct zcomp *comp, int num_strm);
 	void (*destroy)(struct zcomp *comp);
 };
 
@@ -60,4 +61,6 @@ int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
 
 int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
 		size_t src_len, unsigned char *dst);
+
+int zcomp_set_max_streams(struct zcomp *comp, int num_strm);
 #endif /* _ZCOMP_H_ */
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 88ee317ce6d2..c03d0053309b 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -133,9 +133,8 @@ static ssize_t max_comp_streams_store(struct device *dev,
 		return -EINVAL;
 	down_write(&zram->init_lock);
 	if (init_done(zram)) {
-		up_write(&zram->init_lock);
-		pr_info("Can't set max_comp_streams for initialized device\n");
-		return -EBUSY;
+		if (zcomp_set_max_streams(zram->comp, num))
+			pr_info("Cannot change max compression streams\n");
 	}
 	zram->max_comp_streams = num;
 	up_write(&zram->init_lock);