[PATCH 5/8] zram: return zram device_id value from zram_add()

[Sergey Senozhatsky <sergey.senozhatsky@gmail.com>]

ZRAM_CTL_ADD ioctl requires valid device_id to be provided, that can be a
bit inconvenient. Change zram_add() to return negative value upon new device
creation failure, and device_id (>= 0) value otherwise.

This prepares ZRAM_CTL_ADD to perform automatic device_id assignment. New
device_id will be returned back to user-space (so user can reference that
device as zram%d device_id).

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 drivers/block/zram/zram_drv.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 4f87d1e..0154c2d4 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1078,6 +1078,8 @@ static struct zram *zram_lookup(int dev_id)
 	return ERR_PTR(-ENODEV);
 }
 
+/* allocate and initialize new zram device. the function returns >= 0
+ * device_id value upon success, and negative value otherwise. */
 static int zram_add(int device_id)
 {
 	struct zram *zram;
@@ -1161,7 +1163,7 @@ static int zram_add(int device_id)
 	strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
 	zram->meta = NULL;
 	zram->max_comp_streams = 1;
-	return 0;
+	return device_id;
 
 out_free_disk:
 	del_gendisk(zram->disk);
@@ -1303,7 +1305,7 @@ static int __init zram_init(void)
 		mutex_lock(&zram_index_mutex);
 		ret = zram_add(dev_id);
 		mutex_unlock(&zram_index_mutex);
-		if (ret != 0)
+		if (ret < 0)
 			goto out_error;
 	}
 
-- 
2.3.1.167.g7f4ba4b