block: null_blk: Cleanup messages

Use the pr_fmt() macro to prefix all null_blk pr_xxx() messages with
"null_blk:" to clarify which module is printing the messages. Also add
a pr_info() message in null_add_dev() to print the name of a newly
created disk.

Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20220420005718.3780004-4-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/null_blk/main.c

@@ -11,6 +11,9 @@
 #include <linux/init.h>
 #include "null_blk.h"
 
+#undef pr_fmt
+#define pr_fmt(fmt)	"null_blk: " fmt
+
 #define FREE_BATCH		16
 
 #define TICKS_PER_SEC		50ULL
@@ -2069,6 +2072,8 @@ static int null_add_dev(struct nullb_device *dev)
 	list_add_tail(&nullb->list, &nullb_list);
 	mutex_unlock(&lock);
 
+	pr_info("disk %s created\n", nullb->disk_name);
+
 	return 0;
 out_cleanup_zone:
 	null_free_zoned_dev(dev);

drivers/block/null_blk/zoned.c

@@ -6,6 +6,9 @@
 #define CREATE_TRACE_POINTS
 #include "trace.h"
 
+#undef pr_fmt
+#define pr_fmt(fmt)	"null_blk: " fmt
+
 static inline sector_t mb_to_sects(unsigned long mb)
 {
 	return ((sector_t)mb * SZ_1M) >> SECTOR_SHIFT;
@@ -75,8 +78,8 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
 		dev->zone_capacity = dev->zone_size;
 
 	if (dev->zone_capacity > dev->zone_size) {
-		pr_err("null_blk: zone capacity (%lu MB) larger than zone size (%lu MB)\n",
-					dev->zone_capacity, dev->zone_size);
+		pr_err("zone capacity (%lu MB) larger than zone size (%lu MB)\n",
+		       dev->zone_capacity, dev->zone_size);
 		return -EINVAL;
 	}