rbd: define and use rbd_warn()

Define a new function rbd_warn() that produces a boilerplate warning
message, identifying in the resulting message the affected rbd
device in the best way available.  Use it in a few places that now
use pr_warning().

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Dan Mick <dan.mick@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

drivers/block/rbd.c

@@ -294,6 +294,33 @@ static struct device rbd_root_dev = {
 	.release =      rbd_root_dev_release,
 };
 
+static __printf(2, 3)
+void rbd_warn(struct rbd_device *rbd_dev, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	if (!rbd_dev)
+		printk(KERN_WARNING "%s: %pV\n", RBD_DRV_NAME, &vaf);
+	else if (rbd_dev->disk)
+		printk(KERN_WARNING "%s: %s: %pV\n",
+			RBD_DRV_NAME, rbd_dev->disk->disk_name, &vaf);
+	else if (rbd_dev->spec && rbd_dev->spec->image_name)
+		printk(KERN_WARNING "%s: image %s: %pV\n",
+			RBD_DRV_NAME, rbd_dev->spec->image_name, &vaf);
+	else if (rbd_dev->spec && rbd_dev->spec->image_id)
+		printk(KERN_WARNING "%s: id %s: %pV\n",
+			RBD_DRV_NAME, rbd_dev->spec->image_id, &vaf);
+	else	/* punt */
+		printk(KERN_WARNING "%s: rbd_dev %p: %pV\n",
+			RBD_DRV_NAME, rbd_dev, &vaf);
+	va_end(args);
+}
+
 #ifdef RBD_DEBUG
 #define rbd_assert(expr)						\
 		if (unlikely(!(expr))) {				\
@@ -1403,8 +1430,8 @@ static void rbd_watch_cb(u64 ver, u64 notify_id, u8 opcode, void *data)
 		(unsigned int) opcode);
 	rc = rbd_dev_refresh(rbd_dev, &hver);
 	if (rc)
-		pr_warning(RBD_DRV_NAME "%d got notification but failed to "
-			   " update snaps: %d\n", rbd_dev->major, rc);
+		rbd_warn(rbd_dev, "got notification but failed to "
+			   " update snaps: %d\n", rc);
 
 	rbd_req_sync_notify_ack(rbd_dev, hver, notify_id);
 }
@@ -1767,15 +1794,13 @@ rbd_dev_v1_header_read(struct rbd_device *rbd_dev, u64 *version)
 			goto out_err;
 		if (WARN_ON((size_t) ret < size)) {
 			ret = -ENXIO;
-			pr_warning("short header read for image %s"
-					" (want %zd got %d)\n",
-				rbd_dev->spec->image_name, size, ret);
+			rbd_warn(rbd_dev, "short header read (want %zd got %d)",
+				size, ret);
 			goto out_err;
 		}
 		if (!rbd_dev_ondisk_valid(ondisk)) {
 			ret = -ENXIO;
-			pr_warning("invalid header for image %s\n",
-				rbd_dev->spec->image_name);
+			rbd_warn(rbd_dev, "invalid header");
 			goto out_err;
 		}
 
@@ -2630,9 +2655,7 @@ static int rbd_dev_probe_update_spec(struct rbd_device *rbd_dev)
 	if (name)
 		rbd_dev->spec->image_name = (char *) name;
 	else
-		pr_warning(RBD_DRV_NAME "%d "
-			"unable to get image name for image id %s\n",
-			rbd_dev->major, rbd_dev->spec->image_id);
+		rbd_warn(rbd_dev, "unable to get image name");
 
 	/* Look up the snapshot name. */