[PATCH v9 24/29] scsi: sd: add multipath disk class

[John Garry <john.garry@linux.dev>]

Add a new class, sd_mpath_disk_class, which is the multipath version of
the scsi_disk class.

Structure sd_mpath_disk is introduced to manage the multipath gendisk.

Signed-off-by: John Garry <john.garry@linux.dev>
---
 drivers/scsi/sd.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
 drivers/scsi/sd.h |  3 +++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index dc45df819c42..03617029a552 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -70,6 +70,7 @@
 #include <scsi/scsi_ioctl.h>
 #include <scsi/scsicam.h>
 #include <scsi/scsi_common.h>
+#include <scsi/scsi_multipath.h>
 
 #include "sd.h"
 #include "scsi_priv.h"
@@ -113,6 +114,39 @@ static mempool_t *sd_page_pool;
 static mempool_t *sd_large_page_pool;
 static atomic_t sd_large_page_pool_users = ATOMIC_INIT(0);
 static struct lock_class_key sd_bio_compl_lkclass;
+#ifdef CONFIG_SCSI_MULTIPATH
+struct sd_mpath_disk {
+	struct scsi_mpath_head		*scsi_mpath_head;
+};
+
+static void sd_mpath_disk_release(struct device *dev)
+{
+}
+
+static const struct class sd_mpath_disk_class = {
+	.name = "scsi_mpath_disk",
+	.dev_release = sd_mpath_disk_release,
+};
+
+static int sd_mpath_class_register(void)
+{
+	return class_register(&sd_mpath_disk_class);
+}
+
+static void sd_mpath_class_unregister(void)
+{
+	class_unregister(&sd_mpath_disk_class);
+}
+#else /* CONFIG_SCSI_MULTIPATH */
+static int sd_mpath_class_register(void)
+{
+	return 0;
+}
+
+static void sd_mpath_class_unregister(void)
+{
+}
+#endif
 
 static const char *sd_cache_types[] = {
 	"write through", "none", "write back",
@@ -4474,11 +4508,15 @@ static int __init init_sd(void)
 	if (err)
 		goto err_out;
 
+	err = sd_mpath_class_register();
+	if (err)
+		goto err_out_class;
+
 	sd_page_pool = mempool_create_page_pool(SD_MEMPOOL_SIZE, 0);
 	if (!sd_page_pool) {
 		printk(KERN_ERR "sd: can't init discard page pool\n");
 		err = -ENOMEM;
-		goto err_out_class;
+		goto err_out_mpath_class;
 	}
 
 	err = scsi_register_driver(&sd_template);
@@ -4489,6 +4527,8 @@ static int __init init_sd(void)
 
 err_out_driver:
 	mempool_destroy(sd_page_pool);
+err_out_mpath_class:
+	sd_mpath_class_unregister();
 err_out_class:
 	class_unregister(&sd_disk_class);
 err_out:
@@ -4514,6 +4554,7 @@ static void __exit exit_sd(void)
 		mempool_destroy(sd_large_page_pool);
 
 	class_unregister(&sd_disk_class);
+	sd_mpath_class_unregister();
 
 	for (i = 0; i < SD_MAJORS; i++)
 		unregister_blkdev(sd_major(i), "sd");
diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index 574af8243016..22438173ea2f 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -83,6 +83,9 @@ struct zoned_disk_info {
 
 struct scsi_disk {
 	struct scsi_device *device;
+#ifdef CONFIG_SCSI_MULTIPATH
+	struct sd_mpath_disk *sd_mpath_disk;
+#endif
 
 	/*
 	 * disk_dev is used to show attributes in /sys/class/scsi_disk/,
-- 
2.43.0