[PATCH V4 1/3] scsi: core: use put_device() to release host

[Ming Lei <ming.lei@xxxxxxxxxx>]

>From 2a70cffeca09156faf68d933157586b5bf9278fa Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@xxxxxxxxxx>
Date: Mon, 31 May 2021 11:02:01 +0800
Subject: [PATCH V4 1/3] scsi: core: use put_device() to release host

After device is initialized via device_initialize(), or its name is
set via dev_set_name(), the device has to be freed via put_device(),
otherwise device name will be leaked because it is allocated
dynamically in dev_set_name().

Fixes the issue by replacing kfree(shost) via two put_device() since
both .shost_dev and .shost_gendev share same lifetime. Meantime move
get_device(shost->shost_gendev) from scsi_add_host_with_dma to
scsi_host_alloc(), so that we can grab parent's refcnt explicitly when
assigning .shost_dev->parent. With this way code becomes more readable.

Also call put_device(dev->parent) in scsi_host_cls_release() so that
code readability can be improved.

Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: John Garry <john.garry@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
V4:
	- avoid to touch un-initialized device instance

 drivers/scsi/hosts.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 624e2582c3df..181a5d6e3c7b 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -55,7 +55,7 @@ static DEFINE_IDA(host_index_ida);
 
 static void scsi_host_cls_release(struct device *dev)
 {
-	put_device(&class_to_shost(dev)->shost_gendev);
+	put_device(dev->parent);
 }
 
 static struct class shost_class = {
@@ -261,8 +261,6 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	if (error)
 		goto out_del_gendev;
 
-	get_device(&shost->shost_gendev);
-
 	if (shost->transportt->host_size) {
 		shost->shost_data = kzalloc(shost->transportt->host_size,
 					 GFP_KERNEL);
@@ -391,8 +389,10 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	mutex_init(&shost->scan_mutex);
 
 	index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL);
-	if (index < 0)
-		goto fail_kfree;
+	if (index < 0) {
+		kfree(shost);
+		return NULL;
+	}
 	shost->host_no = index;
 
 	shost->dma_channel = 0xff;
@@ -473,7 +473,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	shost->shost_gendev.type = &scsi_host_type;
 
 	device_initialize(&shost->shost_dev);
-	shost->shost_dev.parent = &shost->shost_gendev;
+	shost->shost_dev.parent = get_device(&shost->shost_gendev);
 	shost->shost_dev.class = &shost_class;
 	dev_set_name(&shost->shost_dev, "host%d", shost->host_no);
 	shost->shost_dev.groups = scsi_sysfs_shost_attr_groups;
@@ -502,8 +502,9 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	kthread_stop(shost->ehandler);
  fail_index_remove:
 	ida_simple_remove(&host_index_ida, shost->host_no);
- fail_kfree:
-	kfree(shost);
+	/* free host instance */
+	put_device(&shost->shost_dev);
+	put_device(&shost->shost_gendev);
 	return NULL;
 }
 EXPORT_SYMBOL(scsi_host_alloc);
-- 
2.29.2