scsi: core: Register sysfs attributes earlier

A quote from Documentation/driver-api/driver-model/device.rst:
"Word of warning:  While the kernel allows device_create_file() and
device_remove_file() to be called on a device at any time, userspace has
strict expectations on when attributes get created.  When a new device is
registered in the kernel, a uevent is generated to notify userspace (like
udev) that a new device is available.  If attributes are added after the
device is registered, then userspace won't get notified and userspace will
not know about the new attributes."

Hence register SCSI host sysfs attributes before the SCSI host shost_dev
uevent is emitted instead of after that event has been emitted.

Link: https://lore.kernel.org/r/20211012233558.4066756-2-bvanassche@acm.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hosts.c

@@ -376,7 +376,7 @@ static struct device_type scsi_host_type = {
 struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 {
 	struct Scsi_Host *shost;
-	int index;
+	int index, i, j = 0;
 
 	shost = kzalloc(sizeof(struct Scsi_Host) + privsize, GFP_KERNEL);
 	if (!shost)
@@ -481,7 +481,26 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	shost->shost_dev.parent = &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;
+	shost->shost_dev.groups = shost->shost_dev_attr_groups;
+	shost->shost_dev_attr_groups[j++] = &scsi_shost_attr_group;
+	if (sht->shost_attrs) {
+		shost->lld_attr_group = (struct attribute_group){
+			.attrs = scsi_convert_dev_attrs(&shost->shost_gendev,
+							sht->shost_attrs)
+		};
+		if (shost->lld_attr_group.attrs)
+			shost->shost_dev_attr_groups[j++] =
+				&shost->lld_attr_group;
+	}
+	if (sht->shost_groups) {
+		for (i = 0; sht->shost_groups[i] &&
+			     j < ARRAY_SIZE(shost->shost_dev_attr_groups);
+		     i++, j++) {
+			shost->shost_dev_attr_groups[j] =
+				sht->shost_groups[i];
+		}
+	}
+	WARN_ON_ONCE(j >= ARRAY_SIZE(shost->shost_dev_attr_groups));
 
 	shost->ehandler = kthread_run(scsi_error_handler, shost,
 			"scsi_eh_%d", shost->host_no);

drivers/scsi/scsi_priv.h

@@ -138,13 +138,15 @@ extern int scsi_sysfs_add_sdev(struct scsi_device *);
 extern int scsi_sysfs_add_host(struct Scsi_Host *);
 extern int scsi_sysfs_register(void);
 extern void scsi_sysfs_unregister(void);
+struct attribute **scsi_convert_dev_attrs(struct device *dev,
+					  struct device_attribute **dev_attr);
 extern void scsi_sysfs_device_initialize(struct scsi_device *);
 extern int scsi_sysfs_target_initialize(struct scsi_device *);
 extern struct scsi_transport_template blank_transport_template;
 extern void __scsi_remove_device(struct scsi_device *);
 
 extern struct bus_type scsi_bus_type;
-extern const struct attribute_group *scsi_sysfs_shost_attr_groups[];
+extern const struct attribute_group scsi_shost_attr_group;
 
 /* scsi_netlink.c */
 #ifdef CONFIG_SCSI_NETLINK

drivers/scsi/scsi_sysfs.c

@@ -424,15 +424,10 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
 	NULL
 };
 
-static struct attribute_group scsi_shost_attr_group = {
+const struct attribute_group scsi_shost_attr_group = {
 	.attrs =	scsi_sysfs_shost_attrs,
 };
 
-const struct attribute_group *scsi_sysfs_shost_attr_groups[] = {
-	&scsi_shost_attr_group,
-	NULL
-};
-
 static void scsi_device_cls_release(struct device *class_dev)
 {
 	struct scsi_device *sdev;
@@ -1333,7 +1328,7 @@ static int scsi_target_add(struct scsi_target *starget)
  **/
 int scsi_sysfs_add_sdev(struct scsi_device *sdev)
 {
-	int error, i;
+	int error;
 	struct scsi_target *starget = sdev->sdev_target;
 
 	error = scsi_target_add(starget);
@@ -1386,23 +1381,6 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
 		}
 	}
 
-	/* add additional host specific attributes */
-	if (sdev->host->hostt->sdev_attrs) {
-		for (i = 0; sdev->host->hostt->sdev_attrs[i]; i++) {
-			error = device_create_file(&sdev->sdev_gendev,
-					sdev->host->hostt->sdev_attrs[i]);
-			if (error)
-				return error;
-		}
-	}
-
-	if (sdev->host->hostt->sdev_groups) {
-		error = sysfs_create_groups(&sdev->sdev_gendev.kobj,
-				sdev->host->hostt->sdev_groups);
-		if (error)
-			return error;
-	}
-
 	scsi_autopm_put_device(sdev);
 	return error;
 }
@@ -1442,10 +1420,6 @@ void __scsi_remove_device(struct scsi_device *sdev)
 		if (res != 0)
 			return;
 
-		if (sdev->host->hostt->sdev_groups)
-			sysfs_remove_groups(&sdev->sdev_gendev.kobj,
-					sdev->host->hostt->sdev_groups);
-
 		if (IS_ENABLED(CONFIG_BLK_DEV_BSG) && sdev->bsg_dev)
 			bsg_unregister_queue(sdev->bsg_dev);
 		device_unregister(&sdev->sdev_dev);
@@ -1584,23 +1558,31 @@ EXPORT_SYMBOL(scsi_register_interface);
  **/
 int scsi_sysfs_add_host(struct Scsi_Host *shost)
 {
-	int error, i;
-
-	/* add host specific attributes */
-	if (shost->hostt->shost_attrs) {
-		for (i = 0; shost->hostt->shost_attrs[i]; i++) {
-			error = device_create_file(&shost->shost_dev,
-					shost->hostt->shost_attrs[i]);
-			if (error)
-				return error;
-		}
-	}
-
 	transport_register_device(&shost->shost_gendev);
 	transport_configure_device(&shost->shost_gendev);
 	return 0;
 }
 
+/*
+ * Convert an array of struct device_attribute pointers into an array of
+ * struct attribute pointers.
+ */
+struct attribute **scsi_convert_dev_attrs(struct device *dev,
+					  struct device_attribute **dev_attr)
+{
+	struct attribute **attrs;
+	int i;
+
+	for (i = 0; dev_attr[i]; i++)
+		;
+	attrs = devm_kzalloc(dev, (i + 1) * sizeof(*attrs), GFP_KERNEL);
+	if (!attrs)
+		return NULL;
+	for (i = 0; dev_attr[i]; i++)
+		attrs[i] = &dev_attr[i]->attr;
+	return attrs;
+}
+
 static struct device_type scsi_dev_type = {
 	.name =		"scsi_device",
 	.release =	scsi_device_dev_release,
@@ -1609,8 +1591,10 @@ static struct device_type scsi_dev_type = {
 
 void scsi_sysfs_device_initialize(struct scsi_device *sdev)
 {
+	int i, j = 0;
 	unsigned long flags;
 	struct Scsi_Host *shost = sdev->host;
+	struct scsi_host_template *hostt = shost->hostt;
 	struct scsi_target  *starget = sdev->sdev_target;
 
 	device_initialize(&sdev->sdev_gendev);
@@ -1619,6 +1603,23 @@ void scsi_sysfs_device_initialize(struct scsi_device *sdev)
 	scsi_enable_async_suspend(&sdev->sdev_gendev);
 	dev_set_name(&sdev->sdev_gendev, "%d:%d:%d:%llu",
 		     sdev->host->host_no, sdev->channel, sdev->id, sdev->lun);
+	sdev->gendev_attr_groups[j++] = &scsi_sdev_attr_group;
+	if (hostt->sdev_attrs) {
+		sdev->lld_attr_group = (struct attribute_group){
+			.attrs = scsi_convert_dev_attrs(&sdev->sdev_gendev,
+							hostt->sdev_attrs)
+		};
+		if (sdev->lld_attr_group.attrs)
+			sdev->gendev_attr_groups[j++] = &sdev->lld_attr_group;
+	}
+	if (hostt->sdev_groups) {
+		for (i = 0; hostt->sdev_groups[i] &&
+			     j < ARRAY_SIZE(sdev->gendev_attr_groups);
+		     i++, j++) {
+			sdev->gendev_attr_groups[j] = hostt->sdev_groups[i];
+		}
+	}
+	WARN_ON_ONCE(j >= ARRAY_SIZE(sdev->gendev_attr_groups));
 
 	device_initialize(&sdev->sdev_dev);
 	sdev->sdev_dev.parent = get_device(&sdev->sdev_gendev);

include/scsi/scsi_device.h

@@ -225,6 +225,13 @@ struct scsi_device {
 
 	struct device		sdev_gendev,
 				sdev_dev;
+	struct attribute_group	lld_attr_group;
+	/*
+	 * The array size 6 provides space for one attribute group for the
+	 * SCSI core, four attribute groups defined by SCSI LLDs and one
+	 * terminating NULL pointer.
+	 */
+	const struct attribute_group *gendev_attr_groups[6];
 
 	struct execute_work	ew; /* used to get process context on put */
 	struct work_struct	requeue_work;

include/scsi/scsi_host.h

@@ -483,6 +483,11 @@ struct scsi_host_template {
 	 */
 	struct device_attribute **sdev_attrs;
 
+	/*
+	 * Pointer to the SCSI host sysfs attribute groups, NULL terminated.
+	 */
+	const struct attribute_group **shost_groups;
+
 	/*
 	 * Pointer to the SCSI device attribute groups for this host,
 	 * NULL terminated.
@@ -695,6 +700,13 @@ struct Scsi_Host {
 
 	/* ldm bits */
 	struct device		shost_gendev, shost_dev;
+	struct attribute_group	lld_attr_group;
+	/*
+	 * The array size 3 provides space for one attribute group defined by
+	 * the SCSI core, one attribute group defined by the SCSI LLD and one
+	 * terminating NULL pointer.
+	 */
+	const struct attribute_group *shost_dev_attr_groups[3];
 
 	/*
 	 * Points to the transport data (if any) which is allocated