Subject: [PATCH v2] scsi: core: Fix early registration of sysfs attributes for scsi_device

From: Steffen Maier <[email-masked]>
Date: Mon, 25 Oct 2021 00:16:20 +0200

v4.17 commit 86b87cde0b55 ("scsi: core: host template attribute groups")
introduced explicit sysfs_create_groups() in scsi_sysfs_add_sdev()
and sysfs_remove_groups() in __scsi_remove_device(), both for sdev_gendev,
based on a new field const struct attribute_group **sdev_groups
of struct scsi_host_template.

Commit 92c4b58b15c5 ("scsi: core: Register sysfs attributes earlier")
removed above explicit (de)registration of scsi_device attribute groups.
It also converted all scsi_device attributes and attribute_groups to
end up in a new field const struct attribute_group *gendev_attr_groups[6]
of struct scsi_device. However, that new field was not used anywhere.

Surprisingly, this only caused missing LLDD specific scsi_device sysfs
attributes. Whereas, scsi core attributes from scsi_sdev_attr_groups
did continue to exist because of scsi_dev_type.groups.

Fix it by assigning the pointer of that new field to the groups
field of sdev_gendev so the driver core gets our LLDD groups.
Just like scsi_host_alloc() was changed by the same commit,
although scsi_host_alloc() already had assigned something to
shost_dev.groups so the necessary change was more obvious there.

We separate scsi core attibutes from LLDD specific attributes.
Hence, we keep the initializing assignment scsi_dev_type =
{ .groups = scsi_sdev_attr_groups, } as this takes care of core
attributes. Without the separation, it would cause attribute double
registration due to scsi_dev_type.groups and sdev_gendev.groups.

Since we now no longer have an index offset between left and right
hand side of the assignment in the loop, one counter variable suffices.

Alternative approaches ruled out:
Assigning gendev_attr_groups to sdev_dev has no visible effect.
Assigning sdev->gendev_attr_groups to scsi_dev_type.groups
caused scsi_device of all scsi host types to get LLDD specific
attributes of the LLDD for which the last sdev alloc happened to occur,
as that overwrote scsi_dev_type.groups,
e.g. scsi_debug had zfcp-specific scsi_device attributes.

Signed-off-by: Steffen Maier <[email-masked]>
Fixes: 92c4b58b15c5 ("scsi: core: Register sysfs attributes earlier")
---

Changes in v2:
* integrated Bart's feedback of updating the comment for
  the gendev_attr_groups declaration to match the code change
* in that spirit also adapted the vector size of that field
* eliminated the now unnecessary second loop counter 'j'

 drivers/scsi/scsi_sysfs.c  | 12 ++++++------
 include/scsi/scsi_device.h |  7 +++----
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index c26f0e29e8cd..d73e84e1cb37 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1571,7 +1571,7 @@ static struct device_type scsi_dev_type = {
 
 void scsi_sysfs_device_initialize(struct scsi_device *sdev)
 {
-	int i, j = 0;
+	int i = 0;
 	unsigned long flags;
 	struct Scsi_Host *shost = sdev->host;
 	struct scsi_host_template *hostt = shost->hostt;
@@ -1583,15 +1583,15 @@ 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;
+	sdev->sdev_gendev.groups = sdev->gendev_attr_groups;
 	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];
+			     i < ARRAY_SIZE(sdev->gendev_attr_groups);
+		     i++) {
+			sdev->gendev_attr_groups[i] = hostt->sdev_groups[i];
 		}
 	}
-	WARN_ON_ONCE(j >= ARRAY_SIZE(sdev->gendev_attr_groups));
+	WARN_ON_ONCE(i >= ARRAY_SIZE(sdev->gendev_attr_groups));
 
 	device_initialize(&sdev->sdev_dev);
 	sdev->sdev_dev.parent = get_device(&sdev->sdev_gendev);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index b1e9b3bd3a60..b6f0d031217e 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -226,11 +226,10 @@ struct scsi_device {
 	struct device		sdev_gendev,
 				sdev_dev;
 	/*
-	 * 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.
+	 * The array size 5 provides space for four attribute groups
+	 * defined by SCSI LLDs and one terminating NULL pointer.
 	 */
-	const struct attribute_group *gendev_attr_groups[6];
+	const struct attribute_group *gendev_attr_groups[5];
 
 	struct execute_work	ew; /* used to get process context on put */
 	struct work_struct	requeue_work;
-- 
2.25.1