diff mbox series

[V5] scsi: ufshcd: Fix device links when BOOT WLUN fails to probe

Message ID a1c9bac8-b560-b662-f0aa-58c7e000cbbd@intel.com
State Accepted
Commit bf25967ac54129ffb676ee0dbe3b8b34af6c6232
Headers show
Series [V5] scsi: ufshcd: Fix device links when BOOT WLUN fails to probe | expand

Commit Message

Adrian Hunter Aug. 6, 2021, 1:04 p.m. UTC
Managed device links are deleted by device_del(). However it is possible to
add a device link to a consumer before device_add(), and then discovering
an error prevents the device from being used. In that case normally
references to the device would be dropped and the device would be deleted.
However the device link holds a reference to the device, so the device link
and device remain indefinitely (unless the supplier is deleted).

For UFSHCD, if a LUN fails to probe (e.g. absent BOOT WLUN), the device
will not have been registered but can still have a device link holding a
reference to the device. The unwanted device link will prevent runtime
suspend indefinitely.

Amend device link removal to accept removal of a link with an unregistered
consumer device (suggested by Rafael), and fix UFSHCD by explicitly
deleting the device link when SCSI destroys the SCSI device.

Fixes: b294ff3e34490 ("scsi: ufs: core: Enable power management for wlun")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
---


Patch "driver core: Prevent warning when removing a device link from
unregistered consumer" is already in Linus' tree:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e64daad660a0c9ace3acdc57099fffe5ed83f977


Changes in V5:

  Rebase on 5.15/scsi-staging



 drivers/base/core.c       |  2 ++
 drivers/scsi/ufs/ufshcd.c | 23 +++++++++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

Comments

Martin K. Petersen Aug. 10, 2021, 3:21 a.m. UTC | #1
Adrian,

> Managed device links are deleted by device_del(). However it is

> possible to add a device link to a consumer before device_add(), and

> then discovering an error prevents the device from being used. In that

> case normally references to the device would be dropped and the device

> would be deleted.  However the device link holds a reference to the

> device, so the device link and device remain indefinitely (unless the

> supplier is deleted).


Applied to 5.15/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering
Martin K. Petersen Aug. 17, 2021, 3:17 a.m. UTC | #2
On Fri, 6 Aug 2021 16:04:41 +0300, Adrian Hunter wrote:

> Managed device links are deleted by device_del(). However it is possible to

> add a device link to a consumer before device_add(), and then discovering

> an error prevents the device from being used. In that case normally

> references to the device would be dropped and the device would be deleted.

> However the device link holds a reference to the device, so the device link

> and device remain indefinitely (unless the supplier is deleted).

> 

> [...]


Applied to 5.15/scsi-queue, thanks!

[1/1] scsi: ufshcd: Fix device links when BOOT WLUN fails to probe
      https://git.kernel.org/mkp/scsi/c/bf25967ac541

-- 
Martin K. Petersen	Oracle Linux Engineering
diff mbox series

Patch

diff --git a/drivers/base/core.c b/drivers/base/core.c
index cadcade65825..9badd7f7fe62 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -884,6 +884,8 @@  static void device_link_put_kref(struct device_link *link)
 {
 	if (link->flags & DL_FLAG_STATELESS)
 		kref_put(&link->kref, __device_link_del);
+	else if (!device_is_registered(link->consumer))
+		__device_link_del(&link->kref);
 	else
 		WARN(1, "Unable to drop a managed device link reference\n");
 }
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 6c263e94144b..9f72698ff597 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -5028,6 +5028,7 @@  static int ufshcd_slave_configure(struct scsi_device *sdev)
 static void ufshcd_slave_destroy(struct scsi_device *sdev)
 {
 	struct ufs_hba *hba;
+	unsigned long flags;
 
 	hba = shost_priv(sdev->host);
 
@@ -5035,11 +5036,29 @@  static void ufshcd_slave_destroy(struct scsi_device *sdev)
 
 	/* Drop the reference as it won't be needed anymore */
 	if (ufshcd_scsi_to_upiu_lun(sdev->lun) == UFS_UPIU_UFS_DEVICE_WLUN) {
-		unsigned long flags;
-
 		spin_lock_irqsave(hba->host->host_lock, flags);
 		hba->sdev_ufs_device = NULL;
 		spin_unlock_irqrestore(hba->host->host_lock, flags);
+	} else if (hba->sdev_ufs_device) {
+		struct device *supplier = NULL;
+
+		/* Ensure UFS Device WLUN exists and does not disappear */
+		spin_lock_irqsave(hba->host->host_lock, flags);
+		if (hba->sdev_ufs_device) {
+			supplier = &hba->sdev_ufs_device->sdev_gendev;
+			get_device(supplier);
+		}
+		spin_unlock_irqrestore(hba->host->host_lock, flags);
+
+		if (supplier) {
+			/*
+			 * If a LUN fails to probe (e.g. absent BOOT WLUN), the
+			 * device will not have been registered but can still
+			 * have a device link holding a reference to the device.
+			 */
+			device_link_remove(&sdev->sdev_gendev, supplier);
+			put_device(supplier);
+		}
 	}
 }