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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
To:     jejb@linux.ibm.com, martin.petersen@oracle.com
Cc:     bblock@linux.ibm.com, acelan.kao@canonical.com,
        Kai-Heng Feng <kai.heng.feng@canonical.com>,
        Damien Le Moal <dlemoal@kernel.org>,
        linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] ata: libata: Defer rescan on suspended device
Date:   Tue, 25 Apr 2023 14:17:45 +0800
Message-Id: <20230425061746.503145-1-kai.heng.feng@canonical.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

During system resume, if an EH is schduled after ATA host is resumed
(i.e. ATA_PFLAG_PM_PENDING cleared), but before the disk device is
fully resumed, the device_lock hold by scsi_rescan_device() is never
released so the dpm_resume() of the disk is blocked forerver.

That's because scsi_attach_vpd() is expecting the disk device is in
operational state, as it doesn't work on suspended device.

To avoid such deadlock, defer rescan if the disk is still suspended so
the resume process of the disk device can proceed. At the end of the
resume process, use the complete() callback to schedule the rescan task.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
v2:
 - Schedule rescan task at the end of system resume phase.
 - Wording.

 drivers/ata/libata-core.c | 11 +++++++++++
 drivers/ata/libata-eh.c   | 11 +++++++++--
 include/linux/libata.h    |  1 +
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 14c17c3bda4e..564d72bf1ec6 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -5093,6 +5093,16 @@ static int ata_port_pm_poweroff(struct device *dev)
 	return 0;
 }
 
+static void ata_port_pm_complete(struct device *dev)
+{
+	struct ata_port *ap = to_ata_port(dev);
+
+	if (ap->pflags & ATA_PFLAG_DEFER_RESCAN)
+		schedule_work(&(ap->scsi_rescan_task));
+
+	ap->pflags &= ~ATA_PFLAG_DEFER_RESCAN;
+}
+
 static const unsigned int ata_port_resume_ehi = ATA_EHI_NO_AUTOPSY
 						| ATA_EHI_QUIET;
 
@@ -5158,6 +5168,7 @@ static const struct dev_pm_ops ata_port_pm_ops = {
 	.thaw = ata_port_pm_resume,
 	.poweroff = ata_port_pm_poweroff,
 	.restore = ata_port_pm_resume,
+	.complete = ata_port_pm_complete,
 
 	.runtime_suspend = ata_port_runtime_suspend,
 	.runtime_resume = ata_port_runtime_resume,
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index a6c901811802..0881b590fb7e 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -15,6 +15,7 @@
 #include <linux/blkdev.h>
 #include <linux/export.h>
 #include <linux/pci.h>
+#include <linux/suspend.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_eh.h>
@@ -2983,8 +2984,14 @@ static int ata_eh_revalidate_and_attach(struct ata_link *link,
 			 */
 			ehc->i.flags |= ATA_EHI_SETMODE;
 
-			/* schedule the scsi_rescan_device() here */
-			schedule_work(&(ap->scsi_rescan_task));
+			/* Schedule the scsi_rescan_device() here.
+			 * Defer the rescan if it's in process of
+			 * suspending or resuming.
+			 */
+			if (pm_suspend_target_state != PM_SUSPEND_ON)
+				ap->pflags |= ATA_PFLAG_DEFER_RESCAN;
+			else
+				schedule_work(&(ap->scsi_rescan_task));
 		} else if (dev->class == ATA_DEV_UNKNOWN &&
 			   ehc->tries[dev->devno] &&
 			   ata_class_enabled(ehc->classes[dev->devno])) {
diff --git a/include/linux/libata.h b/include/linux/libata.h
index a759dfbdcc91..aaa549444abc 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -189,6 +189,7 @@ enum {
 	ATA_PFLAG_UNLOADING	= (1 << 9), /* driver is being unloaded */
 	ATA_PFLAG_UNLOADED	= (1 << 10), /* driver is unloaded */
 
+	ATA_PFLAG_DEFER_RESCAN	= (1 << 16), /* peform deferred rescan on system resume */
 	ATA_PFLAG_SUSPENDED	= (1 << 17), /* port is suspended (power) */
 	ATA_PFLAG_PM_PENDING	= (1 << 18), /* PM operation pending */
 	ATA_PFLAG_INIT_GTM_VALID = (1 << 19), /* initial gtm data valid */
-- 
2.34.1