[PATCH v3 2/4] s390/pci: Fix missing device lock in zpci_report_status()

[Niklas Schnelle <schnelle@linux.ibm.com>]

When pdev is non-NULL, zpci_report_status() accesses the device's driver.
To get a consistent state matching the recovery, the device lock needs to
be held. Do so by expanding the existing device lock critical section.

The lock only needs to be held when the pdev is non-NULL, so extract
the pdev-specific reporting into a helper function which also adds a
lockdep assertion to detect calls without the device lock held.

Cc: stable@vger.kernel.org
Fixes: 4ec6054e7321 ("s390/pci: Report PCI error recovery results via SCLP")
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
 arch/s390/pci/pci_event.c  |  2 +-
 arch/s390/pci/pci_report.c | 21 +++++++++++++++------
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c
index 3b4941b65840..ec93f34b6e19 100644
--- a/arch/s390/pci/pci_event.c
+++ b/arch/s390/pci/pci_event.c
@@ -297,8 +297,8 @@ static pci_ers_result_t zpci_event_attempt_error_recovery(struct pci_dev *pdev,
 		driver->err_handler->resume(pdev);
 	pci_uevent_ers(pdev, PCI_ERS_RESULT_RECOVERED);
 out_unlock:
-	device_unlock(&pdev->dev);
 	zpci_report_status(zdev, pdev, "recovery", status_str);
+	device_unlock(&pdev->dev);
 
 	return ers_res;
 }
diff --git a/arch/s390/pci/pci_report.c b/arch/s390/pci/pci_report.c
index 867419779219..72ecabf7003c 100644
--- a/arch/s390/pci/pci_report.c
+++ b/arch/s390/pci/pci_report.c
@@ -87,6 +87,19 @@ static struct debug_view debug_log_view = {
 	NULL
 };
 
+static ssize_t zpci_report_pdev(struct pci_dev *pdev, char *buf, size_t size)
+{
+	struct pci_driver *driver;
+	const char *start = buf;
+	char *end = buf + size;
+
+	device_lock_assert(&pdev->dev);
+	buf += scnprintf(buf, end - buf, "state: %s\n", zpci_state_str(pdev->error_state));
+	driver = to_pci_driver(pdev->dev.driver);
+	buf += scnprintf(buf, end - buf, "driver: %s\n", (driver) ? driver->name : "n/a");
+	return buf - start;
+}
+
 /**
  * zpci_report_status - Report the status of operations on a PCI device
  * @zdev:	The zPCI device for which to report status
@@ -108,7 +121,6 @@ int zpci_report_status(struct zpci_dev *zdev, struct pci_dev *pdev,
 		       const char *operation, const char *status)
 {
 	struct zpci_report_error *report;
-	struct pci_driver *driver = NULL;
 	char *buf, *end;
 	int ret;
 
@@ -122,16 +134,13 @@ int zpci_report_status(struct zpci_dev *zdev, struct pci_dev *pdev,
 	report = (void *)get_zeroed_page(GFP_KERNEL);
 	if (!report)
 		return -ENOMEM;
-	if (pdev)
-		driver = to_pci_driver(pdev->dev.driver);
 
 	buf = report->data.log_data;
 	end = report->data.log_data + ZPCI_REPORT_DATA_SIZE;
 	buf += scnprintf(buf, end - buf, "report: %s\n", operation);
 	buf += scnprintf(buf, end - buf, "status: %s\n", status);
-	buf += scnprintf(buf, end - buf, "state: %s\n",
-			 (pdev) ? zpci_state_str(pdev->error_state) : "n/a");
-	buf += scnprintf(buf, end - buf, "driver: %s\n", (driver) ? driver->name : "n/a");
+	if (pdev)
+		buf += zpci_report_pdev(pdev, buf, end - buf);
 	ret = debug_dump(pci_debug_msg_id, &debug_log_view, buf, end - buf, true);
 	if (ret < 0)
 		pr_err("Reading PCI debug messages failed with code %d\n", ret);

-- 
2.53.0