[PATCH 2/2] PCI: Replace pci_dev->broken_parity_status with accessors

[Maurice Hieronymus <mhi@mailbox.org>]

`broken_parity_status` shares a C bitfield word in `struct pci_dev`
with many other bits. `broken_parity_status_store()` writes it from
sysfs at any time without taking any lock, so userspace can make it
race with every other writer of the same word, e.g. `pci_set_master()`
from a runtime PM resume path, and updates of neighboring bits can be
lost.

Move the bit into the `flags` bitmap modified with atomic bitops,
using the accessor pattern introduced by the previous commit.

Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>
---
 drivers/edac/edac_pci_sysfs.c | 4 ++--
 drivers/pci/pci-sysfs.c       | 4 ++--
 include/linux/pci.h           | 5 ++++-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/edac/edac_pci_sysfs.c b/drivers/edac/edac_pci_sysfs.c
index 9f437f648e4e..fadc61235f1f 100644
--- a/drivers/edac/edac_pci_sysfs.c
+++ b/drivers/edac/edac_pci_sysfs.c
@@ -554,7 +554,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
 	/* check the status reg for errors on boards NOT marked as broken
 	 * if broken, we cannot trust any of the status bits
 	 */
-	if (status && !dev->broken_parity_status) {
+	if (status && !pci_dev_broken_parity_status(dev)) {
 		if (status & (PCI_STATUS_SIG_SYSTEM_ERROR)) {
 			edac_printk(KERN_CRIT, EDAC_PCI,
 				"Signaled System Error on %s\n",
@@ -593,7 +593,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
 		/* check the secondary status reg for errors,
 		 * on NOT broken boards
 		 */
-		if (status && !dev->broken_parity_status) {
+		if (status && !pci_dev_broken_parity_status(dev)) {
 			if (status & (PCI_STATUS_SIG_SYSTEM_ERROR)) {
 				edac_printk(KERN_CRIT, EDAC_PCI, "Bridge "
 					"Signaled System Error on %s\n",
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 5ec0b245a69b..5e094d1e23e3 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -80,7 +80,7 @@ static ssize_t broken_parity_status_show(struct device *dev,
 					 char *buf)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	return sysfs_emit(buf, "%u\n", pdev->broken_parity_status);
+	return sysfs_emit(buf, "%u\n", pci_dev_broken_parity_status(pdev));
 }
 
 static ssize_t broken_parity_status_store(struct device *dev,
@@ -93,7 +93,7 @@ static ssize_t broken_parity_status_store(struct device *dev,
 	if (kstrtoul(buf, 0, &val) < 0)
 		return -EINVAL;
 
-	pdev->broken_parity_status = !!val;
+	pci_dev_assign_broken_parity_status(pdev, val);
 
 	return count;
 }
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 9964646bdd46..fdcd9b1b7371 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -347,10 +347,13 @@ struct rcec_ea;
  *		bookkeeping state, maintained by pci_set_master(),
  *		pci_clear_master() and pci_disable_device(); modifying it
  *		does not itself change the hardware state.
+ * @PCI_DEV_FLAG_BROKEN_PARITY_STATUS: Device generates false positive
+ *		parity errors; set via sysfs.
  * @PCI_DEV_FLAG_COUNT: Number of defined struct_pci_dev_flags.
  */
 enum struct_pci_dev_flags {
 	PCI_DEV_FLAG_BUSMASTER = 0,
+	PCI_DEV_FLAG_BROKEN_PARITY_STATUS = 1,
 
 	PCI_DEV_FLAG_COUNT
 };
@@ -482,7 +485,6 @@ struct pci_dev {
 
 	unsigned int	no_msi:1;		/* May not use MSI */
 	unsigned int	block_cfg_access:1;	/* Config space access blocked */
-	unsigned int	broken_parity_status:1;	/* Generates false positive parity */
 	unsigned int	irq_reroute_variant:2;	/* Needs IRQ rerouting variant */
 	unsigned int	msi_enabled:1;
 	unsigned int	msix_enabled:1;
@@ -626,6 +628,7 @@ static inline void pci_dev_assign_##accessor_name(struct pci_dev *pdev, bool val
 }
 
 __create_pci_dev_flag_accessors(busmaster, PCI_DEV_FLAG_BUSMASTER);
+__create_pci_dev_flag_accessors(broken_parity_status, PCI_DEV_FLAG_BROKEN_PARITY_STATUS);
 
 #undef __create_pci_dev_flag_accessors
 

-- 
2.51.2