[PATCH 10/13] usb: usbip/vhci: convert seqno to seqnum_ops

[Shuah Khan]

seqnum_ops api is introduced to be used when a variable is used as
a sequence/stat counter and doesn't guard object lifetimes. This
clearly differentiates atomic_t usages that guard object lifetimes.

seqnum32 variables wrap around to INT_MIN when it overflows and
should not be used to guard resource lifetimes, device usage and
open counts that control state changes, and pm states.

Convert it to use seqnum_ops. This conversion replaces inc_return()
with _inc() followed by _read().

Signed-off-by: Shuah Khan <sk...@linuxfoundation.org>
---
 drivers/usb/usbip/vhci.h     | 3 ++-
 drivers/usb/usbip/vhci_hcd.c | 9 ++++++---
 drivers/usb/usbip/vhci_rx.c  | 3 ++-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/usbip/vhci.h b/drivers/usb/usbip/vhci.h
index 5659dce1526e..cb76747f423b 100644
--- a/drivers/usb/usbip/vhci.h
+++ b/drivers/usb/usbip/vhci.h
@@ -15,6 +15,7 @@
 #include <linux/usb.h>
 #include <linux/usb/hcd.h>
 #include <linux/wait.h>
+#include <linux/seqnum_ops.h>
 
 struct vhci_device {
        struct usb_device *udev;
@@ -108,7 +109,7 @@ struct vhci_hcd {
        unsigned resuming:1;
        unsigned long re_timeout;
 
-       atomic_t seqnum;
+       struct seqnum32 seqnum;
 
        /*
         * NOTE:
diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 66cde5e5f796..0d854d9707e5 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
+#include <linux/seqnum_ops.h>
 
 #include "usbip_common.h"
 #include "vhci.h"
@@ -665,7 +666,8 @@ static void vhci_tx_urb(struct urb *urb, struct vhci_device 
*vdev)
 
        spin_lock_irqsave(&vdev->priv_lock, flags);
 
-       priv->seqnum = atomic_inc_return(&vhci_hcd->seqnum);
+       seqnum32_inc(&vhci_hcd->seqnum);
+       priv->seqnum = seqnum32_read(&vhci_hcd->seqnum);
        if (priv->seqnum == 0xffff)
                dev_info(&urb->dev->dev, "seqnum max\n");
 
@@ -921,7 +923,8 @@ static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb 
*urb, int status)
                        return -ENOMEM;
                }
 
-               unlink->seqnum = atomic_inc_return(&vhci_hcd->seqnum);
+               seqnum32_inc(&vhci_hcd->seqnum);
+               unlink->seqnum = seqnum32_read(&vhci_hcd->seqnum);
                if (unlink->seqnum == 0xffff)
                        pr_info("seqnum max\n");
 
@@ -1181,7 +1184,7 @@ static int vhci_start(struct usb_hcd *hcd)
                vdev->rhport = rhport;
        }
 
-       atomic_set(&vhci_hcd->seqnum, 0);
+       seqnum32_set(&vhci_hcd->seqnum, 0);
 
        hcd->power_budget = 0; /* no limit */
        hcd->uses_new_polling = 1;
diff --git a/drivers/usb/usbip/vhci_rx.c b/drivers/usb/usbip/vhci_rx.c
index 266024cbb64f..0d0def7ccfee 100644
--- a/drivers/usb/usbip/vhci_rx.c
+++ b/drivers/usb/usbip/vhci_rx.c
@@ -5,6 +5,7 @@
 
 #include <linux/kthread.h>
 #include <linux/slab.h>
+#include <linux/seqnum_ops.h>
 
 #include "usbip_common.h"
 #include "vhci.h"
@@ -68,7 +69,7 @@ static void vhci_recv_ret_submit(struct vhci_device *vdev,
        if (!urb) {
                pr_err("cannot find a urb of seqnum %u max seqnum %d\n",
                        pdu->base.seqnum,
-                       atomic_read(&vhci_hcd->seqnum));
+                       seqnum32_read(&vhci_hcd->seqnum));
                usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
                return;
        }
-- 
2.27.0