[PATCH v2 00/13] Introduce seqnum_ops

[PATCH v2 00/13] Introduce seqnum_ops

[Shuah Khan]

Sequence Number api provides interfaces for unsigned atomic up counters
leveraging atomic_t and atomic64_t ops underneath.

There are a number of atomic_t usages in the kernel where atomic_t api
is used for counting sequence numbers and other statistical counters.
Several of these usages, convert atomic_read() and atomic_inc_return()
return values to unsigned. Introducing sequence number ops supports
these use-cases with a standard core-api.

The atomic_t api provides a wide range of atomic operations as a base
api to implement atomic counters, bitops, spinlock interfaces. The usages
also evolved into being used for resource lifetimes and state management.
The refcount_t api was introduced to address resource lifetime problems
related to atomic_t wrapping. There is a large overlap between the
atomic_t api used for resource lifetimes and just counters, stats, and
sequence numbers. It has become difficult to differentiate between the
atomic_t usages that should be converted to refcount_t and the ones that
can be left alone. Introducing seqnum_ops to wrap the usages that are
stats, counters, sequence numbers makes it easier for tools that scan
for underflow and overflow on atomic_t usages to detect overflow and
underflows to scan just the cases that are prone to errors.

In addition, to supporting sequence number use-cases, Sequence Number Ops
helps differentiate atomic_t counter usages from atomic_t usages that guard
object lifetimes, hence prone to overflow and underflow errors from up
counting use-cases. It becomes easier for tools that scan for underflow and
overflow on atomic_t usages to detect overflow and underflows to scan just
the cases that are prone to errors.

Changes since v1:
- Removed dec based on Greg KH's comments
- Removed read/set/inc based on the discussion with Peter Zijlstra
- Interfaces are restricted to init, increment and return new value,
  and fetch current value.
- Interfaces return u32 and u64 - a few reviewers suggested unsigned.
  After reviewing a few use-cases, I determined this is a good path
  forward. It adds unsigned atomic support that doesn't exist now,
  and simplifies code in drivers that currently convert atomic_t return
  values to unsigned. All the drivers changes included in this series
  used to convert atomic_t returns to unsigned.

Patch v1 thread:
https://lore.kernel.org/lkml/cover.1605027593.git.skhan@linuxfoundation.org/

Counters thread:
lore.kernel.org/lkml/cover.1602209970.git.skhan@linuxfoundation.org

Shuah Khan (13):
  seqnum_ops: Introduce Sequence Number Ops
  selftests: lib:test_seqnum_ops: add new test for seqnum_ops
  drivers/acpi: convert seqno seqnum_ops
  drivers/acpi/apei: convert seqno to seqnum_ops
  drivers/base/test/test_async_driver_probe: convert to use seqnum_ops
  drivers/char/ipmi: convert stats to use seqnum_ops
  drivers/edac: convert pci counters to seqnum_ops
  drivers/oprofile: convert stats to use seqnum_ops
  drivers/staging/rtl8723bs: convert stats to use seqnum_ops
  usb: usbip/vhci: convert seqno to seqnum_ops
  drivers/staging/rtl8188eu: convert stats to use seqnum_ops
  drivers/staging/unisys/visorhba: convert stats to use seqnum_ops
  security/integrity/ima: converts stats to seqnum_ops

 Documentation/core-api/atomic_ops.rst         |   4 +
 Documentation/core-api/index.rst              |   1 +
 Documentation/core-api/seqnum_ops.rst         |  89 +++++++++++++
 MAINTAINERS                                   |   8 ++
 drivers/acpi/acpi_extlog.c                    |   8 +-
 drivers/acpi/apei/ghes.c                      |   8 +-
 drivers/base/test/test_async_driver_probe.c   |  28 +++--
 drivers/char/ipmi/ipmi_msghandler.c           |   9 +-
 drivers/char/ipmi/ipmi_si_intf.c              |   9 +-
 drivers/char/ipmi/ipmi_ssif.c                 |   9 +-
 drivers/edac/edac_pci.h                       |   5 +-
 drivers/edac/edac_pci_sysfs.c                 |  30 ++---
 drivers/oprofile/buffer_sync.c                |   9 +-
 drivers/oprofile/event_buffer.c               |   3 +-
 drivers/oprofile/oprof.c                      |   3 +-
 drivers/oprofile/oprofile_stats.c             |  11 +-
 drivers/oprofile/oprofile_stats.h             |  11 +-
 drivers/oprofile/oprofilefs.c                 |   3 +-
 drivers/staging/rtl8188eu/core/rtw_mlme_ext.c |  23 +++-
 .../staging/rtl8188eu/include/rtw_mlme_ext.h  |   3 +-
 drivers/staging/rtl8723bs/core/rtw_cmd.c      |   3 +-
 drivers/staging/rtl8723bs/core/rtw_mlme_ext.c |  33 +++--
 drivers/staging/rtl8723bs/include/rtw_cmd.h   |   3 +-
 .../staging/rtl8723bs/include/rtw_mlme_ext.h  |   3 +-
 .../staging/unisys/visorhba/visorhba_main.c   |  21 ++--
 drivers/usb/usbip/vhci.h                      |   3 +-
 drivers/usb/usbip/vhci_hcd.c                  |   7 +-
 drivers/usb/usbip/vhci_rx.c                   |   5 +-
 include/linux/oprofile.h                      |   3 +-
 include/linux/seqnum_ops.h                    | 118 +++++++++++++++++
 lib/Kconfig                                   |   9 ++
 lib/Makefile                                  |   1 +
 lib/test_seqnum_ops.c                         | 119 ++++++++++++++++++
 security/integrity/ima/ima.h                  |   5 +-
 security/integrity/ima/ima_api.c              |   3 +-
 security/integrity/ima/ima_fs.c               |   5 +-
 security/integrity/ima/ima_queue.c            |   7 +-
 tools/testing/selftests/lib/Makefile          |   1 +
 tools/testing/selftests/lib/config            |   1 +
 .../testing/selftests/lib/test_seqnum_ops.sh  |  10 ++
 40 files changed, 524 insertions(+), 110 deletions(-)
 create mode 100644 Documentation/core-api/seqnum_ops.rst
 create mode 100644 include/linux/seqnum_ops.h
 create mode 100644 lib/test_seqnum_ops.c
 create mode 100755 tools/testing/selftests/lib/test_seqnum_ops.sh

-- 
2.27.0

[PATCH v2 10/13] usb: usbip/vhci: convert seqno to seqnum_ops

[Shuah Khan]

Sequence Number api provides interfaces for unsigned atomic up counters
leveraging atomic_t and atomic64_t ops underneath. Convert it to use
seqnum_ops.

atomic_t variables used for stats are atomic counters. Convert them to
use seqnum_ops.

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/usb/usbip/vhci.h     | 3 ++-
 drivers/usb/usbip/vhci_hcd.c | 7 ++++---
 drivers/usb/usbip/vhci_rx.c  | 5 +++--
 3 files changed, 9 insertions(+), 6 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..57287165537c 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 +666,7 @@ 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);
+	priv->seqnum = seqnum32_inc_return(&vhci_hcd->seqnum);
 	if (priv->seqnum == 0xffff)
 		dev_info(&urb->dev->dev, "seqnum max\n");
 
@@ -921,7 +922,7 @@ static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
 			return -ENOMEM;
 		}
 
-		unlink->seqnum = atomic_inc_return(&vhci_hcd->seqnum);
+		unlink->seqnum = seqnum32_inc_return(&vhci_hcd->seqnum);
 		if (unlink->seqnum == 0xffff)
 			pr_info("seqnum max\n");
 
@@ -1181,7 +1182,7 @@ static int vhci_start(struct usb_hcd *hcd)
 		vdev->rhport = rhport;
 	}
 
-	atomic_set(&vhci_hcd->seqnum, 0);
+	seqnum32_init(&vhci_hcd->seqnum);
 
 	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..84620538093f 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"
@@ -66,9 +67,9 @@ static void vhci_recv_ret_submit(struct vhci_device *vdev,
 	spin_unlock_irqrestore(&vdev->priv_lock, flags);
 
 	if (!urb) {
-		pr_err("cannot find a urb of seqnum %u max seqnum %d\n",
+		pr_err("cannot find a urb of seqnum %u max seqnum %u\n",
 			pdu->base.seqnum,
-			atomic_read(&vhci_hcd->seqnum));
+			seqnum32_fetch(&vhci_hcd->seqnum));
 		usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
 		return;
 	}
-- 
2.27.0