linux-kernel - [PATCH 12/13] drivers/staging/unisys/visorhba: convert stats to use seqnum

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Message-Id: <6fb679d23de785bbd1be6a528127e29f8ee6abd7.1605027593.git.skhan@linuxfoundation.org>
Date:   Tue, 10 Nov 2020 12:53:38 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     david.kershner@...sys.com, gregkh@...uxfoundation.org,
        keescook@...omium.org, peterz@...radead.org
Cc:     Shuah Khan <skhan@...uxfoundation.org>, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 12/13] drivers/staging/unisys/visorhba: convert stats to use seqnum_ops

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.

atomic_t variables used for error_count and ios_threshold are atomic
counters and guarded by max. values. No change to the behavior with
this change.

Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
 .../staging/unisys/visorhba/visorhba_main.c   | 37 ++++++++++---------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/staging/unisys/visorhba/visorhba_main.c b/drivers/staging/unisys/visorhba/visorhba_main.c
index 7ae5306b92fe..3209958b8aaa 100644
--- a/drivers/staging/unisys/visorhba/visorhba_main.c
+++ b/drivers/staging/unisys/visorhba/visorhba_main.c
@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/seq_file.h>
 #include <linux/visorbus.h>
+#include <linux/seqnum_ops.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_cmnd.h>
@@ -41,8 +42,8 @@ MODULE_ALIAS("visorbus:" VISOR_VHBA_CHANNEL_GUID_STR);
 struct visordisk_info {
 	struct scsi_device *sdev;
 	u32 valid;
-	atomic_t ios_threshold;
-	atomic_t error_count;
+	struct seqnum32 ios_threshold;
+	struct seqnum32 error_count;
 	struct visordisk_info *next;
 };
 
@@ -374,10 +375,10 @@ static int visorhba_abort_handler(struct scsi_cmnd *scsicmd)
 
 	scsidev = scsicmd->device;
 	vdisk = scsidev->hostdata;
-	if (atomic_read(&vdisk->error_count) < VISORHBA_ERROR_COUNT)
-		atomic_inc(&vdisk->error_count);
+	if (seqnum32_read(&vdisk->error_count) < VISORHBA_ERROR_COUNT)
+		seqnum32_inc(&vdisk->error_count);
 	else
-		atomic_set(&vdisk->ios_threshold, IOS_ERROR_THRESHOLD);
+		seqnum32_set(&vdisk->ios_threshold, IOS_ERROR_THRESHOLD);
 	rtn = forward_taskmgmt_command(TASK_MGMT_ABORT_TASK, scsidev);
 	if (rtn == SUCCESS) {
 		scsicmd->result = DID_ABORT << 16;
@@ -401,10 +402,10 @@ static int visorhba_device_reset_handler(struct scsi_cmnd *scsicmd)
 
 	scsidev = scsicmd->device;
 	vdisk = scsidev->hostdata;
-	if (atomic_read(&vdisk->error_count) < VISORHBA_ERROR_COUNT)
-		atomic_inc(&vdisk->error_count);
+	if (seqnum32_read(&vdisk->error_count) < VISORHBA_ERROR_COUNT)
+		seqnum32_inc(&vdisk->error_count);
 	else
-		atomic_set(&vdisk->ios_threshold, IOS_ERROR_THRESHOLD);
+		seqnum32_set(&vdisk->ios_threshold, IOS_ERROR_THRESHOLD);
 	rtn = forward_taskmgmt_command(TASK_MGMT_LUN_RESET, scsidev);
 	if (rtn == SUCCESS) {
 		scsicmd->result = DID_RESET << 16;
@@ -429,10 +430,10 @@ static int visorhba_bus_reset_handler(struct scsi_cmnd *scsicmd)
 	scsidev = scsicmd->device;
 	shost_for_each_device(scsidev, scsidev->host) {
 		vdisk = scsidev->hostdata;
-		if (atomic_read(&vdisk->error_count) < VISORHBA_ERROR_COUNT)
-			atomic_inc(&vdisk->error_count);
+		if (seqnum32_read(&vdisk->error_count) < VISORHBA_ERROR_COUNT)
+			seqnum32_inc(&vdisk->error_count);
 		else
-			atomic_set(&vdisk->ios_threshold, IOS_ERROR_THRESHOLD);
+			seqnum32_set(&vdisk->ios_threshold, IOS_ERROR_THRESHOLD);
 	}
 	rtn = forward_taskmgmt_command(TASK_MGMT_BUS_RESET, scsidev);
 	if (rtn == SUCCESS) {
@@ -803,9 +804,9 @@ static void do_scsi_linuxstat(struct uiscmdrsp *cmdrsp,
 		return;
 	/* Okay see what our error_count is here.... */
 	vdisk = scsidev->hostdata;
-	if (atomic_read(&vdisk->error_count) < VISORHBA_ERROR_COUNT) {
-		atomic_inc(&vdisk->error_count);
-		atomic_set(&vdisk->ios_threshold, IOS_ERROR_THRESHOLD);
+	if (seqnum32_read(&vdisk->error_count) < VISORHBA_ERROR_COUNT) {
+		seqnum32_inc(&vdisk->error_count);
+		seqnum32_set(&vdisk->ios_threshold, IOS_ERROR_THRESHOLD);
 	}
 }
 
@@ -881,10 +882,10 @@ static void do_scsi_nolinuxstat(struct uiscmdrsp *cmdrsp,
 		kfree(buf);
 	} else {
 		vdisk = scsidev->hostdata;
-		if (atomic_read(&vdisk->ios_threshold) > 0) {
-			atomic_dec(&vdisk->ios_threshold);
-			if (atomic_read(&vdisk->ios_threshold) == 0)
-				atomic_set(&vdisk->error_count, 0);
+		if (seqnum32_read(&vdisk->ios_threshold) > 0) {
+			seqnum32_dec(&vdisk->ios_threshold);
+			if (seqnum32_read(&vdisk->ios_threshold) == 0)
+				seqnum32_set(&vdisk->error_count, 0);
 		}
 	}
 }
-- 
2.27.0