scsi-virtio_scsi-to-lose-an-interrupt-on-purpose.patch

From 8c60d975887583b9abb24b47e4f30a7309df206d Mon Sep 17 00:00:00 2001
From: Dongli Zhang <dongli.zhang@oracle.com>
Date: Wed, 19 May 2021 10:32:44 -0700
Subject: [PATCH v5.12 1/1] scsi: virtio_scsi: to lose an interrupt on purpose

This is on top of v5.12.

This is to ignore an interrupt on purpose to emulate the loss of interrupt
issue for virtio-scsi.

vm# echo 1 > /sys/kernel/testsys
[   64.463746] testsys: testsys_debug is set to 1

vm# dd if=/dev/sda of=disk.img bs=4K count=20 oflag=direct

[  113.850136] virtio_scsi: orabug: to lose one interrupt for QID 3

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
 block/blk-mq.c             | 40 ++++++++++++++++++++++++++++++++++++++
 drivers/scsi/virtio_scsi.c |  9 +++++++++
 2 files changed, 49 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index d4d7c1caa439..0193d80a480f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3925,6 +3925,43 @@ unsigned int blk_mq_rq_cpu(struct request *rq)
 }
 EXPORT_SYMBOL(blk_mq_rq_cpu);
 
+int testsys_debug = 0;
+
+static ssize_t
+testsys_show(struct kobject *kobj,
+	     struct kobj_attribute *attr,
+	     char *buf)
+{
+	return sprintf(buf, "%d\n", testsys_debug);
+}
+
+static ssize_t
+testsys_store(struct kobject *kobj,
+	      struct kobj_attribute *attr,
+	      const char *buf, size_t count)
+{
+	sscanf(buf, "%d", &testsys_debug);
+	pr_alert("testsys: testsys_debug is set to %d\n", testsys_debug);
+
+	return count;
+}
+
+static struct kobj_attribute testsys_attr =
+	__ATTR(testsys, 0600,
+	       testsys_show,
+	       testsys_store);
+
+static void testsys_register(void)
+{
+	int ret;
+
+	ret = sysfs_create_file(kernel_kobj, &testsys_attr.attr);
+	if (ret)
+		pr_alert("testsys: failed to create testsys\n");
+	else
+		pr_alert("testsys: the testsys is created successfully\n");
+}
+
 static int __init blk_mq_init(void)
 {
 	int i;
@@ -3941,6 +3978,9 @@ static int __init blk_mq_init(void)
 	cpuhp_setup_state_multi(CPUHP_AP_BLK_MQ_ONLINE, "block/mq:online",
 				blk_mq_hctx_notify_online,
 				blk_mq_hctx_notify_offline);
+
+	testsys_register();
+
 	return 0;
 }
 subsys_initcall(blk_mq_init);
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index b9c86a7e3b97..13da973f9abc 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -189,6 +189,8 @@ static void virtscsi_vq_done(struct virtio_scsi *vscsi,
 	spin_unlock_irqrestore(&virtscsi_vq->vq_lock, flags);
 }
 
+extern int testsys_debug;
+
 static void virtscsi_req_done(struct virtqueue *vq)
 {
 	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
@@ -196,6 +198,13 @@ static void virtscsi_req_done(struct virtqueue *vq)
 	int index = vq->index - VIRTIO_SCSI_VQ_BASE;
 	struct virtio_scsi_vq *req_vq = &vscsi->req_vqs[index];
 
+	 if (testsys_debug) {
+		testsys_debug = 0;
+		pr_alert("orabug: to lose one interrupt for QID %d\n",
+			 vq->index);
+		return;
+	 }
+
 	virtscsi_vq_done(vscsi, req_vq, virtscsi_complete_cmd);
 };
 
-- 
2.17.1