scsi: scsi_debug: Add debugfs interface to fail target reset

The interface is found at
/sys/kernel/debug/scsi_debug/target<h:c:t>/fail_reset where <h:c:t>
identifies the target to inject errors on. It's a simple bool type
interface which would make this target's reset fail if set to 'Y'.

Signed-off-by: Wenchao Hao <haowenchao2@huawei.com>
Link: https://lore.kernel.org/r/20231010092051.608007-10-haowenchao2@huawei.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_debug.c

@@ -42,6 +42,7 @@
 #include <linux/xarray.h>
 #include <linux/prefetch.h>
 #include <linux/debugfs.h>
+#include <linux/async.h>
 
 #include <net/checksum.h>
 
@@ -357,6 +358,11 @@ struct sdebug_dev_info {
 	struct list_head inject_err_list;
 };
 
+struct sdebug_target_info {
+	bool reset_fail;
+	struct dentry *debugfs_entry;
+};
+
 struct sdebug_host_info {
 	struct list_head host_list;
 	int si_idx;	/* sdeb_store_info (per host) xarray index */
@@ -1082,6 +1088,91 @@ static const struct file_operations sdebug_error_fops = {
 	.release = single_release,
 };
 
+static int sdebug_target_reset_fail_show(struct seq_file *m, void *p)
+{
+	struct scsi_target *starget = (struct scsi_target *)m->private;
+	struct sdebug_target_info *targetip =
+		(struct sdebug_target_info *)starget->hostdata;
+
+	if (targetip)
+		seq_printf(m, "%c\n", targetip->reset_fail ? 'Y' : 'N');
+
+	return 0;
+}
+
+static int sdebug_target_reset_fail_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, sdebug_target_reset_fail_show, inode->i_private);
+}
+
+static ssize_t sdebug_target_reset_fail_write(struct file *file,
+		const char __user *ubuf, size_t count, loff_t *ppos)
+{
+	int ret;
+	struct scsi_target *starget =
+		(struct scsi_target *)file->f_inode->i_private;
+	struct sdebug_target_info *targetip =
+		(struct sdebug_target_info *)starget->hostdata;
+
+	if (targetip) {
+		ret = kstrtobool_from_user(ubuf, count, &targetip->reset_fail);
+		return ret < 0 ? ret : count;
+	}
+	return -ENODEV;
+}
+
+static const struct file_operations sdebug_target_reset_fail_fops = {
+	.open	= sdebug_target_reset_fail_open,
+	.read	= seq_read,
+	.write	= sdebug_target_reset_fail_write,
+	.release = single_release,
+};
+
+static int sdebug_target_alloc(struct scsi_target *starget)
+{
+	struct sdebug_target_info *targetip;
+	struct dentry *dentry;
+
+	targetip = kzalloc(sizeof(struct sdebug_target_info), GFP_KERNEL);
+	if (!targetip)
+		return -ENOMEM;
+
+	targetip->debugfs_entry = debugfs_create_dir(dev_name(&starget->dev),
+				sdebug_debugfs_root);
+	if (IS_ERR_OR_NULL(targetip->debugfs_entry))
+		pr_info("%s: failed to create debugfs directory for target %s\n",
+			__func__, dev_name(&starget->dev));
+
+	debugfs_create_file("fail_reset", 0600, targetip->debugfs_entry, starget,
+				&sdebug_target_reset_fail_fops);
+	if (IS_ERR_OR_NULL(dentry))
+		pr_info("%s: failed to create fail_reset file for target %s\n",
+			__func__, dev_name(&starget->dev));
+
+	starget->hostdata = targetip;
+
+	return 0;
+}
+
+static void sdebug_tartget_cleanup_async(void *data, async_cookie_t cookie)
+{
+	struct sdebug_target_info *targetip = data;
+
+	debugfs_remove(targetip->debugfs_entry);
+	kfree(targetip);
+}
+
+static void sdebug_target_destroy(struct scsi_target *starget)
+{
+	struct sdebug_target_info *targetip;
+
+	targetip = (struct sdebug_target_info *)starget->hostdata;
+	if (targetip) {
+		starget->hostdata = NULL;
+		async_schedule(sdebug_tartget_cleanup_async, targetip);
+	}
+}
+
 /* Only do the extra work involved in logical block provisioning if one or
  * more of the lbpu, lbpws or lbpws10 parameters are given and we are doing
  * real reads and writes (i.e. not skipping them for speed).
@@ -5642,11 +5733,25 @@ static int scsi_debug_device_reset(struct scsi_cmnd *SCpnt)
 	return SUCCESS;
 }
 
+static int sdebug_fail_target_reset(struct scsi_cmnd *cmnd)
+{
+	struct scsi_target *starget = scsi_target(cmnd->device);
+	struct sdebug_target_info *targetip =
+		(struct sdebug_target_info *)starget->hostdata;
+
+	if (targetip)
+		return targetip->reset_fail;
+
+	return 0;
+}
+
 static int scsi_debug_target_reset(struct scsi_cmnd *SCpnt)
 {
 	struct scsi_device *sdp = SCpnt->device;
 	struct sdebug_host_info *sdbg_host = shost_to_sdebug_host(sdp->host);
 	struct sdebug_dev_info *devip;
+	u8 *cmd = SCpnt->cmnd;
+	u8 opcode = cmd[0];
 	int k = 0;
 
 	++num_target_resets;
@@ -5664,6 +5769,12 @@ static int scsi_debug_target_reset(struct scsi_cmnd *SCpnt)
 		sdev_printk(KERN_INFO, sdp,
 			    "%s: %d device(s) found in target\n", __func__, k);
 
+	if (sdebug_fail_target_reset(SCpnt)) {
+		scmd_printk(KERN_INFO, SCpnt, "fail target reset 0x%x\n",
+			    opcode);
+		return FAILED;
+	}
+
 	return SUCCESS;
 }
 
@@ -8119,7 +8230,6 @@ static int sdebug_init_cmd_priv(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
 	return 0;
 }
 
-
 static struct scsi_host_template sdebug_driver_template = {
 	.show_info =		scsi_debug_show_info,
 	.write_info =		scsi_debug_write_info,
@@ -8149,6 +8259,8 @@ static struct scsi_host_template sdebug_driver_template = {
 	.track_queue_depth =	1,
 	.cmd_size = sizeof(struct sdebug_scsi_cmd),
 	.init_cmd_priv = sdebug_init_cmd_priv,
+	.target_alloc =		sdebug_target_alloc,
+	.target_destroy =	sdebug_target_destroy,
 };
 
 static int sdebug_driver_probe(struct device *dev)