[PATCHv2 for-next 04/24] block/rnbd-srv: Inject a fault at bio processing

[Gioh Kim <gi-oh.kim@ionos.com>]

From: Gioh Kim <gi-oh.kim@cloud.ionos.com>

If the fault is enabled, it sends an error to the client
so that the client thinks the target device on the server has failed.

Signed-off-by: Gioh Kim <gi-oh.kim@cloud.ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
---
 drivers/block/rnbd/rnbd-srv-sysfs.c | 36 +++++++++++++++++++++++++++++
 drivers/block/rnbd/rnbd-srv.c       |  7 ++++++
 drivers/block/rnbd/rnbd-srv.h       | 13 +++++++++++
 3 files changed, 56 insertions(+)

diff --git a/drivers/block/rnbd/rnbd-srv-sysfs.c b/drivers/block/rnbd/rnbd-srv-sysfs.c
index 05ffe488ddc6..278a981302b9 100644
--- a/drivers/block/rnbd/rnbd-srv-sysfs.c
+++ b/drivers/block/rnbd/rnbd-srv-sysfs.c
@@ -253,3 +253,39 @@ void rnbd_srv_destroy_sysfs_files(void)
 	device_destroy(rnbd_dev_class, MKDEV(0, 0));
 	class_destroy(rnbd_dev_class);
 }
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+void rnbd_srv_fault_inject_init(struct rnbd_srv_fault_inject *fault_inject,
+				const char *dev_name)
+{
+	rnbd_fault_inject_init(&fault_inject->fj, dev_name, -EBUSY);
+	/* injection points */
+	rnbd_fault_inject_add(fault_inject->fj.dir,
+			      "fail-bio", &fault_inject->fail_bio);
+}
+
+void rnbd_srv_fault_inject_fini(struct rnbd_srv_fault_inject *fault_inject)
+{
+	rnbd_fault_inject_final(&fault_inject->fj);
+}
+
+int rnbd_should_fail_bio(struct rnbd_srv_sess_dev *sess_dev)
+{
+	struct rnbd_srv_fault_inject *fault_inject = &sess_dev->fault_inject;
+	if (fault_inject->fail_bio && should_fail(&fault_inject->fj.attr, 1))
+		return fault_inject->fj.status;
+	return 0;
+}
+#else
+void rnbd_srv_fault_inject_init(struct rnbd_srv_fault_inject *fault_inj,
+				const char *dev_name)
+{
+}
+void rnbd_srv_fault_inject_fini(struct rnbd_srv_fault_inject *fault_inject)
+{
+}
+int rnbd_should_fail_bio(struct rnbd_srv_sess_dev *sess_dev)
+{
+	return 0;
+}
+#endif
diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c
index a6a68d44f517..447fb0718525 100644
--- a/drivers/block/rnbd/rnbd-srv.c
+++ b/drivers/block/rnbd/rnbd-srv.c
@@ -88,9 +88,14 @@ void rnbd_endio(void *priv, int error)
 {
 	struct rnbd_io_private *rnbd_priv = priv;
 	struct rnbd_srv_sess_dev *sess_dev = rnbd_priv->sess_dev;
+	int fail_err = 0;
 
 	rnbd_put_sess_dev(sess_dev);
 
+	fail_err = rnbd_should_fail_bio(sess_dev);
+	if (unlikely(fail_err)) /* over-write error which will be sent to client */
+		error = fail_err;
+
 	rtrs_srv_resp_rdma(rnbd_priv->id, error);
 
 	kfree(priv);
@@ -230,6 +235,7 @@ void rnbd_destroy_sess_dev(struct rnbd_srv_sess_dev *sess_dev, bool keep_id)
 	rnbd_put_sess_dev(sess_dev);
 	wait_for_completion(&dc); /* wait for inflights to drop to zero */
 
+	rnbd_srv_fault_inject_fini(&sess_dev->fault_inject);
 	rnbd_dev_close(sess_dev->rnbd_dev);
 	list_del(&sess_dev->sess_list);
 	mutex_lock(&sess_dev->dev->lock);
@@ -811,6 +817,7 @@ static int process_msg_open(struct rtrs_srv *rtrs,
 	rnbd_srv_info(srv_sess_dev, "Opened device '%s'\n", srv_dev->id);
 
 	kfree(full_path);
+	rnbd_srv_fault_inject_init(&srv_sess_dev->fault_inject, kbasename(srv_sess_dev->pathname));
 
 fill_response:
 	rnbd_srv_fill_msg_open_rsp(rsp, srv_sess_dev);
diff --git a/drivers/block/rnbd/rnbd-srv.h b/drivers/block/rnbd/rnbd-srv.h
index b157371c25ed..120e6d64cb82 100644
--- a/drivers/block/rnbd/rnbd-srv.h
+++ b/drivers/block/rnbd/rnbd-srv.h
@@ -45,6 +45,13 @@ struct rnbd_srv_dev {
 	int				open_write_cnt;
 };
 
+struct rnbd_srv_fault_inject {
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+	struct rnbd_fault_inject fj;
+	bool fail_bio;
+#endif
+};
+
 /* Structure which binds N devices and N sessions */
 struct rnbd_srv_sess_dev {
 	/* Entry inside rnbd_srv_dev struct */
@@ -62,6 +69,7 @@ struct rnbd_srv_sess_dev {
 	struct completion               *destroy_comp;
 	char				pathname[NAME_MAX];
 	enum rnbd_access_mode		access_mode;
+	struct rnbd_srv_fault_inject    fault_inject;
 };
 
 void rnbd_srv_sess_dev_force_close(struct rnbd_srv_sess_dev *sess_dev);
@@ -77,4 +85,9 @@ int rnbd_srv_create_sysfs_files(void);
 void rnbd_srv_destroy_sysfs_files(void);
 void rnbd_destroy_sess_dev(struct rnbd_srv_sess_dev *sess_dev, bool keep_id);
 
+void rnbd_srv_fault_inject_init(struct rnbd_srv_fault_inject *fault_inj,
+				const char *dev_name);
+void rnbd_srv_fault_inject_fini(struct rnbd_srv_fault_inject *fault_inject);
+int rnbd_should_fail_bio(struct rnbd_srv_sess_dev *sess_dev);
+
 #endif /* RNBD_SRV_H */
-- 
2.25.1