[PATCH 2/3] xen netback: add fault injection facility

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This patch adds wrapper helpers around generic Xen fault inject facility.
The major reason is to keep all the module fault injection directories
in a dedicated subdirectory instead of Xen fault inject root.

IOW, when using these helpers, per-device and named by device name fault
injection control directories will appear under the following directory:
- /sys/kernel/debug/xen/fault_inject/xen-netback/
instead of:
- /sys/kernel/debug/xen/fault_inject/

Signed-off-by: Stanislav Kinsburskii <staskins@xxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
CC: "David S. Miller" <davem@xxxxxxxxxxxxx>
CC: Matteo Croce <mcroce@xxxxxxxxxx>
CC: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
CC: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
CC: Gerard Garcia <ggarcia@xxxxxxxxxxxx>
CC: David Ahern <dsa@xxxxxxxxxxxxxxxxxxx>
CC: Juergen Gross <jgross@xxxxxxxx>
CC: Amir Levy <amir.jer.levy@xxxxxxxxx>
CC: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>
CC: linux-kernel@xxxxxxxxxxxxxxx
CC: netdev@xxxxxxxxxxxxxxx
CC: xen-devel@xxxxxxxxxxxxxxxxxxxx
CC: Stanislav Kinsburskii <staskins@xxxxxxxxxx>
CC: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
 drivers/net/Kconfig                  |    8 ++
 drivers/net/xen-netback/Makefile     |    1 
 drivers/net/xen-netback/common.h     |    3 +
 drivers/net/xen-netback/netback.c    |    3 +
 drivers/net/xen-netback/netback_fi.c |  119 ++++++++++++++++++++++++++++++++++
 drivers/net/xen-netback/netback_fi.h |   35 ++++++++++
 drivers/net/xen-netback/xenbus.c     |    6 ++
 7 files changed, 175 insertions(+)
 create mode 100644 drivers/net/xen-netback/netback_fi.c
 create mode 100644 drivers/net/xen-netback/netback_fi.h

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 8918466..5cc9acd 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -465,6 +465,14 @@ config XEN_NETDEV_BACKEND
 	  compile this driver as a module, chose M here: the module
 	  will be called xen-netback.
 
+config XEN_NETDEV_BACKEND_FAULT_INJECTION
+	  bool "Xen net-device backend driver fault injection"
+	  depends on XEN_NETDEV_BACKEND
+	  depends on XEN_FAULT_INJECTION
+	  default n
+	  help
+	    Allow to inject errors to Xen backend network driver
+
 config VMXNET3
 	tristate "VMware VMXNET3 ethernet driver"
 	depends on PCI && INET
diff --git a/drivers/net/xen-netback/Makefile b/drivers/net/xen-netback/Makefile
index d49798a..28abcdc 100644
--- a/drivers/net/xen-netback/Makefile
+++ b/drivers/net/xen-netback/Makefile
@@ -1,3 +1,4 @@
 obj-$(CONFIG_XEN_NETDEV_BACKEND) := xen-netback.o
 
 xen-netback-y := netback.o xenbus.o interface.o hash.o rx.o
+xen-netback-$(CONFIG_XEN_NETDEV_BACKEND_FAULT_INJECTION) += netback_fi.o
diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index a46a1e9..30d676d 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -286,6 +286,9 @@ struct xenvif {
 
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *xenvif_dbg_root;
+#ifdef CONFIG_XEN_NETDEV_BACKEND_FAULT_INJECTION
+	void *fi_info;
+#endif
 #endif
 
 	struct xen_netif_ctrl_back_ring ctrl;
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index a27daa2..ecc416e 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -33,6 +33,7 @@
  */
 
 #include "common.h"
+#include "netback_fi.h"
 
 #include <linux/kthread.h>
 #include <linux/if_vlan.h>
@@ -1649,6 +1650,7 @@ static int __init netback_init(void)
 			PTR_ERR(xen_netback_dbg_root));
 #endif /* CONFIG_DEBUG_FS */
 
+	(void) xen_netbk_fi_init();
 	return 0;
 
 failed_init:
@@ -1659,6 +1661,7 @@ module_init(netback_init);
 
 static void __exit netback_fini(void)
 {
+	xen_netbk_fi_fini();
 #ifdef CONFIG_DEBUG_FS
 	if (!IS_ERR_OR_NULL(xen_netback_dbg_root))
 		debugfs_remove_recursive(xen_netback_dbg_root);
diff --git a/drivers/net/xen-netback/netback_fi.c b/drivers/net/xen-netback/netback_fi.c
new file mode 100644
index 0000000..47541d0
--- /dev/null
+++ b/drivers/net/xen-netback/netback_fi.c
@@ -0,0 +1,119 @@
+/*
+ * Fault injection interface for Xen backend network driver
+ *
+ * Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "common.h"
+
+#include <linux/debugfs.h>
+
+#include <xen/fault_inject.h>
+#include "netback_fi.h"
+
+static struct dentry *vif_fi_dir;
+
+static const char *xenvif_fi_names[] = {
+};
+
+struct xenvif_fi {
+	struct dentry *dir;
+	struct xen_fi *faults[XENVIF_FI_MAX];
+};
+
+int xen_netbk_fi_init(void)
+{
+	vif_fi_dir = xen_fi_dir_create("xen-netback");
+	if (!vif_fi_dir)
+		return -ENOMEM;
+	return 0;
+}
+
+void xen_netbk_fi_fini(void)
+{
+	debugfs_remove_recursive(vif_fi_dir);
+}
+
+void xenvif_fi_fini(struct xenvif *vif)
+{
+	struct xenvif_fi *vfi = vif->fi_info;
+	int fi;
+
+	if (!vif->fi_info)
+		return;
+
+	vif->fi_info = NULL;
+
+	for (fi = 0; fi < XENVIF_FI_MAX; fi++)
+		xen_fi_del(vfi->faults[fi]);
+	debugfs_remove_recursive(vfi->dir);
+	kfree(vfi);
+}
+
+int xenvif_fi_init(struct xenvif *vif)
+{
+	struct dentry *parent;
+	struct xenvif_fi *vfi;
+	int fi, err = -ENOMEM;
+
+	parent = vif_fi_dir;
+	if (!parent)
+		return -ENOMEM;
+
+	vfi = kmalloc(sizeof(*vfi), GFP_KERNEL);
+	if (!vfi)
+		return -ENOMEM;
+
+	vfi->dir = debugfs_create_dir(vif->dev->name, parent);
+	if (!vfi->dir)
+		goto err_dir;
+
+	for (fi = 0; fi < XENVIF_FI_MAX; fi++) {
+		vfi->faults[fi] = xen_fi_dir_add(vfi->dir,
+				xenvif_fi_names[fi]);
+		if (!vfi->faults[fi])
+			goto err_fault;
+	}
+
+	vif->fi_info = vfi;
+	return 0;
+
+err_fault:
+	for (; fi > 0; fi--)
+		xen_fi_del(vfi->faults[fi]);
+	debugfs_remove_recursive(vfi->dir);
+err_dir:
+	kfree(vfi);
+	return err;
+}
+
+bool xenvif_should_fail(struct xenvif *vif, xenvif_fi_t type)
+{
+	struct xenvif_fi *vfi = vif->fi_info;
+
+	return xen_should_fail(vfi->faults[type]);
+}
diff --git a/drivers/net/xen-netback/netback_fi.h b/drivers/net/xen-netback/netback_fi.h
new file mode 100644
index 0000000..895c6a6
--- /dev/null
+++ b/drivers/net/xen-netback/netback_fi.h
@@ -0,0 +1,35 @@
+#ifndef _XEN_NETBACK_FI_H
+#define _XEN_NETBACK_FI_H
+
+struct xen_fi;
+
+typedef enum {
+	XENVIF_FI_MAX
+} xenvif_fi_t;
+
+#ifdef CONFIG_XEN_NETDEV_BACKEND_FAULT_INJECTION
+
+int xen_netbk_fi_init(void);
+void xen_netbk_fi_fini(void);
+
+void xenvif_fi_fini(struct xenvif *vif);
+int xenvif_fi_init(struct xenvif *vif);
+
+bool xenvif_should_fail(struct xenvif *vif, xenvif_fi_t type);
+
+#else
+
+static inline int xen_netbk_fi_init(void) { return 0; }
+static inline void xen_netbk_fi_fini(void) { }
+
+static inline void xenvif_fi_fini(struct xenvif *vif) { }
+static inline int xenvif_fi_init(struct xenvif *vif) { return 0; }
+
+static inline bool xenvif_should_fail(struct xenvif *vif, xenvif_fi_t type)
+{
+	return false;
+}
+
+#endif /* CONFIG_XEN_NETDEV_BACKEND_FAULT_INJECTION */
+
+#endif /* _XEN_NETBACK_FI_H */
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index e1aef25..c775ee0 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -21,6 +21,7 @@
 #include "common.h"
 #include <linux/vmalloc.h>
 #include <linux/rtnetlink.h>
+#include "netback_fi.h"
 
 struct backend_info {
 	struct xenbus_device *dev;
@@ -502,6 +503,7 @@ static void backend_disconnect(struct backend_info *be)
 #ifdef CONFIG_DEBUG_FS
 		xenvif_debugfs_delif(vif);
 #endif /* CONFIG_DEBUG_FS */
+		xenvif_fi_fini(vif);
 		xenvif_disconnect_data(vif);
 
 		/* At this point some of the handlers may still be active
@@ -1024,6 +1026,10 @@ static void connect(struct backend_info *be)
 		}
 	}
 
+	err = xenvif_fi_init(be->vif);
+	if (err)
+		goto err;
+
 #ifdef CONFIG_DEBUG_FS
 	xenvif_debugfs_addif(be->vif);
 #endif /* CONFIG_DEBUG_FS */

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