SUNRPC: Move client-side disconnect injection

Disconnect injection stress-tests the ability for both client and
server implementations to behave resiliently in the face of network
instability.

Convert the existing client-side disconnect injection infrastructure
to use the kernel's generic error injection facility. The generic
facility has a richer set of injection criteria.

Signed-off-by: Chuck Lever <[e-mail]>

include/linux/sunrpc/xprt.h

···
 	const char		*address_strings[RPC_DISPLAY_MAX];
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 	struct dentry		*debugfs;		/* debugfs directory */
-	atomic_t		inject_disconnect;
 #endif
 	struct rcu_head		rcu;
 	const struct xprt_class	*xprt_class;
···
 {
 	return test_and_set_bit(XPRT_BINDING, &xprt->state);
 }
-
-#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
-extern unsigned int rpc_inject_disconnect;
-static inline void xprt_inject_disconnect(struct rpc_xprt *xprt)
-{
-	if (!rpc_inject_disconnect)
-		return;
-	if (atomic_dec_return(&xprt->inject_disconnect))
-		return;
-	atomic_set(&xprt->inject_disconnect, rpc_inject_disconnect);
-	xprt->ops->inject_disconnect(xprt);
-}
-#else
-static inline void xprt_inject_disconnect(struct rpc_xprt *xprt)
-{
-}
-#endif
 
 #endif /* _LINUX_SUNRPC_XPRT_H */

net/sunrpc/debugfs.c

···
 static struct dentry *rpc_clnt_dir;
 static struct dentry *rpc_xprt_dir;
 
-unsigned int rpc_inject_disconnect;
-
 static int
 tasks_show(struct seq_file *f, void *v)
 {
···
 	/* make tasks file */
 	debugfs_create_file("info", S_IFREG | 0400, xprt->debugfs, xprt,
 			    &xprt_info_fops);
-
-	atomic_set(&xprt->inject_disconnect, rpc_inject_disconnect);
 }
 
 void
···
 	xprt->debugfs = NULL;
 }
 
-static int
-fault_open(struct inode *inode, struct file *filp)
-{
-	filp->private_data = kmalloc(128, GFP_KERNEL);
-	if (!filp->private_data)
-		return -ENOMEM;
-	return 0;
-}
-
-static int
-fault_release(struct inode *inode, struct file *filp)
-{
-	kfree(filp->private_data);
-	return 0;
-}
-
-static ssize_t
-fault_disconnect_read(struct file *filp, char __user *user_buf,
-		      size_t len, loff_t *offset)
-{
-	char *buffer = (char *)filp->private_data;
-	size_t size;
-
-	size = sprintf(buffer, "%u\n", rpc_inject_disconnect);
-	return simple_read_from_buffer(user_buf, len, offset, buffer, size);
-}
-
-static ssize_t
-fault_disconnect_write(struct file *filp, const char __user *user_buf,
-		       size_t len, loff_t *offset)
-{
-	char buffer[16];
-
-	if (len >= sizeof(buffer))
-		len = sizeof(buffer) - 1;
-	if (copy_from_user(buffer, user_buf, len))
-		return -EFAULT;
-	buffer[len] = '\0';
-	if (kstrtouint(buffer, 10, &rpc_inject_disconnect))
-		return -EINVAL;
-	return len;
-}
-
-static const struct file_operations fault_disconnect_fops = {
-	.owner		= THIS_MODULE,
-	.open		= fault_open,
-	.read		= fault_disconnect_read,
-	.write		= fault_disconnect_write,
-	.release	= fault_release,
-};
-
 #if IS_ENABLED(CONFIG_FAIL_SUNRPC)
 struct fail_sunrpc_attr fail_sunrpc = {
 	.attr			= FAULT_ATTR_INITIALIZER,
 };
 EXPORT_SYMBOL_GPL(fail_sunrpc);
+
+static void fail_sunrpc_init(void)
+{
+	struct dentry *dir;
+
+	dir = fault_create_debugfs_attr("fail_sunrpc", NULL,
+					&fail_sunrpc.attr);
+
+	debugfs_create_bool("ignore-client-disconnect", S_IFREG | 0600, dir,
+			    &fail_sunrpc.ignore_client_disconnect);
+}
+#else
+static void fail_sunrpc_init(void)
+{
+}
 #endif
 
 void __exit
···
 void __init
 sunrpc_debugfs_init(void)
 {
-	struct dentry *rpc_fault_dir;
-
 	topdir = debugfs_create_dir("sunrpc", NULL);
 
 	rpc_clnt_dir = debugfs_create_dir("rpc_clnt", topdir);
 
 	rpc_xprt_dir = debugfs_create_dir("rpc_xprt", topdir);
 
-	rpc_fault_dir = debugfs_create_dir("inject_fault", topdir);
-
-	debugfs_create_file("disconnect", S_IFREG | 0400, rpc_fault_dir, NULL,
-			    &fault_disconnect_fops);
-
-#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
-	fault_create_debugfs_attr("fail_sunrpc", NULL,
-				  &fail_sunrpc.attr);
-#endif
+	fail_sunrpc_init();
 }

net/sunrpc/fail.h

···
 
 struct fail_sunrpc_attr {
 	struct fault_attr	attr;
+
+	bool			ignore_client_disconnect;
 };
 
 extern struct fail_sunrpc_attr fail_sunrpc;

net/sunrpc/xprt.c

···
 
 #include "sunrpc.h"
 #include "sysfs.h"
+#include "fail.h"
 
 /*
  * Local variables
···
 		return;
 	queue_work(xprtiod_workqueue, &xprt->task_cleanup);
 }
+
+#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
+static void xprt_inject_disconnect(struct rpc_xprt *xprt)
+{
+	if (!fail_sunrpc.ignore_client_disconnect &&
+	    should_fail(&fail_sunrpc.attr, 1))
+		xprt->ops->inject_disconnect(xprt);
+}
+#else
+static inline void xprt_inject_disconnect(struct rpc_xprt *xprt)
+{
+}
+#endif
 
 bool xprt_lock_connect(struct rpc_xprt *xprt,
 		struct rpc_task *task,