drivers/xen/xenbus/xenbus_probe_backend.c - linux - Git at Google

 /******************************************************************************
  * Talks to Xen Store to figure out what devices we have (backend half).
  *
  * Copyright (C) 2005 Rusty Russell, IBM Corporation
  * Copyright (C) 2005 Mike Wray, Hewlett-Packard
  * Copyright (C) 2005, 2006 XenSource Ltd
  * Copyright (C) 2007 Solarflare Communications, Inc.
  *
  * 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.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #define DPRINTK(fmt, ...)				\
 	pr_debug("(%s:%d) " fmt "\n",			\
 		 __func__, __LINE__, ##__VA_ARGS__)

 #include <linux/kernel.h>
 #include <linux/err.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
 #include <linux/fcntl.h>
 #include <linux/mm.h>
 #include <linux/notifier.h>
 #include <linux/export.h>
 #include <linux/semaphore.h>

 #include <asm/page.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/hypervisor.h>
 #include <xen/xenbus.h>
 #include <xen/features.h>

 #include "xenbus.h"

 /* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
 static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
 {
 	int domid, err;
 	const char *devid, *type, *frontend;
 	unsigned int typelen;

 	type = strchr(nodename, '/');
 	if (!type)
 		return -EINVAL;
 	type++;
 	typelen = strcspn(type, "/");
 	if (!typelen || type[typelen] != '/')
 		return -EINVAL;

 	devid = strrchr(nodename, '/') + 1;

 	err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
 			    "frontend", NULL, &frontend,
 			    NULL);
 	if (err)
 		return err;
 	if (strlen(frontend) == 0)
 		err = -ERANGE;
 	if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
 		err = -ENOENT;
 	kfree(frontend);

 	if (err)
 		return err;

 	if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s",
 		     typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
 		return -ENOSPC;
 	return 0;
 }

 static int xenbus_uevent_backend(const struct device *dev,
 				 struct kobj_uevent_env *env)
 {
 	const struct xenbus_device *xdev;
 	const struct xenbus_driver *drv;
 	const struct xen_bus_type *bus;

 	DPRINTK("");

 	if (dev == NULL)
 		return -ENODEV;

 	xdev = to_xenbus_device(dev);
 	bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);

 	if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
 		return -ENOMEM;

 	/* stuff we want to pass to /sbin/hotplug */
 	if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
 		return -ENOMEM;

 	if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
 		return -ENOMEM;

 	if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
 		return -ENOMEM;

 	if (dev->driver) {
 		drv = to_xenbus_driver(dev->driver);
 		if (drv && drv->uevent)
 			return drv->uevent(xdev, env);
 	}

 	return 0;
 }

 /* backend/<typename>/<frontend-uuid>/<name> */
 static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
 				     const char *dir,
 				     const char *type,
 				     const char *name)
 {
 	char *nodename;
 	int err;

 	nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
 	if (!nodename)
 		return -ENOMEM;

 	DPRINTK("%s\n", nodename);

 	err = xenbus_probe_node(bus, type, nodename);
 	kfree(nodename);
 	return err;
 }

 /* backend/<typename>/<frontend-domid> */
 static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type,
 				const char *domid)
 {
 	char *nodename;
 	int err = 0;
 	char **dir;
 	unsigned int i, dir_n = 0;

 	DPRINTK("");

 	nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
 	if (!nodename)
 		return -ENOMEM;

 	dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
 	if (IS_ERR(dir)) {
 		kfree(nodename);
 		return PTR_ERR(dir);
 	}

 	for (i = 0; i < dir_n; i++) {
 		err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
 		if (err)
 			break;
 	}
 	kfree(dir);
 	kfree(nodename);
 	return err;
 }

 static bool frontend_will_handle(struct xenbus_watch *watch,
 				 const char *path, const char *token)
 {
 	return watch->nr_pending == 0;
 }

 static void frontend_changed(struct xenbus_watch *watch,
 			     const char *path, const char *token)
 {
 	xenbus_otherend_changed(watch, path, token, 0);
 }

 static struct xen_bus_type xenbus_backend = {
 	.root = "backend",
 	.levels = 3,		/* backend/type/<frontend>/<id> */
 	.get_bus_id = backend_bus_id,
 	.probe = xenbus_probe_backend,
 	.otherend_will_handle = frontend_will_handle,
 	.otherend_changed = frontend_changed,
 	.bus = {
 		.name		= "xen-backend",
 		.match		= xenbus_match,
 		.uevent		= xenbus_uevent_backend,
 		.probe		= xenbus_dev_probe,
 		.remove		= xenbus_dev_remove,
 		.dev_groups	= xenbus_dev_groups,
 	},
 };

 static void backend_changed(struct xenbus_watch *watch,
 			    const char *path, const char *token)
 {
 	DPRINTK("");

 	xenbus_dev_changed(path, &xenbus_backend);
 }

 static struct xenbus_watch be_watch = {
 	.node = "backend",
 	.callback = backend_changed,
 };

 static int read_frontend_details(struct xenbus_device *xendev)
 {
 	return xenbus_read_otherend_details(xendev, "frontend-id", "frontend");
 }

 int xenbus_dev_is_online(struct xenbus_device *dev)
 {
 	return !!xenbus_read_unsigned(dev->nodename, "online", 0);
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_is_online);

 int __xenbus_register_backend(struct xenbus_driver *drv, struct module *owner,
 			      const char *mod_name)
 {
 	drv->read_otherend_details = read_frontend_details;

 	return xenbus_register_driver_common(drv, &xenbus_backend,
 					     owner, mod_name);
 }
 EXPORT_SYMBOL_GPL(__xenbus_register_backend);

 static int backend_probe_and_watch(struct notifier_block *notifier,
 				   unsigned long event,
 				   void *data)
 {
 	/* Enumerate devices in xenstore and watch for changes. */
 	xenbus_probe_devices(&xenbus_backend);
 	register_xenbus_watch(&be_watch);

 	return NOTIFY_DONE;
 }

 static int backend_reclaim_memory(struct device *dev, void *data)
 {
 	const struct xenbus_driver *drv;
 	struct xenbus_device *xdev;

 	if (!dev->driver)
 		return 0;
 	drv = to_xenbus_driver(dev->driver);
 	if (drv && drv->reclaim_memory) {
 		xdev = to_xenbus_device(dev);
 		if (down_trylock(&xdev->reclaim_sem))
 			return 0;
 		drv->reclaim_memory(xdev);
 		up(&xdev->reclaim_sem);
 	}
 	return 0;
 }

 /*
  * Returns 0 always because we are using shrinker to only detect memory
  * pressure.
  */
 static unsigned long backend_shrink_memory_count(struct shrinker *shrinker,
 				struct shrink_control *sc)
 {
 	bus_for_each_dev(&xenbus_backend.bus, NULL, NULL,
 			backend_reclaim_memory);
 	return 0;
 }

 static struct shrinker backend_memory_shrinker = {
 	.count_objects = backend_shrink_memory_count,
 	.seeks = DEFAULT_SEEKS,
 };

 static int __init xenbus_probe_backend_init(void)
 {
 	static struct notifier_block xenstore_notifier = {
 		.notifier_call = backend_probe_and_watch
 	};
 	int err;

 	DPRINTK("");

 	/* Register ourselves with the kernel bus subsystem */
 	err = bus_register(&xenbus_backend.bus);
 	if (err)
 		return err;

 	register_xenstore_notifier(&xenstore_notifier);

 	if (register_shrinker(&backend_memory_shrinker, "xen-backend"))
 		pr_warn("shrinker registration failed\n");

 	return 0;
 }
 subsys_initcall(xenbus_probe_backend_init);
	/******************************************************************************
	* Talks to Xen Store to figure out what devices we have (backend half).
	*
	* Copyright (C) 2005 Rusty Russell, IBM Corporation
	* Copyright (C) 2005 Mike Wray, Hewlett-Packard
	* Copyright (C) 2005, 2006 XenSource Ltd
	* Copyright (C) 2007 Solarflare Communications, Inc.
	*
	* 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.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#define DPRINTK(fmt, ...) \
	pr_debug("(%s:%d) " fmt "\n", \
	__func__, __LINE__, ##__VA_ARGS__)

	#include <linux/kernel.h>
	#include <linux/err.h>
	#include <linux/string.h>
	#include <linux/ctype.h>
	#include <linux/fcntl.h>
	#include <linux/mm.h>
	#include <linux/notifier.h>
	#include <linux/export.h>
	#include <linux/semaphore.h>

	#include <asm/page.h>
	#include <asm/xen/hypervisor.h>
	#include <asm/hypervisor.h>
	#include <xen/xenbus.h>
	#include <xen/features.h>

	#include "xenbus.h"

	/* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
	static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
	{
	int domid, err;
	const char devid, type, *frontend;
	unsigned int typelen;

	type = strchr(nodename, '/');
	if (!type)
	return -EINVAL;
	type++;
	typelen = strcspn(type, "/");
	if (!typelen \|\| type[typelen] != '/')
	return -EINVAL;

	devid = strrchr(nodename, '/') + 1;

	err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
	"frontend", NULL, &frontend,
	NULL);
	if (err)
	return err;
	if (strlen(frontend) == 0)
	err = -ERANGE;
	if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
	err = -ENOENT;
	kfree(frontend);

	if (err)
	return err;

	if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s",
	typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
	return -ENOSPC;
	return 0;
	}

	static int xenbus_uevent_backend(const struct device *dev,
	struct kobj_uevent_env *env)
	{
	const struct xenbus_device *xdev;
	const struct xenbus_driver *drv;
	const struct xen_bus_type *bus;

	DPRINTK("");

	if (dev == NULL)
	return -ENODEV;

	xdev = to_xenbus_device(dev);
	bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);

	if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
	return -ENOMEM;

	/* stuff we want to pass to /sbin/hotplug */
	if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
	return -ENOMEM;

	if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
	return -ENOMEM;

	if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
	return -ENOMEM;

	if (dev->driver) {
	drv = to_xenbus_driver(dev->driver);
	if (drv && drv->uevent)
	return drv->uevent(xdev, env);
	}

	return 0;
	}

	/* backend/<typename>/<frontend-uuid>/<name> */
	static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
	const char *dir,
	const char *type,
	const char *name)
	{
	char *nodename;
	int err;

	nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
	if (!nodename)
	return -ENOMEM;

	DPRINTK("%s\n", nodename);

	err = xenbus_probe_node(bus, type, nodename);
	kfree(nodename);
	return err;
	}

	/* backend/<typename>/<frontend-domid> */
	static int xenbus_probe_backend(struct xen_bus_type bus, const char type,
	const char *domid)
	{
	char *nodename;
	int err = 0;
	char **dir;
	unsigned int i, dir_n = 0;

	DPRINTK("");

	nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
	if (!nodename)
	return -ENOMEM;

	dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
	if (IS_ERR(dir)) {
	kfree(nodename);
	return PTR_ERR(dir);
	}

	for (i = 0; i < dir_n; i++) {
	err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
	if (err)
	break;
	}
	kfree(dir);
	kfree(nodename);
	return err;
	}

	static bool frontend_will_handle(struct xenbus_watch *watch,
	const char path, const char token)
	{
	return watch->nr_pending == 0;
	}

	static void frontend_changed(struct xenbus_watch *watch,
	const char path, const char token)
	{
	xenbus_otherend_changed(watch, path, token, 0);
	}

	static struct xen_bus_type xenbus_backend = {
	.root = "backend",
	.levels = 3, /* backend/type/<frontend>/<id> */
	.get_bus_id = backend_bus_id,
	.probe = xenbus_probe_backend,
	.otherend_will_handle = frontend_will_handle,
	.otherend_changed = frontend_changed,
	.bus = {
	.name = "xen-backend",
	.match = xenbus_match,
	.uevent = xenbus_uevent_backend,
	.probe = xenbus_dev_probe,
	.remove = xenbus_dev_remove,
	.dev_groups = xenbus_dev_groups,
	},
	};

	static void backend_changed(struct xenbus_watch *watch,
	const char path, const char token)
	{
	DPRINTK("");

	xenbus_dev_changed(path, &xenbus_backend);
	}

	static struct xenbus_watch be_watch = {
	.node = "backend",
	.callback = backend_changed,
	};

	static int read_frontend_details(struct xenbus_device *xendev)
	{
	return xenbus_read_otherend_details(xendev, "frontend-id", "frontend");
	}

	int xenbus_dev_is_online(struct xenbus_device *dev)
	{
	return !!xenbus_read_unsigned(dev->nodename, "online", 0);
	}
	EXPORT_SYMBOL_GPL(xenbus_dev_is_online);

	int __xenbus_register_backend(struct xenbus_driver drv, struct module owner,
	const char *mod_name)
	{
	drv->read_otherend_details = read_frontend_details;

	return xenbus_register_driver_common(drv, &xenbus_backend,
	owner, mod_name);
	}
	EXPORT_SYMBOL_GPL(__xenbus_register_backend);

	static int backend_probe_and_watch(struct notifier_block *notifier,
	unsigned long event,
	void *data)
	{
	/* Enumerate devices in xenstore and watch for changes. */
	xenbus_probe_devices(&xenbus_backend);
	register_xenbus_watch(&be_watch);

	return NOTIFY_DONE;
	}

	static int backend_reclaim_memory(struct device dev, void data)
	{
	const struct xenbus_driver *drv;
	struct xenbus_device *xdev;

	if (!dev->driver)
	return 0;
	drv = to_xenbus_driver(dev->driver);
	if (drv && drv->reclaim_memory) {
	xdev = to_xenbus_device(dev);
	if (down_trylock(&xdev->reclaim_sem))
	return 0;
	drv->reclaim_memory(xdev);
	up(&xdev->reclaim_sem);
	}
	return 0;
	}

	/*
	* Returns 0 always because we are using shrinker to only detect memory
	* pressure.
	*/
	static unsigned long backend_shrink_memory_count(struct shrinker *shrinker,
	struct shrink_control *sc)
	{
	bus_for_each_dev(&xenbus_backend.bus, NULL, NULL,
	backend_reclaim_memory);
	return 0;
	}

	static struct shrinker backend_memory_shrinker = {
	.count_objects = backend_shrink_memory_count,
	.seeks = DEFAULT_SEEKS,
	};

	static int __init xenbus_probe_backend_init(void)
	{
	static struct notifier_block xenstore_notifier = {
	.notifier_call = backend_probe_and_watch
	};
	int err;

	DPRINTK("");

	/* Register ourselves with the kernel bus subsystem */
	err = bus_register(&xenbus_backend.bus);
	if (err)
	return err;

	register_xenstore_notifier(&xenstore_notifier);

	if (register_shrinker(&backend_memory_shrinker, "xen-backend"))
	pr_warn("shrinker registration failed\n");

	return 0;
	}
	subsys_initcall(xenbus_probe_backend_init);