From: Alex Zeffertt <alex.zeffertt@xxxxxxxxxxxxx>
The xenfs filesystem exports various interfaces to usermode. Initially
this exports a file to allow usermode to interact with xenbus/xenstore.
Traditionally this appeared in /proc/xen. Rather than extending procfs,
this patch adds a backward-compat mountpoint on /proc/xen, and provides
a xenfs filesystem which can be mounted there.
[
I did quite a lot of work to this code as a result of review, which is
why this is a repost rather than a delta. The changes are:
- Moved the XENFS_SUPER_MAGIC to linux/magic.h
- Added comments to answer the "what's this for?" questions (I hope)
- Split things out into smaller functions
- Cleaned up type of queue_reply(), removed casts
- Added a mutex to protect struct xenbus_file_priv. This protects
the list heads, and the partial message buffer. There were
several ways in which usermode could overwrite the kernel's
memory via races without this locking.
- Fixed a bug in which usermode could start sending a message
which can never be sent, leaving the file descriptor in a
useless state.
I still don't know whether the list_empty test in xenbus_file_poll()
needs a barrier.
-J ]
Signed-off-by: Alex Zeffertt <alex.zeffertt@xxxxxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
drivers/xen/Kconfig | 24 +
drivers/xen/Makefile | 2
drivers/xen/xenbus/xenbus_probe.c | 28 +
drivers/xen/xenbus/xenbus_xs.c | 1
drivers/xen/xenfs/Makefile | 3
drivers/xen/xenfs/super.c | 64 +++
drivers/xen/xenfs/xenbus.c | 593 +++++++++++++++++++++++++++++++++++++
drivers/xen/xenfs/xenfs.h | 6
include/linux/magic.h | 2
include/xen/xenbus.h | 2
10 files changed, 717 insertions(+), 8 deletions(-)
===================================================================
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -17,3 +17,27 @@
is not accidentally visible to other domains. Is it more
secure, but slightly less efficient.
If in doubt, say yes.
+
+config XENFS
+ tristate "Xen filesystem"
+ depends on XEN
+ default y
+ help
+ The xen filesystem provides a way for domains to share
+ information with each other and with the hypervisor.
+ For example, by reading and writing the "xenbus" file, guests
+ may pass arbitrary information to the initial domain.
+ If in doubt, say yes.
+
+config XEN_COMPAT_XENFS
+ bool "Create compatibility mount point /proc/xen"
+ depends on XENFS
+ default y
+ help
+ The old xenstore userspace tools expect to find "xenbus"
+ under /proc/xen, but "xenbus" is now found at the root of the
+ xenfs filesystem. Selecting this causes the kernel to create
+ the compatibilty mount point /proc/xen if it is running on
+ a xen platform.
+ If in doubt, say yes.
+
===================================================================
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -1,5 +1,7 @@
obj-y += grant-table.o features.o events.o manage.o
obj-y += xenbus/
+
obj-$(CONFIG_HOTPLUG_CPU) += cpu_hotplug.o
obj-$(CONFIG_XEN_XENCOMM) += xencomm.o
obj-$(CONFIG_XEN_BALLOON) += balloon.o
+obj-$(CONFIG_XENFS) += xenfs/
\ No newline at end of file
===================================================================
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -40,6 +40,7 @@
#include <linux/ctype.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
+#include <linux/proc_fs.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/mutex.h>
@@ -55,7 +56,10 @@
#include "xenbus_comms.h"
#include "xenbus_probe.h"
+
int xen_store_evtchn;
+EXPORT_SYMBOL(xen_store_evtchn);
+
struct xenstore_domain_interface *xen_store_interface;
static unsigned long xen_store_mfn;
@@ -166,6 +170,9 @@
return read_otherend_details(xendev, "backend-id", "backend");
}
+static struct device_attribute xenbus_dev_attrs[] = {
+ __ATTR_NULL
+};
/* Bus type for frontend drivers. */
static struct xen_bus_type xenbus_frontend = {
@@ -174,12 +181,13 @@
.get_bus_id = frontend_bus_id,
.probe = xenbus_probe_frontend,
.bus = {
- .name = "xen",
- .match = xenbus_match,
- .uevent = xenbus_uevent,
- .probe = xenbus_dev_probe,
- .remove = xenbus_dev_remove,
- .shutdown = xenbus_dev_shutdown,
+ .name = "xen",
+ .match = xenbus_match,
+ .uevent = xenbus_uevent,
+ .probe = xenbus_dev_probe,
+ .remove = xenbus_dev_remove,
+ .shutdown = xenbus_dev_shutdown,
+ .dev_attrs = xenbus_dev_attrs,
},
};
@@ -849,6 +857,14 @@
if (!xen_initial_domain())
xenbus_probe(NULL);
+#ifdef CONFIG_XEN_COMPAT_XENFS
+ /*
+ * Create xenfs mountpoint in /proc for compatibility with
+ * utilities that expect to find "xenbus" under "/proc/xen".
+ */
+ proc_mkdir("xen", NULL);
+#endif
+
return 0;
out_unreg_back:
===================================================================
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -184,6 +184,7 @@
return ret;
}
+EXPORT_SYMBOL(xenbus_dev_request_and_reply);
/* Send message to xs, get kmalloc'ed reply. ERR_PTR() on error. */
static void *xs_talkv(struct xenbus_transaction t,
===================================================================
--- /dev/null
+++ b/drivers/xen/xenfs/Makefile
@@ -0,0 +1,3 @@
+obj-$(CONFIG_XENFS) += xenfs.o
+
+xenfs-objs = super.o xenbus.o
\ No newline at end of file
===================================================================
--- /dev/null
+++ b/drivers/xen/xenfs/super.c
@@ -0,0 +1,64 @@
+/*
+ * xenfs.c - a filesystem for passing info between the a domain and
+ * the hypervisor.
+ *
+ * 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem
+ * and /proc/xen compatibility mount point.
+ * Turned xenfs into a loadable module.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/magic.h>
+
+#include "xenfs.h"
+
+#include <asm/xen/hypervisor.h>
+
+MODULE_DESCRIPTION("Xen filesystem");
+MODULE_LICENSE("GPL");
+
+static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
+{
+ static struct tree_descr xenfs_files[] = {
+ [2] = {"xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR},
+ {""},
+ };
+
+ return simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
+}
+
+static int xenfs_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name,
+ void *data, struct vfsmount *mnt)
+{
+ return get_sb_single(fs_type, flags, data, xenfs_fill_super, mnt);
+}
+
+static struct file_system_type xenfs_type = {
+ .owner = THIS_MODULE,
+ .name = "xenfs",
+ .get_sb = xenfs_get_sb,
+ .kill_sb = kill_litter_super,
+};
+
+static int __init xenfs_init(void)
+{
+ if (xen_pv_domain())
+ return register_filesystem(&xenfs_type);
+
+ printk(KERN_INFO "XENFS: not registering filesystem on non-xen
platform\n");
+ return 0;
+}
+
+static void __exit xenfs_exit(void)
+{
+ if (xen_pv_domain())
+ unregister_filesystem(&xenfs_type);
+}
+
+module_init(xenfs_init);
+module_exit(xenfs_exit);
+
===================================================================
--- /dev/null
+++ b/drivers/xen/xenfs/xenbus.c
@@ -0,0 +1,593 @@
+/*
+ * Driver giving user-space access to the kernel's xenbus connection
+ * to xenstore.
+ *
+ * Copyright (c) 2005, Christian Limpach
+ * Copyright (c) 2005, Rusty Russell, IBM Corporation
+ *
+ * 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.
+ *
+ * Changes:
+ * 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem
+ * and /proc/xen compatibility mount point.
+ * Turned xenfs into a loadable module.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/uio.h>
+#include <linux/notifier.h>
+#include <linux/wait.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+#include <linux/mount.h>
+#include <linux/pagemap.h>
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <linux/namei.h>
+#include <linux/string.h>
+
+#include "xenfs.h"
+#include "../xenbus/xenbus_comms.h"
+
+#include <xen/xenbus.h>
+#include <asm/xen/hypervisor.h>
+
+/*
+ * An element of a list of outstanding transactions, for which we're
+ * still waiting a reply.
+ */
+struct xenbus_transaction_holder {
+ struct list_head list;
+ struct xenbus_transaction handle;
+};
+
+/*
+ * A buffer of data on the queue.
+ */
+struct read_buffer {
+ struct list_head list;
+ unsigned int cons;
+ unsigned int len;
+ char msg[];
+};
+
+struct xenbus_file_priv {
+ /*
+ * msgbuffer_mutex is held while partial requests are built up
+ * and complete requests are acted on. It therefore protects
+ * the "transactions" and "watches" lists, and the partial
+ * request length and buffer.
+ *
+ * reply_mutex protects the reply being built up to return to
+ * usermode. It nests inside msgbuffer_mutex but may be held
+ * alone during a watch callback.
+ */
+ struct mutex msgbuffer_mutex;
+
+ /* In-progress transactions */
+ struct list_head transactions;
+
+ /* Active watches. */
+ struct list_head watches;
+
+ /* Partial request. */
+ unsigned int len;
+ union {
+ struct xsd_sockmsg msg;
+ char buffer[PAGE_SIZE];
+ } u;
+
+ /* Response queue. */
+ struct mutex reply_mutex;
+ struct list_head read_buffers;
+ wait_queue_head_t read_waitq;
+
+};
+
+/* Read out any raw xenbus messages queued up. */
+static ssize_t xenbus_file_read(struct file *filp,
+ char __user *ubuf,
+ size_t len, loff_t *ppos)
+{
+ struct xenbus_file_priv *u = filp->private_data;
+ struct read_buffer *rb;
+ unsigned i;
+ int ret;
+
+ mutex_lock(&u->reply_mutex);
+ while (list_empty(&u->read_buffers)) {
+ mutex_unlock(&u->reply_mutex);
+ ret = wait_event_interruptible(u->read_waitq,
+ !list_empty(&u->read_buffers));
+ if (ret)
+ return ret;
+ mutex_lock(&u->reply_mutex);
+ }
+
+ rb = list_entry(u->read_buffers.next, struct read_buffer, list);
+ i = 0;
+ while (i < len) {
+ unsigned sz = min((unsigned)len - i, rb->cons - rb->len);
+
+ ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
+
+ i += sz - ret;
+ rb->cons += sz - ret;
+
+ if (ret != sz) {
+ if (i == 0)
+ i = -EFAULT;
+ goto out;
+ }
+
+ /* Clear out buffer if it has been consumed */
+ if (rb->cons == rb->len) {
+ list_del(&rb->list);
+ kfree(rb);
+ if (list_empty(&u->read_buffers))
+ break;
+ rb = list_entry(u->read_buffers.next,
+ struct read_buffer, list);
+ }
+ }
+
+out:
+ mutex_unlock(&u->reply_mutex);
+ return i;
+}
+
+/*
+ * Add a buffer to the queue. Caller must hold the appropriate lock
+ * if the queue is not local. (Commonly the caller will build up
+ * multiple queued buffers on a temporary local list, and then add it
+ * to the appropriate list under lock once all the buffers have een
+ * successfully allocated.)
+ */
+static int queue_reply(struct list_head *queue, const void *data, size_t len)
+{
+ struct read_buffer *rb;
+
+ if (len == 0)
+ return 0;
+
+ rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
+ if (rb == NULL)
+ return -ENOMEM;
+
+ rb->cons = 0;
+ rb->len = len;
+
+ memcpy(rb->msg, data, len);
+
+ list_add_tail(&rb->list, queue);
+ return 0;
+}
+
+/*
+ * Free all the read_buffer s on a list.
+ * Caller must have sole reference to list.
+ */
+static void queue_cleanup(struct list_head *list)
+{
+ struct read_buffer *rb;
+
+ while (!list_empty(list)) {
+ rb = list_entry(list->next, struct read_buffer, list);
+ list_del(list->next);
+ kfree(rb);
+ }
+}
+
+struct watch_adapter {
+ struct list_head list;
+ struct xenbus_watch watch;
+ struct xenbus_file_priv *dev_data;
+ char *token;
+};
+
+static void free_watch_adapter(struct watch_adapter *watch)
+{
+ kfree(watch->watch.node);
+ kfree(watch->token);
+ kfree(watch);
+}
+
+static struct watch_adapter *alloc_watch_adapter(const char *path,
+ const char *token)
+{
+ struct watch_adapter *watch;
+
+ watch = kzalloc(sizeof(*watch), GFP_KERNEL);
+ if (watch == NULL)
+ goto out_fail;
+
+ watch->watch.node = kstrdup(path, GFP_KERNEL);
+ if (watch->watch.node == NULL)
+ goto out_free;
+
+ watch->token = kstrdup(token, GFP_KERNEL);
+ if (watch->token == NULL)
+ goto out_free;
+
+ return watch;
+
+out_free:
+ free_watch_adapter(watch);
+
+out_fail:
+ return NULL;
+}
+
+static void watch_fired(struct xenbus_watch *watch,
+ const char **vec,
+ unsigned int len)
+{
+ struct watch_adapter *adap;
+ struct xsd_sockmsg hdr;
+ const char *path, *token;
+ int path_len, tok_len, body_len, data_len = 0;
+ int ret;
+ LIST_HEAD(staging_q);
+
+ adap = container_of(watch, struct watch_adapter, watch);
+
+ path = vec[XS_WATCH_PATH];
+ token = adap->token;
+
+ path_len = strlen(path) + 1;
+ tok_len = strlen(token) + 1;
+ if (len > 2)
+ data_len = vec[len] - vec[2] + 1;
+ body_len = path_len + tok_len + data_len;
+
+ hdr.type = XS_WATCH_EVENT;
+ hdr.len = body_len;
+
+ mutex_lock(&adap->dev_data->reply_mutex);
+
+ ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
+ if (!ret)
+ ret = queue_reply(&staging_q, path, path_len);
+ if (!ret)
+ ret = queue_reply(&staging_q, token, tok_len);
+ if (!ret && len > 2)
+ ret = queue_reply(&staging_q, vec[2], data_len);
+
+ if (!ret) {
+ /* success: pass reply list onto watcher */
+ list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
+ wake_up(&adap->dev_data->read_waitq);
+ } else
+ queue_cleanup(&staging_q);
+
+ mutex_unlock(&adap->dev_data->reply_mutex);
+}
+
+static int xenbus_write_transaction(unsigned msg_type,
+ struct xenbus_file_priv *u)
+{
+ int rc, ret;
+ void *reply;
+ struct xenbus_transaction_holder *trans = NULL;
+ LIST_HEAD(staging_q);
+
+ if (msg_type == XS_TRANSACTION_START) {
+ trans = kmalloc(sizeof(*trans), GFP_KERNEL);
+ if (!trans) {
+ rc = -ENOMEM;
+ goto out;
+ }
+ }
+
+ reply = xenbus_dev_request_and_reply(&u->u.msg);
+ if (IS_ERR(reply)) {
+ kfree(trans);
+ rc = PTR_ERR(reply);
+ goto out;
+ }
+
+ if (msg_type == XS_TRANSACTION_START) {
+ trans->handle.id = simple_strtoul(reply, NULL, 0);
+
+ list_add(&trans->list, &u->transactions);
+ } else if (msg_type == XS_TRANSACTION_END) {
+ list_for_each_entry(trans, &u->transactions, list)
+ if (trans->handle.id == u->u.msg.tx_id)
+ break;
+ BUG_ON(&trans->list == &u->transactions);
+ list_del(&trans->list);
+
+ kfree(trans);
+ }
+
+ mutex_lock(&u->reply_mutex);
+ ret = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg));
+ if (!ret)
+ ret = queue_reply(&staging_q, reply, u->u.msg.len);
+ if (!ret) {
+ list_splice_tail(&staging_q, &u->read_buffers);
+ wake_up(&u->read_waitq);
+ } else {
+ queue_cleanup(&staging_q);
+ rc = ret;
+ }
+ mutex_unlock(&u->reply_mutex);
+
+ kfree(reply);
+
+out:
+ return rc;
+}
+
+static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
+{
+ struct watch_adapter *watch, *tmp_watch;
+ char *path, *token;
+ int err, rc;
+ LIST_HEAD(staging_q);
+
+ path = u->u.buffer + sizeof(u->u.msg);
+ token = memchr(path, 0, u->u.msg.len);
+ if (token == NULL) {
+ rc = -EILSEQ;
+ goto out;
+ }
+ token++;
+
+ if (msg_type == XS_WATCH) {
+ watch = alloc_watch_adapter(path, token);
+ if (watch == NULL) {
+ rc = -ENOMEM;
+ goto out;
+ }
+
+ watch->watch.callback = watch_fired;
+ watch->dev_data = u;
+
+ err = register_xenbus_watch(&watch->watch);
+ if (err) {
+ free_watch_adapter(watch);
+ rc = err;
+ goto out;
+ }
+ list_add(&watch->list, &u->watches);
+ } else {
+ list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
+ if (!strcmp(watch->token, token) &&
+ !strcmp(watch->watch.node, path)) {
+ unregister_xenbus_watch(&watch->watch);
+ list_del(&watch->list);
+ free_watch_adapter(watch);
+ break;
+ }
+ }
+ }
+
+ /* Success. Synthesize a reply to say all is OK. */
+ {
+ struct {
+ struct xsd_sockmsg hdr;
+ char body[3];
+ } __packed reply = {
+ {
+ .type = msg_type,
+ .len = sizeof(reply.body)
+ },
+ "OK"
+ };
+
+ mutex_lock(&u->reply_mutex);
+ rc = queue_reply(&u->read_buffers, &reply, sizeof(reply));
+ mutex_unlock(&u->reply_mutex);
+ }
+
+out:
+ return rc;
+}
+
+static ssize_t xenbus_file_write(struct file *filp,
+ const char __user *ubuf,
+ size_t len, loff_t *ppos)
+{
+ struct xenbus_file_priv *u = filp->private_data;
+ uint32_t msg_type;
+ int rc = len;
+ int ret;
+ LIST_HEAD(staging_q);
+
+ /*
+ * We're expecting usermode to be writing properly formed
+ * xenbus messages. If they write an incomplete message we
+ * buffer it up. Once it is complete, we act on it.
+ */
+
+ /*
+ * Make sure concurrent writers can't stomp all over each
+ * other's messages and make a mess of our partial message
+ * buffer. We don't make any attemppt to stop multiple
+ * writers from making a mess of each other's incomplete
+ * messages; we're just trying to guarantee our own internal
+ * consistency and make sure that single writes are handled
+ * atomically.
+ */
+ mutex_lock(&u->msgbuffer_mutex);
+
+ /* Get this out of the way early to avoid confusion */
+ if (len == 0)
+ goto out;
+
+ /* Can't write a xenbus message larger we can buffer */
+ if ((len + u->len) > sizeof(u->u.buffer)) {
+ /* On error, dump existing buffer */
+ u->len = 0;
+ rc = -EINVAL;
+ goto out;
+ }
+
+ ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
+
+ if (ret == len) {
+ rc = -EFAULT;
+ goto out;
+ }
+
+ /* Deal with a partial copy. */
+ len -= ret;
+ rc = len;
+
+ u->len += len;
+
+ /* Return if we haven't got a full message yet */
+ if (u->len < sizeof(u->u.msg))
+ goto out; /* not even the header yet */
+
+ /* If we're expecting a message that's larger than we can
+ possibly send, dump what we have and return an error. */
+ if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
+ rc = -E2BIG;
+ u->len = 0;
+ goto out;
+ }
+
+ if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
+ goto out; /* incomplete data portion */
+
+ /*
+ * OK, now we have a complete message. Do something with it.
+ */
+
+ msg_type = u->u.msg.type;
+
+ switch (msg_type) {
+ case XS_TRANSACTION_START:
+ case XS_TRANSACTION_END:
+ case XS_DIRECTORY:
+ case XS_READ:
+ case XS_GET_PERMS:
+ case XS_RELEASE:
+ case XS_GET_DOMAIN_PATH:
+ case XS_WRITE:
+ case XS_MKDIR:
+ case XS_RM:
+ case XS_SET_PERMS:
+ /* Send out a transaction */
+ ret = xenbus_write_transaction(msg_type, u);
+ break;
+
+ case XS_WATCH:
+ case XS_UNWATCH:
+ /* (Un)Ask for some path to be watched for changes */
+ ret = xenbus_write_watch(msg_type, u);
+ break;
+
+ default:
+ ret = -EINVAL;
+ break;
+ }
+ if (ret != 0)
+ rc = ret;
+
+ /* Buffered message consumed */
+ u->len = 0;
+
+ out:
+ mutex_unlock(&u->msgbuffer_mutex);
+ return rc;
+}
+
+static int xenbus_file_open(struct inode *inode, struct file *filp)
+{
+ struct xenbus_file_priv *u;
+
+ if (xen_store_evtchn == 0)
+ return -ENOENT;
+
+ nonseekable_open(inode, filp);
+
+ u = kzalloc(sizeof(*u), GFP_KERNEL);
+ if (u == NULL)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&u->transactions);
+ INIT_LIST_HEAD(&u->watches);
+ INIT_LIST_HEAD(&u->read_buffers);
+ init_waitqueue_head(&u->read_waitq);
+
+ mutex_init(&u->reply_mutex);
+ mutex_init(&u->msgbuffer_mutex);
+
+ filp->private_data = u;
+
+ return 0;
+}
+
+static int xenbus_file_release(struct inode *inode, struct file *filp)
+{
+ struct xenbus_file_priv *u = filp->private_data;
+ struct xenbus_transaction_holder *trans, *tmp;
+ struct watch_adapter *watch, *tmp_watch;
+
+ /*
+ * No need for locking here because there are no other users,
+ * by definition.
+ */
+
+ list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
+ xenbus_transaction_end(trans->handle, 1);
+ list_del(&trans->list);
+ kfree(trans);
+ }
+
+ list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
+ unregister_xenbus_watch(&watch->watch);
+ list_del(&watch->list);
+ free_watch_adapter(watch);
+ }
+
+ kfree(u);
+
+ return 0;
+}
+
+static unsigned int xenbus_file_poll(struct file *file, poll_table *wait)
+{
+ struct xenbus_file_priv *u = file->private_data;
+
+ poll_wait(file, &u->read_waitq, wait);
+ if (!list_empty(&u->read_buffers))
+ return POLLIN | POLLRDNORM;
+ return 0;
+}
+
+const struct file_operations xenbus_file_ops = {
+ .read = xenbus_file_read,
+ .write = xenbus_file_write,
+ .open = xenbus_file_open,
+ .release = xenbus_file_release,
+ .poll = xenbus_file_poll,
+};
===================================================================
--- /dev/null
+++ b/drivers/xen/xenfs/xenfs.h
@@ -0,0 +1,6 @@
+#ifndef _XENFS_XENBUS_H
+#define _XENFS_XENBUS_H
+
+extern const struct file_operations xenbus_file_ops;
+
+#endif /* _XENFS_XENBUS_H */
===================================================================
--- a/include/linux/magic.h
+++ b/include/linux/magic.h
@@ -46,5 +46,7 @@
#define FUTEXFS_SUPER_MAGIC 0xBAD1DEA
#define INOTIFYFS_SUPER_MAGIC 0x2BAD1DEA
+#define XENFS_SUPER_MAGIC 0xabba1974
+
#define STACK_END_MAGIC 0x57AC6E9D
#endif /* __LINUX_MAGIC_H__ */
===================================================================
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -136,8 +136,6 @@
/* Nil transaction ID. */
#define XBT_NIL ((struct xenbus_transaction) { 0 })
-int __init xenbus_dev_init(void);
-
char **xenbus_directory(struct xenbus_transaction t,
const char *dir, const char *node, unsigned int *num);
void *xenbus_read(struct xenbus_transaction t,
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