![Jan Beulich](/assets/img/avatar_default.png)
Acked-by: Ian Campbell <ian.campbell@citrix.com> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Jan Beulich <jbeulich@suse.com> [v1: Rebased on upstream] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
630 lines
14 KiB
C
630 lines
14 KiB
C
/*
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* Driver giving user-space access to the kernel's xenbus connection
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* to xenstore.
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*
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* Copyright (c) 2005, Christian Limpach
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* Copyright (c) 2005, Rusty Russell, IBM Corporation
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation; or, when distributed
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* separately from the Linux kernel or incorporated into other
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* software packages, subject to the following license:
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this source file (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use, copy, modify,
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* merge, publish, distribute, sublicense, and/or sell copies of the Software,
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* and to permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*
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* Changes:
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* 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem
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* and /proc/xen compatibility mount point.
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* Turned xenfs into a loadable module.
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*/
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/uio.h>
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#include <linux/notifier.h>
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#include <linux/wait.h>
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#include <linux/fs.h>
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#include <linux/poll.h>
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#include <linux/mutex.h>
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#include <linux/sched.h>
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#include <linux/spinlock.h>
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#include <linux/mount.h>
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#include <linux/pagemap.h>
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#include <linux/uaccess.h>
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#include <linux/init.h>
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#include <linux/namei.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/miscdevice.h>
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#include <linux/module.h>
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#include "xenbus_comms.h"
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#include <xen/xenbus.h>
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#include <xen/xen.h>
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#include <asm/xen/hypervisor.h>
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MODULE_LICENSE("GPL");
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/*
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* An element of a list of outstanding transactions, for which we're
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* still waiting a reply.
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*/
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struct xenbus_transaction_holder {
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struct list_head list;
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struct xenbus_transaction handle;
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};
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/*
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* A buffer of data on the queue.
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*/
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struct read_buffer {
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struct list_head list;
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unsigned int cons;
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unsigned int len;
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char msg[];
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};
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struct xenbus_file_priv {
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/*
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* msgbuffer_mutex is held while partial requests are built up
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* and complete requests are acted on. It therefore protects
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* the "transactions" and "watches" lists, and the partial
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* request length and buffer.
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*
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* reply_mutex protects the reply being built up to return to
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* usermode. It nests inside msgbuffer_mutex but may be held
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* alone during a watch callback.
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*/
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struct mutex msgbuffer_mutex;
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/* In-progress transactions */
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struct list_head transactions;
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/* Active watches. */
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struct list_head watches;
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/* Partial request. */
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unsigned int len;
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union {
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struct xsd_sockmsg msg;
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char buffer[XENSTORE_PAYLOAD_MAX];
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} u;
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/* Response queue. */
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struct mutex reply_mutex;
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struct list_head read_buffers;
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wait_queue_head_t read_waitq;
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};
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/* Read out any raw xenbus messages queued up. */
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static ssize_t xenbus_file_read(struct file *filp,
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char __user *ubuf,
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size_t len, loff_t *ppos)
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{
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struct xenbus_file_priv *u = filp->private_data;
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struct read_buffer *rb;
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unsigned i;
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int ret;
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mutex_lock(&u->reply_mutex);
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again:
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while (list_empty(&u->read_buffers)) {
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mutex_unlock(&u->reply_mutex);
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if (filp->f_flags & O_NONBLOCK)
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return -EAGAIN;
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ret = wait_event_interruptible(u->read_waitq,
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!list_empty(&u->read_buffers));
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if (ret)
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return ret;
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mutex_lock(&u->reply_mutex);
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}
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rb = list_entry(u->read_buffers.next, struct read_buffer, list);
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i = 0;
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while (i < len) {
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unsigned sz = min((unsigned)len - i, rb->len - rb->cons);
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ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
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i += sz - ret;
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rb->cons += sz - ret;
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if (ret != 0) {
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if (i == 0)
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i = -EFAULT;
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goto out;
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}
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/* Clear out buffer if it has been consumed */
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if (rb->cons == rb->len) {
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list_del(&rb->list);
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kfree(rb);
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if (list_empty(&u->read_buffers))
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break;
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rb = list_entry(u->read_buffers.next,
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struct read_buffer, list);
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}
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}
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if (i == 0)
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goto again;
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out:
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mutex_unlock(&u->reply_mutex);
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return i;
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}
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/*
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* Add a buffer to the queue. Caller must hold the appropriate lock
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* if the queue is not local. (Commonly the caller will build up
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* multiple queued buffers on a temporary local list, and then add it
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* to the appropriate list under lock once all the buffers have een
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* successfully allocated.)
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*/
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static int queue_reply(struct list_head *queue, const void *data, size_t len)
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{
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struct read_buffer *rb;
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if (len == 0)
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return 0;
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rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
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if (rb == NULL)
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return -ENOMEM;
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rb->cons = 0;
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rb->len = len;
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memcpy(rb->msg, data, len);
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list_add_tail(&rb->list, queue);
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return 0;
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}
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/*
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* Free all the read_buffer s on a list.
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* Caller must have sole reference to list.
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*/
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static void queue_cleanup(struct list_head *list)
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{
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struct read_buffer *rb;
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while (!list_empty(list)) {
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rb = list_entry(list->next, struct read_buffer, list);
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list_del(list->next);
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kfree(rb);
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}
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}
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struct watch_adapter {
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struct list_head list;
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struct xenbus_watch watch;
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struct xenbus_file_priv *dev_data;
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char *token;
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};
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static void free_watch_adapter(struct watch_adapter *watch)
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{
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kfree(watch->watch.node);
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kfree(watch->token);
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kfree(watch);
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}
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static struct watch_adapter *alloc_watch_adapter(const char *path,
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const char *token)
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{
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struct watch_adapter *watch;
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watch = kzalloc(sizeof(*watch), GFP_KERNEL);
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if (watch == NULL)
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goto out_fail;
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watch->watch.node = kstrdup(path, GFP_KERNEL);
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if (watch->watch.node == NULL)
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goto out_free;
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watch->token = kstrdup(token, GFP_KERNEL);
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if (watch->token == NULL)
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goto out_free;
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return watch;
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out_free:
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free_watch_adapter(watch);
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out_fail:
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return NULL;
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}
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static void watch_fired(struct xenbus_watch *watch,
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const char **vec,
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unsigned int len)
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{
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struct watch_adapter *adap;
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struct xsd_sockmsg hdr;
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const char *path, *token;
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int path_len, tok_len, body_len, data_len = 0;
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int ret;
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LIST_HEAD(staging_q);
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adap = container_of(watch, struct watch_adapter, watch);
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path = vec[XS_WATCH_PATH];
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token = adap->token;
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path_len = strlen(path) + 1;
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tok_len = strlen(token) + 1;
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if (len > 2)
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data_len = vec[len] - vec[2] + 1;
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body_len = path_len + tok_len + data_len;
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hdr.type = XS_WATCH_EVENT;
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hdr.len = body_len;
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mutex_lock(&adap->dev_data->reply_mutex);
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ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
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if (!ret)
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ret = queue_reply(&staging_q, path, path_len);
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if (!ret)
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ret = queue_reply(&staging_q, token, tok_len);
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if (!ret && len > 2)
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ret = queue_reply(&staging_q, vec[2], data_len);
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if (!ret) {
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/* success: pass reply list onto watcher */
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list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
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wake_up(&adap->dev_data->read_waitq);
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} else
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queue_cleanup(&staging_q);
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mutex_unlock(&adap->dev_data->reply_mutex);
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}
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static int xenbus_write_transaction(unsigned msg_type,
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struct xenbus_file_priv *u)
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{
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int rc;
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void *reply;
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struct xenbus_transaction_holder *trans = NULL;
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LIST_HEAD(staging_q);
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if (msg_type == XS_TRANSACTION_START) {
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trans = kmalloc(sizeof(*trans), GFP_KERNEL);
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if (!trans) {
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rc = -ENOMEM;
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goto out;
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}
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}
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reply = xenbus_dev_request_and_reply(&u->u.msg);
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if (IS_ERR(reply)) {
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kfree(trans);
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rc = PTR_ERR(reply);
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goto out;
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}
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if (msg_type == XS_TRANSACTION_START) {
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trans->handle.id = simple_strtoul(reply, NULL, 0);
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list_add(&trans->list, &u->transactions);
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} else if (msg_type == XS_TRANSACTION_END) {
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list_for_each_entry(trans, &u->transactions, list)
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if (trans->handle.id == u->u.msg.tx_id)
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break;
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BUG_ON(&trans->list == &u->transactions);
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list_del(&trans->list);
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kfree(trans);
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}
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mutex_lock(&u->reply_mutex);
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rc = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg));
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if (!rc)
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rc = queue_reply(&staging_q, reply, u->u.msg.len);
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if (!rc) {
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list_splice_tail(&staging_q, &u->read_buffers);
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wake_up(&u->read_waitq);
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} else {
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queue_cleanup(&staging_q);
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}
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mutex_unlock(&u->reply_mutex);
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kfree(reply);
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out:
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return rc;
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}
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static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
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{
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struct watch_adapter *watch, *tmp_watch;
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char *path, *token;
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int err, rc;
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LIST_HEAD(staging_q);
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path = u->u.buffer + sizeof(u->u.msg);
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token = memchr(path, 0, u->u.msg.len);
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if (token == NULL) {
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rc = -EILSEQ;
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goto out;
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}
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token++;
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if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
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rc = -EILSEQ;
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goto out;
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}
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if (msg_type == XS_WATCH) {
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watch = alloc_watch_adapter(path, token);
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if (watch == NULL) {
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rc = -ENOMEM;
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goto out;
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}
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watch->watch.callback = watch_fired;
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watch->dev_data = u;
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err = register_xenbus_watch(&watch->watch);
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if (err) {
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free_watch_adapter(watch);
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rc = err;
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goto out;
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}
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list_add(&watch->list, &u->watches);
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} else {
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list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
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if (!strcmp(watch->token, token) &&
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!strcmp(watch->watch.node, path)) {
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unregister_xenbus_watch(&watch->watch);
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list_del(&watch->list);
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free_watch_adapter(watch);
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break;
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}
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}
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}
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/* Success. Synthesize a reply to say all is OK. */
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{
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struct {
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struct xsd_sockmsg hdr;
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char body[3];
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} __packed reply = {
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{
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.type = msg_type,
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.len = sizeof(reply.body)
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},
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"OK"
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};
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mutex_lock(&u->reply_mutex);
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rc = queue_reply(&u->read_buffers, &reply, sizeof(reply));
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wake_up(&u->read_waitq);
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mutex_unlock(&u->reply_mutex);
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}
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out:
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return rc;
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}
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static ssize_t xenbus_file_write(struct file *filp,
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const char __user *ubuf,
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size_t len, loff_t *ppos)
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{
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struct xenbus_file_priv *u = filp->private_data;
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uint32_t msg_type;
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int rc = len;
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int ret;
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LIST_HEAD(staging_q);
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/*
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* We're expecting usermode to be writing properly formed
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* xenbus messages. If they write an incomplete message we
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* buffer it up. Once it is complete, we act on it.
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*/
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/*
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* Make sure concurrent writers can't stomp all over each
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* other's messages and make a mess of our partial message
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* buffer. We don't make any attemppt to stop multiple
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* writers from making a mess of each other's incomplete
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* messages; we're just trying to guarantee our own internal
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* consistency and make sure that single writes are handled
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* atomically.
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*/
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mutex_lock(&u->msgbuffer_mutex);
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/* Get this out of the way early to avoid confusion */
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if (len == 0)
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goto out;
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/* Can't write a xenbus message larger we can buffer */
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if (len > sizeof(u->u.buffer) - u->len) {
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/* On error, dump existing buffer */
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u->len = 0;
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rc = -EINVAL;
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goto out;
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}
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ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
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if (ret != 0) {
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rc = -EFAULT;
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goto out;
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}
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/* Deal with a partial copy. */
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len -= ret;
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rc = len;
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u->len += len;
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/* Return if we haven't got a full message yet */
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if (u->len < sizeof(u->u.msg))
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goto out; /* not even the header yet */
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/* If we're expecting a message that's larger than we can
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possibly send, dump what we have and return an error. */
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if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
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rc = -E2BIG;
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u->len = 0;
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goto out;
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}
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if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
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goto out; /* incomplete data portion */
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/*
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* OK, now we have a complete message. Do something with it.
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*/
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msg_type = u->u.msg.type;
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switch (msg_type) {
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case XS_WATCH:
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case XS_UNWATCH:
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/* (Un)Ask for some path to be watched for changes */
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ret = xenbus_write_watch(msg_type, u);
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break;
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default:
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/* Send out a transaction */
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ret = xenbus_write_transaction(msg_type, u);
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break;
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}
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if (ret != 0)
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rc = ret;
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/* Buffered message consumed */
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u->len = 0;
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out:
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mutex_unlock(&u->msgbuffer_mutex);
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return rc;
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}
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static int xenbus_file_open(struct inode *inode, struct file *filp)
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{
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struct xenbus_file_priv *u;
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if (xen_store_evtchn == 0)
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return -ENOENT;
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nonseekable_open(inode, filp);
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u = kzalloc(sizeof(*u), GFP_KERNEL);
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if (u == NULL)
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return -ENOMEM;
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INIT_LIST_HEAD(&u->transactions);
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INIT_LIST_HEAD(&u->watches);
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INIT_LIST_HEAD(&u->read_buffers);
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init_waitqueue_head(&u->read_waitq);
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mutex_init(&u->reply_mutex);
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mutex_init(&u->msgbuffer_mutex);
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filp->private_data = u;
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return 0;
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}
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static int xenbus_file_release(struct inode *inode, struct file *filp)
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|
{
|
|
struct xenbus_file_priv *u = filp->private_data;
|
|
struct xenbus_transaction_holder *trans, *tmp;
|
|
struct watch_adapter *watch, *tmp_watch;
|
|
struct read_buffer *rb, *tmp_rb;
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
|
|
list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
|
|
list_del(&rb->list);
|
|
kfree(rb);
|
|
}
|
|
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 xen_xenbus_fops = {
|
|
.read = xenbus_file_read,
|
|
.write = xenbus_file_write,
|
|
.open = xenbus_file_open,
|
|
.release = xenbus_file_release,
|
|
.poll = xenbus_file_poll,
|
|
.llseek = no_llseek,
|
|
};
|
|
EXPORT_SYMBOL_GPL(xen_xenbus_fops);
|
|
|
|
static struct miscdevice xenbus_dev = {
|
|
.minor = MISC_DYNAMIC_MINOR,
|
|
.name = "xen/xenbus",
|
|
.fops = &xen_xenbus_fops,
|
|
};
|
|
|
|
static int __init xenbus_init(void)
|
|
{
|
|
int err;
|
|
|
|
if (!xen_domain())
|
|
return -ENODEV;
|
|
|
|
err = misc_register(&xenbus_dev);
|
|
if (err)
|
|
printk(KERN_ERR "Could not register xenbus frontend device\n");
|
|
return err;
|
|
}
|
|
|
|
static void __exit xenbus_exit(void)
|
|
{
|
|
misc_deregister(&xenbus_dev);
|
|
}
|
|
|
|
module_init(xenbus_init);
|
|
module_exit(xenbus_exit);
|