9p: Reorganization of 9p file system code

This patchset moves non-filesystem interfaces of v9fs from fs/9p to net/9p.
It moves the transport, packet marshalling and connection layers to net/9p
leaving only the VFS related files in fs/9p.  This work is being done in
preparation for in-kernel 9p servers as well as alternate 9p clients (other
than VFS).

Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 1050 insertions, 0 deletions

diff --git a/net/9p/mux.c b/net/9p/mux.c
new file mode 100644
index 00000000000..c3aa87bc8b9
--- /dev/null
+++ b/net/9p/mux.c
@@ -0,0 +1,1050 @@
+/*
+ * net/9p/mux.c
+ *
+ * Protocol Multiplexer
+ *
+ *  Copyright (C) 2004 by Eric Van Hensbergen <ericvh@gmail.com>
+ *  Copyright (C) 2004-2005 by Latchesar Ionkov <lucho@ionkov.net>
+ *
+ *  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.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to:
+ *  Free Software Foundation
+ *  51 Franklin Street, Fifth Floor
+ *  Boston, MA  02111-1301  USA
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/kthread.h>
+#include <linux/idr.h>
+#include <linux/mutex.h>
+#include <net/9p/9p.h>
+#include <net/9p/transport.h>
+#include <net/9p/conn.h>
+
+#define ERREQFLUSH	1
+#define SCHED_TIMEOUT	10
+#define MAXPOLLWADDR	2
+
+enum {
+	Rworksched = 1,		/* read work scheduled or running */
+	Rpending = 2,		/* can read */
+	Wworksched = 4,		/* write work scheduled or running */
+	Wpending = 8,		/* can write */
+};
+
+enum {
+	None,
+	Flushing,
+	Flushed,
+};
+
+struct p9_mux_poll_task;
+
+struct p9_req {
+	spinlock_t lock; /* protect request structure */
+	int tag;
+	struct p9_fcall *tcall;
+	struct p9_fcall *rcall;
+	int err;
+	p9_conn_req_callback cb;
+	void *cba;
+	int flush;
+	struct list_head req_list;
+};
+
+struct p9_conn {
+	spinlock_t lock; /* protect lock structure */
+	struct list_head mux_list;
+	struct p9_mux_poll_task *poll_task;
+	int msize;
+	unsigned char *extended;
+	struct p9_transport *trans;
+	struct p9_idpool *tagpool;
+	int err;
+	wait_queue_head_t equeue;
+	struct list_head req_list;
+	struct list_head unsent_req_list;
+	struct p9_fcall *rcall;
+	int rpos;
+	char *rbuf;
+	int wpos;
+	int wsize;
+	char *wbuf;
+	wait_queue_t poll_wait[MAXPOLLWADDR];
+	wait_queue_head_t *poll_waddr[MAXPOLLWADDR];
+	poll_table pt;
+	struct work_struct rq;
+	struct work_struct wq;
+	unsigned long wsched;
+};
+
+struct p9_mux_poll_task {
+	struct task_struct *task;
+	struct list_head mux_list;
+	int muxnum;
+};
+
+struct p9_mux_rpc {
+	struct p9_conn *m;
+	int err;
+	struct p9_fcall *tcall;
+	struct p9_fcall *rcall;
+	wait_queue_head_t wqueue;
+};
+
+static int p9_poll_proc(void *);
+static void p9_read_work(struct work_struct *work);
+static void p9_write_work(struct work_struct *work);
+static void p9_pollwait(struct file *filp, wait_queue_head_t *wait_address,
+			  poll_table * p);
+static u16 p9_mux_get_tag(struct p9_conn *);
+static void p9_mux_put_tag(struct p9_conn *, u16);
+
+static DEFINE_MUTEX(p9_mux_task_lock);
+static struct workqueue_struct *p9_mux_wq;
+
+static int p9_mux_num;
+static int p9_mux_poll_task_num;
+static struct p9_mux_poll_task p9_mux_poll_tasks[100];
+
+int p9_mux_global_init(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(p9_mux_poll_tasks); i++)
+		p9_mux_poll_tasks[i].task = NULL;
+
+	p9_mux_wq = create_workqueue("v9fs");
+	if (!p9_mux_wq) {
+		printk(KERN_WARNING "v9fs: mux: creating workqueue failed\n");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+void p9_mux_global_exit(void)
+{
+	destroy_workqueue(p9_mux_wq);
+}
+
+/**
+ * p9_mux_calc_poll_procs - calculates the number of polling procs
+ * based on the number of mounted v9fs filesystems.
+ *
+ * The current implementation returns sqrt of the number of mounts.
+ */
+static int p9_mux_calc_poll_procs(int muxnum)
+{
+	int n;
+
+	if (p9_mux_poll_task_num)
+		n = muxnum / p9_mux_poll_task_num +
+		    (muxnum % p9_mux_poll_task_num ? 1 : 0);
+	else
+		n = 1;
+
+	if (n > ARRAY_SIZE(p9_mux_poll_tasks))
+		n = ARRAY_SIZE(p9_mux_poll_tasks);
+
+	return n;
+}
+
+static int p9_mux_poll_start(struct p9_conn *m)
+{
+	int i, n;
+	struct p9_mux_poll_task *vpt, *vptlast;
+	struct task_struct *pproc;
+
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p muxnum %d procnum %d\n", m, p9_mux_num,
+		p9_mux_poll_task_num);
+	mutex_lock(&p9_mux_task_lock);
+
+	n = p9_mux_calc_poll_procs(p9_mux_num + 1);
+	if (n > p9_mux_poll_task_num) {
+		for (i = 0; i < ARRAY_SIZE(p9_mux_poll_tasks); i++) {
+			if (p9_mux_poll_tasks[i].task == NULL) {
+				vpt = &p9_mux_poll_tasks[i];
+				P9_DPRINTK(P9_DEBUG_MUX, "create proc %p\n",
+									vpt);
+				pproc = kthread_create(p9_poll_proc, vpt,
+								"v9fs-poll");
+
+				if (!IS_ERR(pproc)) {
+					vpt->task = pproc;
+					INIT_LIST_HEAD(&vpt->mux_list);
+					vpt->muxnum = 0;
+					p9_mux_poll_task_num++;
+					wake_up_process(vpt->task);
+				}
+				break;
+			}
+		}
+
+		if (i >= ARRAY_SIZE(p9_mux_poll_tasks))
+			P9_DPRINTK(P9_DEBUG_ERROR,
+					"warning: no free poll slots\n");
+	}
+
+	n = (p9_mux_num + 1) / p9_mux_poll_task_num +
+	    ((p9_mux_num + 1) % p9_mux_poll_task_num ? 1 : 0);
+
+	vptlast = NULL;
+	for (i = 0; i < ARRAY_SIZE(p9_mux_poll_tasks); i++) {
+		vpt = &p9_mux_poll_tasks[i];
+		if (vpt->task != NULL) {
+			vptlast = vpt;
+			if (vpt->muxnum < n) {
+				P9_DPRINTK(P9_DEBUG_MUX, "put in proc %d\n", i);
+				list_add(&m->mux_list, &vpt->mux_list);
+				vpt->muxnum++;
+				m->poll_task = vpt;
+				memset(&m->poll_waddr, 0,
+							sizeof(m->poll_waddr));
+				init_poll_funcptr(&m->pt, p9_pollwait);
+				break;
+			}
+		}
+	}
+
+	if (i >= ARRAY_SIZE(p9_mux_poll_tasks)) {
+		if (vptlast == NULL)
+			return -ENOMEM;
+
+		P9_DPRINTK(P9_DEBUG_MUX, "put in proc %d\n", i);
+		list_add(&m->mux_list, &vptlast->mux_list);
+		vptlast->muxnum++;
+		m->poll_task = vptlast;
+		memset(&m->poll_waddr, 0, sizeof(m->poll_waddr));
+		init_poll_funcptr(&m->pt, p9_pollwait);
+	}
+
+	p9_mux_num++;
+	mutex_unlock(&p9_mux_task_lock);
+
+	return 0;
+}
+
+static void p9_mux_poll_stop(struct p9_conn *m)
+{
+	int i;
+	struct p9_mux_poll_task *vpt;
+
+	mutex_lock(&p9_mux_task_lock);
+	vpt = m->poll_task;
+	list_del(&m->mux_list);
+	for (i = 0; i < ARRAY_SIZE(m->poll_waddr); i++) {
+		if (m->poll_waddr[i] != NULL) {
+			remove_wait_queue(m->poll_waddr[i], &m->poll_wait[i]);
+			m->poll_waddr[i] = NULL;
+		}
+	}
+	vpt->muxnum--;
+	if (!vpt->muxnum) {
+		P9_DPRINTK(P9_DEBUG_MUX, "destroy proc %p\n", vpt);
+		kthread_stop(vpt->task);
+		vpt->task = NULL;
+		p9_mux_poll_task_num--;
+	}
+	p9_mux_num--;
+	mutex_unlock(&p9_mux_task_lock);
+}
+
+/**
+ * p9_conn_create - allocate and initialize the per-session mux data
+ * Creates the polling task if this is the first session.
+ *
+ * @trans - transport structure
+ * @msize - maximum message size
+ * @extended - pointer to the extended flag
+ */
+struct p9_conn *p9_conn_create(struct p9_transport *trans, int msize,
+				    unsigned char *extended)
+{
+	int i, n;
+	struct p9_conn *m, *mtmp;
+
+	P9_DPRINTK(P9_DEBUG_MUX, "transport %p msize %d\n", trans, msize);
+	m = kmalloc(sizeof(struct p9_conn), GFP_KERNEL);
+	if (!m)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock_init(&m->lock);
+	INIT_LIST_HEAD(&m->mux_list);
+	m->msize = msize;
+	m->extended = extended;
+	m->trans = trans;
+	m->tagpool = p9_idpool_create();
+	if (!m->tagpool) {
+		kfree(m);
+		return ERR_PTR(PTR_ERR(m->tagpool));
+	}
+
+	m->err = 0;
+	init_waitqueue_head(&m->equeue);
+	INIT_LIST_HEAD(&m->req_list);
+	INIT_LIST_HEAD(&m->unsent_req_list);
+	m->rcall = NULL;
+	m->rpos = 0;
+	m->rbuf = NULL;
+	m->wpos = m->wsize = 0;
+	m->wbuf = NULL;
+	INIT_WORK(&m->rq, p9_read_work);
+	INIT_WORK(&m->wq, p9_write_work);
+	m->wsched = 0;
+	memset(&m->poll_waddr, 0, sizeof(m->poll_waddr));
+	m->poll_task = NULL;
+	n = p9_mux_poll_start(m);
+	if (n)
+		return ERR_PTR(n);
+
+	n = trans->poll(trans, &m->pt);
+	if (n & POLLIN) {
+		P9_DPRINTK(P9_DEBUG_MUX, "mux %p can read\n", m);
+		set_bit(Rpending, &m->wsched);
+	}
+
+	if (n & POLLOUT) {
+		P9_DPRINTK(P9_DEBUG_MUX, "mux %p can write\n", m);
+		set_bit(Wpending, &m->wsched);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(m->poll_waddr); i++) {
+		if (IS_ERR(m->poll_waddr[i])) {
+			p9_mux_poll_stop(m);
+			mtmp = (void *)m->poll_waddr;	/* the error code */
+			kfree(m);
+			m = mtmp;
+			break;
+		}
+	}
+
+	return m;
+}
+EXPORT_SYMBOL(p9_conn_create);
+
+/**
+ * p9_mux_destroy - cancels all pending requests and frees mux resources
+ */
+void p9_conn_destroy(struct p9_conn *m)
+{
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p prev %p next %p\n", m,
+		m->mux_list.prev, m->mux_list.next);
+	p9_conn_cancel(m, -ECONNRESET);
+
+	if (!list_empty(&m->req_list)) {
+		/* wait until all processes waiting on this session exit */
+		P9_DPRINTK(P9_DEBUG_MUX,
+			"mux %p waiting for empty request queue\n", m);
+		wait_event_timeout(m->equeue, (list_empty(&m->req_list)), 5000);
+		P9_DPRINTK(P9_DEBUG_MUX, "mux %p request queue empty: %d\n", m,
+			list_empty(&m->req_list));
+	}
+
+	p9_mux_poll_stop(m);
+	m->trans = NULL;
+	p9_idpool_destroy(m->tagpool);
+	kfree(m);
+}
+EXPORT_SYMBOL(p9_conn_destroy);
+
+/**
+ * p9_pollwait - called by files poll operation to add v9fs-poll task
+ * 	to files wait queue
+ */
+static void
+p9_pollwait(struct file *filp, wait_queue_head_t *wait_address,
+	      poll_table * p)
+{
+	int i;
+	struct p9_conn *m;
+
+	m = container_of(p, struct p9_conn, pt);
+	for (i = 0; i < ARRAY_SIZE(m->poll_waddr); i++)
+		if (m->poll_waddr[i] == NULL)
+			break;
+
+	if (i >= ARRAY_SIZE(m->poll_waddr)) {
+		P9_DPRINTK(P9_DEBUG_ERROR, "not enough wait_address slots\n");
+		return;
+	}
+
+	m->poll_waddr[i] = wait_address;
+
+	if (!wait_address) {
+		P9_DPRINTK(P9_DEBUG_ERROR, "no wait_address\n");
+		m->poll_waddr[i] = ERR_PTR(-EIO);
+		return;
+	}
+
+	init_waitqueue_entry(&m->poll_wait[i], m->poll_task->task);
+	add_wait_queue(wait_address, &m->poll_wait[i]);
+}
+
+/**
+ * p9_poll_mux - polls a mux and schedules read or write works if necessary
+ */
+static void p9_poll_mux(struct p9_conn *m)
+{
+	int n;
+
+	if (m->err < 0)
+		return;
+
+	n = m->trans->poll(m->trans, NULL);
+	if (n < 0 || n & (POLLERR | POLLHUP | POLLNVAL)) {
+		P9_DPRINTK(P9_DEBUG_MUX, "error mux %p err %d\n", m, n);
+		if (n >= 0)
+			n = -ECONNRESET;
+		p9_conn_cancel(m, n);
+	}
+
+	if (n & POLLIN) {
+		set_bit(Rpending, &m->wsched);
+		P9_DPRINTK(P9_DEBUG_MUX, "mux %p can read\n", m);
+		if (!test_and_set_bit(Rworksched, &m->wsched)) {
+			P9_DPRINTK(P9_DEBUG_MUX, "schedule read work %p\n", m);
+			queue_work(p9_mux_wq, &m->rq);
+		}
+	}
+
+	if (n & POLLOUT) {
+		set_bit(Wpending, &m->wsched);
+		P9_DPRINTK(P9_DEBUG_MUX, "mux %p can write\n", m);
+		if ((m->wsize || !list_empty(&m->unsent_req_list))
+		    && !test_and_set_bit(Wworksched, &m->wsched)) {
+			P9_DPRINTK(P9_DEBUG_MUX, "schedule write work %p\n", m);
+			queue_work(p9_mux_wq, &m->wq);
+		}
+	}
+}
+
+/**
+ * p9_poll_proc - polls all v9fs transports for new events and queues
+ * 	the appropriate work to the work queue
+ */
+static int p9_poll_proc(void *a)
+{
+	struct p9_conn *m, *mtmp;
+	struct p9_mux_poll_task *vpt;
+
+	vpt = a;
+	P9_DPRINTK(P9_DEBUG_MUX, "start %p %p\n", current, vpt);
+	while (!kthread_should_stop()) {
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		list_for_each_entry_safe(m, mtmp, &vpt->mux_list, mux_list) {
+			p9_poll_mux(m);
+		}
+
+		P9_DPRINTK(P9_DEBUG_MUX, "sleeping...\n");
+		schedule_timeout(SCHED_TIMEOUT * HZ);
+	}
+
+	__set_current_state(TASK_RUNNING);
+	P9_DPRINTK(P9_DEBUG_MUX, "finish\n");
+	return 0;
+}
+
+/**
+ * p9_write_work - called when a transport can send some data
+ */
+static void p9_write_work(struct work_struct *work)
+{
+	int n, err;
+	struct p9_conn *m;
+	struct p9_req *req;
+
+	m = container_of(work, struct p9_conn, wq);
+
+	if (m->err < 0) {
+		clear_bit(Wworksched, &m->wsched);
+		return;
+	}
+
+	if (!m->wsize) {
+		if (list_empty(&m->unsent_req_list)) {
+			clear_bit(Wworksched, &m->wsched);
+			return;
+		}
+
+		spin_lock(&m->lock);
+again:
+		req = list_entry(m->unsent_req_list.next, struct p9_req,
+			       req_list);
+		list_move_tail(&req->req_list, &m->req_list);
+		if (req->err == ERREQFLUSH)
+			goto again;
+
+		m->wbuf = req->tcall->sdata;
+		m->wsize = req->tcall->size;
+		m->wpos = 0;
+		spin_unlock(&m->lock);
+	}
+
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p pos %d size %d\n", m, m->wpos,
+								m->wsize);
+	clear_bit(Wpending, &m->wsched);
+	err = m->trans->write(m->trans, m->wbuf + m->wpos, m->wsize - m->wpos);
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p sent %d bytes\n", m, err);
+	if (err == -EAGAIN) {
+		clear_bit(Wworksched, &m->wsched);
+		return;
+	}
+
+	if (err <= 0)
+		goto error;
+
+	m->wpos += err;
+	if (m->wpos == m->wsize)
+		m->wpos = m->wsize = 0;
+
+	if (m->wsize == 0 && !list_empty(&m->unsent_req_list)) {
+		if (test_and_clear_bit(Wpending, &m->wsched))
+			n = POLLOUT;
+		else
+			n = m->trans->poll(m->trans, NULL);
+
+		if (n & POLLOUT) {
+			P9_DPRINTK(P9_DEBUG_MUX, "schedule write work %p\n", m);
+			queue_work(p9_mux_wq, &m->wq);
+		} else
+			clear_bit(Wworksched, &m->wsched);
+	} else
+		clear_bit(Wworksched, &m->wsched);
+
+	return;
+
+error:
+	p9_conn_cancel(m, err);
+	clear_bit(Wworksched, &m->wsched);
+}
+
+static void process_request(struct p9_conn *m, struct p9_req *req)
+{
+	int ecode;
+	struct p9_str *ename;
+
+	if (!req->err && req->rcall->id == P9_RERROR) {
+		ecode = req->rcall->params.rerror.errno;
+		ename = &req->rcall->params.rerror.error;
+
+		P9_DPRINTK(P9_DEBUG_MUX, "Rerror %.*s\n", ename->len,
+								ename->str);
+
+		if (*m->extended)
+			req->err = -ecode;
+
+		if (!req->err) {
+			req->err = p9_errstr2errno(ename->str, ename->len);
+
+			if (!req->err) {	/* string match failed */
+				PRINT_FCALL_ERROR("unknown error", req->rcall);
+			}
+
+			if (!req->err)
+				req->err = -ESERVERFAULT;
+		}
+	} else if (req->tcall && req->rcall->id != req->tcall->id + 1) {
+		P9_DPRINTK(P9_DEBUG_ERROR,
+				"fcall mismatch: expected %d, got %d\n",
+				req->tcall->id + 1, req->rcall->id);
+		if (!req->err)
+			req->err = -EIO;
+	}
+}
+
+/**
+ * p9_read_work - called when there is some data to be read from a transport
+ */
+static void p9_read_work(struct work_struct *work)
+{
+	int n, err;
+	struct p9_conn *m;
+	struct p9_req *req, *rptr, *rreq;
+	struct p9_fcall *rcall;
+	char *rbuf;
+
+	m = container_of(work, struct p9_conn, rq);
+
+	if (m->err < 0)
+		return;
+
+	rcall = NULL;
+	P9_DPRINTK(P9_DEBUG_MUX, "start mux %p pos %d\n", m, m->rpos);
+
+	if (!m->rcall) {
+		m->rcall =
+		    kmalloc(sizeof(struct p9_fcall) + m->msize, GFP_KERNEL);
+		if (!m->rcall) {
+			err = -ENOMEM;
+			goto error;
+		}
+
+		m->rbuf = (char *)m->rcall + sizeof(struct p9_fcall);
+		m->rpos = 0;
+	}
+
+	clear_bit(Rpending, &m->wsched);
+	err = m->trans->read(m->trans, m->rbuf + m->rpos, m->msize - m->rpos);
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p got %d bytes\n", m, err);
+	if (err == -EAGAIN) {
+		clear_bit(Rworksched, &m->wsched);
+		return;
+	}
+
+	if (err <= 0)
+		goto error;
+
+	m->rpos += err;
+	while (m->rpos > 4) {
+		n = le32_to_cpu(*(__le32 *) m->rbuf);
+		if (n >= m->msize) {
+			P9_DPRINTK(P9_DEBUG_ERROR,
+				"requested packet size too big: %d\n", n);
+			err = -EIO;
+			goto error;
+		}
+
+		if (m->rpos < n)
+			break;
+
+		err =
+		    p9_deserialize_fcall(m->rbuf, n, m->rcall, *m->extended);
+		if (err < 0) {
+			goto error;
+		}
+
+#ifdef CONFIG_NET_9P_DEBUG
+		if ((p9_debug_level&P9_DEBUG_FCALL) == P9_DEBUG_FCALL) {
+			char buf[150];
+
+			p9_printfcall(buf, sizeof(buf), m->rcall,
+				*m->extended);
+			printk(KERN_NOTICE ">>> %p %s\n", m, buf);
+		}
+#endif
+
+		rcall = m->rcall;
+		rbuf = m->rbuf;
+		if (m->rpos > n) {
+			m->rcall = kmalloc(sizeof(struct p9_fcall) + m->msize,
+					   GFP_KERNEL);
+			if (!m->rcall) {
+				err = -ENOMEM;
+				goto error;
+			}
+
+			m->rbuf = (char *)m->rcall + sizeof(struct p9_fcall);
+			memmove(m->rbuf, rbuf + n, m->rpos - n);
+			m->rpos -= n;
+		} else {
+			m->rcall = NULL;
+			m->rbuf = NULL;
+			m->rpos = 0;
+		}
+
+		P9_DPRINTK(P9_DEBUG_MUX, "mux %p fcall id %d tag %d\n", m,
+							rcall->id, rcall->tag);
+
+		req = NULL;
+		spin_lock(&m->lock);
+		list_for_each_entry_safe(rreq, rptr, &m->req_list, req_list) {
+			if (rreq->tag == rcall->tag) {
+				req = rreq;
+				if (req->flush != Flushing)
+					list_del(&req->req_list);
+				break;
+			}
+		}
+		spin_unlock(&m->lock);
+
+		if (req) {
+			req->rcall = rcall;
+			process_request(m, req);
+
+			if (req->flush != Flushing) {
+				if (req->cb)
+					(*req->cb) (req, req->cba);
+				else
+					kfree(req->rcall);
+
+				wake_up(&m->equeue);
+			}
+		} else {
+			if (err >= 0 && rcall->id != P9_RFLUSH)
+				P9_DPRINTK(P9_DEBUG_ERROR,
+				  "unexpected response mux %p id %d tag %d\n",
+				  m, rcall->id, rcall->tag);
+			kfree(rcall);
+		}
+	}
+
+	if (!list_empty(&m->req_list)) {
+		if (test_and_clear_bit(Rpending, &m->wsched))
+			n = POLLIN;
+		else
+			n = m->trans->poll(m->trans, NULL);
+
+		if (n & POLLIN) {
+			P9_DPRINTK(P9_DEBUG_MUX, "schedule read work %p\n", m);
+			queue_work(p9_mux_wq, &m->rq);
+		} else
+			clear_bit(Rworksched, &m->wsched);
+	} else
+		clear_bit(Rworksched, &m->wsched);
+
+	return;
+
+error:
+	p9_conn_cancel(m, err);
+	clear_bit(Rworksched, &m->wsched);
+}
+
+/**
+ * p9_send_request - send 9P request
+ * The function can sleep until the request is scheduled for sending.
+ * The function can be interrupted. Return from the function is not
+ * a guarantee that the request is sent successfully. Can return errors
+ * that can be retrieved by PTR_ERR macros.
+ *
+ * @m: mux data
+ * @tc: request to be sent
+ * @cb: callback function to call when response is received
+ * @cba: parameter to pass to the callback function
+ */
+static struct p9_req *p9_send_request(struct p9_conn *m,
+					  struct p9_fcall *tc,
+					  p9_conn_req_callback cb, void *cba)
+{
+	int n;
+	struct p9_req *req;
+
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p task %p tcall %p id %d\n", m, current,
+		tc, tc->id);
+	if (m->err < 0)
+		return ERR_PTR(m->err);
+
+	req = kmalloc(sizeof(struct p9_req), GFP_KERNEL);
+	if (!req)
+		return ERR_PTR(-ENOMEM);
+
+	if (tc->id == P9_TVERSION)
+		n = P9_NOTAG;
+	else
+		n = p9_mux_get_tag(m);
+
+	if (n < 0)
+		return ERR_PTR(-ENOMEM);
+
+	p9_set_tag(tc, n);
+
+#ifdef CONFIG_NET_9P_DEBUG
+	if ((p9_debug_level&P9_DEBUG_FCALL) == P9_DEBUG_FCALL) {
+		char buf[150];
+
+		p9_printfcall(buf, sizeof(buf), tc, *m->extended);
+		printk(KERN_NOTICE "<<< %p %s\n", m, buf);
+	}
+#endif
+
+	spin_lock_init(&req->lock);
+	req->tag = n;
+	req->tcall = tc;
+	req->rcall = NULL;
+	req->err = 0;
+	req->cb = cb;
+	req->cba = cba;
+	req->flush = None;
+
+	spin_lock(&m->lock);
+	list_add_tail(&req->req_list, &m->unsent_req_list);
+	spin_unlock(&m->lock);
+
+	if (test_and_clear_bit(Wpending, &m->wsched))
+		n = POLLOUT;
+	else
+		n = m->trans->poll(m->trans, NULL);
+
+	if (n & POLLOUT && !test_and_set_bit(Wworksched, &m->wsched))
+		queue_work(p9_mux_wq, &m->wq);
+
+	return req;
+}
+
+static void p9_mux_free_request(struct p9_conn *m, struct p9_req *req)
+{
+	p9_mux_put_tag(m, req->tag);
+	kfree(req);
+}
+
+static void p9_mux_flush_cb(struct p9_req *freq, void *a)
+{
+	p9_conn_req_callback cb;
+	int tag;
+	struct p9_conn *m;
+	struct p9_req *req, *rreq, *rptr;
+
+	m = a;
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p tc %p rc %p err %d oldtag %d\n", m,
+		freq->tcall, freq->rcall, freq->err,
+		freq->tcall->params.tflush.oldtag);
+
+	spin_lock(&m->lock);
+	cb = NULL;
+	tag = freq->tcall->params.tflush.oldtag;
+	req = NULL;
+	list_for_each_entry_safe(rreq, rptr, &m->req_list, req_list) {
+		if (rreq->tag == tag) {
+			req = rreq;
+			list_del(&req->req_list);
+			break;
+		}
+	}
+	spin_unlock(&m->lock);
+
+	if (req) {
+		spin_lock(&req->lock);
+		req->flush = Flushed;
+		spin_unlock(&req->lock);
+
+		if (req->cb)
+			(*req->cb) (req, req->cba);
+		else
+			kfree(req->rcall);
+
+		wake_up(&m->equeue);
+	}
+
+	kfree(freq->tcall);
+	kfree(freq->rcall);
+	p9_mux_free_request(m, freq);
+}
+
+static int
+p9_mux_flush_request(struct p9_conn *m, struct p9_req *req)
+{
+	struct p9_fcall *fc;
+	struct p9_req *rreq, *rptr;
+
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p req %p tag %d\n", m, req, req->tag);
+
+	/* if a response was received for a request, do nothing */
+	spin_lock(&req->lock);
+	if (req->rcall || req->err) {
+		spin_unlock(&req->lock);
+		P9_DPRINTK(P9_DEBUG_MUX,
+			"mux %p req %p response already received\n", m, req);
+		return 0;
+	}
+
+	req->flush = Flushing;
+	spin_unlock(&req->lock);
+
+	spin_lock(&m->lock);
+	/* if the request is not sent yet, just remove it from the list */
+	list_for_each_entry_safe(rreq, rptr, &m->unsent_req_list, req_list) {
+		if (rreq->tag == req->tag) {
+			P9_DPRINTK(P9_DEBUG_MUX,
+			   "mux %p req %p request is not sent yet\n", m, req);
+			list_del(&rreq->req_list);
+			req->flush = Flushed;
+			spin_unlock(&m->lock);
+			if (req->cb)
+				(*req->cb) (req, req->cba);
+			return 0;
+		}
+	}
+	spin_unlock(&m->lock);
+
+	clear_thread_flag(TIF_SIGPENDING);
+	fc = p9_create_tflush(req->tag);
+	p9_send_request(m, fc, p9_mux_flush_cb, m);
+	return 1;
+}
+
+static void
+p9_conn_rpc_cb(struct p9_req *req, void *a)
+{
+	struct p9_mux_rpc *r;
+
+	P9_DPRINTK(P9_DEBUG_MUX, "req %p r %p\n", req, a);
+	r = a;
+	r->rcall = req->rcall;
+	r->err = req->err;
+
+	if (req->flush != None && !req->err)
+		r->err = -ERESTARTSYS;
+
+	wake_up(&r->wqueue);
+}
+
+/**
+ * p9_mux_rpc - sends 9P request and waits until a response is available.
+ *	The function can be interrupted.
+ * @m: mux data
+ * @tc: request to be sent
+ * @rc: pointer where a pointer to the response is stored
+ */
+int
+p9_conn_rpc(struct p9_conn *m, struct p9_fcall *tc,
+	     struct p9_fcall **rc)
+{
+	int err, sigpending;
+	unsigned long flags;
+	struct p9_req *req;
+	struct p9_mux_rpc r;
+
+	r.err = 0;
+	r.tcall = tc;
+	r.rcall = NULL;
+	r.m = m;
+	init_waitqueue_head(&r.wqueue);
+
+	if (rc)
+		*rc = NULL;
+
+	sigpending = 0;
+	if (signal_pending(current)) {
+		sigpending = 1;
+		clear_thread_flag(TIF_SIGPENDING);
+	}
+
+	req = p9_send_request(m, tc, p9_conn_rpc_cb, &r);
+	if (IS_ERR(req)) {
+		err = PTR_ERR(req);
+		P9_DPRINTK(P9_DEBUG_MUX, "error %d\n", err);
+		return err;
+	}
+
+	err = wait_event_interruptible(r.wqueue, r.rcall != NULL || r.err < 0);
+	if (r.err < 0)
+		err = r.err;
+
+	if (err == -ERESTARTSYS && m->trans->status == Connected
+							&& m->err == 0) {
+		if (p9_mux_flush_request(m, req)) {
+			/* wait until we get response of the flush message */
+			do {
+				clear_thread_flag(TIF_SIGPENDING);
+				err = wait_event_interruptible(r.wqueue,
+					r.rcall || r.err);
+			} while (!r.rcall && !r.err && err == -ERESTARTSYS &&
+				m->trans->status == Connected && !m->err);
+
+			err = -ERESTARTSYS;
+		}
+		sigpending = 1;
+	}
+
+	if (sigpending) {
+		spin_lock_irqsave(&current->sighand->siglock, flags);
+		recalc_sigpending();
+		spin_unlock_irqrestore(&current->sighand->siglock, flags);
+	}
+
+	if (rc)
+		*rc = r.rcall;
+	else
+		kfree(r.rcall);
+
+	p9_mux_free_request(m, req);
+	if (err > 0)
+		err = -EIO;
+
+	return err;
+}
+EXPORT_SYMBOL(p9_conn_rpc);
+
+#ifdef P9_NONBLOCK
+/**
+ * p9_conn_rpcnb - sends 9P request without waiting for response.
+ * @m: mux data
+ * @tc: request to be sent
+ * @cb: callback function to be called when response arrives
+ * @cba: value to pass to the callback function
+ */
+int p9_conn_rpcnb(struct p9_conn *m, struct p9_fcall *tc,
+		   p9_conn_req_callback cb, void *a)
+{
+	int err;
+	struct p9_req *req;
+
+	req = p9_send_request(m, tc, cb, a);
+	if (IS_ERR(req)) {
+		err = PTR_ERR(req);
+		P9_DPRINTK(P9_DEBUG_MUX, "error %d\n", err);
+		return PTR_ERR(req);
+	}
+
+	P9_DPRINTK(P9_DEBUG_MUX, "mux %p tc %p tag %d\n", m, tc, req->tag);
+	return 0;
+}
+EXPORT_SYMBOL(p9_conn_rpcnb);
+#endif /* P9_NONBLOCK */
+
+/**
+ * p9_conn_cancel - cancel all pending requests with error
+ * @m: mux data
+ * @err: error code
+ */
+void p9_conn_cancel(struct p9_conn *m, int err)
+{
+	struct p9_req *req, *rtmp;
+	LIST_HEAD(cancel_list);
+
+	P9_DPRINTK(P9_DEBUG_ERROR, "mux %p err %d\n", m, err);
+	m->err = err;
+	spin_lock(&m->lock);
+	list_for_each_entry_safe(req, rtmp, &m->req_list, req_list) {
+		list_move(&req->req_list, &cancel_list);
+	}
+	list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) {
+		list_move(&req->req_list, &cancel_list);
+	}
+	spin_unlock(&m->lock);
+
+	list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) {
+		list_del(&req->req_list);
+		if (!req->err)
+			req->err = err;
+
+		if (req->cb)
+			(*req->cb) (req, req->cba);
+		else
+			kfree(req->rcall);
+	}
+
+	wake_up(&m->equeue);
+}
+EXPORT_SYMBOL(p9_conn_cancel);
+
+static u16 p9_mux_get_tag(struct p9_conn *m)
+{
+	int tag;
+
+	tag = p9_idpool_get(m->tagpool);
+	if (tag < 0)
+		return P9_NOTAG;
+	else
+		return (u16) tag;
+}
+
+static void p9_mux_put_tag(struct p9_conn *m, u16 tag)
+{
+	if (tag != P9_NOTAG && p9_idpool_check(tag, m->tagpool))
+		p9_idpool_put(tag, m->tagpool);
+}