[PATCH] v9fs: new multiplexer implementation

New multiplexer implementation. Decreases the number of kernel threads
required. Better handling when the user process receives a signal.

Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Cc: Eric Van Hensbergen <ericvh@ericvh.myip.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 794 insertions, 328 deletions

diff --git a/fs/9p/mux.c b/fs/9p/mux.c
index 8835b576f744..62b6ad0767e1 100644
--- a/fs/9p/mux.c
+++ b/fs/9p/mux.c
@@ -4,7 +4,7 @@
  * Protocol Multiplexer
  *
  *  Copyright (C) 2004 by Eric Van Hensbergen <ericvh@gmail.com>
- *  Copyright (C) 2004 by Latchesar Ionkov <lucho@ionkov.net>
+ *  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 as published by
@@ -28,6 +28,7 @@
 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
+#include <linux/poll.h>
 #include <linux/kthread.h>
 #include <linux/idr.h>
 
@@ -38,438 +39,903 @@
 #include "conv.h"
 #include "mux.h"
 
-/**
- * dprintcond - print condition of session info
- * @v9ses: session info structure
- * @req: RPC request structure
- *
- */
+#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 */
+};
+
+struct v9fs_mux_poll_task;
+
+struct v9fs_req {
+        int tag;
+        struct v9fs_fcall *tcall;
+        struct v9fs_fcall *rcall;
+        int err;
+        v9fs_mux_req_callback cb;
+        void *cba;
+        struct list_head req_list;
+};
+
+struct v9fs_mux_data {
+        spinlock_t lock;
+        struct list_head mux_list;
+        struct v9fs_mux_poll_task *poll_task;
+        int msize;
+        unsigned char *extended;
+        struct v9fs_transport *trans;
+        struct v9fs_idpool tidpool;
+        int err;
+        wait_queue_head_t equeue;
+        struct list_head req_list;
+        struct list_head unsent_req_list;
+        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 v9fs_mux_poll_task {
+        struct task_struct *task;
+        struct list_head mux_list;
+        int muxnum;
+};
+
+struct v9fs_mux_rpc {
+        struct v9fs_mux_data *m;
+        struct v9fs_req *req;
+        int err;
+        struct v9fs_fcall *rcall;
+        wait_queue_head_t wqueue;
+};
+
+static int v9fs_poll_proc(void *);
+static void v9fs_read_work(void *);
+static void v9fs_write_work(void *);
+static void v9fs_pollwait(struct file *filp, wait_queue_head_t * wait_address,
+                          poll_table * p);
+
+static DECLARE_MUTEX(v9fs_mux_task_lock);
+static struct workqueue_struct *v9fs_mux_wq;
+
+static int v9fs_mux_num;
+static int v9fs_mux_poll_task_num;
+static struct v9fs_mux_poll_task v9fs_mux_poll_tasks[100];
+
+void v9fs_mux_global_init(void)
+{
+        int i;
+
+        for (i = 0; i < ARRAY_SIZE(v9fs_mux_poll_tasks); i++)
+                v9fs_mux_poll_tasks[i].task = NULL;
+
+        v9fs_mux_wq = create_workqueue("v9fs");
+}
 
-static inline int
-dprintcond(struct v9fs_session_info *v9ses, struct v9fs_rpcreq *req)
+void v9fs_mux_global_exit(void)
 {
-        dprintk(DEBUG_MUX, "condition: %d, %p\n", v9ses->transport->status,
-                req->rcall);
-        return 0;
+        destroy_workqueue(v9fs_mux_wq);
 }
 
 /**
- * xread - force read of a certain number of bytes
- * @v9ses: session info structure
- * @ptr: pointer to buffer
- * @sz: number of bytes to read
+ * v9fs_mux_calc_poll_procs - calculates the number of polling procs
+ * based on the number of mounted v9fs filesystems.
  *
- * Chuck Cranor CS-533 project1
+ * The current implementation returns sqrt of the number of mounts.
  */
+inline int v9fs_mux_calc_poll_procs(int muxnum)
+{
+        int n;
+
+        if (v9fs_mux_poll_task_num)
+                n = muxnum / v9fs_mux_poll_task_num +
+                    (muxnum % v9fs_mux_poll_task_num ? 1 : 0);
+        else
+                n = 1;
+
+        if (n > ARRAY_SIZE(v9fs_mux_poll_tasks))
+                n = ARRAY_SIZE(v9fs_mux_poll_tasks);
 
-static int xread(struct v9fs_session_info *v9ses, void *ptr, unsigned long sz)
+        return n;
+}
+
+static void v9fs_mux_poll_start(struct v9fs_mux_data *m)
 {
-        int rd = 0;
-        int ret = 0;
-        while (rd < sz) {
-                ret = v9ses->transport->read(v9ses->transport, ptr, sz - rd);
-                if (ret <= 0) {
-                        dprintk(DEBUG_ERROR, "xread errno %d\n", ret);
-                        return ret;
+        int i, n;
+        struct v9fs_mux_poll_task *vpt, *vptlast;
+
+        dprintk(DEBUG_MUX, "mux %p muxnum %d procnum %d\n", m, v9fs_mux_num,
+                v9fs_mux_poll_task_num);
+        up(&v9fs_mux_task_lock);
+
+        n = v9fs_mux_calc_poll_procs(v9fs_mux_num + 1);
+        if (n > v9fs_mux_poll_task_num) {
+                for (i = 0; i < ARRAY_SIZE(v9fs_mux_poll_tasks); i++) {
+                        if (v9fs_mux_poll_tasks[i].task == NULL) {
+                                vpt = &v9fs_mux_poll_tasks[i];
+                                dprintk(DEBUG_MUX, "create proc %p\n", vpt);
+                                vpt->task = kthread_create(v9fs_poll_proc,
+                                        vpt, "v9fs-poll");
+                                INIT_LIST_HEAD(&vpt->mux_list);
+                                vpt->muxnum = 0;
+                                v9fs_mux_poll_task_num++;
+                                wake_up_process(vpt->task);
+                                break;
+                        }
                 }
-                rd += ret;
-                ptr += ret;
-        }
-        return (rd);
-}
 
-/**
- * read_message - read a full 9P2000 fcall packet
- * @v9ses: session info structure
- * @rcall: fcall structure to read into
- * @rcalllen: size of fcall buffer
- *
- */
+                if (i >= ARRAY_SIZE(v9fs_mux_poll_tasks))
+                        dprintk(DEBUG_ERROR, "warning: no free poll slots\n");
+        }
 
-static int
-read_message(struct v9fs_session_info *v9ses,
-             struct v9fs_fcall *rcall, int rcalllen)
-{
-        unsigned char buf[4];
-        void *data;
-        int size = 0;
-        int res = 0;
-
-        res = xread(v9ses, buf, sizeof(buf));
-        if (res < 0) {
-                dprintk(DEBUG_ERROR,
-                        "Reading of count field failed returned: %d\n", res);
-                return res;
+        n = (v9fs_mux_num + 1) / v9fs_mux_poll_task_num +
+            ((v9fs_mux_num + 1) % v9fs_mux_poll_task_num ? 1 : 0);
+
+        vptlast = NULL;
+        for (i = 0; i < ARRAY_SIZE(v9fs_mux_poll_tasks); i++) {
+                vpt = &v9fs_mux_poll_tasks[i];
+                if (vpt->task != NULL) {
+                        vptlast = vpt;
+                        if (vpt->muxnum < n) {
+                                dprintk(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, v9fs_pollwait);
+                                break;
+                        }
+                }
         }
 
-        if (res < 4) {
-                dprintk(DEBUG_ERROR,
-                        "Reading of count field failed returned: %d\n", res);
-                return -EIO;
+        if (i >= ARRAY_SIZE(v9fs_mux_poll_tasks)) {
+                dprintk(DEBUG_MUX, "put in proc %d\n", i);
+                list_add(&m->mux_list, &vptlast->mux_list);
+                vptlast->muxnum++;
+                m->poll_task = vpt;
+                memset(&m->poll_waddr, 0, sizeof(m->poll_waddr));
+                init_poll_funcptr(&m->pt, v9fs_pollwait);
         }
 
-        size = buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);
-        dprintk(DEBUG_MUX, "got a packet count: %d\n", size);
+        v9fs_mux_num++;
+        down(&v9fs_mux_task_lock);
+}
 
-        /* adjust for the four bytes of size */
-        size -= 4;
+static void v9fs_mux_poll_stop(struct v9fs_mux_data *m)
+{
+        int i;
+        struct v9fs_mux_poll_task *vpt;
+
+        up(&v9fs_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) {
+                dprintk(DEBUG_MUX, "destroy proc %p\n", vpt);
+                send_sig(SIGKILL, vpt->task, 1);
+                vpt->task = NULL;
+                v9fs_mux_poll_task_num--;
+        }
+        v9fs_mux_num--;
+        down(&v9fs_mux_task_lock);
+}
 
-        if (size > v9ses->maxdata) {
-                dprintk(DEBUG_ERROR, "packet too big: %d\n", size);
-                return -E2BIG;
+/**
+ * v9fs_mux_init - 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 v9fs_mux_data *v9fs_mux_init(struct v9fs_transport *trans, int msize,
+                                    unsigned char *extended)
+{
+        int i, n;
+        struct v9fs_mux_data *m, *mtmp;
+
+        dprintk(DEBUG_MUX, "transport %p msize %d\n", trans, msize);
+        m = kmalloc(sizeof(struct v9fs_mux_data) + 2 * msize, 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;
+        idr_init(&m->tidpool.pool);
+        init_MUTEX(&m->tidpool.lock);
+        m->err = 0;
+        init_waitqueue_head(&m->equeue);
+        INIT_LIST_HEAD(&m->req_list);
+        INIT_LIST_HEAD(&m->unsent_req_list);
+        m->rpos = 0;
+        m->rbuf = (char *)m + sizeof(struct v9fs_mux_data);
+        m->wpos = m->wsize = 0;
+        m->wbuf = m->rbuf + msize;
+        INIT_WORK(&m->rq, v9fs_read_work, m);
+        INIT_WORK(&m->wq, v9fs_write_work, m);
+        m->wsched = 0;
+        memset(&m->poll_waddr, 0, sizeof(m->poll_waddr));
+        v9fs_mux_poll_start(m);
+
+        n = trans->poll(trans, &m->pt);
+        if (n & POLLIN) {
+                dprintk(DEBUG_MUX, "mux %p can read\n", m);
+                set_bit(Rpending, &m->wsched);
         }
 
-        data = kmalloc(size, GFP_KERNEL);
-        if (!data) {
-                eprintk(KERN_WARNING, "out of memory\n");
-                return -ENOMEM;
+        if (n & POLLOUT) {
+                dprintk(DEBUG_MUX, "mux %p can write\n", m);
+                set_bit(Wpending, &m->wsched);
         }
 
-        res = xread(v9ses, data, size);
-        if (res < size) {
-                dprintk(DEBUG_ERROR, "Reading of fcall failed returned: %d\n",
-                        res);
-                kfree(data);
-                return res;
+        for(i = 0; i < ARRAY_SIZE(m->poll_waddr); i++) {
+                if (IS_ERR(m->poll_waddr[i])) {
+                        v9fs_mux_poll_stop(m);
+                        mtmp = (void *)m->poll_waddr;   /* the error code */
+                        kfree(m);
+                        m = mtmp;
+                        break;
+                }
         }
 
-        /* we now have an in-memory string that is the reply.
-         * deserialize it. There is very little to go wrong at this point
-         * save for v9fs_alloc errors.
-         */
-        res = v9fs_deserialize_fcall(v9ses, size, data, v9ses->maxdata,
-                                     rcall, rcalllen);
+        return m;
+}
 
-        kfree(data);
+/**
+ * v9fs_mux_destroy - cancels all pending requests and frees mux resources
+ */
+void v9fs_mux_destroy(struct v9fs_mux_data *m)
+{
+        dprintk(DEBUG_MUX, "mux %p prev %p next %p\n", m,
+                m->mux_list.prev, m->mux_list.next);
+        v9fs_mux_cancel(m, -ECONNRESET);
+
+        if (!list_empty(&m->req_list)) {
+                /* wait until all processes waiting on this session exit */
+                dprintk(DEBUG_MUX, "mux %p waiting for empty request queue\n",
+                        m);
+                wait_event_timeout(m->equeue, (list_empty(&m->req_list)), 5000);
+                dprintk(DEBUG_MUX, "mux %p request queue empty: %d\n", m,
+                        list_empty(&m->req_list));
+        }
 
-        if (res < 0)
-                return res;
+        v9fs_mux_poll_stop(m);
+        m->trans = NULL;
 
-        return 0;
+        kfree(m);
 }
 
 /**
- * v9fs_recv - receive an RPC response for a particular tag
- * @v9ses: session info structure
- * @req: RPC request structure
- *
+ * v9fs_pollwait - called by files poll operation to add v9fs-poll task
+ *      to files wait queue
  */
-
-static int v9fs_recv(struct v9fs_session_info *v9ses, struct v9fs_rpcreq *req)
+static void
+v9fs_pollwait(struct file *filp, wait_queue_head_t * wait_address,
+              poll_table * p)
 {
-        int ret = 0;
-
-        dprintk(DEBUG_MUX, "waiting for response: %d\n", req->tcall->tag);
-        ret = wait_event_interruptible(v9ses->read_wait,
-                       ((v9ses->transport->status != Connected) ||
-                        (req->rcall != 0) || (req->err < 0) ||
-                        dprintcond(v9ses, req)));
+        int i;
+        struct v9fs_mux_data *m;
 
-        dprintk(DEBUG_MUX, "got it: rcall %p\n", req->rcall);
+        m = container_of(p, struct v9fs_mux_data, pt);
+        for(i = 0; i < ARRAY_SIZE(m->poll_waddr); i++)
+                if (m->poll_waddr[i] == NULL)
+                        break;
 
-        spin_lock(&v9ses->muxlock);
-        list_del(&req->next);
-        spin_unlock(&v9ses->muxlock);
+        if (i >= ARRAY_SIZE(m->poll_waddr)) {
+                dprintk(DEBUG_ERROR, "not enough wait_address slots\n");
+                return;
+        }
 
-        if (req->err < 0)
-                return req->err;
+        m->poll_waddr[i] = wait_address;
 
-        if (v9ses->transport->status == Disconnected)
-                return -ECONNRESET;
+        if (!wait_address) {
+                dprintk(DEBUG_ERROR, "no wait_address\n");
+                m->poll_waddr[i] = ERR_PTR(-EIO);
+                return;
+        }
 
-        return ret;
+        init_waitqueue_entry(&m->poll_wait[i], m->poll_task->task);
+        add_wait_queue(wait_address, &m->poll_wait[i]);
 }
 
 /**
- * v9fs_send - send a 9P request
- * @v9ses: session info structure
- * @req: RPC request to send
- *
+ * v9fs_poll_mux - polls a mux and schedules read or write works if necessary
  */
-
-static int v9fs_send(struct v9fs_session_info *v9ses, struct v9fs_rpcreq *req)
+static inline void v9fs_poll_mux(struct v9fs_mux_data *m)
 {
-        int ret = -1;
-        void *data = NULL;
-        struct v9fs_fcall *tcall = req->tcall;
-
-        data = kmalloc(v9ses->maxdata + V9FS_IOHDRSZ, GFP_KERNEL);
-        if (!data)
-                return -ENOMEM;
-
-        tcall->size = 0;        /* enforce size recalculation */
-        ret =
-            v9fs_serialize_fcall(v9ses, tcall, data,
-                                 v9ses->maxdata + V9FS_IOHDRSZ);
-        if (ret < 0)
-                goto free_data;
-
-        spin_lock(&v9ses->muxlock);
-        list_add(&req->next, &v9ses->mux_fcalls);
-        spin_unlock(&v9ses->muxlock);
-
-        dprintk(DEBUG_MUX, "sending message: tag %d size %d\n", tcall->tag,
-                tcall->size);
-        ret = v9ses->transport->write(v9ses->transport, data, tcall->size);
-
-        if (ret != tcall->size) {
-                spin_lock(&v9ses->muxlock);
-                list_del(&req->next);
-                kfree(req->rcall);
+        int n;
 
-                spin_unlock(&v9ses->muxlock);
-                if (ret >= 0)
-                        ret = -EREMOTEIO;
-        } else
-                ret = 0;
+        if (m->err < 0)
+                return;
+
+        n = m->trans->poll(m->trans, NULL);
+        if (n < 0 || n & (POLLERR | POLLHUP | POLLNVAL)) {
+                dprintk(DEBUG_MUX, "error mux %p err %d\n", m, n);
+                if (n >= 0)
+                        n = -ECONNRESET;
+                v9fs_mux_cancel(m, n);
+        }
+
+        if (n & POLLIN) {
+                set_bit(Rpending, &m->wsched);
+                dprintk(DEBUG_MUX, "mux %p can read\n", m);
+                if (!test_and_set_bit(Rworksched, &m->wsched)) {
+                        dprintk(DEBUG_MUX, "schedule read work mux %p\n", m);
+                        queue_work(v9fs_mux_wq, &m->rq);
+                }
+        }
 
-      free_data:
-        kfree(data);
-        return ret;
+        if (n & POLLOUT) {
+                set_bit(Wpending, &m->wsched);
+                dprintk(DEBUG_MUX, "mux %p can write\n", m);
+                if ((m->wsize || !list_empty(&m->unsent_req_list))
+                    && !test_and_set_bit(Wworksched, &m->wsched)) {
+                        dprintk(DEBUG_MUX, "schedule write work mux %p\n", m);
+                        queue_work(v9fs_mux_wq, &m->wq);
+                }
+        }
 }
 
 /**
- * v9fs_mux_rpc - send a request, receive a response
- * @v9ses: session info structure
- * @tcall: fcall to send
- * @rcall: buffer to place response into
- *
+ * v9fs_poll_proc - polls all v9fs transports for new events and queues
+ *      the appropriate work to the work queue
  */
-
-long
-v9fs_mux_rpc(struct v9fs_session_info *v9ses, struct v9fs_fcall *tcall,
-             struct v9fs_fcall **rcall)
+static int v9fs_poll_proc(void *a)
 {
-        int tid = -1;
-        struct v9fs_fcall *fcall = NULL;
-        struct v9fs_rpcreq req;
-        int ret = -1;
+        struct v9fs_mux_data *m, *mtmp;
+        struct v9fs_mux_poll_task *vpt;
 
-        if (!v9ses)
-                return -EINVAL;
+        vpt = a;
+        dprintk(DEBUG_MUX, "start %p %p\n", current, vpt);
+        allow_signal(SIGKILL);
+        while (!kthread_should_stop()) {
+                set_current_state(TASK_INTERRUPTIBLE);
+                if (signal_pending(current))
+                        break;
 
-        if (!v9ses->transport || v9ses->transport->status != Connected)
-                return -EIO;
+                list_for_each_entry_safe(m, mtmp, &vpt->mux_list, mux_list) {
+                        v9fs_poll_mux(m);
+                }
+
+                dprintk(DEBUG_MUX, "sleeping...\n");
+                schedule_timeout(SCHED_TIMEOUT * HZ);
+        }
 
-        if (rcall)
-                *rcall = NULL;
+        __set_current_state(TASK_RUNNING);
+        dprintk(DEBUG_MUX, "finish\n");
+        return 0;
+}
 
-        if (tcall->id != TVERSION) {
-                tid = v9fs_get_idpool(&v9ses->tidpool);
-                if (tid < 0)
-                        return -ENOMEM;
+static inline int v9fs_write_req(struct v9fs_mux_data *m, struct v9fs_req *req)
+{
+        int n;
+
+        list_move_tail(&req->req_list, &m->req_list);
+        n = v9fs_serialize_fcall(req->tcall, m->wbuf, m->msize, *m->extended);
+        if (n < 0) {
+                req->err = n;
+                list_del(&req->req_list);
+                if (req->cb) {
+                        spin_unlock(&m->lock);
+                        (*req->cb) (req->cba, req->tcall, req->rcall, req->err);
+                        req->cb = NULL;
+                        spin_lock(&m->lock);
+                } else
+                        kfree(req->rcall);
+
+                kfree(req);
         }
 
-        tcall->tag = tid;
+        return n;
+}
 
-        req.tcall = tcall;
-        req.err = 0;
-        req.rcall = NULL;
+/**
+ * v9fs_write_work - called when a transport can send some data
+ */
+static void v9fs_write_work(void *a)
+{
+        int n, err;
+        struct v9fs_mux_data *m;
+        struct v9fs_req *req, *rtmp;
 
-        ret = v9fs_send(v9ses, &req);
+        m = a;
 
-        if (ret < 0) {
-                if (tcall->id != TVERSION)
-                        v9fs_put_idpool(tid, &v9ses->tidpool);
-                dprintk(DEBUG_MUX, "error %d\n", ret);
-                return ret;
+        if (m->err < 0) {
+                clear_bit(Wworksched, &m->wsched);
+                return;
         }
 
-        ret = v9fs_recv(v9ses, &req);
-
-        fcall = req.rcall;
-
-        dprintk(DEBUG_MUX, "received: tag=%x, ret=%d\n", tcall->tag, ret);
-        if (ret == -ERESTARTSYS) {
-                if (v9ses->transport->status != Disconnected
-                    && tcall->id != TFLUSH) {
-                        unsigned long flags;
-
-                        dprintk(DEBUG_MUX, "flushing the tag: %d\n",
-                                tcall->tag);
-                        clear_thread_flag(TIF_SIGPENDING);
-                        v9fs_t_flush(v9ses, tcall->tag);
-                        spin_lock_irqsave(&current->sighand->siglock, flags);
-                        recalc_sigpending();
-                        spin_unlock_irqrestore(&current->sighand->siglock,
-                                               flags);
-                        dprintk(DEBUG_MUX, "flushing done\n");
+        if (!m->wsize) {
+                if (list_empty(&m->unsent_req_list)) {
+                        clear_bit(Wworksched, &m->wsched);
+                        return;
                 }
 
-                goto release_req;
-        } else if (ret < 0)
-                goto release_req;
-
-        if (!fcall)
-                ret = -EIO;
-        else {
-                if (fcall->id == RERROR) {
-                        ret = v9fs_errstr2errno(fcall->params.rerror.error);
-                        if (ret == 0) { /* string match failed */
-                                if (fcall->params.rerror.errno)
-                                        ret = -(fcall->params.rerror.errno);
-                                else
-                                        ret = -ESERVERFAULT;
-                        }
-                } else if (fcall->id != tcall->id + 1) {
-                        dprintk(DEBUG_ERROR,
-                                "fcall mismatch: expected %d, got %d\n",
-                                tcall->id + 1, fcall->id);
-                        ret = -EIO;
+                err = 0;
+                spin_lock(&m->lock);
+                list_for_each_entry_safe(req, rtmp, &m->unsent_req_list,
+                                         req_list) {
+                        err = v9fs_write_req(m, req);
+                        if (err > 0)
+                                break;
                 }
+
+                m->wsize = err;
+                m->wpos = 0;
+                spin_unlock(&m->lock);
         }
 
-      release_req:
-        if (tcall->id != TVERSION)
-                v9fs_put_idpool(tid, &v9ses->tidpool);
-        if (rcall)
-                *rcall = fcall;
-        else
-                kfree(fcall);
+        dprintk(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);
+        dprintk(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) {
+                        dprintk(DEBUG_MUX, "schedule write work mux %p\n", m);
+                        queue_work(v9fs_mux_wq, &m->wq);
+                } else
+                        clear_bit(Wworksched, &m->wsched);
+        } else
+                clear_bit(Wworksched, &m->wsched);
 
-        return ret;
+        return;
+
+      error:
+        v9fs_mux_cancel(m, err);
+        clear_bit(Wworksched, &m->wsched);
 }
 
-/**
- * v9fs_mux_cancel_requests - cancels all pending requests
- *
- * @v9ses: session info structure
- * @err: error code to return to the requests
- */
-void v9fs_mux_cancel_requests(struct v9fs_session_info *v9ses, int err)
+static void process_request(struct v9fs_mux_data *m, struct v9fs_req *req)
 {
-        struct v9fs_rpcreq *rptr;
-        struct v9fs_rpcreq *rreq;
+        int ecode, tag;
+        char *ename;
+
+        tag = req->tag;
+        if (req->rcall->id == RERROR && !req->err) {
+                ecode = req->rcall->params.rerror.errno;
+                ename = req->rcall->params.rerror.error;
 
-        dprintk(DEBUG_MUX, " %d\n", err);
-        spin_lock(&v9ses->muxlock);
-        list_for_each_entry_safe(rreq, rptr, &v9ses->mux_fcalls, next) {
-                rreq->err = err;
+                dprintk(DEBUG_MUX, "Rerror %s\n", ename);
+
+                if (*m->extended)
+                        req->err = -ecode;
+
+                if (!req->err) {
+                        req->err = v9fs_errstr2errno(ename);
+
+                        if (!req->err) {        /* string match failed */
+                                dprintk(DEBUG_ERROR, "unknown error: %s\n",
+                                        ename);
+                        }
+
+                        if (!req->err)
+                                req->err = -ESERVERFAULT;
+                }
+        } else if (req->tcall && req->rcall->id != req->tcall->id + 1) {
+                dprintk(DEBUG_ERROR, "fcall mismatch: expected %d, got %d\n",
+                        req->tcall->id + 1, req->rcall->id);
+                if (!req->err)
+                        req->err = -EIO;
         }
-        spin_unlock(&v9ses->muxlock);
-        wake_up_all(&v9ses->read_wait);
+
+        if (req->cb && req->err != ERREQFLUSH) {
+                dprintk(DEBUG_MUX, "calling callback tcall %p rcall %p\n",
+                        req->tcall, req->rcall);
+
+                (*req->cb) (req->cba, req->tcall, req->rcall, req->err);
+                req->cb = NULL;
+        } else
+                kfree(req->rcall);
+
+        if (tag != V9FS_NOTAG)
+                v9fs_put_idpool(tag, &m->tidpool);
+
+        wake_up(&m->equeue);
+        kfree(req);
 }
 
 /**
- * v9fs_recvproc - kproc to handle demultiplexing responses
- * @data: session info structure
- *
+ * v9fs_read_work - called when there is some data to be read from a transport
  */
-
-static int v9fs_recvproc(void *data)
+static void v9fs_read_work(void *a)
 {
-        struct v9fs_session_info *v9ses = (struct v9fs_session_info *)data;
-        struct v9fs_fcall *rcall = NULL;
-        struct v9fs_rpcreq *rptr;
-        struct v9fs_rpcreq *req;
-        struct v9fs_rpcreq *rreq;
-        int err = 0;
+        int n, err, rcallen;
+        struct v9fs_mux_data *m;
+        struct v9fs_req *req, *rptr, *rreq;
+        struct v9fs_fcall *rcall;
+
+        m = a;
+
+        if (m->err < 0)
+                return;
+
+        rcall = NULL;
+        dprintk(DEBUG_MUX, "start mux %p pos %d\n", m, m->rpos);
+        clear_bit(Rpending, &m->wsched);
+        err = m->trans->read(m->trans, m->rbuf + m->rpos, m->msize - m->rpos);
+        dprintk(DEBUG_MUX, "mux %p got %d bytes\n", m, err);
+        if (err == -EAGAIN) {
+                clear_bit(Rworksched, &m->wsched);
+                return;
+        }
 
-        allow_signal(SIGKILL);
-        set_current_state(TASK_INTERRUPTIBLE);
-        complete(&v9ses->proccmpl);
-        while (!kthread_should_stop() && err >= 0) {
-                req = rptr = rreq = NULL;
+        if (err <= 0)
+                goto error;
 
-                rcall = kmalloc(v9ses->maxdata + V9FS_IOHDRSZ, GFP_KERNEL);
-                if (!rcall) {
-                        eprintk(KERN_ERR, "no memory for buffers\n");
+        m->rpos += err;
+        while (m->rpos > 4) {
+                n = le32_to_cpu(*(__le32 *) m->rbuf);
+                if (n >= m->msize) {
+                        dprintk(DEBUG_ERROR,
+                                "requested packet size too big: %d\n", n);
+                        err = -EIO;
+                        goto error;
+                }
+
+                if (m->rpos < n)
                         break;
+
+                rcallen = n + V9FS_FCALLHDRSZ;
+                rcall = kmalloc(rcallen, GFP_KERNEL);
+                if (!rcall) {
+                        err = -ENOMEM;
+                        goto error;
                 }
 
-                err = read_message(v9ses, rcall, v9ses->maxdata + V9FS_IOHDRSZ);
-                spin_lock(&v9ses->muxlock);
+                dump_data(m->rbuf, n);
+                err = v9fs_deserialize_fcall(m->rbuf, n, rcall, rcallen,
+                                             *m->extended);
                 if (err < 0) {
-                        list_for_each_entry_safe(rreq, rptr, &v9ses->mux_fcalls, next) {
-                                rreq->err = err;
-                        }
-                        if(err != -ERESTARTSYS)
-                                eprintk(KERN_ERR,
-                                        "Transport error while reading message %d\n", err);
-                } else {
-                        list_for_each_entry_safe(rreq, rptr, &v9ses->mux_fcalls, next) {
-                                if (rreq->tcall->tag == rcall->tag) {
-                                        req = rreq;
-                                        req->rcall = rcall;
-                                        break;
-                                }
-                        }
+                        kfree(rcall);
+                        goto error;
                 }
 
-                if (req && (req->tcall->id == TFLUSH)) {
-                        struct v9fs_rpcreq *treq = NULL;
-                        list_for_each_entry_safe(treq, rptr, &v9ses->mux_fcalls, next) {
-                                if (treq->tcall->tag ==
-                                    req->tcall->params.tflush.oldtag) {
-                                        list_del(&rptr->next);
-                                        kfree(treq->rcall);
-                                        break;
-                                }
+                dprintk(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;
+                                req->rcall = rcall;
+                                list_del(&req->req_list);
+                                spin_unlock(&m->lock);
+                                process_request(m, req);
+                                break;
                         }
                 }
 
-                spin_unlock(&v9ses->muxlock);
-
                 if (!req) {
-                        if (err >= 0)
+                        spin_unlock(&m->lock);
+                        if (err >= 0 && rcall->id != RFLUSH)
                                 dprintk(DEBUG_ERROR,
-                                        "unexpected response: id %d tag %d\n",
-                                        rcall->id, rcall->tag);
-
+                                        "unexpected response mux %p id %d tag %d\n",
+                                        m, rcall->id, rcall->tag);
                         kfree(rcall);
                 }
 
-                wake_up_all(&v9ses->read_wait);
-                set_current_state(TASK_INTERRUPTIBLE);
+                if (m->rpos > n)
+                        memmove(m->rbuf, m->rbuf + n, m->rpos - n);
+                m->rpos -= n;
         }
 
-        v9ses->transport->close(v9ses->transport);
-
-        /* Inform all pending processes about the failure */
-        wake_up_all(&v9ses->read_wait);
-
-        if (signal_pending(current))
-                complete(&v9ses->proccmpl);
+        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) {
+                        dprintk(DEBUG_MUX, "schedule read work mux %p\n", m);
+                        queue_work(v9fs_mux_wq, &m->rq);
+                } else
+                        clear_bit(Rworksched, &m->wsched);
+        } else
+                clear_bit(Rworksched, &m->wsched);
 
-        dprintk(DEBUG_MUX, "recvproc: end\n");
-        v9ses->recvproc = NULL;
+        return;
 
-        return err >= 0;
+      error:
+        v9fs_mux_cancel(m, err);
+        clear_bit(Rworksched, &m->wsched);
 }
 
 /**
- * v9fs_mux_init - initialize multiplexer (spawn kproc)
- * @v9ses: session info structure
- * @dev_name: mount device information (to create unique kproc)
+ * v9fs_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 succesfully. 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 v9fs_req *v9fs_send_request(struct v9fs_mux_data *m,
+                                          struct v9fs_fcall *tc,
+                                          v9fs_mux_req_callback cb, void *cba)
+{
+        int n;
+        struct v9fs_req *req;
+
+        dprintk(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 v9fs_req), GFP_KERNEL);
+        if (!req)
+                return ERR_PTR(-ENOMEM);
 
-int v9fs_mux_init(struct v9fs_session_info *v9ses, const char *dev_name)
+        if (tc->id == TVERSION)
+                n = V9FS_NOTAG;
+        else
+                n = v9fs_get_idpool(&m->tidpool);
+
+        if (n < 0)
+                return ERR_PTR(-ENOMEM);
+
+        tc->tag = n;
+        req->tag = n;
+        req->tcall = tc;
+        req->rcall = NULL;
+        req->err = 0;
+        req->cb = cb;
+        req->cba = cba;
+
+        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(v9fs_mux_wq, &m->wq);
+
+        return req;
+}
+
+static inline void
+v9fs_mux_flush_cb(void *a, struct v9fs_fcall *tc, struct v9fs_fcall *rc,
+                  int err)
 {
-        char procname[60];
-
-        strncpy(procname, dev_name, sizeof(procname));
-        procname[sizeof(procname) - 1] = 0;
-
-        init_waitqueue_head(&v9ses->read_wait);
-        init_completion(&v9ses->fcread);
-        init_completion(&v9ses->proccmpl);
-        spin_lock_init(&v9ses->muxlock);
-        INIT_LIST_HEAD(&v9ses->mux_fcalls);
-        v9ses->recvproc = NULL;
-        v9ses->curfcall = NULL;
-
-        v9ses->recvproc = kthread_create(v9fs_recvproc, v9ses,
-                                         "v9fs_recvproc %s", procname);
-
-        if (IS_ERR(v9ses->recvproc)) {
-                eprintk(KERN_ERR, "cannot create receiving thread\n");
-                v9fs_session_close(v9ses);
-                return -ECONNABORTED;
+        v9fs_mux_req_callback cb;
+        int tag;
+        struct v9fs_mux_data *m;
+        struct v9fs_req *req, *rptr;
+
+        m = a;
+        dprintk(DEBUG_MUX, "mux %p tc %p rc %p err %d oldtag %d\n", m, tc,
+                rc, err, tc->params.tflush.oldtag);
+
+        spin_lock(&m->lock);
+        cb = NULL;
+        tag = tc->params.tflush.oldtag;
+        list_for_each_entry_safe(req, rptr, &m->req_list, req_list) {
+                if (req->tag == tag) {
+                        list_del(&req->req_list);
+                        if (req->cb) {
+                                cb = req->cb;
+                                req->cb = NULL;
+                                spin_unlock(&m->lock);
+                                (*cb) (req->cba, req->tcall, req->rcall,
+                                       req->err);
+                        }
+                        kfree(req);
+                        wake_up(&m->equeue);
+                        break;
+                }
+        }
+
+        if (!cb)
+                spin_unlock(&m->lock);
+
+        if (v9fs_check_idpool(tag, &m->tidpool))
+                v9fs_put_idpool(tag, &m->tidpool);
+
+        kfree(tc);
+        kfree(rc);
+}
+
+static void
+v9fs_mux_flush_request(struct v9fs_mux_data *m, struct v9fs_req *req)
+{
+        struct v9fs_fcall *fc;
+
+        dprintk(DEBUG_MUX, "mux %p req %p tag %d\n", m, req, req->tag);
+
+        fc = kmalloc(sizeof(struct v9fs_fcall), GFP_KERNEL);
+        fc->id = TFLUSH;
+        fc->params.tflush.oldtag = req->tag;
+
+        v9fs_send_request(m, fc, v9fs_mux_flush_cb, m);
+}
+
+static void
+v9fs_mux_rpc_cb(void *a, struct v9fs_fcall *tc, struct v9fs_fcall *rc, int err)
+{
+        struct v9fs_mux_rpc *r;
+
+        if (err == ERREQFLUSH) {
+                dprintk(DEBUG_MUX, "err req flush\n");
+                return;
+        }
+
+        r = a;
+        dprintk(DEBUG_MUX, "mux %p req %p tc %p rc %p err %d\n", r->m, r->req,
+                tc, rc, err);
+        r->rcall = rc;
+        r->err = err;
+        wake_up(&r->wqueue);
+}
+
+/**
+ * v9fs_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
+v9fs_mux_rpc(struct v9fs_mux_data *m, struct v9fs_fcall *tc,
+             struct v9fs_fcall **rc)
+{
+        int err;
+        unsigned long flags;
+        struct v9fs_req *req;
+        struct v9fs_mux_rpc r;
+
+        r.err = 0;
+        r.rcall = NULL;
+        r.m = m;
+        init_waitqueue_head(&r.wqueue);
+
+        if (rc)
+                *rc = NULL;
+
+        req = v9fs_send_request(m, tc, v9fs_mux_rpc_cb, &r);
+        if (IS_ERR(req)) {
+                err = PTR_ERR(req);
+                dprintk(DEBUG_MUX, "error %d\n", err);
+                return PTR_ERR(req);
+        }
+
+        r.req = req;
+        dprintk(DEBUG_MUX, "mux %p tc %p tag %d rpc %p req %p\n", m, tc,
+                req->tag, &r, req);
+        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) {
+                spin_lock(&m->lock);
+                req->tcall = NULL;
+                req->err = ERREQFLUSH;
+                spin_unlock(&m->lock);
+
+                clear_thread_flag(TIF_SIGPENDING);
+                v9fs_mux_flush_request(m, req);
+                spin_lock_irqsave(&current->sighand->siglock, flags);
+                recalc_sigpending();
+                spin_unlock_irqrestore(&current->sighand->siglock, flags);
         }
 
-        wake_up_process(v9ses->recvproc);
-        wait_for_completion(&v9ses->proccmpl);
+        if (!err) {
+                if (r.rcall)
+                        dprintk(DEBUG_MUX, "got response id %d tag %d\n",
+                                r.rcall->id, r.rcall->tag);
+
+                if (rc)
+                        *rc = r.rcall;
+                else
+                        kfree(r.rcall);
+        } else {
+                kfree(r.rcall);
+                dprintk(DEBUG_MUX, "got error %d\n", err);
+                if (err > 0)
+                        err = -EIO;
+        }
+
+        return err;
+}
+
+/**
+ * v9fs_mux_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 v9fs_mux_rpcnb(struct v9fs_mux_data *m, struct v9fs_fcall *tc,
+                   v9fs_mux_req_callback cb, void *a)
+{
+        int err;
+        struct v9fs_req *req;
+
+        req = v9fs_send_request(m, tc, cb, a);
+        if (IS_ERR(req)) {
+                err = PTR_ERR(req);
+                dprintk(DEBUG_MUX, "error %d\n", err);
+                return PTR_ERR(req);
+        }
 
+        dprintk(DEBUG_MUX, "mux %p tc %p tag %d\n", m, tc, req->tag);
         return 0;
 }
+
+/**
+ * v9fs_mux_cancel - cancel all pending requests with error
+ * @m: mux data
+ * @err: error code
+ */
+void v9fs_mux_cancel(struct v9fs_mux_data *m, int err)
+{
+        struct v9fs_req *req, *rtmp;
+        LIST_HEAD(cancel_list);
+
+        dprintk(DEBUG_MUX, "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);
+        }
+        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->cba, req->tcall, req->rcall, req->err);
+                else
+                        kfree(req->rcall);
+
+                kfree(req);
+        }
+
+        wake_up(&m->equeue);
+}