9p: block-based virtio client

This replaces the console-based virto client with a block-based
client using a single request queue.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 210 insertions, 134 deletions

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 42eea5fe2628..0f590227943b 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -1,17 +1,8 @@
 /*
  * The Guest 9p transport driver
  *
- * This is a trivial pipe-based transport driver based on the lguest console
- * code: we use lguest's DMA mechanism to send bytes out, and register a
- * DMA buffer to receive bytes in.  It is assumed to be present and available
- * from the very beginning of boot.
- *
- * This may be have been done by just instaniating another HVC console,
- * but HVC's blocksize of 16 bytes is annoying and painful to performance.
- *
- * A more efficient transport could be built based on the virtio block driver
- * but it requires some changes in the 9p transport model (which are in
- * progress)
+ * This is a block based transport driver based on the lguest block driver
+ * code.
  *
  */
 /*
@@ -55,11 +46,25 @@
 #include <linux/virtio.h>
 #include <linux/virtio_9p.h>
 
+#define VIRTQUEUE_NUM   128
+
 /* a single mutex to manage channel initialization and attachment */
 static DECLARE_MUTEX(virtio_9p_lock);
 /* global which tracks highest initialized channel */
 static int chan_index;
 
+#define P9_INIT_MAXTAG  16
+
+#define REQ_STATUS_IDLE 0
+#define REQ_STATUS_SENT 1
+#define REQ_STATUS_RCVD 2
+#define REQ_STATUS_FLSH 3
+
+struct p9_req_t {
+        int status;
+        wait_queue_head_t *wq;
+};
+
 /* We keep all per-channel information in a structure.
  * This structure is allocated within the devices dev->mem space.
  * A pointer to the structure will get put in the transport private.
@@ -68,16 +73,57 @@ static struct virtio_chan {
         bool initialized;               /* channel is initialized */
         bool inuse;                     /* channel is in use */
 
-        struct virtqueue *in_vq, *out_vq;
+        spinlock_t lock;
+
         struct virtio_device *vdev;
+        struct virtqueue *vq;
 
-        /* This is our input buffer, and how much data is left in it. */
-        unsigned int in_len;
-        char *in, *inbuf;
+        struct p9_idpool *tagpool;
+        struct p9_req_t *reqs;
+        int max_tag;
 
-        wait_queue_head_t wq;           /* waitq for buffer */
+        /* Scatterlist: can be too big for stack. */
+        struct scatterlist sg[VIRTQUEUE_NUM];
 } channels[MAX_9P_CHAN];
 
+/* Lookup requests by tag */
+static struct p9_req_t *p9_lookup_tag(struct virtio_chan *c, u16 tag)
+{
+        /* This looks up the original request by tag so we know which
+         * buffer to read the data into */
+        tag++;
+
+        while (tag >= c->max_tag) {
+                int old_max = c->max_tag;
+                int count;
+
+                if (c->max_tag)
+                        c->max_tag *= 2;
+                else
+                        c->max_tag = P9_INIT_MAXTAG;
+
+                c->reqs = krealloc(c->reqs, sizeof(struct p9_req_t)*c->max_tag,
+                                                                GFP_ATOMIC);
+                if (!c->reqs) {
+                        printk(KERN_ERR "Couldn't grow tag array\n");
+                        BUG();
+                }
+                for (count = old_max; count < c->max_tag; count++) {
+                        c->reqs[count].status = REQ_STATUS_IDLE;
+                        c->reqs[count].wq = kmalloc(sizeof(wait_queue_t),
+                                                                GFP_ATOMIC);
+                        if (!c->reqs[count].wq) {
+                                printk(KERN_ERR "Couldn't grow tag array\n");
+                                BUG();
+                        }
+                        init_waitqueue_head(c->reqs[count].wq);
+                }
+        }
+
+        return &c->reqs[tag];
+}
+
+
 /* How many bytes left in this page. */
 static unsigned int rest_of_page(void *data)
 {
@@ -86,128 +132,163 @@ static unsigned int rest_of_page(void *data)
 
 static int p9_virtio_write(struct p9_trans *trans, void *buf, int count)
 {
-        struct virtio_chan *chan = (struct virtio_chan *) trans->priv;
-        struct virtqueue *out_vq = chan->out_vq;
-        struct scatterlist sg[1];
-        unsigned int len;
+        /* Only use the rpc mechanism for now */
+        return count;
+}
 
-        P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio write (%d)\n", count);
+static int p9_virtio_read(struct p9_trans *trans, void *buf, int count)
+{
+        /* Only use the rpc mechanism for now */
+        return 0;
+}
 
-        /* keep it simple - make sure we don't overflow a page */
-        if (rest_of_page(buf) < count)
-                count = rest_of_page(buf);
+/* The poll function is used by 9p transports to determine if there
+ * is there is activity available on a particular channel.  In our case
+ * we use it to wait for a callback from the input routines.
+ */
+static unsigned int
+p9_virtio_poll(struct p9_trans *trans, struct poll_table_struct *pt)
+{
+        /* Only use the rpc mechanism for now */
+        return 0;
+}
 
-        sg_init_one(sg, buf, count);
+static void p9_virtio_close(struct p9_trans *trans)
+{
+        struct virtio_chan *chan = trans->priv;
+        int count;
+        unsigned int flags;
 
-        /* add_buf wants a token to identify this buffer: we hand it any
-         * non-NULL pointer, since there's only ever one buffer. */
-        if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) {
-                /* Tell Host to go! */
-                out_vq->vq_ops->kick(out_vq);
-                /* Chill out until it's done with the buffer. */
-                while (!out_vq->vq_ops->get_buf(out_vq, &len))
-                        cpu_relax();
-        }
+        spin_lock_irqsave(&chan->lock, flags);
+        p9_idpool_destroy(chan->tagpool);
+        for (count = 0; count < chan->max_tag; count++)
+                kfree(chan->reqs[count].wq);
+        kfree(chan->reqs);
+        chan->max_tag = 0;
+        spin_unlock_irqrestore(&chan->lock, flags);
 
-        P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio wrote (%d)\n", count);
+        down(&virtio_9p_lock);
+        chan->inuse = false;
+        up(&virtio_9p_lock);
 
-        /* We're expected to return the amount of data we wrote: all of it. */
-        return count;
+        kfree(trans);
 }
 
-/* Create a scatter-gather list representing our input buffer and put it in the
- * queue. */
-static void add_inbuf(struct virtio_chan *chan)
+static void req_done(struct virtqueue *vq)
 {
-        struct scatterlist sg[1];
+        struct virtio_chan *chan = vq->vdev->priv;
+        struct p9_fcall *rc;
+        unsigned int len;
+        unsigned long flags;
+        struct p9_req_t *req;
+
+        spin_lock_irqsave(&chan->lock, flags);
+        while ((rc = chan->vq->vq_ops->get_buf(chan->vq, &len)) != NULL) {
+                req = p9_lookup_tag(chan, rc->tag);
+                req->status = REQ_STATUS_RCVD;
+                wake_up(req->wq);
+        }
+        /* In case queue is stopped waiting for more buffers. */
+        spin_unlock_irqrestore(&chan->lock, flags);
+}
 
-        sg_init_one(sg, chan->inbuf, PAGE_SIZE);
+static int
+pack_sg_list(struct scatterlist *sg, int start, int limit, char *data,
+                                                                int count)
+{
+        int s;
+        int index = start;
+
+        while (count) {
+                s = rest_of_page(data);
+                if (s > count)
+                        s = count;
+                sg_set_buf(&sg[index++], data, s);
+                count -= s;
+                data += s;
+                if (index > limit)
+                        BUG();
+        }
 
-        /* We should always be able to add one buffer to an empty queue. */
-        if (chan->in_vq->vq_ops->add_buf(chan->in_vq, sg, 0, 1, chan->inbuf))
-                BUG();
-        chan->in_vq->vq_ops->kick(chan->in_vq);
+        return index-start;
 }
 
-static int p9_virtio_read(struct p9_trans *trans, void *buf, int count)
+static int
+p9_virtio_rpc(struct p9_trans *t, struct p9_fcall *tc, struct p9_fcall **rc,
+                int msize, int dotu)
 {
-        struct virtio_chan *chan = (struct virtio_chan *) trans->priv;
-        struct virtqueue *in_vq = chan->in_vq;
-
-        P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio read (%d)\n", count);
+        int in, out;
+        int n, err, size;
+        struct virtio_chan *chan = t->priv;
+        char *rdata;
+        struct p9_req_t *req;
+        unsigned long flags;
+
+        if (*rc == NULL) {
+                *rc = kmalloc(sizeof(struct p9_fcall) + msize, GFP_KERNEL);
+                if (!*rc)
+                        return -ENOMEM;
+        }
 
-        /* If we don't have an input queue yet, we can't get input. */
-        BUG_ON(!in_vq);
+        rdata = (char *)*rc+sizeof(struct p9_fcall);
 
-        /* No buffer?  Try to get one. */
-        if (!chan->in_len) {
-                chan->in = in_vq->vq_ops->get_buf(in_vq, &chan->in_len);
-                if (!chan->in)
-                        return 0;
+        spin_lock_irqsave(&chan->lock, flags);
+        n = P9_NOTAG;
+        if (tc->id != P9_TVERSION) {
+                n = p9_idpool_get(chan->tagpool);
+                if (n < 0)
+                        return -ENOMEM;
         }
 
-        /* You want more than we have to give?  Well, try wanting less! */
-        if (chan->in_len < count)
-                count = chan->in_len;
+        req = p9_lookup_tag(chan, n);
+        spin_unlock_irqrestore(&chan->lock, flags);
 
-        /* Copy across to their buffer and increment offset. */
-        memcpy(buf, chan->in, count);
-        chan->in += count;
-        chan->in_len -= count;
+        p9_set_tag(tc, n);
 
-        /* Finished?  Re-register buffer so Host will use it again. */
-        if (chan->in_len == 0)
-                add_inbuf(chan);
+        P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio rpc tag %d\n", n);
 
-        P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio finished read (%d)\n",
-                                                                        count);
+        out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, tc->sdata, tc->size);
+        in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata, msize);
 
-        return count;
-}
+        req->status = REQ_STATUS_SENT;
 
-/* The poll function is used by 9p transports to determine if there
- * is there is activity available on a particular channel.  In our case
- * we use it to wait for a callback from the input routines.
- */
-static unsigned int
-p9_virtio_poll(struct p9_trans *trans, struct poll_table_struct *pt)
-{
-        struct virtio_chan *chan = (struct virtio_chan *)trans->priv;
-        struct virtqueue *in_vq = chan->in_vq;
-        int ret = POLLOUT; /* we can always handle more output */
+        if (chan->vq->vq_ops->add_buf(chan->vq, chan->sg, out, in, tc)) {
+                P9_DPRINTK(P9_DEBUG_TRANS,
+                        "9p debug: virtio rpc add_buf returned failure");
+                return -EIO;
+        }
 
-        poll_wait(NULL, &chan->wq, pt);
+        chan->vq->vq_ops->kick(chan->vq);
 
-        /* No buffer?  Try to get one. */
-        if (!chan->in_len)
-                chan->in = in_vq->vq_ops->get_buf(in_vq, &chan->in_len);
+        wait_event(*req->wq, req->status == REQ_STATUS_RCVD);
 
-        if (chan->in_len)
-                ret |= POLLIN;
+        size = le32_to_cpu(*(__le32 *) rdata);
 
-        return ret;
-}
+        err = p9_deserialize_fcall(rdata, size, *rc, dotu);
+        if (err < 0) {
+                P9_DPRINTK(P9_DEBUG_TRANS,
+                        "9p debug: virtio rpc deserialize returned %d\n", err);
+                return err;
+        }
 
-static void p9_virtio_close(struct p9_trans *trans)
-{
-        struct virtio_chan *chan = trans->priv;
+#ifdef CONFIG_NET_9P_DEBUG
+        if ((p9_debug_level&P9_DEBUG_FCALL) == P9_DEBUG_FCALL) {
+                char buf[150];
 
-        down(&virtio_9p_lock);
-        chan->inuse = false;
-        up(&virtio_9p_lock);
+                p9_printfcall(buf, sizeof(buf), *rc, dotu);
+                printk(KERN_NOTICE ">>> %p %s\n", t, buf);
+        }
+#endif
 
-        kfree(trans);
-}
+        if (n != P9_NOTAG && p9_idpool_check(n, chan->tagpool))
+                p9_idpool_put(n, chan->tagpool);
 
-static void p9_virtio_intr(struct virtqueue *q)
-{
-        struct virtio_chan *chan = q->vdev->priv;
+        req->status = REQ_STATUS_IDLE;
 
-        P9_DPRINTK(P9_DEBUG_TRANS, "9p poll_wakeup: %p\n", &chan->wq);
-        wake_up_interruptible(&chan->wq);
+        return 0;
 }
 
-static int p9_virtio_probe(struct virtio_device *dev)
+static int p9_virtio_probe(struct virtio_device *vdev)
 {
         int err;
         struct virtio_chan *chan;
@@ -221,44 +302,29 @@ static int p9_virtio_probe(struct virtio_device *dev)
         if (chan_index > MAX_9P_CHAN) {
                 printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
                 BUG();
-        }
-
-        chan->vdev = dev;
-
-        /* This is the scratch page we use to receive console input */
-        chan->inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
-        if (!chan->inbuf) {
                 err = -ENOMEM;
                 goto fail;
         }
 
-        /* Find the input queue. */
-        dev->priv = chan;
-        chan->in_vq = dev->config->find_vq(dev, 0, p9_virtio_intr);
-        if (IS_ERR(chan->in_vq)) {
-                err = PTR_ERR(chan->in_vq);
-                goto free;
-        }
+        chan->vdev = vdev;
 
-        chan->out_vq = dev->config->find_vq(dev, 1, NULL);
-        if (IS_ERR(chan->out_vq)) {
-                err = PTR_ERR(chan->out_vq);
-                goto free_in_vq;
+        /* We expect one virtqueue, for requests. */
+        chan->vq = vdev->config->find_vq(vdev, 0, req_done);
+        if (IS_ERR(chan->vq)) {
+                err = PTR_ERR(chan->vq);
+                goto out_free_vq;
         }
+        chan->vq->vdev->priv = chan;
+        spin_lock_init(&chan->lock);
 
-        init_waitqueue_head(&chan->wq);
+        sg_init_table(chan->sg, VIRTQUEUE_NUM);
 
-        /* Register the input buffer the first time. */
-        add_inbuf(chan);
         chan->inuse = false;
         chan->initialized = true;
-
         return 0;
 
-free_in_vq:
-        dev->config->del_vq(chan->in_vq);
-free:
-        kfree(chan->inbuf);
+out_free_vq:
+        vdev->config->del_vq(chan->vq);
 fail:
         down(&virtio_9p_lock);
         chan_index--;
@@ -274,8 +340,8 @@ fail:
 static struct p9_trans *p9_virtio_create(const char *devname, char *args)
 {
         struct p9_trans *trans;
-        int index = 0;
         struct virtio_chan *chan = channels;
+        int index = 0;
 
         down(&virtio_9p_lock);
         while (index < MAX_9P_CHAN) {
@@ -290,9 +356,18 @@ static struct p9_trans *p9_virtio_create(const char *devname, char *args)
         up(&virtio_9p_lock);
 
         if (index >= MAX_9P_CHAN) {
-                printk(KERN_ERR "9p: virtio: couldn't find a free channel\n");
-                return NULL;
+                printk(KERN_ERR "9p: no channels available\n");
+                return ERR_PTR(-ENODEV);
+        }
+
+        chan->tagpool = p9_idpool_create();
+        if (IS_ERR(chan->tagpool)) {
+                printk(KERN_ERR "9p: couldn't allocate tagpool\n");
+                return ERR_PTR(-ENOMEM);
         }
+        p9_idpool_get(chan->tagpool); /* reserve tag 0 */
+        chan->max_tag = 0;
+        chan->reqs = NULL;
 
         trans = kmalloc(sizeof(struct p9_trans), GFP_KERNEL);
         if (!trans) {
@@ -304,6 +379,7 @@ static struct p9_trans *p9_virtio_create(const char *devname, char *args)
         trans->read = p9_virtio_read;
         trans->close = p9_virtio_close;
         trans->poll = p9_virtio_poll;
+        trans->rpc = p9_virtio_rpc;
         trans->priv = chan;
 
         return trans;
@@ -327,7 +403,7 @@ static struct virtio_driver p9_virtio_drv = {
 static struct p9_trans_module p9_virtio_trans = {
         .name = "virtio",
         .create = p9_virtio_create,
-        .maxsize = PAGE_SIZE,
+        .maxsize = PAGE_SIZE*16,
         .def = 0,
 };