memcg: optimize per-cpu statistics

[linux-2.6/sactl.git] / net / 9p / trans_virtio.c

/*
 * The Guest 9p transport driver
 *
 * This is a block based transport driver based on the lguest block driver
 * code.
 *
 */
/*
 *  Copyright (C) 2007 Eric Van Hensbergen, IBM Corporation
 *
 *  Based on virtio console driver
 *  Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  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/in.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/ipv6.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/un.h>
#include <linux/uaccess.h>
#include <linux/inet.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <net/9p/9p.h>
#include <linux/parser.h>
#include <net/9p/transport.h>
#include <linux/scatterlist.h>
#include <linux/virtio.h>
#include <linux/virtio_9p.h>

#define VIRTQUEUE_NUM   128

/* a single mutex to manage channel initialization and attachment */
static DEFINE_MUTEX(virtio_9p_lock);
/* global which tracks highest initialized channel */
static int chan_index;

#define P9_INIT_MAXTAG  16


/**
 * enum p9_req_status_t - virtio request status
 * @REQ_STATUS_IDLE: request slot unused
 * @REQ_STATUS_SENT: request sent to server
 * @REQ_STATUS_RCVD: response received from server
 * @REQ_STATUS_FLSH: request has been flushed
 *
 * The @REQ_STATUS_IDLE state is used to mark a request slot as unused
 * but use is actually tracked by the idpool structure which handles tag
 * id allocation.
 *
 */

enum p9_req_status_t {
        REQ_STATUS_IDLE,
        REQ_STATUS_SENT,
        REQ_STATUS_RCVD,
        REQ_STATUS_FLSH,
};

/**
 * struct p9_req_t - virtio request slots
 * @status: status of this request slot
 * @wq: wait_queue for the client to block on for this request
 *
 * The virtio transport uses an array to track outstanding requests
 * instead of a list.  While this may incurr overhead during initial
 * allocation or expansion, it makes request lookup much easier as the
 * tag id is a index into an array.  (We use tag+1 so that we can accomodate
 * the -1 tag for the T_VERSION request).
 * This also has the nice effect of only having to allocate wait_queues
 * once, instead of constantly allocating and freeing them.  Its possible
 * other resources could benefit from this scheme as well.
 *
 */

struct p9_req_t {
        int status;
        wait_queue_head_t *wq;
};

/**
 * struct virtio_chan - per-instance transport information
 * @initialized: whether the channel is initialized
 * @inuse: whether the channel is in use
 * @lock: protects multiple elements within this structure
 * @vdev: virtio dev associated with this channel
 * @vq: virtio queue associated with this channel
 * @tagpool: accounting for tag ids (and request slots)
 * @reqs: array of request slots
 * @max_tag: current number of request_slots allocated
 * @sg: scatter gather list which is used to pack a request (protected?)
 *
 * 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.
 *
 */

static struct virtio_chan {
        bool initialized;
        bool inuse;

        spinlock_t lock;

        struct virtio_device *vdev;
        struct virtqueue *vq;

        struct p9_idpool *tagpool;
        struct p9_req_t *reqs;
        int max_tag;

        /* Scatterlist: can be too big for stack. */
        struct scatterlist sg[VIRTQUEUE_NUM];
} channels[MAX_9P_CHAN];

/**
 * p9_lookup_tag - Lookup requests by tag
 * @c: virtio channel to lookup tag within
 * @tag: numeric id for transaction
 *
 * this is a simple array lookup, but will grow the
 * request_slots as necessary to accomodate transaction
 * ids which did not previously have a slot.
 *
 * Bugs: there is currently no upper limit on request slots set
 * here, but that should be constrained by the id accounting.
 */

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_head_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)
{
        return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
}

/**
 * p9_virtio_close - reclaim resources of a channel
 * @trans: transport state
 *
 * This reclaims a channel by freeing its resources and
 * reseting its inuse flag.
 *
 */

static void p9_virtio_close(struct p9_trans *trans)
{
        struct virtio_chan *chan = trans->priv;
        int count;
        unsigned long flags;

        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);

        mutex_lock(&virtio_9p_lock);
        chan->inuse = false;
        mutex_unlock(&virtio_9p_lock);

        kfree(trans);
}

/**
 * req_done - callback which signals activity from the server
 * @vq: virtio queue activity was received on
 *
 * This notifies us that the server has triggered some activity
 * on the virtio channel - most likely a response to request we
 * sent.  Figure out which requests now have responses and wake up
 * those threads.
 *
 * Bugs: could do with some additional sanity checking, but appears to work.
 *
 */

static void req_done(struct virtqueue *vq)
{
        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);
}

/**
 * pack_sg_list - pack a scatter gather list from a linear buffer
 * @sg: scatter/gather list to pack into
 * @start: which segment of the sg_list to start at
 * @limit: maximum segment to pack data to
 * @data: data to pack into scatter/gather list
 * @count: amount of data to pack into the scatter/gather list
 *
 * sg_lists have multiple segments of various sizes.  This will pack
 * arbitrary data into an existing scatter gather list, segmenting the
 * data as necessary within constraints.
 *
 */

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;
                BUG_ON(index > limit);
        }

        return index-start;
}

/**
 * p9_virtio_rpc - issue a request and wait for a response
 * @t: transport state
 * @tc: &p9_fcall request to transmit
 * @rc: &p9_fcall to put reponse into
 *
 */

static int
p9_virtio_rpc(struct p9_trans *t, struct p9_fcall *tc, struct p9_fcall **rc)
{
        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) + t->msize, GFP_KERNEL);
                if (!*rc)
                        return -ENOMEM;
        }

        rdata = (char *)*rc+sizeof(struct p9_fcall);

        n = P9_NOTAG;
        if (tc->id != P9_TVERSION) {
                n = p9_idpool_get(chan->tagpool);
                if (n < 0)
                        return -ENOMEM;
        }

        spin_lock_irqsave(&chan->lock, flags);
        req = p9_lookup_tag(chan, n);
        spin_unlock_irqrestore(&chan->lock, flags);

        p9_set_tag(tc, n);

        P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio rpc tag %d\n", n);

        out = pack_sg_list(chan->sg, 0, VIRTQUEUE_NUM, tc->sdata, tc->size);
        in = pack_sg_list(chan->sg, out, VIRTQUEUE_NUM-out, rdata, t->msize);

        req->status = REQ_STATUS_SENT;

        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;
        }

        chan->vq->vq_ops->kick(chan->vq);

        wait_event(*req->wq, req->status == REQ_STATUS_RCVD);

        size = le32_to_cpu(*(__le32 *) rdata);

        err = p9_deserialize_fcall(rdata, size, *rc, t->extended);
        if (err < 0) {
                P9_DPRINTK(P9_DEBUG_TRANS,
                        "9p debug: virtio rpc deserialize returned %d\n", err);
                return err;
        }

#ifdef CONFIG_NET_9P_DEBUG
        if ((p9_debug_level&P9_DEBUG_FCALL) == P9_DEBUG_FCALL) {
                char buf[150];

                p9_printfcall(buf, sizeof(buf), *rc, t->extended);
                printk(KERN_NOTICE ">>> %p %s\n", t, buf);
        }
#endif

        if (n != P9_NOTAG && p9_idpool_check(n, chan->tagpool))
                p9_idpool_put(n, chan->tagpool);

        req->status = REQ_STATUS_IDLE;

        return 0;
}

/**
 * p9_virtio_probe - probe for existence of 9P virtio channels
 * @vdev: virtio device to probe
 *
 * This probes for existing virtio channels.  At present only
 * a single channel is in use, so in the future more work may need
 * to be done here.
 *
 */

static int p9_virtio_probe(struct virtio_device *vdev)
{
        int err;
        struct virtio_chan *chan;
        int index;

        mutex_lock(&virtio_9p_lock);
        index = chan_index++;
        chan = &channels[index];
        mutex_unlock(&virtio_9p_lock);

        if (chan_index > MAX_9P_CHAN) {
                printk(KERN_ERR "9p: virtio: Maximum channels exceeded\n");
                BUG();
                err = -ENOMEM;
                goto fail;
        }

        chan->vdev = vdev;

        /* 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);

        sg_init_table(chan->sg, VIRTQUEUE_NUM);

        chan->inuse = false;
        chan->initialized = true;
        return 0;

out_free_vq:
        vdev->config->del_vq(chan->vq);
fail:
        mutex_lock(&virtio_9p_lock);
        chan_index--;
        mutex_unlock(&virtio_9p_lock);
        return err;
}


/**
 * p9_virtio_create - allocate a new virtio channel
 * @devname: string identifying the channel to connect to (unused)
 * @args: args passed from sys_mount() for per-transport options (unused)
 * @msize: requested maximum packet size
 * @extended: 9p2000.u enabled flag
 *
 * This sets up a transport channel for 9p communication.  Right now
 * we only match the first available channel, but eventually we couldlook up
 * alternate channels by matching devname versus a virtio_config entry.
 * We use a simple reference count mechanism to ensure that only a single
 * mount has a channel open at a time.
 *
 * Bugs: doesn't allow identification of a specific channel
 * to allocate, channels are allocated sequentially. This was
 * a pragmatic decision to get things rolling, but ideally some
 * way of identifying the channel to attach to would be nice
 * if we are going to support multiple channels.
 *
 */

static struct p9_trans *
p9_virtio_create(const char *devname, char *args, int msize,
                                                        unsigned char extended)
{
        struct p9_trans *trans;
        struct virtio_chan *chan = channels;
        int index = 0;

        mutex_lock(&virtio_9p_lock);
        while (index < MAX_9P_CHAN) {
                if (chan->initialized && !chan->inuse) {
                        chan->inuse = true;
                        break;
                } else {
                        index++;
                        chan = &channels[index];
                }
        }
        mutex_unlock(&virtio_9p_lock);

        if (index >= MAX_9P_CHAN) {
                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) {
                printk(KERN_ERR "9p: couldn't allocate transport\n");
                return ERR_PTR(-ENOMEM);
        }
        trans->extended = extended;
        trans->msize = msize;
        trans->close = p9_virtio_close;
        trans->rpc = p9_virtio_rpc;
        trans->priv = chan;

        return trans;
}

/**
 * p9_virtio_remove - clean up resources associated with a virtio device
 * @vdev: virtio device to remove
 *
 */

static void p9_virtio_remove(struct virtio_device *vdev)
{
        struct virtio_chan *chan = vdev->priv;

        BUG_ON(chan->inuse);

        if (chan->initialized) {
                vdev->config->del_vq(chan->vq);
                chan->initialized = false;
        }
}

#define VIRTIO_ID_9P 9

static struct virtio_device_id id_table[] = {
        { VIRTIO_ID_9P, VIRTIO_DEV_ANY_ID },
        { 0 },
};

/* The standard "struct lguest_driver": */
static struct virtio_driver p9_virtio_drv = {
        .driver.name =  KBUILD_MODNAME,
        .driver.owner = THIS_MODULE,
        .id_table =     id_table,
        .probe =        p9_virtio_probe,
        .remove =       p9_virtio_remove,
};

static struct p9_trans_module p9_virtio_trans = {
        .name = "virtio",
        .create = p9_virtio_create,
        .maxsize = PAGE_SIZE*16,
        .def = 0,
        .owner = THIS_MODULE,
};

/* The standard init function */
static int __init p9_virtio_init(void)
{
        int count;

        for (count = 0; count < MAX_9P_CHAN; count++)
                channels[count].initialized = false;

        v9fs_register_trans(&p9_virtio_trans);
        return register_virtio_driver(&p9_virtio_drv);
}

static void __exit p9_virtio_cleanup(void)
{
        unregister_virtio_driver(&p9_virtio_drv);
        v9fs_unregister_trans(&p9_virtio_trans);
}

module_init(p9_virtio_init);
module_exit(p9_virtio_cleanup);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_AUTHOR("Eric Van Hensbergen <ericvh@gmail.com>");
MODULE_DESCRIPTION("Virtio 9p Transport");
MODULE_LICENSE("GPL");