aoechr.c

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/* Copyright (c) 2012 Coraid, Inc.  See COPYING for GPL terms. */
/*
 * aoechr.c
 * AoE character device driver
 */

#include <linux/hdreg.h>
#include <linux/blkdev.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/skbuff.h>
#include <linux/export.h>
#include "aoe.h"

enum {
    //MINOR_STAT = 1, (moved to sysfs)
    MINOR_ERR = 2,
    MINOR_DISCOVER,
    MINOR_INTERFACES,
    MINOR_REVALIDATE,
    MINOR_FLUSH,
    MSGSZ = 2048,
    NMSG = 100,     /* message backlog to retain */
};

struct aoe_chardev {
    ulong minor;
    char name[32];
};

enum { EMFL_VALID = 1 };

struct ErrMsg {
    short flags;
    short len;
    char *msg;
};

static DEFINE_MUTEX(aoechr_mutex);
static struct ErrMsg emsgs[NMSG];
static int emsgs_head_idx, emsgs_tail_idx;
static struct completion emsgs_comp;
static spinlock_t emsgs_lock;
static int nblocked_emsgs_readers;
static struct class *aoe_class;
static struct aoe_chardev chardevs[] = {
    { MINOR_ERR, "err" },
    { MINOR_DISCOVER, "discover" },
    { MINOR_INTERFACES, "interfaces" },
    { MINOR_REVALIDATE, "revalidate" },
    { MINOR_FLUSH, "flush" },
};

static int
discover(void)
{
    aoecmd_cfg(0xffff, 0xff);
    return 0;
}

static int
interfaces(const char __user *str, size_t size)
{
    if (set_aoe_iflist(str, size)) {
        printk(KERN_ERR
            "aoe: could not set interface list: too many interfaces\n");
        return -EINVAL;
    }
    return 0;
}

static int
revalidate(const char __user *str, size_t size)
{
    int major, minor, n;
    ulong flags;
    struct aoedev *d;
    struct sk_buff *skb;
    char buf[16];

    if (size >= sizeof buf)
        return -EINVAL;
    buf[sizeof buf - 1] = '\0';
    if (copy_from_user(buf, str, size))
        return -EFAULT;

    n = sscanf(buf, "e%d.%d", &major, &minor);
    if (n != 2) {
        pr_err("aoe: invalid device specification %s\n", buf);
        return -EINVAL;
    }
    d = aoedev_by_aoeaddr(major, minor, 0);
    if (!d)
        return -EINVAL;
    spin_lock_irqsave(&d->lock, flags);
    aoecmd_cleanslate(d);
    aoecmd_cfg(major, minor);
loop:
    skb = aoecmd_ata_id(d);
    spin_unlock_irqrestore(&d->lock, flags);
    /* try again if we are able to sleep a bit,
     * otherwise give up this revalidation
     */
    if (!skb && !msleep_interruptible(250)) {
        spin_lock_irqsave(&d->lock, flags);
        goto loop;
    }
    aoedev_put(d);
    if (skb) {
        struct sk_buff_head queue;
        __skb_queue_head_init(&queue);
        __skb_queue_tail(&queue, skb);
        aoenet_xmit(&queue);
    }
    return 0;
}

void
aoechr_error(char *msg)
{
    struct ErrMsg *em;
    char *mp;
    ulong flags, n;

    n = strlen(msg);

    spin_lock_irqsave(&emsgs_lock, flags);

    em = emsgs + emsgs_tail_idx;
    if ((em->flags & EMFL_VALID)) {
bail:       spin_unlock_irqrestore(&emsgs_lock, flags);
        return;
    }

    mp = kmalloc(n, GFP_ATOMIC);
    if (mp == NULL) {
        printk(KERN_ERR "aoe: allocation failure, len=%ld\n", n);
        goto bail;
    }

    memcpy(mp, msg, n);
    em->msg = mp;
    em->flags |= EMFL_VALID;
    em->len = n;

    emsgs_tail_idx++;
    emsgs_tail_idx %= ARRAY_SIZE(emsgs);

    spin_unlock_irqrestore(&emsgs_lock, flags);

    if (nblocked_emsgs_readers)
        complete(&emsgs_comp);
}

static ssize_t
aoechr_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offp)
{
    int ret = -EINVAL;

    switch ((unsigned long) filp->private_data) {
    default:
        printk(KERN_INFO "aoe: can't write to that file.\n");
        break;
    case MINOR_DISCOVER:
        ret = discover();
        break;
    case MINOR_INTERFACES:
        ret = interfaces(buf, cnt);
        break;
    case MINOR_REVALIDATE:
        ret = revalidate(buf, cnt);
        break;
    case MINOR_FLUSH:
        ret = aoedev_flush(buf, cnt);
        break;
    }
    if (ret == 0)
        ret = cnt;
    return ret;
}

static int
aoechr_open(struct inode *inode, struct file *filp)
{
    int n, i;

    mutex_lock(&aoechr_mutex);
    n = iminor(inode);
    filp->private_data = (void *) (unsigned long) n;

    for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
        if (chardevs[i].minor == n) {
            mutex_unlock(&aoechr_mutex);
            return 0;
        }
    mutex_unlock(&aoechr_mutex);
    return -EINVAL;
}

static int
aoechr_rel(struct inode *inode, struct file *filp)
{
    return 0;
}

static ssize_t
aoechr_read(struct file *filp, char __user *buf, size_t cnt, loff_t *off)
{
    unsigned long n;
    char *mp;
    struct ErrMsg *em;
    ssize_t len;
    ulong flags;

    n = (unsigned long) filp->private_data;
    if (n != MINOR_ERR)
        return -EFAULT;

    spin_lock_irqsave(&emsgs_lock, flags);

    for (;;) {
        em = emsgs + emsgs_head_idx;
        if ((em->flags & EMFL_VALID) != 0)
            break;
        if (filp->f_flags & O_NDELAY) {
            spin_unlock_irqrestore(&emsgs_lock, flags);
            return -EAGAIN;
        }
        nblocked_emsgs_readers++;

        spin_unlock_irqrestore(&emsgs_lock, flags);

        n = wait_for_completion_interruptible(&emsgs_comp);

        spin_lock_irqsave(&emsgs_lock, flags);

        nblocked_emsgs_readers--;

        if (n) {
            spin_unlock_irqrestore(&emsgs_lock, flags);
            return -ERESTARTSYS;
        }
    }
    if (em->len > cnt) {
        spin_unlock_irqrestore(&emsgs_lock, flags);
        return -EAGAIN;
    }
    mp = em->msg;
    len = em->len;
    em->msg = NULL;
    em->flags &= ~EMFL_VALID;

    emsgs_head_idx++;
    emsgs_head_idx %= ARRAY_SIZE(emsgs);

    spin_unlock_irqrestore(&emsgs_lock, flags);

    n = copy_to_user(buf, mp, len);
    kfree(mp);
    return n == 0 ? len : -EFAULT;
}

static const struct file_operations aoe_fops = {
    .write = aoechr_write,
    .read = aoechr_read,
    .open = aoechr_open,
    .release = aoechr_rel,
    .owner = THIS_MODULE,
    .llseek = noop_llseek,
};

static char *aoe_devnode(struct device *dev, umode_t *mode)
{
    return kasprintf(GFP_KERNEL, "etherd/%s", dev_name(dev));
}

int __init
aoechr_init(void)
{
    int n, i;

    n = register_chrdev(AOE_MAJOR, "aoechr", &aoe_fops);
    if (n < 0) { 
        printk(KERN_ERR "aoe: can't register char device\n");
        return n;
    }
    init_completion(&emsgs_comp);
    spin_lock_init(&emsgs_lock);
    aoe_class = class_create(THIS_MODULE, "aoe");
    if (IS_ERR(aoe_class)) {
        unregister_chrdev(AOE_MAJOR, "aoechr");
        return PTR_ERR(aoe_class);
    }
    aoe_class->devnode = aoe_devnode;

    for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
        device_create(aoe_class, NULL,
                  MKDEV(AOE_MAJOR, chardevs[i].minor), NULL,
                  chardevs[i].name);

    return 0;
}

void
aoechr_exit(void)
{
    int i;

    for (i = 0; i < ARRAY_SIZE(chardevs); ++i)
        device_destroy(aoe_class, MKDEV(AOE_MAJOR, chardevs[i].minor));
    class_destroy(aoe_class);
    unregister_chrdev(AOE_MAJOR, "aoechr");
}