aoecmd.c

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/* Copyright (c) 2012 Coraid, Inc.  See COPYING for GPL terms. */
/*
 * aoecmd.c
 * Filesystem request handling methods
 */

#include <linux/ata.h>
#include <linux/slab.h>
#include <linux/hdreg.h>
#include <linux/blkdev.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/genhd.h>
#include <linux/moduleparam.h>
#include <linux/workqueue.h>
#include <linux/kthread.h>
#include <net/net_namespace.h>
#include <asm/unaligned.h>
#include <linux/uio.h>
#include "aoe.h"

#define MAXIOC (8192)   /* default meant to avoid most soft lockups */

static void ktcomplete(struct frame *, struct sk_buff *);

static struct buf *nextbuf(struct aoedev *);

static int aoe_deadsecs = 60 * 3;
module_param(aoe_deadsecs, int, 0644);
MODULE_PARM_DESC(aoe_deadsecs, "After aoe_deadsecs seconds, give up and fail dev.");

static int aoe_maxout = 16;
module_param(aoe_maxout, int, 0644);
MODULE_PARM_DESC(aoe_maxout,
    "Only aoe_maxout outstanding packets for every MAC on eX.Y.");

static wait_queue_head_t ktiowq;
static struct ktstate kts;

/* io completion queue */
static struct {
    struct list_head head;
    spinlock_t lock;
} iocq;

static struct sk_buff *
new_skb(ulong len)
{
    struct sk_buff *skb;

    skb = alloc_skb(len, GFP_ATOMIC);
    if (skb) {
        skb_reset_mac_header(skb);
        skb_reset_network_header(skb);
        skb->protocol = __constant_htons(ETH_P_AOE);
        skb_checksum_none_assert(skb);
    }
    return skb;
}

static struct frame *
getframe(struct aoedev *d, u32 tag)
{
    struct frame *f;
    struct list_head *head, *pos, *nx;
    u32 n;

    n = tag % NFACTIVE;
    head = &d->factive[n];
    list_for_each_safe(pos, nx, head) {
        f = list_entry(pos, struct frame, head);
        if (f->tag == tag) {
            list_del(pos);
            return f;
        }
    }
    return NULL;
}

/*
 * Leave the top bit clear so we have tagspace for userland.
 * The bottom 16 bits are the xmit tick for rexmit/rttavg processing.
 * This driver reserves tag -1 to mean "unused frame."
 */
static int
newtag(struct aoedev *d)
{
    register ulong n;

    n = jiffies & 0xffff;
    return n |= (++d->lasttag & 0x7fff) << 16;
}

static u32
aoehdr_atainit(struct aoedev *d, struct aoetgt *t, struct aoe_hdr *h)
{
    u32 host_tag = newtag(d);

    memcpy(h->src, t->ifp->nd->dev_addr, sizeof h->src);
    memcpy(h->dst, t->addr, sizeof h->dst);
    h->type = __constant_cpu_to_be16(ETH_P_AOE);
    h->verfl = AOE_HVER;
    h->major = cpu_to_be16(d->aoemajor);
    h->minor = d->aoeminor;
    h->cmd = AOECMD_ATA;
    h->tag = cpu_to_be32(host_tag);

    return host_tag;
}

static inline void
put_lba(struct aoe_atahdr *ah, sector_t lba)
{
    ah->lba0 = lba;
    ah->lba1 = lba >>= 8;
    ah->lba2 = lba >>= 8;
    ah->lba3 = lba >>= 8;
    ah->lba4 = lba >>= 8;
    ah->lba5 = lba >>= 8;
}

static struct aoeif *
ifrotate(struct aoetgt *t)
{
    struct aoeif *ifp;

    ifp = t->ifp;
    ifp++;
    if (ifp >= &t->ifs[NAOEIFS] || ifp->nd == NULL)
        ifp = t->ifs;
    if (ifp->nd == NULL)
        return NULL;
    return t->ifp = ifp;
}

static void
skb_pool_put(struct aoedev *d, struct sk_buff *skb)
{
    __skb_queue_tail(&d->skbpool, skb);
}

static struct sk_buff *
skb_pool_get(struct aoedev *d)
{
    struct sk_buff *skb = skb_peek(&d->skbpool);

    if (skb && atomic_read(&skb_shinfo(skb)->dataref) == 1) {
        __skb_unlink(skb, &d->skbpool);
        return skb;
    }
    if (skb_queue_len(&d->skbpool) < NSKBPOOLMAX &&
        (skb = new_skb(ETH_ZLEN)))
        return skb;

    return NULL;
}

void
aoe_freetframe(struct frame *f)
{
    struct aoetgt *t;

    t = f->t;
    f->buf = NULL;
    f->bv = NULL;
    f->r_skb = NULL;
    list_add(&f->head, &t->ffree);
}

static struct frame *
newtframe(struct aoedev *d, struct aoetgt *t)
{
    struct frame *f;
    struct sk_buff *skb;
    struct list_head *pos;

    if (list_empty(&t->ffree)) {
        if (t->falloc >= NSKBPOOLMAX*2)
            return NULL;
        f = kcalloc(1, sizeof(*f), GFP_ATOMIC);
        if (f == NULL)
            return NULL;
        t->falloc++;
        f->t = t;
    } else {
        pos = t->ffree.next;
        list_del(pos);
        f = list_entry(pos, struct frame, head);
    }

    skb = f->skb;
    if (skb == NULL) {
        f->skb = skb = new_skb(ETH_ZLEN);
        if (!skb) {
bail:           aoe_freetframe(f);
            return NULL;
        }
    }

    if (atomic_read(&skb_shinfo(skb)->dataref) != 1) {
        skb = skb_pool_get(d);
        if (skb == NULL)
            goto bail;
        skb_pool_put(d, f->skb);
        f->skb = skb;
    }

    skb->truesize -= skb->data_len;
    skb_shinfo(skb)->nr_frags = skb->data_len = 0;
    skb_trim(skb, 0);
    return f;
}

static struct frame *
newframe(struct aoedev *d)
{
    struct frame *f;
    struct aoetgt *t, **tt;
    int totout = 0;

    if (d->targets[0] == NULL) {    /* shouldn't happen, but I'm paranoid */
        printk(KERN_ERR "aoe: NULL TARGETS!\n");
        return NULL;
    }
    tt = d->tgt;    /* last used target */
    for (;;) {
        tt++;
        if (tt >= &d->targets[NTARGETS] || !*tt)
            tt = d->targets;
        t = *tt;
        totout += t->nout;
        if (t->nout < t->maxout
        && t != d->htgt
        && t->ifp->nd) {
            f = newtframe(d, t);
            if (f) {
                ifrotate(t);
                d->tgt = tt;
                return f;
            }
        }
        if (tt == d->tgt)   /* we've looped and found nada */
            break;
    }
    if (totout == 0) {
        d->kicked++;
        d->flags |= DEVFL_KICKME;
    }
    return NULL;
}

static void
skb_fillup(struct sk_buff *skb, struct bio_vec *bv, ulong off, ulong cnt)
{
    int frag = 0;
    ulong fcnt;
loop:
    fcnt = bv->bv_len - (off - bv->bv_offset);
    if (fcnt > cnt)
        fcnt = cnt;
    skb_fill_page_desc(skb, frag++, bv->bv_page, off, fcnt);
    cnt -= fcnt;
    if (cnt <= 0)
        return;
    bv++;
    off = bv->bv_offset;
    goto loop;
}

static void
fhash(struct frame *f)
{
    struct aoedev *d = f->t->d;
    u32 n;

    n = f->tag % NFACTIVE;
    list_add_tail(&f->head, &d->factive[n]);
}

static int
aoecmd_ata_rw(struct aoedev *d)
{
    struct frame *f;
    struct aoe_hdr *h;
    struct aoe_atahdr *ah;
    struct buf *buf;
    struct aoetgt *t;
    struct sk_buff *skb;
    struct sk_buff_head queue;
    ulong bcnt, fbcnt;
    char writebit, extbit;

    writebit = 0x10;
    extbit = 0x4;

    buf = nextbuf(d);
    if (buf == NULL)
        return 0;
    f = newframe(d);
    if (f == NULL)
        return 0;
    t = *d->tgt;
    bcnt = d->maxbcnt;
    if (bcnt == 0)
        bcnt = DEFAULTBCNT;
    if (bcnt > buf->resid)
        bcnt = buf->resid;
    fbcnt = bcnt;
    f->bv = buf->bv;
    f->bv_off = f->bv->bv_offset + (f->bv->bv_len - buf->bv_resid);
    do {
        if (fbcnt < buf->bv_resid) {
            buf->bv_resid -= fbcnt;
            buf->resid -= fbcnt;
            break;
        }
        fbcnt -= buf->bv_resid;
        buf->resid -= buf->bv_resid;
        if (buf->resid == 0) {
            d->ip.buf = NULL;
            break;
        }
        buf->bv++;
        buf->bv_resid = buf->bv->bv_len;
        WARN_ON(buf->bv_resid == 0);
    } while (fbcnt);

    /* initialize the headers & frame */
    skb = f->skb;
    h = (struct aoe_hdr *) skb_mac_header(skb);
    ah = (struct aoe_atahdr *) (h+1);
    skb_put(skb, sizeof *h + sizeof *ah);
    memset(h, 0, skb->len);
    f->tag = aoehdr_atainit(d, t, h);
    fhash(f);
    t->nout++;
    f->waited = 0;
    f->buf = buf;
    f->bcnt = bcnt;
    f->lba = buf->sector;

    /* set up ata header */
    ah->scnt = bcnt >> 9;
    put_lba(ah, buf->sector);
    if (d->flags & DEVFL_EXT) {
        ah->aflags |= AOEAFL_EXT;
    } else {
        extbit = 0;
        ah->lba3 &= 0x0f;
        ah->lba3 |= 0xe0;   /* LBA bit + obsolete 0xa0 */
    }
    if (bio_data_dir(buf->bio) == WRITE) {
        skb_fillup(skb, f->bv, f->bv_off, bcnt);
        ah->aflags |= AOEAFL_WRITE;
        skb->len += bcnt;
        skb->data_len = bcnt;
        skb->truesize += bcnt;
        t->wpkts++;
    } else {
        t->rpkts++;
        writebit = 0;
    }

    ah->cmdstat = ATA_CMD_PIO_READ | writebit | extbit;

    /* mark all tracking fields and load out */
    buf->nframesout += 1;
    buf->sector += bcnt >> 9;

    skb->dev = t->ifp->nd;
    skb = skb_clone(skb, GFP_ATOMIC);
    if (skb) {
        __skb_queue_head_init(&queue);
        __skb_queue_tail(&queue, skb);
        aoenet_xmit(&queue);
    }
    return 1;
}

/* some callers cannot sleep, and they can call this function,
 * transmitting the packets later, when interrupts are on
 */
static void
aoecmd_cfg_pkts(ushort aoemajor, unsigned char aoeminor, struct sk_buff_head *queue)
{
    struct aoe_hdr *h;
    struct aoe_cfghdr *ch;
    struct sk_buff *skb;
    struct net_device *ifp;

    rcu_read_lock();
    for_each_netdev_rcu(&init_net, ifp) {
        dev_hold(ifp);
        if (!is_aoe_netif(ifp))
            goto cont;

        skb = new_skb(sizeof *h + sizeof *ch);
        if (skb == NULL) {
            printk(KERN_INFO "aoe: skb alloc failure\n");
            goto cont;
        }
        skb_put(skb, sizeof *h + sizeof *ch);
        skb->dev = ifp;
        __skb_queue_tail(queue, skb);
        h = (struct aoe_hdr *) skb_mac_header(skb);
        memset(h, 0, sizeof *h + sizeof *ch);

        memset(h->dst, 0xff, sizeof h->dst);
        memcpy(h->src, ifp->dev_addr, sizeof h->src);
        h->type = __constant_cpu_to_be16(ETH_P_AOE);
        h->verfl = AOE_HVER;
        h->major = cpu_to_be16(aoemajor);
        h->minor = aoeminor;
        h->cmd = AOECMD_CFG;

cont:
        dev_put(ifp);
    }
    rcu_read_unlock();
}

static void
resend(struct aoedev *d, struct frame *f)
{
    struct sk_buff *skb;
    struct sk_buff_head queue;
    struct aoe_hdr *h;
    struct aoe_atahdr *ah;
    struct aoetgt *t;
    char buf[128];
    u32 n;

    t = f->t;
    n = newtag(d);
    skb = f->skb;
    if (ifrotate(t) == NULL) {
        /* probably can't happen, but set it up to fail anyway */
        pr_info("aoe: resend: no interfaces to rotate to.\n");
        ktcomplete(f, NULL);
        return;
    }
    h = (struct aoe_hdr *) skb_mac_header(skb);
    ah = (struct aoe_atahdr *) (h+1);

    snprintf(buf, sizeof buf,
        "%15s e%ld.%d oldtag=%08x@%08lx newtag=%08x s=%pm d=%pm nout=%d\n",
        "retransmit", d->aoemajor, d->aoeminor, f->tag, jiffies, n,
        h->src, h->dst, t->nout);
    aoechr_error(buf);

    f->tag = n;
    fhash(f);
    h->tag = cpu_to_be32(n);
    memcpy(h->dst, t->addr, sizeof h->dst);
    memcpy(h->src, t->ifp->nd->dev_addr, sizeof h->src);

    skb->dev = t->ifp->nd;
    skb = skb_clone(skb, GFP_ATOMIC);
    if (skb == NULL)
        return;
    __skb_queue_head_init(&queue);
    __skb_queue_tail(&queue, skb);
    aoenet_xmit(&queue);
}

static int
tsince(u32 tag)
{
    int n;

    n = jiffies & 0xffff;
    n -= tag & 0xffff;
    if (n < 0)
        n += 1<<16;
    return n;
}

static struct aoeif *
getif(struct aoetgt *t, struct net_device *nd)
{
    struct aoeif *p, *e;

    p = t->ifs;
    e = p + NAOEIFS;
    for (; p < e; p++)
        if (p->nd == nd)
            return p;
    return NULL;
}

static void
ejectif(struct aoetgt *t, struct aoeif *ifp)
{
    struct aoeif *e;
    struct net_device *nd;
    ulong n;

    nd = ifp->nd;
    e = t->ifs + NAOEIFS - 1;
    n = (e - ifp) * sizeof *ifp;
    memmove(ifp, ifp+1, n);
    e->nd = NULL;
    dev_put(nd);
}

static int
sthtith(struct aoedev *d)
{
    struct frame *f, *nf;
    struct list_head *nx, *pos, *head;
    struct sk_buff *skb;
    struct aoetgt *ht = d->htgt;
    int i;

    for (i = 0; i < NFACTIVE; i++) {
        head = &d->factive[i];
        list_for_each_safe(pos, nx, head) {
            f = list_entry(pos, struct frame, head);
            if (f->t != ht)
                continue;

            nf = newframe(d);
            if (!nf)
                return 0;

            /* remove frame from active list */
            list_del(pos);

            /* reassign all pertinent bits to new outbound frame */
            skb = nf->skb;
            nf->skb = f->skb;
            nf->buf = f->buf;
            nf->bcnt = f->bcnt;
            nf->lba = f->lba;
            nf->bv = f->bv;
            nf->bv_off = f->bv_off;
            nf->waited = 0;
            f->skb = skb;
            aoe_freetframe(f);
            ht->nout--;
            nf->t->nout++;
            resend(d, nf);
        }
    }
    /* We've cleaned up the outstanding so take away his
     * interfaces so he won't be used.  We should remove him from
     * the target array here, but cleaning up a target is
     * involved.  PUNT!
     */
    memset(ht->ifs, 0, sizeof ht->ifs);
    d->htgt = NULL;
    return 1;
}

static inline unsigned char
ata_scnt(unsigned char *packet) {
    struct aoe_hdr *h;
    struct aoe_atahdr *ah;

    h = (struct aoe_hdr *) packet;
    ah = (struct aoe_atahdr *) (h+1);
    return ah->scnt;
}

static void
rexmit_timer(ulong vp)
{
    struct aoedev *d;
    struct aoetgt *t, **tt, **te;
    struct aoeif *ifp;
    struct frame *f;
    struct list_head *head, *pos, *nx;
    LIST_HEAD(flist);
    register long timeout;
    ulong flags, n;
    int i;

    d = (struct aoedev *) vp;

    /* timeout is always ~150% of the moving average */
    timeout = d->rttavg;
    timeout += timeout >> 1;

    spin_lock_irqsave(&d->lock, flags);

    if (d->flags & DEVFL_TKILL) {
        spin_unlock_irqrestore(&d->lock, flags);
        return;
    }

    /* collect all frames to rexmit into flist */
    for (i = 0; i < NFACTIVE; i++) {
        head = &d->factive[i];
        list_for_each_safe(pos, nx, head) {
            f = list_entry(pos, struct frame, head);
            if (tsince(f->tag) < timeout)
                break;  /* end of expired frames */
            /* move to flist for later processing */
            list_move_tail(pos, &flist);
        }
    }
    /* window check */
    tt = d->targets;
    te = tt + d->ntargets;
    for (; tt < te && (t = *tt); tt++) {
        if (t->nout == t->maxout
        && t->maxout < t->nframes
        && (jiffies - t->lastwadj)/HZ > 10) {
            t->maxout++;
            t->lastwadj = jiffies;
        }
    }

    if (!list_empty(&flist)) {  /* retransmissions necessary */
        n = d->rttavg <<= 1;
        if (n > MAXTIMER)
            d->rttavg = MAXTIMER;
    }

    /* process expired frames */
    while (!list_empty(&flist)) {
        pos = flist.next;
        f = list_entry(pos, struct frame, head);
        n = f->waited += timeout;
        n /= HZ;
        if (n > aoe_deadsecs) {
            /* Waited too long.  Device failure.
             * Hang all frames on first hash bucket for downdev
             * to clean up.
             */
            list_splice(&flist, &d->factive[0]);
            aoedev_downdev(d);
            break;
        }
        list_del(pos);

        t = f->t;
        if (n > aoe_deadsecs/2)
            d->htgt = t; /* see if another target can help */

        if (t->nout == t->maxout) {
            if (t->maxout > 1)
                t->maxout--;
            t->lastwadj = jiffies;
        }

        ifp = getif(t, f->skb->dev);
        if (ifp && ++ifp->lost > (t->nframes << 1)
        && (ifp != t->ifs || t->ifs[1].nd)) {
            ejectif(t, ifp);
            ifp = NULL;
        }
        resend(d, f);
    }

    if ((d->flags & DEVFL_KICKME || d->htgt) && d->blkq) {
        d->flags &= ~DEVFL_KICKME;
        d->blkq->request_fn(d->blkq);
    }

    d->timer.expires = jiffies + TIMERTICK;
    add_timer(&d->timer);

    spin_unlock_irqrestore(&d->lock, flags);
}

static unsigned long
rqbiocnt(struct request *r)
{
    struct bio *bio;
    unsigned long n = 0;

    __rq_for_each_bio(bio, r)
        n++;
    return n;
}

/* This can be removed if we are certain that no users of the block
 * layer will ever use zero-count pages in bios.  Otherwise we have to
 * protect against the put_page sometimes done by the network layer.
 *
 * See http://oss.sgi.com/archives/xfs/2007-01/msg00594.html for
 * discussion.
 *
 * We cannot use get_page in the workaround, because it insists on a
 * positive page count as a precondition.  So we use _count directly.
 */
static void
bio_pageinc(struct bio *bio)
{
    struct bio_vec *bv;
    struct page *page;
    int i;

    bio_for_each_segment(bv, bio, i) {
        page = bv->bv_page;
        /* Non-zero page count for non-head members of
         * compound pages is no longer allowed by the kernel,
         * but this has never been seen here.
         */
        if (unlikely(PageCompound(page)))
            if (compound_trans_head(page) != page) {
                pr_crit("page tail used for block I/O\n");
                BUG();
            }
        atomic_inc(&page->_count);
    }
}

static void
bio_pagedec(struct bio *bio)
{
    struct bio_vec *bv;
    int i;

    bio_for_each_segment(bv, bio, i)
        atomic_dec(&bv->bv_page->_count);
}

static void
bufinit(struct buf *buf, struct request *rq, struct bio *bio)
{
    struct bio_vec *bv;

    memset(buf, 0, sizeof(*buf));
    buf->rq = rq;
    buf->bio = bio;
    buf->resid = bio->bi_size;
    buf->sector = bio->bi_sector;
    bio_pageinc(bio);
    buf->bv = bv = &bio->bi_io_vec[bio->bi_idx];
    buf->bv_resid = bv->bv_len;
    WARN_ON(buf->bv_resid == 0);
}

static struct buf *
nextbuf(struct aoedev *d)
{
    struct request *rq;
    struct request_queue *q;
    struct buf *buf;
    struct bio *bio;

    q = d->blkq;
    if (q == NULL)
        return NULL;    /* initializing */
    if (d->ip.buf)
        return d->ip.buf;
    rq = d->ip.rq;
    if (rq == NULL) {
        rq = blk_peek_request(q);
        if (rq == NULL)
            return NULL;
        blk_start_request(rq);
        d->ip.rq = rq;
        d->ip.nxbio = rq->bio;
        rq->special = (void *) rqbiocnt(rq);
    }
    buf = mempool_alloc(d->bufpool, GFP_ATOMIC);
    if (buf == NULL) {
        pr_err("aoe: nextbuf: unable to mempool_alloc!\n");
        return NULL;
    }
    bio = d->ip.nxbio;
    bufinit(buf, rq, bio);
    bio = bio->bi_next;
    d->ip.nxbio = bio;
    if (bio == NULL)
        d->ip.rq = NULL;
    return d->ip.buf = buf;
}

/* enters with d->lock held */
void
aoecmd_work(struct aoedev *d)
{
    if (d->htgt && !sthtith(d))
        return;
    while (aoecmd_ata_rw(d))
        ;
}

/* this function performs work that has been deferred until sleeping is OK
 */
void
aoecmd_sleepwork(struct work_struct *work)
{
    struct aoedev *d = container_of(work, struct aoedev, work);
    struct block_device *bd;
    u64 ssize;

    if (d->flags & DEVFL_GDALLOC)
        aoeblk_gdalloc(d);

    if (d->flags & DEVFL_NEWSIZE) {
        ssize = get_capacity(d->gd);
        bd = bdget_disk(d->gd, 0);
        if (bd) {
            mutex_lock(&bd->bd_inode->i_mutex);
            i_size_write(bd->bd_inode, (loff_t)ssize<<9);
            mutex_unlock(&bd->bd_inode->i_mutex);
            bdput(bd);
        }
        spin_lock_irq(&d->lock);
        d->flags |= DEVFL_UP;
        d->flags &= ~DEVFL_NEWSIZE;
        spin_unlock_irq(&d->lock);
    }
}

static void
ataid_complete(struct aoedev *d, struct aoetgt *t, unsigned char *id)
{
    u64 ssize;
    u16 n;

    /* word 83: command set supported */
    n = get_unaligned_le16(&id[83 << 1]);

    /* word 86: command set/feature enabled */
    n |= get_unaligned_le16(&id[86 << 1]);

    if (n & (1<<10)) {  /* bit 10: LBA 48 */
        d->flags |= DEVFL_EXT;

        /* word 100: number lba48 sectors */
        ssize = get_unaligned_le64(&id[100 << 1]);

        /* set as in ide-disk.c:init_idedisk_capacity */
        d->geo.cylinders = ssize;
        d->geo.cylinders /= (255 * 63);
        d->geo.heads = 255;
        d->geo.sectors = 63;
    } else {
        d->flags &= ~DEVFL_EXT;

        /* number lba28 sectors */
        ssize = get_unaligned_le32(&id[60 << 1]);

        /* NOTE: obsolete in ATA 6 */
        d->geo.cylinders = get_unaligned_le16(&id[54 << 1]);
        d->geo.heads = get_unaligned_le16(&id[55 << 1]);
        d->geo.sectors = get_unaligned_le16(&id[56 << 1]);
    }

    if (d->ssize != ssize)
        printk(KERN_INFO
            "aoe: %pm e%ld.%d v%04x has %llu sectors\n",
            t->addr,
            d->aoemajor, d->aoeminor,
            d->fw_ver, (long long)ssize);
    d->ssize = ssize;
    d->geo.start = 0;
    if (d->flags & (DEVFL_GDALLOC|DEVFL_NEWSIZE))
        return;
    if (d->gd != NULL) {
        set_capacity(d->gd, ssize);
        d->flags |= DEVFL_NEWSIZE;
    } else
        d->flags |= DEVFL_GDALLOC;
    schedule_work(&d->work);
}

static void
calc_rttavg(struct aoedev *d, int rtt)
{
    register long n;

    n = rtt;
    if (n < 0) {
        n = -rtt;
        if (n < MINTIMER)
            n = MINTIMER;
        else if (n > MAXTIMER)
            n = MAXTIMER;
        d->mintimer += (n - d->mintimer) >> 1;
    } else if (n < d->mintimer)
        n = d->mintimer;
    else if (n > MAXTIMER)
        n = MAXTIMER;

    /* g == .25; cf. Congestion Avoidance and Control, Jacobson & Karels; 1988 */
    n -= d->rttavg;
    d->rttavg += n >> 2;
}

static struct aoetgt *
gettgt(struct aoedev *d, char *addr)
{
    struct aoetgt **t, **e;

    t = d->targets;
    e = t + NTARGETS;
    for (; t < e && *t; t++)
        if (memcmp((*t)->addr, addr, sizeof((*t)->addr)) == 0)
            return *t;
    return NULL;
}

static void
bvcpy(struct bio_vec *bv, ulong off, struct sk_buff *skb, long cnt)
{
    ulong fcnt;
    char *p;
    int soff = 0;
loop:
    fcnt = bv->bv_len - (off - bv->bv_offset);
    if (fcnt > cnt)
        fcnt = cnt;
    p = page_address(bv->bv_page) + off;
    skb_copy_bits(skb, soff, p, fcnt);
    soff += fcnt;
    cnt -= fcnt;
    if (cnt <= 0)
        return;
    bv++;
    off = bv->bv_offset;
    goto loop;
}

void
aoe_end_request(struct aoedev *d, struct request *rq, int fastfail)
{
    struct bio *bio;
    int bok;
    struct request_queue *q;

    q = d->blkq;
    if (rq == d->ip.rq)
        d->ip.rq = NULL;
    do {
        bio = rq->bio;
        bok = !fastfail && test_bit(BIO_UPTODATE, &bio->bi_flags);
    } while (__blk_end_request(rq, bok ? 0 : -EIO, bio->bi_size));

    /* cf. http://lkml.org/lkml/2006/10/31/28 */
    if (!fastfail)
        __blk_run_queue(q);
}

static void
aoe_end_buf(struct aoedev *d, struct buf *buf)
{
    struct request *rq;
    unsigned long n;

    if (buf == d->ip.buf)
        d->ip.buf = NULL;
    rq = buf->rq;
    bio_pagedec(buf->bio);
    mempool_free(buf, d->bufpool);
    n = (unsigned long) rq->special;
    rq->special = (void *) --n;
    if (n == 0)
        aoe_end_request(d, rq, 0);
}

static void
ktiocomplete(struct frame *f)
{
    struct aoe_hdr *hin, *hout;
    struct aoe_atahdr *ahin, *ahout;
    struct buf *buf;
    struct sk_buff *skb;
    struct aoetgt *t;
    struct aoeif *ifp;
    struct aoedev *d;
    long n;

    if (f == NULL)
        return;

    t = f->t;
    d = t->d;

    hout = (struct aoe_hdr *) skb_mac_header(f->skb);
    ahout = (struct aoe_atahdr *) (hout+1);
    buf = f->buf;
    skb = f->r_skb;
    if (skb == NULL)
        goto noskb; /* just fail the buf. */

    hin = (struct aoe_hdr *) skb->data;
    skb_pull(skb, sizeof(*hin));
    ahin = (struct aoe_atahdr *) skb->data;
    skb_pull(skb, sizeof(*ahin));
    if (ahin->cmdstat & 0xa9) { /* these bits cleared on success */
        pr_err("aoe: ata error cmd=%2.2Xh stat=%2.2Xh from e%ld.%d\n",
            ahout->cmdstat, ahin->cmdstat,
            d->aoemajor, d->aoeminor);
noskb:  if (buf)
            clear_bit(BIO_UPTODATE, &buf->bio->bi_flags);
        goto badrsp;
    }

    n = ahout->scnt << 9;
    switch (ahout->cmdstat) {
    case ATA_CMD_PIO_READ:
    case ATA_CMD_PIO_READ_EXT:
        if (skb->len < n) {
            pr_err("aoe: runt data size in read.  skb->len=%d need=%ld\n",
                skb->len, n);
            clear_bit(BIO_UPTODATE, &buf->bio->bi_flags);
            break;
        }
        bvcpy(f->bv, f->bv_off, skb, n);
    case ATA_CMD_PIO_WRITE:
    case ATA_CMD_PIO_WRITE_EXT:
        spin_lock_irq(&d->lock);
        ifp = getif(t, skb->dev);
        if (ifp)
            ifp->lost = 0;
        if (d->htgt == t) /* I'll help myself, thank you. */
            d->htgt = NULL;
        spin_unlock_irq(&d->lock);
        break;
    case ATA_CMD_ID_ATA:
        if (skb->len < 512) {
            pr_info("aoe: runt data size in ataid.  skb->len=%d\n",
                skb->len);
            break;
        }
        if (skb_linearize(skb))
            break;
        spin_lock_irq(&d->lock);
        ataid_complete(d, t, skb->data);
        spin_unlock_irq(&d->lock);
        break;
    default:
        pr_info("aoe: unrecognized ata command %2.2Xh for %d.%d\n",
            ahout->cmdstat,
            be16_to_cpu(get_unaligned(&hin->major)),
            hin->minor);
    }
badrsp:
    spin_lock_irq(&d->lock);

    aoe_freetframe(f);

    if (buf && --buf->nframesout == 0 && buf->resid == 0)
        aoe_end_buf(d, buf);

    aoecmd_work(d);

    spin_unlock_irq(&d->lock);
    aoedev_put(d);
    dev_kfree_skb(skb);
}

/* Enters with iocq.lock held.
 * Returns true iff responses needing processing remain.
 */
static int
ktio(void)
{
    struct frame *f;
    struct list_head *pos;
    int i;

    for (i = 0; ; ++i) {
        if (i == MAXIOC)
            return 1;
        if (list_empty(&iocq.head))
            return 0;
        pos = iocq.head.next;
        list_del(pos);
        spin_unlock_irq(&iocq.lock);
        f = list_entry(pos, struct frame, head);
        ktiocomplete(f);
        spin_lock_irq(&iocq.lock);
    }
}

static int
kthread(void *vp)
{
    struct ktstate *k;
    DECLARE_WAITQUEUE(wait, current);
    int more;

    k = vp;
    current->flags |= PF_NOFREEZE;
    set_user_nice(current, -10);
    complete(&k->rendez);   /* tell spawner we're running */
    do {
        spin_lock_irq(k->lock);
        more = k->fn();
        if (!more) {
            add_wait_queue(k->waitq, &wait);
            __set_current_state(TASK_INTERRUPTIBLE);
        }
        spin_unlock_irq(k->lock);
        if (!more) {
            schedule();
            remove_wait_queue(k->waitq, &wait);
        } else
            cond_resched();
    } while (!kthread_should_stop());
    complete(&k->rendez);   /* tell spawner we're stopping */
    return 0;
}

void
aoe_ktstop(struct ktstate *k)
{
    kthread_stop(k->task);
    wait_for_completion(&k->rendez);
}

int
aoe_ktstart(struct ktstate *k)
{
    struct task_struct *task;

    init_completion(&k->rendez);
    task = kthread_run(kthread, k, k->name);
    if (task == NULL || IS_ERR(task))
        return -ENOMEM;
    k->task = task;
    wait_for_completion(&k->rendez); /* allow kthread to start */
    init_completion(&k->rendez);    /* for waiting for exit later */
    return 0;
}

/* pass it off to kthreads for processing */
static void
ktcomplete(struct frame *f, struct sk_buff *skb)
{
    ulong flags;

    f->r_skb = skb;
    spin_lock_irqsave(&iocq.lock, flags);
    list_add_tail(&f->head, &iocq.head);
    spin_unlock_irqrestore(&iocq.lock, flags);
    wake_up(&ktiowq);
}

struct sk_buff *
aoecmd_ata_rsp(struct sk_buff *skb)
{
    struct aoedev *d;
    struct aoe_hdr *h;
    struct frame *f;
    struct aoetgt *t;
    u32 n;
    ulong flags;
    char ebuf[128];
    u16 aoemajor;

    h = (struct aoe_hdr *) skb->data;
    aoemajor = be16_to_cpu(get_unaligned(&h->major));
    d = aoedev_by_aoeaddr(aoemajor, h->minor, 0);
    if (d == NULL) {
        snprintf(ebuf, sizeof ebuf, "aoecmd_ata_rsp: ata response "
            "for unknown device %d.%d\n",
            aoemajor, h->minor);
        aoechr_error(ebuf);
        return skb;
    }

    spin_lock_irqsave(&d->lock, flags);

    n = be32_to_cpu(get_unaligned(&h->tag));
    f = getframe(d, n);
    if (f == NULL) {
        calc_rttavg(d, -tsince(n));
        spin_unlock_irqrestore(&d->lock, flags);
        aoedev_put(d);
        snprintf(ebuf, sizeof ebuf,
            "%15s e%d.%d    tag=%08x@%08lx\n",
            "unexpected rsp",
            get_unaligned_be16(&h->major),
            h->minor,
            get_unaligned_be32(&h->tag),
            jiffies);
        aoechr_error(ebuf);
        return skb;
    }
    t = f->t;
    calc_rttavg(d, tsince(f->tag));
    t->nout--;
    aoecmd_work(d);

    spin_unlock_irqrestore(&d->lock, flags);

    ktcomplete(f, skb);

    /*
     * Note here that we do not perform an aoedev_put, as we are
     * leaving this reference for the ktio to release.
     */
    return NULL;
}

void
aoecmd_cfg(ushort aoemajor, unsigned char aoeminor)
{
    struct sk_buff_head queue;

    __skb_queue_head_init(&queue);
    aoecmd_cfg_pkts(aoemajor, aoeminor, &queue);
    aoenet_xmit(&queue);
}
 
struct sk_buff *
aoecmd_ata_id(struct aoedev *d)
{
    struct aoe_hdr *h;
    struct aoe_atahdr *ah;
    struct frame *f;
    struct sk_buff *skb;
    struct aoetgt *t;

    f = newframe(d);
    if (f == NULL)
        return NULL;

    t = *d->tgt;

    /* initialize the headers & frame */
    skb = f->skb;
    h = (struct aoe_hdr *) skb_mac_header(skb);
    ah = (struct aoe_atahdr *) (h+1);
    skb_put(skb, sizeof *h + sizeof *ah);
    memset(h, 0, skb->len);
    f->tag = aoehdr_atainit(d, t, h);
    fhash(f);
    t->nout++;
    f->waited = 0;

    /* set up ata header */
    ah->scnt = 1;
    ah->cmdstat = ATA_CMD_ID_ATA;
    ah->lba3 = 0xa0;

    skb->dev = t->ifp->nd;

    d->rttavg = MAXTIMER;
    d->timer.function = rexmit_timer;

    return skb_clone(skb, GFP_ATOMIC);
}
 
static struct aoetgt *
addtgt(struct aoedev *d, char *addr, ulong nframes)
{
    struct aoetgt *t, **tt, **te;

    tt = d->targets;
    te = tt + NTARGETS;
    for (; tt < te && *tt; tt++)
        ;

    if (tt == te) {
        printk(KERN_INFO
            "aoe: device addtgt failure; too many targets\n");
        return NULL;
    }
    t = kzalloc(sizeof(*t), GFP_ATOMIC);
    if (!t) {
        printk(KERN_INFO "aoe: cannot allocate memory to add target\n");
        return NULL;
    }

    d->ntargets++;
    t->nframes = nframes;
    t->d = d;
    memcpy(t->addr, addr, sizeof t->addr);
    t->ifp = t->ifs;
    t->maxout = t->nframes;
    INIT_LIST_HEAD(&t->ffree);
    return *tt = t;
}

static void
setdbcnt(struct aoedev *d)
{
    struct aoetgt **t, **e;
    int bcnt = 0;

    t = d->targets;
    e = t + NTARGETS;
    for (; t < e && *t; t++)
        if (bcnt == 0 || bcnt > (*t)->minbcnt)
            bcnt = (*t)->minbcnt;
    if (bcnt != d->maxbcnt) {
        d->maxbcnt = bcnt;
        pr_info("aoe: e%ld.%d: setting %d byte data frames\n",
            d->aoemajor, d->aoeminor, bcnt);
    }
}

static void
setifbcnt(struct aoetgt *t, struct net_device *nd, int bcnt)
{
    struct aoedev *d;
    struct aoeif *p, *e;
    int minbcnt;

    d = t->d;
    minbcnt = bcnt;
    p = t->ifs;
    e = p + NAOEIFS;
    for (; p < e; p++) {
        if (p->nd == NULL)
            break;      /* end of the valid interfaces */
        if (p->nd == nd) {
            p->bcnt = bcnt; /* we're updating */
            nd = NULL;
        } else if (minbcnt > p->bcnt)
            minbcnt = p->bcnt; /* find the min interface */
    }
    if (nd) {
        if (p == e) {
            pr_err("aoe: device setifbcnt failure; too many interfaces.\n");
            return;
        }
        dev_hold(nd);
        p->nd = nd;
        p->bcnt = bcnt;
    }
    t->minbcnt = minbcnt;
    setdbcnt(d);
}

void
aoecmd_cfg_rsp(struct sk_buff *skb)
{
    struct aoedev *d;
    struct aoe_hdr *h;
    struct aoe_cfghdr *ch;
    struct aoetgt *t;
    ulong flags, aoemajor;
    struct sk_buff *sl;
    struct sk_buff_head queue;
    u16 n;

    sl = NULL;
    h = (struct aoe_hdr *) skb_mac_header(skb);
    ch = (struct aoe_cfghdr *) (h+1);

    /*
     * Enough people have their dip switches set backwards to
     * warrant a loud message for this special case.
     */
    aoemajor = get_unaligned_be16(&h->major);
    if (aoemajor == 0xfff) {
        printk(KERN_ERR "aoe: Warning: shelf address is all ones.  "
            "Check shelf dip switches.\n");
        return;
    }
    if (aoemajor == 0xffff) {
        pr_info("aoe: e%ld.%d: broadcast shelf number invalid\n",
            aoemajor, (int) h->minor);
        return;
    }
    if (h->minor == 0xff) {
        pr_info("aoe: e%ld.%d: broadcast slot number invalid\n",
            aoemajor, (int) h->minor);
        return;
    }

    n = be16_to_cpu(ch->bufcnt);
    if (n > aoe_maxout) /* keep it reasonable */
        n = aoe_maxout;

    d = aoedev_by_aoeaddr(aoemajor, h->minor, 1);
    if (d == NULL) {
        pr_info("aoe: device allocation failure\n");
        return;
    }

    spin_lock_irqsave(&d->lock, flags);

    t = gettgt(d, h->src);
    if (!t) {
        t = addtgt(d, h->src, n);
        if (!t)
            goto bail;
    }
    n = skb->dev->mtu;
    n -= sizeof(struct aoe_hdr) + sizeof(struct aoe_atahdr);
    n /= 512;
    if (n > ch->scnt)
        n = ch->scnt;
    n = n ? n * 512 : DEFAULTBCNT;
    setifbcnt(t, skb->dev, n);

    /* don't change users' perspective */
    if (d->nopen == 0) {
        d->fw_ver = be16_to_cpu(ch->fwver);
        sl = aoecmd_ata_id(d);
    }
bail:
    spin_unlock_irqrestore(&d->lock, flags);
    aoedev_put(d);
    if (sl) {
        __skb_queue_head_init(&queue);
        __skb_queue_tail(&queue, sl);
        aoenet_xmit(&queue);
    }
}

void
aoecmd_cleanslate(struct aoedev *d)
{
    struct aoetgt **t, **te;

    d->mintimer = MINTIMER;
    d->maxbcnt = 0;

    t = d->targets;
    te = t + NTARGETS;
    for (; t < te && *t; t++)
        (*t)->maxout = (*t)->nframes;
}

void
aoe_failbuf(struct aoedev *d, struct buf *buf)
{
    if (buf == NULL)
        return;
    buf->resid = 0;
    clear_bit(BIO_UPTODATE, &buf->bio->bi_flags);
    if (buf->nframesout == 0)
        aoe_end_buf(d, buf);
}

void
aoe_flush_iocq(void)
{
    struct frame *f;
    struct aoedev *d;
    LIST_HEAD(flist);
    struct list_head *pos;
    struct sk_buff *skb;
    ulong flags;

    spin_lock_irqsave(&iocq.lock, flags);
    list_splice_init(&iocq.head, &flist);
    spin_unlock_irqrestore(&iocq.lock, flags);
    while (!list_empty(&flist)) {
        pos = flist.next;
        list_del(pos);
        f = list_entry(pos, struct frame, head);
        d = f->t->d;
        skb = f->r_skb;
        spin_lock_irqsave(&d->lock, flags);
        if (f->buf) {
            f->buf->nframesout--;
            aoe_failbuf(d, f->buf);
        }
        aoe_freetframe(f);
        spin_unlock_irqrestore(&d->lock, flags);
        dev_kfree_skb(skb);
        aoedev_put(d);
    }
}

int __init
aoecmd_init(void)
{
    INIT_LIST_HEAD(&iocq.head);
    spin_lock_init(&iocq.lock);
    init_waitqueue_head(&ktiowq);
    kts.name = "aoe_ktio";
    kts.fn = ktio;
    kts.waitq = &ktiowq;
    kts.lock = &iocq.lock;
    return aoe_ktstart(&kts);
}

void
aoecmd_exit(void)
{
    aoe_ktstop(&kts);
    aoe_flush_iocq();
}