aoe: kernel thread handles I/O completions for simple locking

Make the frames the aoe driver uses to track the relationship between bios
and packets more flexible and detached, so that they can be passed to an
"aoe_ktio" thread for completion of I/O.

The frames are handled much like skbs, with a capped amount of
preallocation so that real-world use cases are likely to run smoothly and
degenerate gracefully even under memory pressure.

Decoupling I/O completion from the receive path and serializing it in a
process makes it easier to think about the correctness of the locking in
the driver, especially in the case of a remote MAC address becoming
unusable.

[dan.carpenter@oracle.com: cleanup an allocation a bit]
Signed-off-by: Ed Cashin <ecashin@coraid.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 471 insertions, 261 deletions

diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index 9a58242290c0..59b333c902a6 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -12,10 +12,17 @@
 #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 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.");
@@ -25,6 +32,15 @@ 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)
 {
@@ -41,15 +57,21 @@ new_skb(ulong len)
 }
 
 static struct frame *
-getframe(struct aoetgt *t, int tag)
+getframe(struct aoetgt *t, u32 tag)
 {
-	struct frame *f, *e;
+	struct frame *f;
+	struct list_head *head, *pos, *nx;
+	u32 n;
 
-	f = t->frames;
-	e = f + t->nframes;
-	for (; f<e; f++)
-		if (f->tag == tag)
+	n = tag % NFACTIVE;
+	head = &t->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;
 }
 
@@ -67,7 +89,7 @@ newtag(struct aoetgt *t)
 	return n |= (++t->lasttag & 0x7fff) << 16;
 }
 
-static int
+static u32
 aoehdr_atainit(struct aoedev *d, struct aoetgt *t, struct aoe_hdr *h)
 {
 	u32 host_tag = newtag(t);
@@ -129,75 +151,96 @@ skb_pool_get(struct aoedev *d)
 	return NULL;
 }
 
-/* freeframe is where we do our load balancing so it's a little hairy. */
+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 *
-freeframe(struct aoedev *d)
+newtframe(struct aoedev *d, struct aoetgt *t)
 {
-	struct frame *f, *e, *rf;
-	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;
 	}
-	t = d->tgt;
-	t++;
-	if (t >= &d->targets[NTARGETS] || !*t)
-		t = d->targets;
+	tt = d->tgt;	/* last used target */
 	for (;;) {
-		if ((*t)->nout < (*t)->maxout
+		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) {
-			rf = NULL;
-			f = (*t)->frames;
-			e = f + (*t)->nframes;
-			for (; f < e; f++) {
-				if (f->tag != FREETAG)
-					continue;
-				skb = f->skb;
-				if (!skb
-				&& !(f->skb = skb = new_skb(ETH_ZLEN)))
-					continue;
-				if (atomic_read(&skb_shinfo(skb)->dataref)
-					!= 1) {
-					if (!rf)
-						rf = f;
-					continue;
-				}
-gotone:				skb->truesize -= skb->data_len;
-				skb_shinfo(skb)->nr_frags = skb->data_len = 0;
-				skb_trim(skb, 0);
-				d->tgt = t;
-				ifrotate(*t);
+		&& t->ifp->nd) {
+			f = newtframe(d, t);
+			if (f) {
+				d->tgt = tt;
+				ifrotate(t);
 				return f;
 			}
-			/* Work can be done, but the network layer is
-			   holding our precious packets.  Try to grab
-			   one from the pool. */
-			f = rf;
-			if (f == NULL) {	/* more paranoia */
-				printk(KERN_ERR
-					"aoe: freeframe: %s.\n",
-					"unexpected null rf");
-				d->flags |= DEVFL_KICKME;
-				return NULL;
-			}
-			skb = skb_pool_get(d);
-			if (skb) {
-				skb_pool_put(d, f->skb);
-				f->skb = skb;
-				goto gotone;
-			}
-			(*t)->dataref++;
-			if ((*t)->nout == 0)
-				d->flags |= DEVFL_KICKME;
 		}
-		if (t == d->tgt)	/* we've looped and found nada */
+		if (tt == d->tgt)	/* we've looped and found nada */
 			break;
-		t++;
-		if (t >= &d->targets[NTARGETS] || !*t)
-			t = d->targets;
+	}
+	if (totout == 0) {
+		d->kicked++;
+		d->flags |= DEVFL_KICKME;
 	}
 	return NULL;
 }
@@ -220,6 +263,16 @@ loop:
 	goto loop;
 }
 
+static void
+fhash(struct frame *f)
+{
+	struct aoetgt *t = f->t;
+	u32 n;
+
+	n = f->tag % NFACTIVE;
+	list_add_tail(&f->head, &t->factive[n]);
+}
+
 static int
 aoecmd_ata_rw(struct aoedev *d)
 {
@@ -236,7 +289,7 @@ aoecmd_ata_rw(struct aoedev *d)
 	writebit = 0x10;
 	extbit = 0x4;
 
-	f = freeframe(d);
+	f = newframe(d);
 	if (f == NULL)
 		return 0;
 	t = *d->tgt;
@@ -274,6 +327,7 @@ aoecmd_ata_rw(struct aoedev *d)
 	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;
@@ -358,14 +412,16 @@ cont:
 }
 
 static void
-resend(struct aoedev *d, struct aoetgt *t, struct frame *f)
+resend(struct aoedev *d, struct frame *f)
 {
 	struct sk_buff *skb;
 	struct aoe_hdr *h;
 	struct aoe_atahdr *ah;
+	struct aoetgt *t;
 	char buf[128];
 	u32 n;
 
+	t = f->t;
 	ifrotate(t);
 	n = newtag(t);
 	skb = f->skb;
@@ -379,28 +435,11 @@ resend(struct aoedev *d, struct aoetgt *t, struct frame *f)
 	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);
 
-	switch (ah->cmdstat) {
-	default:
-		break;
-	case ATA_CMD_PIO_READ:
-	case ATA_CMD_PIO_READ_EXT:
-	case ATA_CMD_PIO_WRITE:
-	case ATA_CMD_PIO_WRITE_EXT:
-		put_lba(ah, f->lba);
-
-		n = f->bcnt;
-		ah->scnt = n >> 9;
-		if (ah->aflags & AOEAFL_WRITE) {
-			skb_fillup(skb, f->bv, f->bv_off, n);
-			skb->len = sizeof *h + sizeof *ah + n;
-			skb->data_len = n;
-			skb->truesize += n;
-		}
-	}
 	skb->dev = t->ifp->nd;
 	skb = skb_clone(skb, GFP_ATOMIC);
 	if (skb == NULL)
@@ -409,7 +448,7 @@ resend(struct aoedev *d, struct aoetgt *t, struct frame *f)
 }
 
 static int
-tsince(int tag)
+tsince(u32 tag)
 {
 	int n;
 
@@ -463,26 +502,38 @@ ejectif(struct aoetgt *t, struct aoeif *ifp)
 static int
 sthtith(struct aoedev *d)
 {
-	struct frame *f, *e, *nf;
+	struct frame *f, *nf;
+	struct list_head *nx, *pos, *head;
 	struct sk_buff *skb;
-	struct aoetgt *ht = *d->htgt;
-
-	f = ht->frames;
-	e = f + ht->nframes;
-	for (; f < e; f++) {
-		if (f->tag == FREETAG)
-			continue;
-		nf = freeframe(d);
-		if (!nf)
-			return 0;
-		skb = nf->skb;
-		*nf = *f;
-		f->skb = skb;
-		f->tag = FREETAG;
-		nf->waited = 0;
-		ht->nout--;
-		(*d->tgt)->nout++;
-		resend(d, *d->tgt, nf);
+	struct aoetgt *ht = d->htgt;
+	int i;
+
+	for (i = 0; i < NFACTIVE; i++) {
+		head = &ht->factive[i];
+		list_for_each_safe(pos, nx, head) {
+			f = list_entry(pos, struct frame, head);
+			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);
+		}
 	}
 	/* he's clean, he's useless.  take away his interfaces */
 	memset(ht->ifs, 0, sizeof ht->ifs);
@@ -507,9 +558,12 @@ rexmit_timer(ulong vp)
 	struct aoedev *d;
 	struct aoetgt *t, **tt, **te;
 	struct aoeif *ifp;
-	struct frame *f, *e;
+	struct frame *f;
+	struct list_head *head, *pos, *nx;
+	LIST_HEAD(flist);
 	register long timeout;
 	ulong flags, n;
+	int i;
 
 	d = (struct aoedev *) vp;
 
@@ -523,41 +577,21 @@ rexmit_timer(ulong vp)
 		spin_unlock_irqrestore(&d->lock, flags);
 		return;
 	}
+
+	/* collect all frames to rexmit into flist */
 	tt = d->targets;
 	te = tt + NTARGETS;
 	for (; tt < te && *tt; tt++) {
 		t = *tt;
-		f = t->frames;
-		e = f + t->nframes;
-		for (; f < e; f++) {
-			if (f->tag == FREETAG
-			|| tsince(f->tag) < timeout)
-				continue;
-			n = f->waited += timeout;
-			n /= HZ;
-			if (n > aoe_deadsecs) {
-				/* waited too long.  device failure. */
-				aoedev_downdev(d);
-				break;
-			}
-
-			if (n > HELPWAIT /* see if another target can help */
-			&& (tt != d->targets || d->targets[1]))
-				d->htgt = tt;
-
-			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;
+		for (i = 0; i < NFACTIVE; i++) {
+			head = &t->factive[i];
+			list_for_each_safe(pos, nx, head) {
+				f = list_entry(pos, struct frame, head);
+				if (tsince(f->tag) < timeout)
+					continue;
+				/* move to flist for later processing */
+				list_move_tail(pos, &flist);
 			}
-			resend(d, t, f);
 		}
 
 		/* window check */
@@ -569,6 +603,44 @@ rexmit_timer(ulong vp)
 		}
 	}
 
+	/* 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, &f->t->factive[0]);
+			aoedev_downdev(d);
+			break;
+		}
+		list_del(pos);
+
+		t = f->t;
+		if (n > HELPWAIT) {
+			/* see if another target can help */
+			if (d->ntargets > 1)
+				d->htgt = t;
+		}
+		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 (!skb_queue_empty(&d->sendq)) {
 		n = d->rttavg <<= 1;
 		if (n > MAXTIMER)
@@ -750,7 +822,7 @@ diskstats(struct gendisk *disk, struct bio *bio, ulong duration, sector_t sector
 }
 
 static void
-bvcpy(struct bio_vec *bv, ulong off, struct sk_buff *skb, ulong cnt)
+bvcpy(struct bio_vec *bv, ulong off, struct sk_buff *skb, long cnt)
 {
 	ulong fcnt;
 	char *p;
@@ -771,60 +843,225 @@ loop:
 }
 
 static void
-fadvance(struct frame *f, ulong cnt)
+ktiocomplete(struct frame *f)
 {
-	ulong fcnt;
+	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;
 
-	f->lba += cnt >> 9;
-loop:
-	fcnt = f->bv->bv_len - (f->bv_off - f->bv->bv_offset);
-	if (fcnt > cnt) {
-		f->bv_off += cnt;
+	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)
+			buf->flags |= BUFFL_FAIL;
+		goto badrsp;
 	}
-	cnt -= fcnt;
-	f->bv++;
-	f->bv_off = f->bv->bv_offset;
-	goto loop;
+
+	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);
+			buf->flags |= BUFFL_FAIL;
+			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 (n > DEFAULTBCNT)
+				ifp->lostjumbo = 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) {
+		struct bio *bio = buf->bio;
+
+		diskstats(d->gd, bio, jiffies - buf->stime, buf->sector);
+		n = (buf->flags & BUFFL_FAIL) ? -EIO : 0;
+		mempool_free(buf, d->bufpool);
+		spin_unlock_irq(&d->lock);
+		if (n != -EIO)
+			bio_flush_dcache_pages(buf->bio);
+		bio_endio(bio, n);
+	} else
+		spin_unlock_irq(&d->lock);
+	dev_kfree_skb(skb);
 }
 
-void
+/* 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;
+}
+
+static void
+aoe_ktstop(struct ktstate *k)
+{
+	kthread_stop(k->task);
+	wait_for_completion(&k->rendez);
+}
+
+static 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 sk_buff_head queue;
 	struct aoedev *d;
-	struct aoe_hdr *hin, *hout;
-	struct aoe_atahdr *ahin, *ahout;
+	struct aoe_hdr *h;
 	struct frame *f;
-	struct buf *buf;
 	struct aoetgt *t;
-	struct aoeif *ifp;
-	register long n;
+	u32 n;
 	ulong flags;
 	char ebuf[128];
 	u16 aoemajor;
 
-	hin = (struct aoe_hdr *) skb_mac_header(skb);
-	skb_pull(skb, sizeof(*hin));
-	aoemajor = get_unaligned_be16(&hin->major);
-	d = aoedev_by_aoeaddr(aoemajor, hin->minor);
+	h = (struct aoe_hdr *) skb->data;
+	aoemajor = be16_to_cpu(get_unaligned(&h->major));
+	d = aoedev_by_aoeaddr(aoemajor, h->minor);
 	if (d == NULL) {
 		snprintf(ebuf, sizeof ebuf, "aoecmd_ata_rsp: ata response "
 			"for unknown device %d.%d\n",
-			 aoemajor, hin->minor);
+			aoemajor, h->minor);
 		aoechr_error(ebuf);
-		return;
+		return skb;
 	}
 
 	spin_lock_irqsave(&d->lock, flags);
 
-	n = get_unaligned_be32(&hin->tag);
-	t = gettgt(d, hin->src);
+	n = be32_to_cpu(get_unaligned(&h->tag));
+	t = gettgt(d, h->src);
 	if (t == NULL) {
 		printk(KERN_INFO "aoe: can't find target e%ld.%d:%pm\n",
-			d->aoemajor, d->aoeminor, hin->src);
+		       d->aoemajor, d->aoeminor, h->src);
 		spin_unlock_irqrestore(&d->lock, flags);
-		return;
+		return skb;
 	}
 	f = getframe(t, n);
 	if (f == NULL) {
@@ -833,102 +1070,26 @@ aoecmd_ata_rsp(struct sk_buff *skb)
 		snprintf(ebuf, sizeof ebuf,
 			"%15s e%d.%d    tag=%08x@%08lx\n",
 			"unexpected rsp",
-			get_unaligned_be16(&hin->major),
-			hin->minor,
-			get_unaligned_be32(&hin->tag),
+			get_unaligned_be16(&h->major),
+			h->minor,
+			get_unaligned_be32(&h->tag),
 			jiffies);
 		aoechr_error(ebuf);
-		return;
+		return skb;
 	}
-
 	calc_rttavg(d, tsince(f->tag));
-
-	ahin = (struct aoe_atahdr *) skb->data;
-	skb_pull(skb, sizeof(*ahin));
-	hout = (struct aoe_hdr *) skb_mac_header(f->skb);
-	ahout = (struct aoe_atahdr *) (hout+1);
-	buf = f->buf;
-
-	if (ahin->cmdstat & 0xa9) {	/* these bits cleared on success */
-		printk(KERN_ERR
-			"aoe: ata error cmd=%2.2Xh stat=%2.2Xh from e%ld.%d\n",
-			ahout->cmdstat, ahin->cmdstat,
-			d->aoemajor, d->aoeminor);
-		if (buf)
-			buf->flags |= BUFFL_FAIL;
-	} else {
-		if (d->htgt && t == *d->htgt) /* I'll help myself, thank you. */
-			d->htgt = NULL;
-		n = ahout->scnt << 9;
-		switch (ahout->cmdstat) {
-		case ATA_CMD_PIO_READ:
-		case ATA_CMD_PIO_READ_EXT:
-			if (skb->len < n) {
-				printk(KERN_ERR
-					"aoe: %s.  skb->len=%d need=%ld\n",
-					"runt data size in read", skb->len, n);
-				/* fail frame f?  just returning will rexmit. */
-				spin_unlock_irqrestore(&d->lock, flags);
-				return;
-			}
-			bvcpy(f->bv, f->bv_off, skb, n);
-		case ATA_CMD_PIO_WRITE:
-		case ATA_CMD_PIO_WRITE_EXT:
-			ifp = getif(t, skb->dev);
-			if (ifp) {
-				ifp->lost = 0;
-				if (n > DEFAULTBCNT)
-					ifp->lostjumbo = 0;
-			}
-			if (f->bcnt -= n) {
-				fadvance(f, n);
-				resend(d, t, f);
-				goto xmit;
-			}
-			break;
-		case ATA_CMD_ID_ATA:
-			if (skb->len < 512) {
-				printk(KERN_INFO
-					"aoe: runt data size in ataid.  skb->len=%d\n",
-					skb->len);
-				spin_unlock_irqrestore(&d->lock, flags);
-				return;
-			}
-			if (skb_linearize(skb))
-				break;
-			ataid_complete(d, t, skb->data);
-			break;
-		default:
-			printk(KERN_INFO
-				"aoe: unrecognized ata command %2.2Xh for %d.%d\n",
-				ahout->cmdstat,
-				get_unaligned_be16(&hin->major),
-				hin->minor);
-		}
-	}
-
-	if (buf && --buf->nframesout == 0 && buf->resid == 0) {
-		diskstats(d->gd, buf->bio, jiffies - buf->stime, buf->sector);
-		if (buf->flags & BUFFL_FAIL)
-			bio_endio(buf->bio, -EIO);
-		else {
-			bio_flush_dcache_pages(buf->bio);
-			bio_endio(buf->bio, 0);
-		}
-		mempool_free(buf, d->bufpool);
-	}
-
-	f->buf = NULL;
-	f->tag = FREETAG;
 	t->nout--;
-
 	aoecmd_work(d);
-xmit:
-	__skb_queue_head_init(&queue);
-	skb_queue_splice_init(&d->sendq, &queue);
 
 	spin_unlock_irqrestore(&d->lock, flags);
-	aoenet_xmit(&queue);
+
+	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
@@ -950,7 +1111,7 @@ aoecmd_ata_id(struct aoedev *d)
 	struct sk_buff *skb;
 	struct aoetgt *t;
 
-	f = freeframe(d);
+	f = newframe(d);
 	if (f == NULL)
 		return NULL;
 
@@ -963,6 +1124,7 @@ aoecmd_ata_id(struct aoedev *d)
 	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;
 
@@ -983,7 +1145,7 @@ static struct aoetgt *
 addtgt(struct aoedev *d, char *addr, ulong nframes)
 {
 	struct aoetgt *t, **tt, **te;
-	struct frame *f, *e;
+	int i;
 
 	tt = d->targets;
 	te = tt + NTARGETS;
@@ -995,23 +1157,21 @@ addtgt(struct aoedev *d, char *addr, ulong nframes)
 			"aoe: device addtgt failure; too many targets\n");
 		return NULL;
 	}
-	t = kcalloc(1, sizeof *t, GFP_ATOMIC);
-	f = kcalloc(nframes, sizeof *f, GFP_ATOMIC);
-	if (!t || !f) {
-		kfree(f);
-		kfree(t);
+	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->frames = f;
-	e = f + nframes;
-	for (; f < e; f++)
-		f->tag = FREETAG;
+	t->d = d;
 	memcpy(t->addr, addr, sizeof t->addr);
 	t->ifp = t->ifs;
 	t->maxout = t->nframes;
+	INIT_LIST_HEAD(&t->ffree);
+	for (i = 0; i < NFACTIVE; ++i)
+		INIT_LIST_HEAD(&t->factive[i]);
 	return *tt = t;
 }
 
@@ -1136,3 +1296,53 @@ aoecmd_cleanslate(struct aoedev *d)
 		}
 	}
 }
+
+static void
+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);
+	}
+}
+
+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);
+	flush_iocq();
+}