diff --git a/engines/libaio.c b/engines/libaio.c
index cb488ef..510ecab 100644
--- a/engines/libaio.c
+++ b/engines/libaio.c
@@ -18,6 +18,8 @@
 struct libaio_data {
 	io_context_t aio_ctx;
 	struct io_event *aio_events;
+	struct iocb **iocbs;
+	int iocbs_nr;
 };
 
 static int fio_libaio_prep(struct thread_data fio_unused *td, struct io_u *io_u)
@@ -68,40 +70,60 @@
 static int fio_libaio_queue(struct thread_data *td, struct io_u *io_u)
 {
 	struct libaio_data *ld = td->io_ops->data;
-	struct iocb *iocb = &io_u->iocb;
-	long ret;
 
+	if (ld->iocbs_nr == (int) td->iodepth)
+		return FIO_Q_BUSY;
+
+	/*
+	 * fsync is tricky, since it can fail and we need to do it
+	 * serialized with other io. the reason is that linux doesn't
+	 * support aio fsync yet. So return busy for the case where we
+	 * have pending io, to let fio complete those first.
+	 */
+	if (io_u->ddir == DDIR_SYNC) {
+		if (ld->iocbs_nr)
+			return FIO_Q_BUSY;
+		if (fsync(io_u->file->fd) < 0)
+			io_u->error = errno;
+
+		return FIO_Q_COMPLETED;
+	}
+
+	ld->iocbs[ld->iocbs_nr] = &io_u->iocb;
+	ld->iocbs_nr++;
+	return FIO_Q_QUEUED;
+}
+
+static int fio_libaio_commit(struct thread_data *td)
+{
+	struct libaio_data *ld = td->io_ops->data;
+	struct iocb **iocbs;
+	int ret, iocbs_nr;
+
+	if (!ld->iocbs_nr)
+		return 0;
+
+	iocbs_nr = ld->iocbs_nr;
+	iocbs = ld->iocbs;
 	do {
-		ret = io_submit(ld->aio_ctx, 1, &iocb);
-		if (ret == 1)
-			return FIO_Q_QUEUED;
-		else if (ret == -EAGAIN || !ret)
+		ret = io_submit(ld->aio_ctx, iocbs_nr, iocbs);
+		if (ret == iocbs_nr) {
+			ret = 0;
+			break;
+		} else if (ret > 0) {
+			iocbs += ret;
+			iocbs_nr -= ret;
+			continue;
+		} else if (ret == -EAGAIN || !ret)
 			usleep(100);
 		else if (ret == -EINTR)
 			continue;
-		else if (ret == -EINVAL && io_u->ddir == DDIR_SYNC) {
-			/*
-			 * the async fsync doesn't currently seem to be
-			 * supported, so just fsync if we fail with EINVAL
-			 * for a sync. since buffered io is also sync
-			 * with libaio (still), we don't have pending
-			 * requests to flush first.
-			 */
-			if (fsync(io_u->file->fd) < 0)
-				ret = -errno;
-			else
-				ret = FIO_Q_COMPLETED;
-			break;
-		} else
+		else
 			break;
 	} while (1);
 
-	if (ret <= 0) {
-		io_u->resid = io_u->xfer_buflen;
-		io_u->error = -ret;
-		td_verror(td, io_u->error);
-		return FIO_Q_COMPLETED;
-	}
+	if (!ret)
+		ld->iocbs_nr = 0;
 
 	return ret;
 }
@@ -121,6 +143,8 @@
 		io_destroy(ld->aio_ctx);
 		if (ld->aio_events)
 			free(ld->aio_events);
+		if (ld->iocbs)
+			free(ld->iocbs);
 
 		free(ld);
 		td->io_ops->data = NULL;
@@ -140,6 +164,10 @@
 
 	ld->aio_events = malloc(td->iodepth * sizeof(struct io_event));
 	memset(ld->aio_events, 0, td->iodepth * sizeof(struct io_event));
+	ld->iocbs = malloc(td->iodepth * sizeof(struct iocb *));
+	memset(ld->iocbs, 0, sizeof(struct iocb *));
+	ld->iocbs_nr = 0;
+
 	td->io_ops->data = ld;
 	return 0;
 }
@@ -150,6 +178,7 @@
 	.init		= fio_libaio_init,
 	.prep		= fio_libaio_prep,
 	.queue		= fio_libaio_queue,
+	.commit		= fio_libaio_commit,
 	.cancel		= fio_libaio_cancel,
 	.getevents	= fio_libaio_getevents,
 	.event		= fio_libaio_event,
diff --git a/fio.c b/fio.c
index 6e78949..858d6b8 100644
--- a/fio.c
+++ b/fio.c
@@ -209,6 +209,7 @@
 		return 1;
 	}
 
+requeue:
 	ret = td_io_queue(td, io_u);
 	if (ret < 0) {
 		td_verror(td, io_u->error);
@@ -224,6 +225,10 @@
 		}
 
 		io_u_sync_complete(td, io_u, NULL);
+	} else if (ret == FIO_Q_BUSY) {
+		if (td_io_commit(td))
+			return 1;
+		goto requeue;
 	}
 
 	return 0;
@@ -285,6 +290,10 @@
 			continue;
 		case FIO_Q_QUEUED:
 			break;
+		case FIO_Q_BUSY:
+			requeue_io_u(td, &io_u);
+			ret = td_io_commit(td);
+			break;
 		default:
 			assert(ret < 0);
 			td_verror(td, -ret);
@@ -299,7 +308,7 @@
 		 * completed io_u's first.
 		 */
 		min_events = 0;
-		if (queue_full(td))
+		if (queue_full(td) || ret == FIO_Q_BUSY)
 			min_events = 1;
 
 		/*
@@ -403,6 +412,10 @@
 			break;
 		case FIO_Q_QUEUED:
 			break;
+		case FIO_Q_BUSY:
+			requeue_io_u(td, &io_u);
+			ret = td_io_commit(td);
+			break;
 		default:
 			assert(ret < 0);
 			put_io_u(td, io_u);
@@ -412,14 +425,15 @@
 		if (ret < 0 || td->error)
 			break;
 
-		add_slat_sample(td, io_u->ddir, mtime_since(&io_u->start_time, &io_u->issue_time));
+		if (io_u)
+			add_slat_sample(td, io_u->ddir, mtime_since(&io_u->start_time, &io_u->issue_time));
 
 		/*
 		 * See if we need to complete some commands
 		 */
-		if (ret == FIO_Q_QUEUED) {
+		if (ret == FIO_Q_QUEUED || ret == FIO_Q_BUSY) {
 			min_evts = 0;
-			if (queue_full(td))
+			if (queue_full(td) || ret == FIO_Q_BUSY)
 				min_evts = 1;
 
 			fio_gettime(&comp_time, NULL);
@@ -633,6 +647,7 @@
 
 	INIT_LIST_HEAD(&td->io_u_freelist);
 	INIT_LIST_HEAD(&td->io_u_busylist);
+	INIT_LIST_HEAD(&td->io_u_requeues);
 	INIT_LIST_HEAD(&td->io_hist_list);
 	INIT_LIST_HEAD(&td->io_log_list);
 
diff --git a/fio.h b/fio.h
index aa66ecd..baaa9a8 100644
--- a/fio.h
+++ b/fio.h
@@ -135,6 +135,7 @@
 enum {
 	FIO_Q_COMPLETED	= 0,		/* completed sync */
 	FIO_Q_QUEUED	= 1,		/* queued, will complete async */
+	FIO_Q_BUSY	= 2,		/* no more room, call ->commit() */
 };
 
 #define FIO_HDR_MAGIC	0xf00baaef
@@ -334,6 +335,7 @@
 	unsigned long total_io_u;
 	struct list_head io_u_freelist;
 	struct list_head io_u_busylist;
+	struct list_head io_u_requeues;
 
 	/*
 	 * Rate state
@@ -352,6 +354,7 @@
 	unsigned long long start_offset;
 	unsigned long long total_io_size;
 
+	unsigned long io_issues[2];
 	unsigned long long io_blocks[2];
 	unsigned long long io_bytes[2];
 	unsigned long long zone_bytes;
@@ -608,6 +611,7 @@
 extern struct io_u *__get_io_u(struct thread_data *);
 extern struct io_u *get_io_u(struct thread_data *, struct fio_file *);
 extern void put_io_u(struct thread_data *, struct io_u *);
+extern void requeue_io_u(struct thread_data *, struct io_u **);
 extern long io_u_sync_complete(struct thread_data *, struct io_u *, endio_handler *);
 extern long io_u_queued_complete(struct thread_data *, int, endio_handler *);
 
@@ -619,6 +623,7 @@
 extern int td_io_queue(struct thread_data *, struct io_u *);
 extern int td_io_sync(struct thread_data *, struct fio_file *);
 extern int td_io_getevents(struct thread_data *, int, int, struct timespec *);
+extern int td_io_commit(struct thread_data *);
 
 /*
  * This is a pretty crappy semaphore implementation, but with the use that fio
@@ -662,6 +667,7 @@
 	int (*init)(struct thread_data *);
 	int (*prep)(struct thread_data *, struct io_u *);
 	int (*queue)(struct thread_data *, struct io_u *);
+	int (*commit)(struct thread_data *);
 	int (*getevents)(struct thread_data *, int, int, struct timespec *);
 	struct io_u *(*event)(struct thread_data *, int);
 	int (*cancel)(struct thread_data *, struct io_u *);
@@ -671,7 +677,7 @@
 	unsigned long priv;
 };
 
-#define FIO_IOOPS_VERSION	4
+#define FIO_IOOPS_VERSION	5
 
 extern struct ioengine_ops *load_ioengine(struct thread_data *, const char *);
 extern int register_ioengine(struct ioengine_ops *);
diff --git a/io_u.c b/io_u.c
index c04c9de..781599f 100644
--- a/io_u.c
+++ b/io_u.c
@@ -199,6 +199,16 @@
 	td->cur_depth--;
 }
 
+void requeue_io_u(struct thread_data *td, struct io_u **io_u)
+{
+	struct io_u *__io_u = *io_u;
+
+	list_del(&__io_u->list);
+	list_add_tail(&__io_u->list, &td->io_u_requeues);
+	td->cur_depth--;
+	*io_u = NULL;
+}
+
 static int fill_io_u(struct thread_data *td, struct fio_file *f,
 		     struct io_u *io_u)
 {
@@ -211,8 +221,8 @@
 	/*
 	 * see if it's time to sync
 	 */
-	if (td->fsync_blocks && !(td->io_blocks[DDIR_WRITE] % td->fsync_blocks)
-	    && should_fsync(td)) {
+	if (td->fsync_blocks && !(td->io_issues[DDIR_WRITE] % td->fsync_blocks)
+	    && td->io_issues[DDIR_WRITE] && should_fsync(td)) {
 		io_u->ddir = DDIR_SYNC;
 		io_u->file = f;
 		return 0;
@@ -310,12 +320,18 @@
 {
 	struct io_u *io_u = NULL;
 
-	if (!queue_full(td)) {
+	if (!list_empty(&td->io_u_requeues))
+		io_u = list_entry(td->io_u_requeues.next, struct io_u, list);
+	else if (!queue_full(td)) {
 		io_u = list_entry(td->io_u_freelist.next, struct io_u, list);
 
 		io_u->buflen = 0;
-		io_u->error = 0;
 		io_u->resid = 0;
+		io_u->file = NULL;
+	}
+
+	if (io_u) {
+		io_u->error = 0;
 		list_del(&io_u->list);
 		list_add(&io_u->list, &td->io_u_busylist);
 		td->cur_depth++;
@@ -337,6 +353,12 @@
 	if (!io_u)
 		return NULL;
 
+	/*
+	 * from a requeue, io_u already setup
+	 */
+	if (io_u->file)
+		return io_u;
+
 	if (td->zone_bytes >= td->zone_size) {
 		td->zone_bytes = 0;
 		f->last_pos += td->zone_skip;
@@ -477,8 +499,14 @@
 	struct io_completion_data icd;
 	int ret;
 
-	if (min_events > 0)
+	if (min_events > 0) {
 		tsp = &ts;
+		ret = td_io_commit(td);
+		if (ret < 0) {
+			td_verror(td, -ret);
+			return ret;
+		}
+	}
 
 	ret = td_io_getevents(td, min_events, td->cur_depth, tsp);
 	if (ret < 0) {
diff --git a/ioengines.c b/ioengines.c
index 1b510df..16ea928 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -189,6 +189,9 @@
 {
 	fio_gettime(&io_u->issue_time, NULL);
 
+	if (io_u->ddir != DDIR_SYNC)
+		td->io_issues[io_u->ddir]++;
+
 	return td->io_ops->queue(td, io_u);
 }
 
@@ -199,3 +202,11 @@
 
 	return 0;
 }
+
+int td_io_commit(struct thread_data *td)
+{
+	if (td->io_ops->commit)
+		return td->io_ops->commit(td);
+
+	return 0;
+}