Date:	Thu, 28 Jul 2011 22:29:05 +0800
From:	Liu Yuan <namei.unix@...il.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Avi Kivity <avi@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH] vhost-blk: An in-kernel accelerator for virtio-blk

From: Liu Yuan <tailai.ly@...bao.com>

Vhost-blk driver is an in-kernel accelerator, intercepting the
IO requests from KVM virtio-capable guests. It is based on the
vhost infrastructure.

This is supposed to be a module over latest kernel tree, but it
needs some symbols from fs/aio.c and fs/eventfd.c to compile with.
So currently, after applying the patch, you need to *recomplie*
the kernel.

Usage:
$kernel-src: make M=drivers/vhost
$kernel-src: sudo insmod drivers/vhost/vhost_blk.ko

After insmod, you'll see /dev/vhost-blk created. done!

Signed-off-by: Liu Yuan <tailai.ly@...bao.com>
---
 drivers/vhost/Makefile |    3 +
 drivers/vhost/blk.c    |  568 ++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/vhost/vhost.h  |   11 +
 fs/aio.c               |   44 ++---
 fs/eventfd.c           |    1 +
 include/linux/aio.h    |   31 +++
 6 files changed, 631 insertions(+), 27 deletions(-)
 create mode 100644 drivers/vhost/blk.c

diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
index 72dd020..31f8b2e 100644
--- a/drivers/vhost/Makefile
+++ b/drivers/vhost/Makefile
@@ -1,2 +1,5 @@
 obj-$(CONFIG_VHOST_NET) += vhost_net.o
+obj-m += vhost_blk.o
+
 vhost_net-y := vhost.o net.o
+vhost_blk-y := vhost.o blk.o
diff --git a/drivers/vhost/blk.c b/drivers/vhost/blk.c
new file mode 100644
index 0000000..f3462be
--- /dev/null
+++ b/drivers/vhost/blk.c
@@ -0,0 +1,568 @@
+/* Copyright (C) 2011 Taobao, Inc.
+ * Author: Liu Yuan <tailai.ly@...bao.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * Vhost-blk driver is an in-kernel accelerator, intercepting the
+ * IO requests from KVM virtio-capable guests. It is based on the
+ * vhost infrastructure.
+ */
+
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/virtio_net.h>
+#include <linux/vhost.h>
+#include <linux/eventfd.h>
+#include <linux/mutex.h>
+#include <linux/workqueue.h>
+#include <linux/virtio_blk.h>
+#include <linux/file.h>
+#include <linux/mmu_context.h>
+#include <linux/kthread.h>
+#include <linux/anon_inodes.h>
+#include <linux/syscalls.h>
+#include <linux/blkdev.h>
+
+#include "vhost.h"
+
+#define DEBUG 0
+
+#if DEBUG > 0
+#define dprintk         printk
+#else
+#define dprintk(x...)   do { ; } while (0)
+#endif
+
+enum {
+	virtqueue_max = 1,
+};
+
+#define MAX_EVENTS 128
+
+struct vhost_blk {
+	struct vhost_virtqueue vq;
+	struct vhost_dev dev;
+	int should_stop;
+	struct kioctx *ioctx;
+	struct eventfd_ctx *ectx;
+	struct file *efile;
+	struct task_struct *worker;
+};
+
+struct used_info {
+	void *status;
+	int head;
+	int len;
+};
+
+static struct io_event events[MAX_EVENTS];
+
+static void blk_flush(struct vhost_blk *blk)
+{
+       vhost_poll_flush(&blk->vq.poll);
+}
+
+static long blk_set_features(struct vhost_blk *blk, u64 features)
+{
+	blk->dev.acked_features = features;
+	return 0;
+}
+
+static void blk_stop(struct vhost_blk *blk)
+{
+	struct vhost_virtqueue *vq = &blk->vq;
+	struct file *f;
+
+	mutex_lock(&vq->mutex);
+	f = rcu_dereference_protected(vq->private_data,
+					lockdep_is_held(&vq->mutex));
+	rcu_assign_pointer(vq->private_data, NULL);
+	mutex_unlock(&vq->mutex);
+
+	if (f)
+		fput(f);
+}
+
+static long blk_set_backend(struct vhost_blk *blk, struct vhost_vring_file *backend)
+{
+	int idx = backend->index;
+	struct vhost_virtqueue *vq = &blk->vq;
+	struct file *file, *oldfile;
+	int ret;
+
+	mutex_lock(&blk->dev.mutex);
+	ret = vhost_dev_check_owner(&blk->dev);
+	if (ret)
+		goto err_dev;
+	if (idx >= virtqueue_max) {
+		ret = -ENOBUFS;
+		goto err_dev;
+	}
+
+	mutex_lock(&vq->mutex);
+
+	if (!vhost_vq_access_ok(vq)) {
+		ret = -EFAULT;
+		goto err_vq;
+	}
+
+	file = fget(backend->fd);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		goto err_vq;
+	}
+
+	oldfile = rcu_dereference_protected(vq->private_data,
+						lockdep_is_held(&vq->mutex));
+	if (file != oldfile)
+		rcu_assign_pointer(vq->private_data, file);
+
+	mutex_unlock(&vq->mutex);
+
+	if (oldfile) {
+		blk_flush(blk);
+		fput(oldfile);
+	}
+
+	mutex_unlock(&blk->dev.mutex);
+	return 0;
+err_vq:
+	mutex_unlock(&vq->mutex);
+err_dev:
+	mutex_unlock(&blk->dev.mutex);
+	return ret;
+}
+
+static long blk_reset_owner(struct vhost_blk *b)
+{
+	int ret;
+
+        mutex_lock(&b->dev.mutex);
+        ret = vhost_dev_check_owner(&b->dev);
+        if (ret)
+                goto err;
+        blk_stop(b);
+        blk_flush(b);
+        ret = vhost_dev_reset_owner(&b->dev);
+	if (b->worker) {
+		b->should_stop = 1;
+		smp_mb();
+		eventfd_signal(b->ectx, 1);
+	}
+err:
+        mutex_unlock(&b->dev.mutex);
+        return ret;
+}
+
+static int kernel_io_setup(unsigned nr_events, struct kioctx **ioctx)
+{
+	int ret = 0;
+	*ioctx = ioctx_alloc(nr_events);
+	if (IS_ERR(ioctx))
+		ret = PTR_ERR(ioctx);
+	return ret;
+}
+
+static inline int kernel_read_events(struct kioctx *ctx, long min_nr, long nr, struct io_event *event,
+			struct timespec *ts)
+{
+        mm_segment_t old_fs;
+        int ret;
+
+        old_fs = get_fs();
+        set_fs(get_ds());
+	ret = read_events(ctx, min_nr, nr, event, ts);
+        set_fs(old_fs);
+
+	return ret;
+}
+
+static inline ssize_t io_event_ret(struct io_event *ev)
+{
+    return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res);
+}
+
+static inline void aio_prep_req(struct kiocb *iocb, struct eventfd_ctx *ectx, struct file *file,
+		struct iovec *iov, int nvecs, u64 offset, int opcode, struct used_info *ui)
+{
+	iocb->ki_filp = file;
+	iocb->ki_eventfd = ectx;
+	iocb->ki_pos = offset;
+	iocb->ki_buf = (void *)iov;
+	iocb->ki_left = iocb->ki_nbytes = nvecs;
+	iocb->ki_opcode = opcode;
+	iocb->ki_obj.user = ui;
+}
+
+static inline int kernel_io_submit(struct vhost_blk *blk, struct iovec *iov, u64 nvecs, loff_t pos, int opcode, int head, int len)
+{
+	int ret = -EAGAIN;
+	struct kiocb *req;
+	struct kioctx *ioctx = blk->ioctx;
+	struct used_info *ui = kzalloc(sizeof *ui, GFP_KERNEL);
+	struct file *f = blk->vq.private_data;
+
+	try_get_ioctx(ioctx);
+	atomic_long_inc_not_zero(&f->f_count);
+	eventfd_ctx_get(blk->ectx);
+
+
+	req = aio_get_req(ioctx); /* return 2 refs of req*/
+	if (unlikely(!req))
+		goto out;
+
+	ui->head = head;
+	ui->status = blk->vq.iov[nvecs + 1].iov_base;
+	ui->len = len;
+	aio_prep_req(req, blk->ectx, f, iov, nvecs, pos, opcode, ui);
+
+	ret = aio_setup_iocb(req, 0);
+	if (unlikely(ret))
+		goto out_put_req;
+
+	spin_lock_irq(&ioctx->ctx_lock);
+	if (unlikely(ioctx->dead)) {
+		spin_unlock_irq(&ioctx->ctx_lock);
+		ret = -EINVAL;
+		goto out_put_req;
+	}
+
+	aio_run_iocb(req);
+	if (!list_empty(&ioctx->run_list)) {
+		while (__aio_run_iocbs(ioctx))
+			;
+	}
+	spin_unlock_irq(&ioctx->ctx_lock);
+
+	aio_put_req(req);
+	put_ioctx(blk->ioctx);
+
+	return ret;
+
+out_put_req:
+	aio_put_req(req);
+	aio_put_req(req);
+out:
+	put_ioctx(blk->ioctx);
+	return ret;
+}
+
+static int blk_completion_worker(void *priv)
+{
+	struct vhost_blk *blk = priv;
+	u64 count;
+	int ret;
+
+	use_mm(blk->dev.mm);
+	for (;;) {
+		struct timespec ts = { 0 };
+		int i, nr;
+
+		do {
+		ret = eventfd_ctx_read(blk->ectx, 0, &count);
+		} while (unlikely(ret == -ERESTARTSYS));
+
+		if (unlikely(blk->should_stop))
+			break;
+
+		do {
+		nr = kernel_read_events(blk->ioctx, count, MAX_EVENTS, events, &ts);
+		} while (unlikely(nr == -EINTR));
+		dprintk("%s, count %llu, nr %d\n", __func__, count, nr);
+
+		if (unlikely(nr < 0))
+			continue;
+
+		for (i = 0; i < nr; i++) {
+			struct used_info *u = (struct used_info *)events[i].obj;
+			int len, status;
+
+			dprintk("%s, head %d complete in %d\n", __func__, u->head, i);
+			len = io_event_ret(&events[i]);
+			//status = u->len == len ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR;
+			status = len > 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR;
+			if (copy_to_user(u->status, &status, sizeof status)) {
+				vq_err(&blk->vq, "%s failed to write status\n", __func__);
+				BUG(); /* FIXME: maybe a bit radical? */
+			}
+			vhost_add_used(&blk->vq, u->head, u->len);
+			kfree(u);
+		}
+
+		vhost_signal(&blk->dev, &blk->vq);
+	}
+	unuse_mm(blk->dev.mm);
+	return 0;
+}
+
+static int completion_thread_setup(struct vhost_blk *blk)
+{
+	int ret = 0;
+	struct task_struct *worker;
+	worker = kthread_create(blk_completion_worker, blk, "vhost-blk-%d", current->pid);
+	if (IS_ERR(worker)) {
+		ret = PTR_ERR(worker);
+		goto err;
+	}
+	blk->worker = worker;
+	blk->should_stop = 0;
+	smp_mb();
+	wake_up_process(worker);
+err:
+	return ret;
+}
+
+static void completion_thread_destory(struct vhost_blk *blk)
+{
+	if (blk->worker) {
+		blk->should_stop = 1;
+		smp_mb();
+		eventfd_signal(blk->ectx, 1);
+	}
+}
+
+
+static long blk_set_owner(struct vhost_blk *blk)
+{
+	return completion_thread_setup(blk);
+}
+
+static long vhost_blk_ioctl(struct file *f, unsigned int ioctl,
+		unsigned long arg)
+{
+	struct vhost_blk *blk = f->private_data;
+	struct vhost_vring_file backend;
+	u64 features = VHOST_BLK_FEATURES;
+	int ret = -EFAULT;
+
+	switch (ioctl) {
+		case VHOST_NET_SET_BACKEND:
+			if(copy_from_user(&backend, (void __user *)arg, sizeof backend))
+				break;
+			ret = blk_set_backend(blk, &backend);
+			break;
+		case VHOST_GET_FEATURES:
+			features = VHOST_BLK_FEATURES;
+			if (copy_to_user((void __user *)arg , &features, sizeof features))
+				break;
+			ret = 0;
+			break;
+		case VHOST_SET_FEATURES:
+			if (copy_from_user(&features, (void __user *)arg, sizeof features))
+				break;
+			if (features & ~VHOST_BLK_FEATURES) {
+				ret = -EOPNOTSUPP;
+				break;
+			}
+			ret = blk_set_features(blk, features);
+			break;
+		case VHOST_RESET_OWNER:
+			ret = blk_reset_owner(blk);
+			break;
+		default:
+			mutex_lock(&blk->dev.mutex);
+			ret = vhost_dev_ioctl(&blk->dev, ioctl, arg);
+			if (!ret && ioctl == VHOST_SET_OWNER)
+				ret = blk_set_owner(blk);
+			blk_flush(blk);
+			mutex_unlock(&blk->dev.mutex);
+			break;
+	}
+	return ret;
+}
+
+#define BLK_HDR 0
+#define BLK_HDR_LEN 16
+
+static inline int do_request(struct vhost_virtqueue *vq, struct virtio_blk_outhdr *hdr,
+		u64 nr_vecs, int head)
+{
+	struct file *f = vq->private_data;
+	struct vhost_blk *blk = container_of(vq->dev, struct vhost_blk, dev);
+	struct iovec *iov = &vq->iov[BLK_HDR + 1];
+	loff_t pos = hdr->sector << 9;
+	int ret = 0, len = 0, status;
+//	int i;
+
+	dprintk("sector %llu, num %lu, type %d\n", hdr->sector, iov->iov_len / 512, hdr->type);
+	//Guest virtio-blk driver dosen't use len currently.
+	//for (i = 0; i < nr_vecs; i++) {
+	//	len += iov[i].iov_len;
+	//}
+	switch (hdr->type) {
+	case VIRTIO_BLK_T_OUT:
+		kernel_io_submit(blk, iov, nr_vecs, pos, IOCB_CMD_PWRITEV, head, len);
+		break;
+	case VIRTIO_BLK_T_IN:
+		kernel_io_submit(blk, iov, nr_vecs, pos, IOCB_CMD_PREADV, head, len);
+		break;
+	case VIRTIO_BLK_T_FLUSH:
+		ret = vfs_fsync(f, 1);
+		/* fall through */
+	case VIRTIO_BLK_T_GET_ID:
+		status = ret < 0 ? VIRTIO_BLK_S_IOERR :VIRTIO_BLK_S_OK;
+		if ((vq->iov[nr_vecs + 1].iov_len != 1))
+			BUG();
+
+		if (copy_to_user(vq->iov[nr_vecs + 1].iov_base, &status, sizeof status)) {
+				vq_err(vq, "%s failed to write status!\n", __func__);
+				vhost_discard_vq_desc(vq, 1);
+				ret = -EFAULT;
+				break;
+			}
+
+		vhost_add_used_and_signal(&blk->dev, vq, head, ret);
+		break;
+	default:
+		pr_info("%s, unsupported request type %d\n", __func__, hdr->type);
+		vhost_discard_vq_desc(vq, 1);
+		ret = -EFAULT;
+		break;
+	}
+	return ret;
+}
+
+static inline void handle_kick(struct vhost_blk *blk)
+{
+	struct vhost_virtqueue *vq = &blk->vq;
+	struct virtio_blk_outhdr hdr;
+	u64 nr_vecs;
+	int in, out, head;
+	struct blk_plug plug;
+
+	mutex_lock(&vq->mutex);
+	vhost_disable_notify(&blk->dev, vq);
+
+	blk_start_plug(&plug);
+	for (;;) {
+		head = vhost_get_vq_desc(&blk->dev, vq, vq->iov,
+				ARRAY_SIZE(vq->iov),
+				&out, &in, NULL, NULL);
+		/* No awailable descriptors from Guest? */
+		if (head == vq->num) {
+			if (unlikely(vhost_enable_notify(&blk->dev, vq))) {
+				vhost_disable_notify(&blk->dev, vq);
+				continue;
+			}
+			break;
+		}
+		if (unlikely(head < 0))
+			break;
+
+		dprintk("head %d, in %d, out %d\n", head, in, out);
+		if(unlikely(vq->iov[BLK_HDR].iov_len != BLK_HDR_LEN)) {
+			vq_err(vq, "%s bad block header lengh!\n", __func__);
+			vhost_discard_vq_desc(vq, 1);
+			break;
+		}
+
+		if (copy_from_user(&hdr, vq->iov[BLK_HDR].iov_base, sizeof hdr)) {
+			vq_err(vq, "%s failed to get block header!\n", __func__);
+			vhost_discard_vq_desc(vq, 1);
+			break;
+		}
+
+		if (hdr.type == VIRTIO_BLK_T_IN || hdr.type == VIRTIO_BLK_T_GET_ID)
+			nr_vecs = in - 1;
+		else
+			nr_vecs = out - 1;
+
+		if (do_request(vq, &hdr, nr_vecs, head) < 0)
+			break;
+	}
+	blk_finish_plug(&plug);
+	mutex_unlock(&vq->mutex);
+}
+
+static void handle_guest_kick(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue, poll.work);
+	struct vhost_blk *blk = container_of(vq->dev, struct vhost_blk, dev);
+	handle_kick(blk);
+}
+
+static void eventfd_setup(struct vhost_blk *blk)
+{
+	blk->efile = eventfd_file_create(0, 0);
+	blk->ectx = eventfd_ctx_fileget(blk->efile);
+}
+
+static int vhost_blk_open(struct inode *inode, struct file *f)
+{
+	int ret = -ENOMEM;
+	struct vhost_blk *blk = kmalloc(sizeof *blk, GFP_KERNEL);
+	if (!blk)
+		goto err;
+
+	blk->vq.handle_kick = handle_guest_kick;
+	ret = vhost_dev_init(&blk->dev, &blk->vq, virtqueue_max);
+	if (ret < 0)
+		goto err_init;
+
+	ret = kernel_io_setup(MAX_EVENTS, &blk->ioctx);
+	if (ret < 0)
+		goto err_io_setup;
+
+	eventfd_setup(blk);
+	f->private_data = blk;
+	return ret;
+err_init:
+err_io_setup:
+	kfree(blk);
+err:
+	return ret;
+}
+
+static void eventfd_destroy(struct vhost_blk *blk)
+{
+	eventfd_ctx_put(blk->ectx);
+	fput(blk->efile);
+}
+
+static int vhost_blk_release(struct inode *inode, struct file *f)
+{
+	struct vhost_blk *blk = f->private_data;
+
+	blk_stop(blk);
+	blk_flush(blk);
+	vhost_dev_cleanup(&blk->dev);
+	/* Yet another flush? See comments in vhost_net_release() */
+	blk_flush(blk);
+	completion_thread_destory(blk);
+	eventfd_destroy(blk);
+	kfree(blk);
+
+	return 0;
+}
+
+const static struct file_operations vhost_blk_fops = {
+	.owner          = THIS_MODULE,
+	.release        = vhost_blk_release,
+	.open           = vhost_blk_open,
+	.unlocked_ioctl = vhost_blk_ioctl,
+	.llseek		= noop_llseek,
+};
+
+
+static struct miscdevice vhost_blk_misc = {
+	234,
+	"vhost-blk",
+	&vhost_blk_fops,
+};
+
+int vhost_blk_init(void)
+{
+	return misc_register(&vhost_blk_misc);
+}
+void vhost_blk_exit(void)
+{
+	misc_deregister(&vhost_blk_misc);
+}
+
+module_init(vhost_blk_init);
+module_exit(vhost_blk_exit);
+
+MODULE_VERSION("0.0.1");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Liu Yuan");
+MODULE_DESCRIPTION("Host kernel accelerator for virtio_blk");
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8e03379..9e17152 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -12,6 +12,7 @@
 #include <linux/virtio_config.h>
 #include <linux/virtio_ring.h>
 #include <asm/atomic.h>
+#include <linux/virtio_blk.h>
 
 struct vhost_device;
 
@@ -174,6 +175,16 @@ enum {
 			 (1ULL << VHOST_F_LOG_ALL) |
 			 (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
 			 (1ULL << VIRTIO_NET_F_MRG_RXBUF),
+
+	VHOST_BLK_FEATURES =	(1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
+				(1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
+				(1ULL << VIRTIO_RING_F_EVENT_IDX) |
+				(1ULL << VIRTIO_BLK_F_SEG_MAX) |
+				(1ULL << VIRTIO_BLK_F_GEOMETRY) |
+				(1ULL << VIRTIO_BLK_F_TOPOLOGY) |
+				(1ULL << VIRTIO_BLK_F_SCSI) |
+				(1ULL << VIRTIO_BLK_F_BLK_SIZE),
+
 };
 
 static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
diff --git a/fs/aio.c b/fs/aio.c
index e29ec48..534d396 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -215,7 +215,7 @@ static void ctx_rcu_free(struct rcu_head *head)
  *	Called when the last user of an aio context has gone away,
  *	and the struct needs to be freed.
  */
-static void __put_ioctx(struct kioctx *ctx)
+void __put_ioctx(struct kioctx *ctx)
 {
 	BUG_ON(ctx->reqs_active);
 
@@ -227,29 +227,12 @@ static void __put_ioctx(struct kioctx *ctx)
 	pr_debug("__put_ioctx: freeing %p\n", ctx);
 	call_rcu(&ctx->rcu_head, ctx_rcu_free);
 }
-
-static inline void get_ioctx(struct kioctx *kioctx)
-{
-	BUG_ON(atomic_read(&kioctx->users) <= 0);
-	atomic_inc(&kioctx->users);
-}
-
-static inline int try_get_ioctx(struct kioctx *kioctx)
-{
-	return atomic_inc_not_zero(&kioctx->users);
-}
-
-static inline void put_ioctx(struct kioctx *kioctx)
-{
-	BUG_ON(atomic_read(&kioctx->users) <= 0);
-	if (unlikely(atomic_dec_and_test(&kioctx->users)))
-		__put_ioctx(kioctx);
-}
+EXPORT_SYMBOL(__put_ioctx);
 
 /* ioctx_alloc
  *	Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
  */
-static struct kioctx *ioctx_alloc(unsigned nr_events)
+struct kioctx *ioctx_alloc(unsigned nr_events)
 {
 	struct mm_struct *mm;
 	struct kioctx *ctx;
@@ -327,6 +310,7 @@ out_freectx:
 	dprintk("aio: error allocating ioctx %p\n", ctx);
 	return ctx;
 }
+EXPORT_SYMBOL(ioctx_alloc);
 
 /* aio_cancel_all
  *	Cancels all outstanding aio requests on an aio context.  Used 
@@ -437,7 +421,7 @@ void exit_aio(struct mm_struct *mm)
  * This prevents races between the aio code path referencing the
  * req (after submitting it) and aio_complete() freeing the req.
  */
-static struct kiocb *__aio_get_req(struct kioctx *ctx)
+struct kiocb *__aio_get_req(struct kioctx *ctx)
 {
 	struct kiocb *req = NULL;
 	struct aio_ring *ring;
@@ -480,7 +464,7 @@ static struct kiocb *__aio_get_req(struct kioctx *ctx)
 	return req;
 }
 
-static inline struct kiocb *aio_get_req(struct kioctx *ctx)
+struct kiocb *aio_get_req(struct kioctx *ctx)
 {
 	struct kiocb *req;
 	/* Handle a potential starvation case -- should be exceedingly rare as 
@@ -494,6 +478,7 @@ static inline struct kiocb *aio_get_req(struct kioctx *ctx)
 	}
 	return req;
 }
+EXPORT_SYMBOL(aio_get_req);
 
 static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
 {
@@ -659,7 +644,7 @@ static inline int __queue_kicked_iocb(struct kiocb *iocb)
  * simplifies the coding of individual aio operations as
  * it avoids various potential races.
  */
-static ssize_t aio_run_iocb(struct kiocb *iocb)
+ssize_t aio_run_iocb(struct kiocb *iocb)
 {
 	struct kioctx	*ctx = iocb->ki_ctx;
 	ssize_t (*retry)(struct kiocb *);
@@ -753,6 +738,7 @@ out:
 	}
 	return ret;
 }
+EXPORT_SYMBOL(aio_run_iocb);
 
 /*
  * __aio_run_iocbs:
@@ -761,7 +747,7 @@ out:
  * Assumes it is operating within the aio issuer's mm
  * context.
  */
-static int __aio_run_iocbs(struct kioctx *ctx)
+int __aio_run_iocbs(struct kioctx *ctx)
 {
 	struct kiocb *iocb;
 	struct list_head run_list;
@@ -784,6 +770,7 @@ static int __aio_run_iocbs(struct kioctx *ctx)
 		return 1;
 	return 0;
 }
+EXPORT_SYMBOL(__aio_run_iocbs);
 
 static void aio_queue_work(struct kioctx * ctx)
 {
@@ -1074,7 +1061,7 @@ static inline void clear_timeout(struct aio_timeout *to)
 	del_singleshot_timer_sync(&to->timer);
 }
 
-static int read_events(struct kioctx *ctx,
+int read_events(struct kioctx *ctx,
 			long min_nr, long nr,
 			struct io_event __user *event,
 			struct timespec __user *timeout)
@@ -1190,11 +1177,12 @@ out:
 	destroy_timer_on_stack(&to.timer);
 	return i ? i : ret;
 }
+EXPORT_SYMBOL(read_events);
 
 /* Take an ioctx and remove it from the list of ioctx's.  Protects 
  * against races with itself via ->dead.
  */
-static void io_destroy(struct kioctx *ioctx)
+void io_destroy(struct kioctx *ioctx)
 {
 	struct mm_struct *mm = current->mm;
 	int was_dead;
@@ -1221,6 +1209,7 @@ static void io_destroy(struct kioctx *ioctx)
 	wake_up_all(&ioctx->wait);
 	put_ioctx(ioctx);	/* once for the lookup */
 }
+EXPORT_SYMBOL(io_destroy);
 
 /* sys_io_setup:
  *	Create an aio_context capable of receiving at least nr_events.
@@ -1423,7 +1412,7 @@ static ssize_t aio_setup_single_vector(struct kiocb *kiocb)
  *	Performs the initial checks and aio retry method
  *	setup for the kiocb at the time of io submission.
  */
-static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
+ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
 {
 	struct file *file = kiocb->ki_filp;
 	ssize_t ret = 0;
@@ -1513,6 +1502,7 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
 
 	return 0;
 }
+EXPORT_SYMBOL(aio_setup_iocb);
 
 static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
 			 struct iocb *iocb, bool compat)
diff --git a/fs/eventfd.c b/fs/eventfd.c
index d9a5917..6343bc9 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -406,6 +406,7 @@ struct file *eventfd_file_create(unsigned int count, int flags)
 
 	return file;
 }
+EXPORT_SYMBOL_GPL(eventfd_file_create);
 
 SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
 {
diff --git a/include/linux/aio.h b/include/linux/aio.h
index 7a8db41..d63bc04 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -214,6 +214,37 @@ struct mm_struct;
 extern void exit_aio(struct mm_struct *mm);
 extern long do_io_submit(aio_context_t ctx_id, long nr,
 			 struct iocb __user *__user *iocbpp, bool compat);
+extern void __put_ioctx(struct kioctx *ctx);
+extern struct kioctx *ioctx_alloc(unsigned nr_events);
+extern struct kiocb *aio_get_req(struct kioctx *ctx);
+extern ssize_t aio_run_iocb(struct kiocb *iocb);
+extern int __aio_run_iocbs(struct kioctx *ctx);
+extern int read_events(struct kioctx *ctx,
+                        long min_nr, long nr,
+                        struct io_event __user *event,
+                        struct timespec __user *timeout);
+extern void io_destroy(struct kioctx *ioctx);
+extern ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat);
+extern void __put_ioctx(struct kioctx *ctx);
+
+static inline void get_ioctx(struct kioctx *kioctx)
+{
+        BUG_ON(atomic_read(&kioctx->users) <= 0);
+        atomic_inc(&kioctx->users);
+}
+
+static inline int try_get_ioctx(struct kioctx *kioctx)
+{
+        return atomic_inc_not_zero(&kioctx->users);
+}
+
+static inline void put_ioctx(struct kioctx *kioctx)
+{
+        BUG_ON(atomic_read(&kioctx->users) <= 0);
+        if (unlikely(atomic_dec_and_test(&kioctx->users)))
+                __put_ioctx(kioctx);
+}
+
 #else
 static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
 static inline int aio_put_req(struct kiocb *iocb) { return 0; }
-- 
1.7.5.1

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