Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1542 insertions, 0 deletions

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
new file mode 100644
index 0000000000..5f1be1da92
--- /dev/null
+++ b/fs/fuse/virtio_fs.c
@@ -0,0 +1,1542 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio-fs: Virtio Filesystem
+ * Copyright (C) 2018 Red Hat, Inc.
+ */
+
+#include <linux/fs.h>
+#include <linux/dax.h>
+#include <linux/pci.h>
+#include <linux/pfn_t.h>
+#include <linux/memremap.h>
+#include <linux/module.h>
+#include <linux/virtio.h>
+#include <linux/virtio_fs.h>
+#include <linux/delay.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/highmem.h>
+#include <linux/uio.h>
+#include "fuse_i.h"
+
+/* Used to help calculate the FUSE connection's max_pages limit for a request's
+ * size. Parts of the struct fuse_req are sliced into scattergather lists in
+ * addition to the pages used, so this can help account for that overhead.
+ */
+#define FUSE_HEADER_OVERHEAD    4
+
+/* List of virtio-fs device instances and a lock for the list. Also provides
+ * mutual exclusion in device removal and mounting path
+ */
+static DEFINE_MUTEX(virtio_fs_mutex);
+static LIST_HEAD(virtio_fs_instances);
+
+enum {
+	VQ_HIPRIO,
+	VQ_REQUEST
+};
+
+#define VQ_NAME_LEN	24
+
+/* Per-virtqueue state */
+struct virtio_fs_vq {
+	spinlock_t lock;
+	struct virtqueue *vq;     /* protected by ->lock */
+	struct work_struct done_work;
+	struct list_head queued_reqs;
+	struct list_head end_reqs;	/* End these requests */
+	struct delayed_work dispatch_work;
+	struct fuse_dev *fud;
+	bool connected;
+	long in_flight;
+	struct completion in_flight_zero; /* No inflight requests */
+	char name[VQ_NAME_LEN];
+} ____cacheline_aligned_in_smp;
+
+/* A virtio-fs device instance */
+struct virtio_fs {
+	struct kref refcount;
+	struct list_head list;    /* on virtio_fs_instances */
+	char *tag;
+	struct virtio_fs_vq *vqs;
+	unsigned int nvqs;               /* number of virtqueues */
+	unsigned int num_request_queues; /* number of request queues */
+	struct dax_device *dax_dev;
+
+	/* DAX memory window where file contents are mapped */
+	void *window_kaddr;
+	phys_addr_t window_phys_addr;
+	size_t window_len;
+};
+
+struct virtio_fs_forget_req {
+	struct fuse_in_header ih;
+	struct fuse_forget_in arg;
+};
+
+struct virtio_fs_forget {
+	/* This request can be temporarily queued on virt queue */
+	struct list_head list;
+	struct virtio_fs_forget_req req;
+};
+
+struct virtio_fs_req_work {
+	struct fuse_req *req;
+	struct virtio_fs_vq *fsvq;
+	struct work_struct done_work;
+};
+
+static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
+				 struct fuse_req *req, bool in_flight);
+
+static const struct constant_table dax_param_enums[] = {
+	{"always",	FUSE_DAX_ALWAYS },
+	{"never",	FUSE_DAX_NEVER },
+	{"inode",	FUSE_DAX_INODE_USER },
+	{}
+};
+
+enum {
+	OPT_DAX,
+	OPT_DAX_ENUM,
+};
+
+static const struct fs_parameter_spec virtio_fs_parameters[] = {
+	fsparam_flag("dax", OPT_DAX),
+	fsparam_enum("dax", OPT_DAX_ENUM, dax_param_enums),
+	{}
+};
+
+static int virtio_fs_parse_param(struct fs_context *fsc,
+				 struct fs_parameter *param)
+{
+	struct fs_parse_result result;
+	struct fuse_fs_context *ctx = fsc->fs_private;
+	int opt;
+
+	opt = fs_parse(fsc, virtio_fs_parameters, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case OPT_DAX:
+		ctx->dax_mode = FUSE_DAX_ALWAYS;
+		break;
+	case OPT_DAX_ENUM:
+		ctx->dax_mode = result.uint_32;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void virtio_fs_free_fsc(struct fs_context *fsc)
+{
+	struct fuse_fs_context *ctx = fsc->fs_private;
+
+	kfree(ctx);
+}
+
+static inline struct virtio_fs_vq *vq_to_fsvq(struct virtqueue *vq)
+{
+	struct virtio_fs *fs = vq->vdev->priv;
+
+	return &fs->vqs[vq->index];
+}
+
+/* Should be called with fsvq->lock held. */
+static inline void inc_in_flight_req(struct virtio_fs_vq *fsvq)
+{
+	fsvq->in_flight++;
+}
+
+/* Should be called with fsvq->lock held. */
+static inline void dec_in_flight_req(struct virtio_fs_vq *fsvq)
+{
+	WARN_ON(fsvq->in_flight <= 0);
+	fsvq->in_flight--;
+	if (!fsvq->in_flight)
+		complete(&fsvq->in_flight_zero);
+}
+
+static void release_virtio_fs_obj(struct kref *ref)
+{
+	struct virtio_fs *vfs = container_of(ref, struct virtio_fs, refcount);
+
+	kfree(vfs->vqs);
+	kfree(vfs);
+}
+
+/* Make sure virtiofs_mutex is held */
+static void virtio_fs_put(struct virtio_fs *fs)
+{
+	kref_put(&fs->refcount, release_virtio_fs_obj);
+}
+
+static void virtio_fs_fiq_release(struct fuse_iqueue *fiq)
+{
+	struct virtio_fs *vfs = fiq->priv;
+
+	mutex_lock(&virtio_fs_mutex);
+	virtio_fs_put(vfs);
+	mutex_unlock(&virtio_fs_mutex);
+}
+
+static void virtio_fs_drain_queue(struct virtio_fs_vq *fsvq)
+{
+	WARN_ON(fsvq->in_flight < 0);
+
+	/* Wait for in flight requests to finish.*/
+	spin_lock(&fsvq->lock);
+	if (fsvq->in_flight) {
+		/* We are holding virtio_fs_mutex. There should not be any
+		 * waiters waiting for completion.
+		 */
+		reinit_completion(&fsvq->in_flight_zero);
+		spin_unlock(&fsvq->lock);
+		wait_for_completion(&fsvq->in_flight_zero);
+	} else {
+		spin_unlock(&fsvq->lock);
+	}
+
+	flush_work(&fsvq->done_work);
+	flush_delayed_work(&fsvq->dispatch_work);
+}
+
+static void virtio_fs_drain_all_queues_locked(struct virtio_fs *fs)
+{
+	struct virtio_fs_vq *fsvq;
+	int i;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		fsvq = &fs->vqs[i];
+		virtio_fs_drain_queue(fsvq);
+	}
+}
+
+static void virtio_fs_drain_all_queues(struct virtio_fs *fs)
+{
+	/* Provides mutual exclusion between ->remove and ->kill_sb
+	 * paths. We don't want both of these draining queue at the
+	 * same time. Current completion logic reinits completion
+	 * and that means there should not be any other thread
+	 * doing reinit or waiting for completion already.
+	 */
+	mutex_lock(&virtio_fs_mutex);
+	virtio_fs_drain_all_queues_locked(fs);
+	mutex_unlock(&virtio_fs_mutex);
+}
+
+static void virtio_fs_start_all_queues(struct virtio_fs *fs)
+{
+	struct virtio_fs_vq *fsvq;
+	int i;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		fsvq = &fs->vqs[i];
+		spin_lock(&fsvq->lock);
+		fsvq->connected = true;
+		spin_unlock(&fsvq->lock);
+	}
+}
+
+/* Add a new instance to the list or return -EEXIST if tag name exists*/
+static int virtio_fs_add_instance(struct virtio_fs *fs)
+{
+	struct virtio_fs *fs2;
+	bool duplicate = false;
+
+	mutex_lock(&virtio_fs_mutex);
+
+	list_for_each_entry(fs2, &virtio_fs_instances, list) {
+		if (strcmp(fs->tag, fs2->tag) == 0)
+			duplicate = true;
+	}
+
+	if (!duplicate)
+		list_add_tail(&fs->list, &virtio_fs_instances);
+
+	mutex_unlock(&virtio_fs_mutex);
+
+	if (duplicate)
+		return -EEXIST;
+	return 0;
+}
+
+/* Return the virtio_fs with a given tag, or NULL */
+static struct virtio_fs *virtio_fs_find_instance(const char *tag)
+{
+	struct virtio_fs *fs;
+
+	mutex_lock(&virtio_fs_mutex);
+
+	list_for_each_entry(fs, &virtio_fs_instances, list) {
+		if (strcmp(fs->tag, tag) == 0) {
+			kref_get(&fs->refcount);
+			goto found;
+		}
+	}
+
+	fs = NULL; /* not found */
+
+found:
+	mutex_unlock(&virtio_fs_mutex);
+
+	return fs;
+}
+
+static void virtio_fs_free_devs(struct virtio_fs *fs)
+{
+	unsigned int i;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		struct virtio_fs_vq *fsvq = &fs->vqs[i];
+
+		if (!fsvq->fud)
+			continue;
+
+		fuse_dev_free(fsvq->fud);
+		fsvq->fud = NULL;
+	}
+}
+
+/* Read filesystem name from virtio config into fs->tag (must kfree()). */
+static int virtio_fs_read_tag(struct virtio_device *vdev, struct virtio_fs *fs)
+{
+	char tag_buf[sizeof_field(struct virtio_fs_config, tag)];
+	char *end;
+	size_t len;
+
+	virtio_cread_bytes(vdev, offsetof(struct virtio_fs_config, tag),
+			   &tag_buf, sizeof(tag_buf));
+	end = memchr(tag_buf, '\0', sizeof(tag_buf));
+	if (end == tag_buf)
+		return -EINVAL; /* empty tag */
+	if (!end)
+		end = &tag_buf[sizeof(tag_buf)];
+
+	len = end - tag_buf;
+	fs->tag = devm_kmalloc(&vdev->dev, len + 1, GFP_KERNEL);
+	if (!fs->tag)
+		return -ENOMEM;
+	memcpy(fs->tag, tag_buf, len);
+	fs->tag[len] = '\0';
+	return 0;
+}
+
+/* Work function for hiprio completion */
+static void virtio_fs_hiprio_done_work(struct work_struct *work)
+{
+	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+						 done_work);
+	struct virtqueue *vq = fsvq->vq;
+
+	/* Free completed FUSE_FORGET requests */
+	spin_lock(&fsvq->lock);
+	do {
+		unsigned int len;
+		void *req;
+
+		virtqueue_disable_cb(vq);
+
+		while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
+			kfree(req);
+			dec_in_flight_req(fsvq);
+		}
+	} while (!virtqueue_enable_cb(vq) && likely(!virtqueue_is_broken(vq)));
+	spin_unlock(&fsvq->lock);
+}
+
+static void virtio_fs_request_dispatch_work(struct work_struct *work)
+{
+	struct fuse_req *req;
+	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+						 dispatch_work.work);
+	int ret;
+
+	pr_debug("virtio-fs: worker %s called.\n", __func__);
+	while (1) {
+		spin_lock(&fsvq->lock);
+		req = list_first_entry_or_null(&fsvq->end_reqs, struct fuse_req,
+					       list);
+		if (!req) {
+			spin_unlock(&fsvq->lock);
+			break;
+		}
+
+		list_del_init(&req->list);
+		spin_unlock(&fsvq->lock);
+		fuse_request_end(req);
+	}
+
+	/* Dispatch pending requests */
+	while (1) {
+		spin_lock(&fsvq->lock);
+		req = list_first_entry_or_null(&fsvq->queued_reqs,
+					       struct fuse_req, list);
+		if (!req) {
+			spin_unlock(&fsvq->lock);
+			return;
+		}
+		list_del_init(&req->list);
+		spin_unlock(&fsvq->lock);
+
+		ret = virtio_fs_enqueue_req(fsvq, req, true);
+		if (ret < 0) {
+			if (ret == -ENOMEM || ret == -ENOSPC) {
+				spin_lock(&fsvq->lock);
+				list_add_tail(&req->list, &fsvq->queued_reqs);
+				schedule_delayed_work(&fsvq->dispatch_work,
+						      msecs_to_jiffies(1));
+				spin_unlock(&fsvq->lock);
+				return;
+			}
+			req->out.h.error = ret;
+			spin_lock(&fsvq->lock);
+			dec_in_flight_req(fsvq);
+			spin_unlock(&fsvq->lock);
+			pr_err("virtio-fs: virtio_fs_enqueue_req() failed %d\n",
+			       ret);
+			fuse_request_end(req);
+		}
+	}
+}
+
+/*
+ * Returns 1 if queue is full and sender should wait a bit before sending
+ * next request, 0 otherwise.
+ */
+static int send_forget_request(struct virtio_fs_vq *fsvq,
+			       struct virtio_fs_forget *forget,
+			       bool in_flight)
+{
+	struct scatterlist sg;
+	struct virtqueue *vq;
+	int ret = 0;
+	bool notify;
+	struct virtio_fs_forget_req *req = &forget->req;
+
+	spin_lock(&fsvq->lock);
+	if (!fsvq->connected) {
+		if (in_flight)
+			dec_in_flight_req(fsvq);
+		kfree(forget);
+		goto out;
+	}
+
+	sg_init_one(&sg, req, sizeof(*req));
+	vq = fsvq->vq;
+	dev_dbg(&vq->vdev->dev, "%s\n", __func__);
+
+	ret = virtqueue_add_outbuf(vq, &sg, 1, forget, GFP_ATOMIC);
+	if (ret < 0) {
+		if (ret == -ENOMEM || ret == -ENOSPC) {
+			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Will try later\n",
+				 ret);
+			list_add_tail(&forget->list, &fsvq->queued_reqs);
+			schedule_delayed_work(&fsvq->dispatch_work,
+					      msecs_to_jiffies(1));
+			if (!in_flight)
+				inc_in_flight_req(fsvq);
+			/* Queue is full */
+			ret = 1;
+		} else {
+			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Dropping it.\n",
+				 ret);
+			kfree(forget);
+			if (in_flight)
+				dec_in_flight_req(fsvq);
+		}
+		goto out;
+	}
+
+	if (!in_flight)
+		inc_in_flight_req(fsvq);
+	notify = virtqueue_kick_prepare(vq);
+	spin_unlock(&fsvq->lock);
+
+	if (notify)
+		virtqueue_notify(vq);
+	return ret;
+out:
+	spin_unlock(&fsvq->lock);
+	return ret;
+}
+
+static void virtio_fs_hiprio_dispatch_work(struct work_struct *work)
+{
+	struct virtio_fs_forget *forget;
+	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+						 dispatch_work.work);
+	pr_debug("virtio-fs: worker %s called.\n", __func__);
+	while (1) {
+		spin_lock(&fsvq->lock);
+		forget = list_first_entry_or_null(&fsvq->queued_reqs,
+					struct virtio_fs_forget, list);
+		if (!forget) {
+			spin_unlock(&fsvq->lock);
+			return;
+		}
+
+		list_del(&forget->list);
+		spin_unlock(&fsvq->lock);
+		if (send_forget_request(fsvq, forget, true))
+			return;
+	}
+}
+
+/* Allocate and copy args into req->argbuf */
+static int copy_args_to_argbuf(struct fuse_req *req)
+{
+	struct fuse_args *args = req->args;
+	unsigned int offset = 0;
+	unsigned int num_in;
+	unsigned int num_out;
+	unsigned int len;
+	unsigned int i;
+
+	num_in = args->in_numargs - args->in_pages;
+	num_out = args->out_numargs - args->out_pages;
+	len = fuse_len_args(num_in, (struct fuse_arg *) args->in_args) +
+	      fuse_len_args(num_out, args->out_args);
+
+	req->argbuf = kmalloc(len, GFP_ATOMIC);
+	if (!req->argbuf)
+		return -ENOMEM;
+
+	for (i = 0; i < num_in; i++) {
+		memcpy(req->argbuf + offset,
+		       args->in_args[i].value,
+		       args->in_args[i].size);
+		offset += args->in_args[i].size;
+	}
+
+	return 0;
+}
+
+/* Copy args out of and free req->argbuf */
+static void copy_args_from_argbuf(struct fuse_args *args, struct fuse_req *req)
+{
+	unsigned int remaining;
+	unsigned int offset;
+	unsigned int num_in;
+	unsigned int num_out;
+	unsigned int i;
+
+	remaining = req->out.h.len - sizeof(req->out.h);
+	num_in = args->in_numargs - args->in_pages;
+	num_out = args->out_numargs - args->out_pages;
+	offset = fuse_len_args(num_in, (struct fuse_arg *)args->in_args);
+
+	for (i = 0; i < num_out; i++) {
+		unsigned int argsize = args->out_args[i].size;
+
+		if (args->out_argvar &&
+		    i == args->out_numargs - 1 &&
+		    argsize > remaining) {
+			argsize = remaining;
+		}
+
+		memcpy(args->out_args[i].value, req->argbuf + offset, argsize);
+		offset += argsize;
+
+		if (i != args->out_numargs - 1)
+			remaining -= argsize;
+	}
+
+	/* Store the actual size of the variable-length arg */
+	if (args->out_argvar)
+		args->out_args[args->out_numargs - 1].size = remaining;
+
+	kfree(req->argbuf);
+	req->argbuf = NULL;
+}
+
+/* Work function for request completion */
+static void virtio_fs_request_complete(struct fuse_req *req,
+				       struct virtio_fs_vq *fsvq)
+{
+	struct fuse_pqueue *fpq = &fsvq->fud->pq;
+	struct fuse_args *args;
+	struct fuse_args_pages *ap;
+	unsigned int len, i, thislen;
+	struct page *page;
+
+	/*
+	 * TODO verify that server properly follows FUSE protocol
+	 * (oh.uniq, oh.len)
+	 */
+	args = req->args;
+	copy_args_from_argbuf(args, req);
+
+	if (args->out_pages && args->page_zeroing) {
+		len = args->out_args[args->out_numargs - 1].size;
+		ap = container_of(args, typeof(*ap), args);
+		for (i = 0; i < ap->num_pages; i++) {
+			thislen = ap->descs[i].length;
+			if (len < thislen) {
+				WARN_ON(ap->descs[i].offset);
+				page = ap->pages[i];
+				zero_user_segment(page, len, thislen);
+				len = 0;
+			} else {
+				len -= thislen;
+			}
+		}
+	}
+
+	spin_lock(&fpq->lock);
+	clear_bit(FR_SENT, &req->flags);
+	spin_unlock(&fpq->lock);
+
+	fuse_request_end(req);
+	spin_lock(&fsvq->lock);
+	dec_in_flight_req(fsvq);
+	spin_unlock(&fsvq->lock);
+}
+
+static void virtio_fs_complete_req_work(struct work_struct *work)
+{
+	struct virtio_fs_req_work *w =
+		container_of(work, typeof(*w), done_work);
+
+	virtio_fs_request_complete(w->req, w->fsvq);
+	kfree(w);
+}
+
+static void virtio_fs_requests_done_work(struct work_struct *work)
+{
+	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+						 done_work);
+	struct fuse_pqueue *fpq = &fsvq->fud->pq;
+	struct virtqueue *vq = fsvq->vq;
+	struct fuse_req *req;
+	struct fuse_req *next;
+	unsigned int len;
+	LIST_HEAD(reqs);
+
+	/* Collect completed requests off the virtqueue */
+	spin_lock(&fsvq->lock);
+	do {
+		virtqueue_disable_cb(vq);
+
+		while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
+			spin_lock(&fpq->lock);
+			list_move_tail(&req->list, &reqs);
+			spin_unlock(&fpq->lock);
+		}
+	} while (!virtqueue_enable_cb(vq) && likely(!virtqueue_is_broken(vq)));
+	spin_unlock(&fsvq->lock);
+
+	/* End requests */
+	list_for_each_entry_safe(req, next, &reqs, list) {
+		list_del_init(&req->list);
+
+		/* blocking async request completes in a worker context */
+		if (req->args->may_block) {
+			struct virtio_fs_req_work *w;
+
+			w = kzalloc(sizeof(*w), GFP_NOFS | __GFP_NOFAIL);
+			INIT_WORK(&w->done_work, virtio_fs_complete_req_work);
+			w->fsvq = fsvq;
+			w->req = req;
+			schedule_work(&w->done_work);
+		} else {
+			virtio_fs_request_complete(req, fsvq);
+		}
+	}
+}
+
+/* Virtqueue interrupt handler */
+static void virtio_fs_vq_done(struct virtqueue *vq)
+{
+	struct virtio_fs_vq *fsvq = vq_to_fsvq(vq);
+
+	dev_dbg(&vq->vdev->dev, "%s %s\n", __func__, fsvq->name);
+
+	schedule_work(&fsvq->done_work);
+}
+
+static void virtio_fs_init_vq(struct virtio_fs_vq *fsvq, char *name,
+			      int vq_type)
+{
+	strscpy(fsvq->name, name, VQ_NAME_LEN);
+	spin_lock_init(&fsvq->lock);
+	INIT_LIST_HEAD(&fsvq->queued_reqs);
+	INIT_LIST_HEAD(&fsvq->end_reqs);
+	init_completion(&fsvq->in_flight_zero);
+
+	if (vq_type == VQ_REQUEST) {
+		INIT_WORK(&fsvq->done_work, virtio_fs_requests_done_work);
+		INIT_DELAYED_WORK(&fsvq->dispatch_work,
+				  virtio_fs_request_dispatch_work);
+	} else {
+		INIT_WORK(&fsvq->done_work, virtio_fs_hiprio_done_work);
+		INIT_DELAYED_WORK(&fsvq->dispatch_work,
+				  virtio_fs_hiprio_dispatch_work);
+	}
+}
+
+/* Initialize virtqueues */
+static int virtio_fs_setup_vqs(struct virtio_device *vdev,
+			       struct virtio_fs *fs)
+{
+	struct virtqueue **vqs;
+	vq_callback_t **callbacks;
+	const char **names;
+	unsigned int i;
+	int ret = 0;
+
+	virtio_cread_le(vdev, struct virtio_fs_config, num_request_queues,
+			&fs->num_request_queues);
+	if (fs->num_request_queues == 0)
+		return -EINVAL;
+
+	fs->nvqs = VQ_REQUEST + fs->num_request_queues;
+	fs->vqs = kcalloc(fs->nvqs, sizeof(fs->vqs[VQ_HIPRIO]), GFP_KERNEL);
+	if (!fs->vqs)
+		return -ENOMEM;
+
+	vqs = kmalloc_array(fs->nvqs, sizeof(vqs[VQ_HIPRIO]), GFP_KERNEL);
+	callbacks = kmalloc_array(fs->nvqs, sizeof(callbacks[VQ_HIPRIO]),
+					GFP_KERNEL);
+	names = kmalloc_array(fs->nvqs, sizeof(names[VQ_HIPRIO]), GFP_KERNEL);
+	if (!vqs || !callbacks || !names) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* Initialize the hiprio/forget request virtqueue */
+	callbacks[VQ_HIPRIO] = virtio_fs_vq_done;
+	virtio_fs_init_vq(&fs->vqs[VQ_HIPRIO], "hiprio", VQ_HIPRIO);
+	names[VQ_HIPRIO] = fs->vqs[VQ_HIPRIO].name;
+
+	/* Initialize the requests virtqueues */
+	for (i = VQ_REQUEST; i < fs->nvqs; i++) {
+		char vq_name[VQ_NAME_LEN];
+
+		snprintf(vq_name, VQ_NAME_LEN, "requests.%u", i - VQ_REQUEST);
+		virtio_fs_init_vq(&fs->vqs[i], vq_name, VQ_REQUEST);
+		callbacks[i] = virtio_fs_vq_done;
+		names[i] = fs->vqs[i].name;
+	}
+
+	ret = virtio_find_vqs(vdev, fs->nvqs, vqs, callbacks, names, NULL);
+	if (ret < 0)
+		goto out;
+
+	for (i = 0; i < fs->nvqs; i++)
+		fs->vqs[i].vq = vqs[i];
+
+	virtio_fs_start_all_queues(fs);
+out:
+	kfree(names);
+	kfree(callbacks);
+	kfree(vqs);
+	if (ret)
+		kfree(fs->vqs);
+	return ret;
+}
+
+/* Free virtqueues (device must already be reset) */
+static void virtio_fs_cleanup_vqs(struct virtio_device *vdev)
+{
+	vdev->config->del_vqs(vdev);
+}
+
+/* Map a window offset to a page frame number.  The window offset will have
+ * been produced by .iomap_begin(), which maps a file offset to a window
+ * offset.
+ */
+static long virtio_fs_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
+				    long nr_pages, enum dax_access_mode mode,
+				    void **kaddr, pfn_t *pfn)
+{
+	struct virtio_fs *fs = dax_get_private(dax_dev);
+	phys_addr_t offset = PFN_PHYS(pgoff);
+	size_t max_nr_pages = fs->window_len / PAGE_SIZE - pgoff;
+
+	if (kaddr)
+		*kaddr = fs->window_kaddr + offset;
+	if (pfn)
+		*pfn = phys_to_pfn_t(fs->window_phys_addr + offset,
+					PFN_DEV | PFN_MAP);
+	return nr_pages > max_nr_pages ? max_nr_pages : nr_pages;
+}
+
+static int virtio_fs_zero_page_range(struct dax_device *dax_dev,
+				     pgoff_t pgoff, size_t nr_pages)
+{
+	long rc;
+	void *kaddr;
+
+	rc = dax_direct_access(dax_dev, pgoff, nr_pages, DAX_ACCESS, &kaddr,
+			       NULL);
+	if (rc < 0)
+		return dax_mem2blk_err(rc);
+
+	memset(kaddr, 0, nr_pages << PAGE_SHIFT);
+	dax_flush(dax_dev, kaddr, nr_pages << PAGE_SHIFT);
+	return 0;
+}
+
+static const struct dax_operations virtio_fs_dax_ops = {
+	.direct_access = virtio_fs_direct_access,
+	.zero_page_range = virtio_fs_zero_page_range,
+};
+
+static void virtio_fs_cleanup_dax(void *data)
+{
+	struct dax_device *dax_dev = data;
+
+	kill_dax(dax_dev);
+	put_dax(dax_dev);
+}
+
+static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
+{
+	struct virtio_shm_region cache_reg;
+	struct dev_pagemap *pgmap;
+	bool have_cache;
+
+	if (!IS_ENABLED(CONFIG_FUSE_DAX))
+		return 0;
+
+	/* Get cache region */
+	have_cache = virtio_get_shm_region(vdev, &cache_reg,
+					   (u8)VIRTIO_FS_SHMCAP_ID_CACHE);
+	if (!have_cache) {
+		dev_notice(&vdev->dev, "%s: No cache capability\n", __func__);
+		return 0;
+	}
+
+	if (!devm_request_mem_region(&vdev->dev, cache_reg.addr, cache_reg.len,
+				     dev_name(&vdev->dev))) {
+		dev_warn(&vdev->dev, "could not reserve region addr=0x%llx len=0x%llx\n",
+			 cache_reg.addr, cache_reg.len);
+		return -EBUSY;
+	}
+
+	dev_notice(&vdev->dev, "Cache len: 0x%llx @ 0x%llx\n", cache_reg.len,
+		   cache_reg.addr);
+
+	pgmap = devm_kzalloc(&vdev->dev, sizeof(*pgmap), GFP_KERNEL);
+	if (!pgmap)
+		return -ENOMEM;
+
+	pgmap->type = MEMORY_DEVICE_FS_DAX;
+
+	/* Ideally we would directly use the PCI BAR resource but
+	 * devm_memremap_pages() wants its own copy in pgmap.  So
+	 * initialize a struct resource from scratch (only the start
+	 * and end fields will be used).
+	 */
+	pgmap->range = (struct range) {
+		.start = (phys_addr_t) cache_reg.addr,
+		.end = (phys_addr_t) cache_reg.addr + cache_reg.len - 1,
+	};
+	pgmap->nr_range = 1;
+
+	fs->window_kaddr = devm_memremap_pages(&vdev->dev, pgmap);
+	if (IS_ERR(fs->window_kaddr))
+		return PTR_ERR(fs->window_kaddr);
+
+	fs->window_phys_addr = (phys_addr_t) cache_reg.addr;
+	fs->window_len = (phys_addr_t) cache_reg.len;
+
+	dev_dbg(&vdev->dev, "%s: window kaddr 0x%px phys_addr 0x%llx len 0x%llx\n",
+		__func__, fs->window_kaddr, cache_reg.addr, cache_reg.len);
+
+	fs->dax_dev = alloc_dax(fs, &virtio_fs_dax_ops);
+	if (IS_ERR(fs->dax_dev))
+		return PTR_ERR(fs->dax_dev);
+
+	return devm_add_action_or_reset(&vdev->dev, virtio_fs_cleanup_dax,
+					fs->dax_dev);
+}
+
+static int virtio_fs_probe(struct virtio_device *vdev)
+{
+	struct virtio_fs *fs;
+	int ret;
+
+	fs = kzalloc(sizeof(*fs), GFP_KERNEL);
+	if (!fs)
+		return -ENOMEM;
+	kref_init(&fs->refcount);
+	vdev->priv = fs;
+
+	ret = virtio_fs_read_tag(vdev, fs);
+	if (ret < 0)
+		goto out;
+
+	ret = virtio_fs_setup_vqs(vdev, fs);
+	if (ret < 0)
+		goto out;
+
+	/* TODO vq affinity */
+
+	ret = virtio_fs_setup_dax(vdev, fs);
+	if (ret < 0)
+		goto out_vqs;
+
+	/* Bring the device online in case the filesystem is mounted and
+	 * requests need to be sent before we return.
+	 */
+	virtio_device_ready(vdev);
+
+	ret = virtio_fs_add_instance(fs);
+	if (ret < 0)
+		goto out_vqs;
+
+	return 0;
+
+out_vqs:
+	virtio_reset_device(vdev);
+	virtio_fs_cleanup_vqs(vdev);
+	kfree(fs->vqs);
+
+out:
+	vdev->priv = NULL;
+	kfree(fs);
+	return ret;
+}
+
+static void virtio_fs_stop_all_queues(struct virtio_fs *fs)
+{
+	struct virtio_fs_vq *fsvq;
+	int i;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		fsvq = &fs->vqs[i];
+		spin_lock(&fsvq->lock);
+		fsvq->connected = false;
+		spin_unlock(&fsvq->lock);
+	}
+}
+
+static void virtio_fs_remove(struct virtio_device *vdev)
+{
+	struct virtio_fs *fs = vdev->priv;
+
+	mutex_lock(&virtio_fs_mutex);
+	/* This device is going away. No one should get new reference */
+	list_del_init(&fs->list);
+	virtio_fs_stop_all_queues(fs);
+	virtio_fs_drain_all_queues_locked(fs);
+	virtio_reset_device(vdev);
+	virtio_fs_cleanup_vqs(vdev);
+
+	vdev->priv = NULL;
+	/* Put device reference on virtio_fs object */
+	virtio_fs_put(fs);
+	mutex_unlock(&virtio_fs_mutex);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int virtio_fs_freeze(struct virtio_device *vdev)
+{
+	/* TODO need to save state here */
+	pr_warn("virtio-fs: suspend/resume not yet supported\n");
+	return -EOPNOTSUPP;
+}
+
+static int virtio_fs_restore(struct virtio_device *vdev)
+{
+	 /* TODO need to restore state here */
+	return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+
+static const struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_FS, VIRTIO_DEV_ANY_ID },
+	{},
+};
+
+static const unsigned int feature_table[] = {};
+
+static struct virtio_driver virtio_fs_driver = {
+	.driver.name		= KBUILD_MODNAME,
+	.driver.owner		= THIS_MODULE,
+	.id_table		= id_table,
+	.feature_table		= feature_table,
+	.feature_table_size	= ARRAY_SIZE(feature_table),
+	.probe			= virtio_fs_probe,
+	.remove			= virtio_fs_remove,
+#ifdef CONFIG_PM_SLEEP
+	.freeze			= virtio_fs_freeze,
+	.restore		= virtio_fs_restore,
+#endif
+};
+
+static void virtio_fs_wake_forget_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->lock)
+{
+	struct fuse_forget_link *link;
+	struct virtio_fs_forget *forget;
+	struct virtio_fs_forget_req *req;
+	struct virtio_fs *fs;
+	struct virtio_fs_vq *fsvq;
+	u64 unique;
+
+	link = fuse_dequeue_forget(fiq, 1, NULL);
+	unique = fuse_get_unique(fiq);
+
+	fs = fiq->priv;
+	fsvq = &fs->vqs[VQ_HIPRIO];
+	spin_unlock(&fiq->lock);
+
+	/* Allocate a buffer for the request */
+	forget = kmalloc(sizeof(*forget), GFP_NOFS | __GFP_NOFAIL);
+	req = &forget->req;
+
+	req->ih = (struct fuse_in_header){
+		.opcode = FUSE_FORGET,
+		.nodeid = link->forget_one.nodeid,
+		.unique = unique,
+		.len = sizeof(*req),
+	};
+	req->arg = (struct fuse_forget_in){
+		.nlookup = link->forget_one.nlookup,
+	};
+
+	send_forget_request(fsvq, forget, false);
+	kfree(link);
+}
+
+static void virtio_fs_wake_interrupt_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->lock)
+{
+	/*
+	 * TODO interrupts.
+	 *
+	 * Normal fs operations on a local filesystems aren't interruptible.
+	 * Exceptions are blocking lock operations; for example fcntl(F_SETLKW)
+	 * with shared lock between host and guest.
+	 */
+	spin_unlock(&fiq->lock);
+}
+
+/* Count number of scatter-gather elements required */
+static unsigned int sg_count_fuse_pages(struct fuse_page_desc *page_descs,
+				       unsigned int num_pages,
+				       unsigned int total_len)
+{
+	unsigned int i;
+	unsigned int this_len;
+
+	for (i = 0; i < num_pages && total_len; i++) {
+		this_len =  min(page_descs[i].length, total_len);
+		total_len -= this_len;
+	}
+
+	return i;
+}
+
+/* Return the number of scatter-gather list elements required */
+static unsigned int sg_count_fuse_req(struct fuse_req *req)
+{
+	struct fuse_args *args = req->args;
+	struct fuse_args_pages *ap = container_of(args, typeof(*ap), args);
+	unsigned int size, total_sgs = 1 /* fuse_in_header */;
+
+	if (args->in_numargs - args->in_pages)
+		total_sgs += 1;
+
+	if (args->in_pages) {
+		size = args->in_args[args->in_numargs - 1].size;
+		total_sgs += sg_count_fuse_pages(ap->descs, ap->num_pages,
+						 size);
+	}
+
+	if (!test_bit(FR_ISREPLY, &req->flags))
+		return total_sgs;
+
+	total_sgs += 1 /* fuse_out_header */;
+
+	if (args->out_numargs - args->out_pages)
+		total_sgs += 1;
+
+	if (args->out_pages) {
+		size = args->out_args[args->out_numargs - 1].size;
+		total_sgs += sg_count_fuse_pages(ap->descs, ap->num_pages,
+						 size);
+	}
+
+	return total_sgs;
+}
+
+/* Add pages to scatter-gather list and return number of elements used */
+static unsigned int sg_init_fuse_pages(struct scatterlist *sg,
+				       struct page **pages,
+				       struct fuse_page_desc *page_descs,
+				       unsigned int num_pages,
+				       unsigned int total_len)
+{
+	unsigned int i;
+	unsigned int this_len;
+
+	for (i = 0; i < num_pages && total_len; i++) {
+		sg_init_table(&sg[i], 1);
+		this_len =  min(page_descs[i].length, total_len);
+		sg_set_page(&sg[i], pages[i], this_len, page_descs[i].offset);
+		total_len -= this_len;
+	}
+
+	return i;
+}
+
+/* Add args to scatter-gather list and return number of elements used */
+static unsigned int sg_init_fuse_args(struct scatterlist *sg,
+				      struct fuse_req *req,
+				      struct fuse_arg *args,
+				      unsigned int numargs,
+				      bool argpages,
+				      void *argbuf,
+				      unsigned int *len_used)
+{
+	struct fuse_args_pages *ap = container_of(req->args, typeof(*ap), args);
+	unsigned int total_sgs = 0;
+	unsigned int len;
+
+	len = fuse_len_args(numargs - argpages, args);
+	if (len)
+		sg_init_one(&sg[total_sgs++], argbuf, len);
+
+	if (argpages)
+		total_sgs += sg_init_fuse_pages(&sg[total_sgs],
+						ap->pages, ap->descs,
+						ap->num_pages,
+						args[numargs - 1].size);
+
+	if (len_used)
+		*len_used = len;
+
+	return total_sgs;
+}
+
+/* Add a request to a virtqueue and kick the device */
+static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
+				 struct fuse_req *req, bool in_flight)
+{
+	/* requests need at least 4 elements */
+	struct scatterlist *stack_sgs[6];
+	struct scatterlist stack_sg[ARRAY_SIZE(stack_sgs)];
+	struct scatterlist **sgs = stack_sgs;
+	struct scatterlist *sg = stack_sg;
+	struct virtqueue *vq;
+	struct fuse_args *args = req->args;
+	unsigned int argbuf_used = 0;
+	unsigned int out_sgs = 0;
+	unsigned int in_sgs = 0;
+	unsigned int total_sgs;
+	unsigned int i;
+	int ret;
+	bool notify;
+	struct fuse_pqueue *fpq;
+
+	/* Does the sglist fit on the stack? */
+	total_sgs = sg_count_fuse_req(req);
+	if (total_sgs > ARRAY_SIZE(stack_sgs)) {
+		sgs = kmalloc_array(total_sgs, sizeof(sgs[0]), GFP_ATOMIC);
+		sg = kmalloc_array(total_sgs, sizeof(sg[0]), GFP_ATOMIC);
+		if (!sgs || !sg) {
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	/* Use a bounce buffer since stack args cannot be mapped */
+	ret = copy_args_to_argbuf(req);
+	if (ret < 0)
+		goto out;
+
+	/* Request elements */
+	sg_init_one(&sg[out_sgs++], &req->in.h, sizeof(req->in.h));
+	out_sgs += sg_init_fuse_args(&sg[out_sgs], req,
+				     (struct fuse_arg *)args->in_args,
+				     args->in_numargs, args->in_pages,
+				     req->argbuf, &argbuf_used);
+
+	/* Reply elements */
+	if (test_bit(FR_ISREPLY, &req->flags)) {
+		sg_init_one(&sg[out_sgs + in_sgs++],
+			    &req->out.h, sizeof(req->out.h));
+		in_sgs += sg_init_fuse_args(&sg[out_sgs + in_sgs], req,
+					    args->out_args, args->out_numargs,
+					    args->out_pages,
+					    req->argbuf + argbuf_used, NULL);
+	}
+
+	WARN_ON(out_sgs + in_sgs != total_sgs);
+
+	for (i = 0; i < total_sgs; i++)
+		sgs[i] = &sg[i];
+
+	spin_lock(&fsvq->lock);
+
+	if (!fsvq->connected) {
+		spin_unlock(&fsvq->lock);
+		ret = -ENOTCONN;
+		goto out;
+	}
+
+	vq = fsvq->vq;
+	ret = virtqueue_add_sgs(vq, sgs, out_sgs, in_sgs, req, GFP_ATOMIC);
+	if (ret < 0) {
+		spin_unlock(&fsvq->lock);
+		goto out;
+	}
+
+	/* Request successfully sent. */
+	fpq = &fsvq->fud->pq;
+	spin_lock(&fpq->lock);
+	list_add_tail(&req->list, fpq->processing);
+	spin_unlock(&fpq->lock);
+	set_bit(FR_SENT, &req->flags);
+	/* matches barrier in request_wait_answer() */
+	smp_mb__after_atomic();
+
+	if (!in_flight)
+		inc_in_flight_req(fsvq);
+	notify = virtqueue_kick_prepare(vq);
+
+	spin_unlock(&fsvq->lock);
+
+	if (notify)
+		virtqueue_notify(vq);
+
+out:
+	if (ret < 0 && req->argbuf) {
+		kfree(req->argbuf);
+		req->argbuf = NULL;
+	}
+	if (sgs != stack_sgs) {
+		kfree(sgs);
+		kfree(sg);
+	}
+
+	return ret;
+}
+
+static void virtio_fs_wake_pending_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->lock)
+{
+	unsigned int queue_id = VQ_REQUEST; /* TODO multiqueue */
+	struct virtio_fs *fs;
+	struct fuse_req *req;
+	struct virtio_fs_vq *fsvq;
+	int ret;
+
+	WARN_ON(list_empty(&fiq->pending));
+	req = list_last_entry(&fiq->pending, struct fuse_req, list);
+	clear_bit(FR_PENDING, &req->flags);
+	list_del_init(&req->list);
+	WARN_ON(!list_empty(&fiq->pending));
+	spin_unlock(&fiq->lock);
+
+	fs = fiq->priv;
+
+	pr_debug("%s: opcode %u unique %#llx nodeid %#llx in.len %u out.len %u\n",
+		  __func__, req->in.h.opcode, req->in.h.unique,
+		 req->in.h.nodeid, req->in.h.len,
+		 fuse_len_args(req->args->out_numargs, req->args->out_args));
+
+	fsvq = &fs->vqs[queue_id];
+	ret = virtio_fs_enqueue_req(fsvq, req, false);
+	if (ret < 0) {
+		if (ret == -ENOMEM || ret == -ENOSPC) {
+			/*
+			 * Virtqueue full. Retry submission from worker
+			 * context as we might be holding fc->bg_lock.
+			 */
+			spin_lock(&fsvq->lock);
+			list_add_tail(&req->list, &fsvq->queued_reqs);
+			inc_in_flight_req(fsvq);
+			schedule_delayed_work(&fsvq->dispatch_work,
+						msecs_to_jiffies(1));
+			spin_unlock(&fsvq->lock);
+			return;
+		}
+		req->out.h.error = ret;
+		pr_err("virtio-fs: virtio_fs_enqueue_req() failed %d\n", ret);
+
+		/* Can't end request in submission context. Use a worker */
+		spin_lock(&fsvq->lock);
+		list_add_tail(&req->list, &fsvq->end_reqs);
+		schedule_delayed_work(&fsvq->dispatch_work, 0);
+		spin_unlock(&fsvq->lock);
+		return;
+	}
+}
+
+static const struct fuse_iqueue_ops virtio_fs_fiq_ops = {
+	.wake_forget_and_unlock		= virtio_fs_wake_forget_and_unlock,
+	.wake_interrupt_and_unlock	= virtio_fs_wake_interrupt_and_unlock,
+	.wake_pending_and_unlock	= virtio_fs_wake_pending_and_unlock,
+	.release			= virtio_fs_fiq_release,
+};
+
+static inline void virtio_fs_ctx_set_defaults(struct fuse_fs_context *ctx)
+{
+	ctx->rootmode = S_IFDIR;
+	ctx->default_permissions = 1;
+	ctx->allow_other = 1;
+	ctx->max_read = UINT_MAX;
+	ctx->blksize = 512;
+	ctx->destroy = true;
+	ctx->no_control = true;
+	ctx->no_force_umount = true;
+}
+
+static int virtio_fs_fill_super(struct super_block *sb, struct fs_context *fsc)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	struct fuse_conn *fc = fm->fc;
+	struct virtio_fs *fs = fc->iq.priv;
+	struct fuse_fs_context *ctx = fsc->fs_private;
+	unsigned int i;
+	int err;
+
+	virtio_fs_ctx_set_defaults(ctx);
+	mutex_lock(&virtio_fs_mutex);
+
+	/* After holding mutex, make sure virtiofs device is still there.
+	 * Though we are holding a reference to it, drive ->remove might
+	 * still have cleaned up virtual queues. In that case bail out.
+	 */
+	err = -EINVAL;
+	if (list_empty(&fs->list)) {
+		pr_info("virtio-fs: tag <%s> not found\n", fs->tag);
+		goto err;
+	}
+
+	err = -ENOMEM;
+	/* Allocate fuse_dev for hiprio and notification queues */
+	for (i = 0; i < fs->nvqs; i++) {
+		struct virtio_fs_vq *fsvq = &fs->vqs[i];
+
+		fsvq->fud = fuse_dev_alloc();
+		if (!fsvq->fud)
+			goto err_free_fuse_devs;
+	}
+
+	/* virtiofs allocates and installs its own fuse devices */
+	ctx->fudptr = NULL;
+	if (ctx->dax_mode != FUSE_DAX_NEVER) {
+		if (ctx->dax_mode == FUSE_DAX_ALWAYS && !fs->dax_dev) {
+			err = -EINVAL;
+			pr_err("virtio-fs: dax can't be enabled as filesystem"
+			       " device does not support it.\n");
+			goto err_free_fuse_devs;
+		}
+		ctx->dax_dev = fs->dax_dev;
+	}
+	err = fuse_fill_super_common(sb, ctx);
+	if (err < 0)
+		goto err_free_fuse_devs;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		struct virtio_fs_vq *fsvq = &fs->vqs[i];
+
+		fuse_dev_install(fsvq->fud, fc);
+	}
+
+	/* Previous unmount will stop all queues. Start these again */
+	virtio_fs_start_all_queues(fs);
+	fuse_send_init(fm);
+	mutex_unlock(&virtio_fs_mutex);
+	return 0;
+
+err_free_fuse_devs:
+	virtio_fs_free_devs(fs);
+err:
+	mutex_unlock(&virtio_fs_mutex);
+	return err;
+}
+
+static void virtio_fs_conn_destroy(struct fuse_mount *fm)
+{
+	struct fuse_conn *fc = fm->fc;
+	struct virtio_fs *vfs = fc->iq.priv;
+	struct virtio_fs_vq *fsvq = &vfs->vqs[VQ_HIPRIO];
+
+	/* Stop dax worker. Soon evict_inodes() will be called which
+	 * will free all memory ranges belonging to all inodes.
+	 */
+	if (IS_ENABLED(CONFIG_FUSE_DAX))
+		fuse_dax_cancel_work(fc);
+
+	/* Stop forget queue. Soon destroy will be sent */
+	spin_lock(&fsvq->lock);
+	fsvq->connected = false;
+	spin_unlock(&fsvq->lock);
+	virtio_fs_drain_all_queues(vfs);
+
+	fuse_conn_destroy(fm);
+
+	/* fuse_conn_destroy() must have sent destroy. Stop all queues
+	 * and drain one more time and free fuse devices. Freeing fuse
+	 * devices will drop their reference on fuse_conn and that in
+	 * turn will drop its reference on virtio_fs object.
+	 */
+	virtio_fs_stop_all_queues(vfs);
+	virtio_fs_drain_all_queues(vfs);
+	virtio_fs_free_devs(vfs);
+}
+
+static void virtio_kill_sb(struct super_block *sb)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	bool last;
+
+	/* If mount failed, we can still be called without any fc */
+	if (sb->s_root) {
+		last = fuse_mount_remove(fm);
+		if (last)
+			virtio_fs_conn_destroy(fm);
+	}
+	kill_anon_super(sb);
+	fuse_mount_destroy(fm);
+}
+
+static int virtio_fs_test_super(struct super_block *sb,
+				struct fs_context *fsc)
+{
+	struct fuse_mount *fsc_fm = fsc->s_fs_info;
+	struct fuse_mount *sb_fm = get_fuse_mount_super(sb);
+
+	return fsc_fm->fc->iq.priv == sb_fm->fc->iq.priv;
+}
+
+static int virtio_fs_get_tree(struct fs_context *fsc)
+{
+	struct virtio_fs *fs;
+	struct super_block *sb;
+	struct fuse_conn *fc = NULL;
+	struct fuse_mount *fm;
+	unsigned int virtqueue_size;
+	int err = -EIO;
+
+	/* This gets a reference on virtio_fs object. This ptr gets installed
+	 * in fc->iq->priv. Once fuse_conn is going away, it calls ->put()
+	 * to drop the reference to this object.
+	 */
+	fs = virtio_fs_find_instance(fsc->source);
+	if (!fs) {
+		pr_info("virtio-fs: tag <%s> not found\n", fsc->source);
+		return -EINVAL;
+	}
+
+	virtqueue_size = virtqueue_get_vring_size(fs->vqs[VQ_REQUEST].vq);
+	if (WARN_ON(virtqueue_size <= FUSE_HEADER_OVERHEAD))
+		goto out_err;
+
+	err = -ENOMEM;
+	fc = kzalloc(sizeof(struct fuse_conn), GFP_KERNEL);
+	if (!fc)
+		goto out_err;
+
+	fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL);
+	if (!fm)
+		goto out_err;
+
+	fuse_conn_init(fc, fm, fsc->user_ns, &virtio_fs_fiq_ops, fs);
+	fc->release = fuse_free_conn;
+	fc->delete_stale = true;
+	fc->auto_submounts = true;
+	fc->sync_fs = true;
+
+	/* Tell FUSE to split requests that exceed the virtqueue's size */
+	fc->max_pages_limit = min_t(unsigned int, fc->max_pages_limit,
+				    virtqueue_size - FUSE_HEADER_OVERHEAD);
+
+	fsc->s_fs_info = fm;
+	sb = sget_fc(fsc, virtio_fs_test_super, set_anon_super_fc);
+	if (fsc->s_fs_info)
+		fuse_mount_destroy(fm);
+	if (IS_ERR(sb))
+		return PTR_ERR(sb);
+
+	if (!sb->s_root) {
+		err = virtio_fs_fill_super(sb, fsc);
+		if (err) {
+			deactivate_locked_super(sb);
+			return err;
+		}
+
+		sb->s_flags |= SB_ACTIVE;
+	}
+
+	WARN_ON(fsc->root);
+	fsc->root = dget(sb->s_root);
+	return 0;
+
+out_err:
+	kfree(fc);
+	mutex_lock(&virtio_fs_mutex);
+	virtio_fs_put(fs);
+	mutex_unlock(&virtio_fs_mutex);
+	return err;
+}
+
+static const struct fs_context_operations virtio_fs_context_ops = {
+	.free		= virtio_fs_free_fsc,
+	.parse_param	= virtio_fs_parse_param,
+	.get_tree	= virtio_fs_get_tree,
+};
+
+static int virtio_fs_init_fs_context(struct fs_context *fsc)
+{
+	struct fuse_fs_context *ctx;
+
+	if (fsc->purpose == FS_CONTEXT_FOR_SUBMOUNT)
+		return fuse_init_fs_context_submount(fsc);
+
+	ctx = kzalloc(sizeof(struct fuse_fs_context), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	fsc->fs_private = ctx;
+	fsc->ops = &virtio_fs_context_ops;
+	return 0;
+}
+
+static struct file_system_type virtio_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "virtiofs",
+	.init_fs_context = virtio_fs_init_fs_context,
+	.kill_sb	= virtio_kill_sb,
+};
+
+static int __init virtio_fs_init(void)
+{
+	int ret;
+
+	ret = register_virtio_driver(&virtio_fs_driver);
+	if (ret < 0)
+		return ret;
+
+	ret = register_filesystem(&virtio_fs_type);
+	if (ret < 0) {
+		unregister_virtio_driver(&virtio_fs_driver);
+		return ret;
+	}
+
+	return 0;
+}
+module_init(virtio_fs_init);
+
+static void __exit virtio_fs_exit(void)
+{
+	unregister_filesystem(&virtio_fs_type);
+	unregister_virtio_driver(&virtio_fs_driver);
+}
+module_exit(virtio_fs_exit);
+
+MODULE_AUTHOR("Stefan Hajnoczi <stefanha@redhat.com>");
+MODULE_DESCRIPTION("Virtio Filesystem");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_FS(KBUILD_MODNAME);
+MODULE_DEVICE_TABLE(virtio, id_table);