path: root/fs/fuse/virtio_fs.c

// SPDX-License-Identifier: GPL-2.0
/*
 * virtio-fs: Virtio Filesystem
 * Copyright (C) 2018 Red Hat, Inc.
 */

#include <linux/fs.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/highmem.h>
#include "fuse_i.h"

/* 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
};

/* 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 delayed_work dispatch_work;
	struct fuse_dev *fud;
	bool connected;
	long in_flight;
	char name[24];
} ____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 virtio_fs_forget {
	struct fuse_in_header ih;
	struct fuse_forget_in arg;
	/* This request can be temporarily queued on virt queue */
	struct list_head list;
};

static inline struct virtio_fs_vq *vq_to_fsvq(struct virtqueue *vq)
{
	struct virtio_fs *fs = vq->vdev->priv;

	return &fs->vqs[vq->index];
}

static inline struct fuse_pqueue *vq_to_fpq(struct virtqueue *vq)
{
	return &vq_to_fsvq(vq)->fud->pq;
}

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.*/
	while (1) {
		spin_lock(&fsvq->lock);
		if (!fsvq->in_flight) {
			spin_unlock(&fsvq->lock);
			break;
		}
		spin_unlock(&fsvq->lock);
		/* TODO use completion instead of timeout */
		usleep_range(1000, 2000);
	}

	flush_work(&fsvq->done_work);
	flush_delayed_work(&fsvq->dispatch_work);
}

static inline void drain_hiprio_queued_reqs(struct virtio_fs_vq *fsvq)
{
	struct virtio_fs_forget *forget;

	spin_lock(&fsvq->lock);
	while (1) {
		forget = list_first_entry_or_null(&fsvq->queued_reqs,
						struct virtio_fs_forget, list);
		if (!forget)
			break;
		list_del(&forget->list);
		kfree(forget);
	}
	spin_unlock(&fsvq->lock);
}

static void virtio_fs_drain_all_queues(struct virtio_fs *fs)
{
	struct virtio_fs_vq *fsvq;
	int i;

	for (i = 0; i < fs->nvqs; i++) {
		fsvq = &fs->vqs[i];
		if (i == VQ_HIPRIO)
			drain_hiprio_queued_reqs(fsvq);

		virtio_fs_drain_queue(fsvq);
	}
}

static void virtio_fs_start_all_queues(struct