path: root/fs/fuse/dev.c

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2005  Miklos Szeredi <miklos@szeredi.hu>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/

#include "fuse_i.h"

#include <linux/init.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/uio.h>
#include <linux/miscdevice.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/slab.h>

MODULE_ALIAS_MISCDEV(FUSE_MINOR);

static kmem_cache_t *fuse_req_cachep;

static struct fuse_conn *fuse_get_conn(struct file *file)
{
	struct fuse_conn *fc;
	spin_lock(&fuse_lock);
	fc = file->private_data;
	if (fc && !fc->connected)
		fc = NULL;
	spin_unlock(&fuse_lock);
	return fc;
}

static void fuse_request_init(struct fuse_req *req)
{
	memset(req, 0, sizeof(*req));
	INIT_LIST_HEAD(&req->list);
	init_waitqueue_head(&req->waitq);
	atomic_set(&req->count, 1);
}

struct fuse_req *fuse_request_alloc(void)
{
	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, SLAB_KERNEL);
	if (req)
		fuse_request_init(req);
	return req;
}

void fuse_request_free(struct fuse_req *req)
{
	kmem_cache_free(fuse_req_cachep, req);
}

static void block_sigs(sigset_t *oldset)
{
	sigset_t mask;

	siginitsetinv(&mask, sigmask(SIGKILL));
	sigprocmask(SIG_BLOCK, &mask, oldset);
}

static void restore_sigs(sigset_t *oldset)
{
	sigprocmask(SIG_SETMASK, oldset, NULL);
}

/*
 * Reset request, so that it can be reused
 *
 * The caller must be _very_ careful to make sure, that it is holding
 * the only reference to req
 */
void fuse_reset_request(struct fuse_req *req)
{
	int preallocated = req->preallocated;
	BUG_ON(atomic_read(&req->count) != 1);
	fuse_request_init(req);
	req->preallocated = preallocated;
}

static void __fuse_get_request(struct fuse_req *req)
{
	atomic_inc(&req->count);
}

/* Must be called with > 1 refcount */
static void __fuse_put_request(struct fuse_req *req)
{
	BUG_ON(atomic_read(&req->count) < 2);
	atomic_dec(&req->count);
}

static struct fuse_req *do_get_request(struct fuse_conn *fc)
{
	struct fuse_req *req;

	spin_lock(&fuse_lock);
	BUG_ON(list_empty(&fc->unused_list));
	req = list_entry(fc->unused_list.next, struct fuse_req, list);
	list_del_init(&req->list);
	spin_unlock(&fuse_lock);
	fuse_request_init(req);
	req->preallocated = 1;
	req->in.h.uid = current->fsuid;
	req->in.h.gid = current->fsgid;
	req->in.h.pid = current->pid;
	return req;
}

/* This can return NULL, but only in case it's interrupted by a SIGKILL */
struct fuse_req *fuse_get_request(struct fuse_conn *fc)
{
	int intr;
	sigset_t oldset;

	atomic_inc(&fc->num_waiting);
	block_sigs(&oldset);
	intr = down_interruptible(&fc->outstanding_sem);
	restore_sigs(&oldset);
	if (intr) {
		atomic_dec(&fc->num_waiting);
		return NULL;
	}
	return do_get_request(fc);
}

/* Must be called with fuse_lock held */
static void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req)
{
	if (req->preallocated) {
		atomic_dec(&fc->num_waiting);
		list_add(&req->list, &fc->unused_list);
	} else
		fuse_request_free(req);

	/* If we are in debt decrease that first */
	if (fc->outstanding_debt)
		fc->outstanding_debt--;
	else
		up(&fc->outstanding_sem);
}

void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
	if (atomic_dec_and_test(&req->count)) {
		spin_lock(&fuse_lock);
		fuse_putback_request(fc, req);
		spin_unlock(&fuse_lock);
	}
}

static void fuse_put_request_locked(struct fuse_conn *fc, struct fuse_req *req)
{
	if (atomic_dec_and_test(&req->count))
		fuse_putback_request(fc, req);
}

void fuse_release_background(struct fuse_req *req)
{
	iput(req->inode);
	iput(req->inode2);
	if (req->file)
		fput(req->file);
	spin_lock(