path: root/fs/fuse/dev.c

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2006  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)
{
	/*
	 * Lockless access is OK, because file->private data is set
	 * once during mount and is valid until the file is released.
	 */
	return file->private_data;
}

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)
{
	BUG_ON(atomic_read(&req->count) != 1);
	fuse_request_init(req);
}

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);
}

struct fuse_req *fuse_get_req(struct fuse_conn *fc)
{
	struct fuse_req *req;
	sigset_t oldset;
	int err;

	block_sigs(&oldset);
	err = wait_event_interruptible(fc->blocked_waitq, !fc->blocked);
	restore_sigs(&oldset);
	if (err)
		return ERR_PTR(-EINTR);

	req = fuse_request_alloc();
	if (!req)
		return ERR_PTR(-ENOMEM);

	atomic_inc(&fc->num_waiting);
	fuse_request_init(req);
	req->in.h.uid = current->fsuid;
	req->in.h.gid = current->fsgid;
	req->in.h.pid = current->pid;
	return req;
}

void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
	if (atomic_dec_and_test(&req->count)) {
		atomic_dec(&fc->num_waiting);
		fuse_request_free(req);
	}
}

void fuse_remove_background(struct fuse_conn *fc, struct fuse_req *req)
{
	list_del_init(&req->bg_entry);
	if (fc->num_background == FUSE_MAX_BACKGROUND) {
		fc->blocked = 0;
		wake_up_all(&fc->blocked_waitq);
	}
	fc->num_background--;
}

/*
 * This function is called when a request is finished.  Either a reply
 * has arrived or it was interrupted (and not yet sent) or some error
 * occurred during communication with userspace, or the device file
 * was closed.  In case of a background request the reference to the
 * stored objects are released.  The requester thread is woken up (if
 * still waiting), the 'end' callback is called if given, else the
 * reference to the request is released
 *
 * Releasing extra reference for foreground requests must be done
 * within the same locked region as setting state to finished.  This
 * is because fuse_reset_request() may be called after request is
 * finished and it must be the sole possessor.  If request is
 * interrupted and put in the background, it will return with an error
 * and hence never be reset and reused.
 *
 * Called with fc->lock, unlocks it
 */
static void request_end(struct fuse_conn *fc, struct fuse_req *req)
{
	list_del(&req->list);
	req->state = FUSE_REQ_FINISHED;
	if (!req->background) {
		spin_unlock(&fc->lock);
		wake_up(&req->waitq);
		fuse_put_request(fc, req);
	} else {
		struct inode *inode = req->inode;
		struct inode *inode2 = req->inode2;
		struct file *file = req->file;
		void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
		req->end = NULL;
		req->inode = NULL;
		req->inode2 = NULL;
		req->file = NULL;
		if (!list_empty(&req->bg_entry))
			fuse_remove_background(fc, req);
		spin_unlock(&fc->lock);

		if (end)
			end(fc, req);
		else