/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2004  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>
#ifdef KERNEL_2_6
#include <linux/kobject.h>
#else
#include <linux/proc_fs.h>
#endif
#include <linux/miscdevice.h>
#include <linux/pagemap.h>
#include <linux/file.h>

static kmem_cache_t *fuse_req_cachep;

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

static inline 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 int get_unique(struct fuse_conn *fc)
{
	fc->reqctr++;
	/* zero is special */
	if (fc->reqctr == 0)
		fc->reqctr = 1;
	return fc->reqctr;
}

#ifdef KERNEL_2_6
static inline void block_sigs(sigset_t *oldset)
{
	sigset_t sigmask;

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

static inline void restore_sigs(sigset_t *oldset)
{
	sigprocmask(SIG_SETMASK, oldset, NULL);
}
#else
static inline void block_sigs(sigset_t *oldset)
{
	spin_lock_irq(&current->sigmask_lock);
	*oldset = current->blocked;
	siginitsetinv(&current->blocked, sigmask(SIGKILL) & ~oldset->sig[0]);
	recalc_sigpending(current);
	spin_unlock_irq(&current->sigmask_lock);
}

static inline void restore_sigs(sigset_t *oldset)
{
	spin_lock_irq(&current->sigmask_lock);
	current->blocked = *oldset;
	recalc_sigpending(current);
	spin_unlock_irq(&current->sigmask_lock);
}
#endif

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)
{
	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;
}

struct fuse_req *fuse_get_request(struct fuse_conn *fc)
{
	if (down_interruptible(&fc->unused_sem))
		return NULL;
	return  do_get_request(fc);
}

struct fuse_req *fuse_get_request_nonint(struct fuse_conn *fc)
{
	int intr;
	sigset_t oldset;

	block_sigs(&oldset);
	intr = down_interruptible(&fc->unused_sem);
	restore_sigs(&oldset);
	return intr ? NULL : do_get_request(fc);
}

void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req)
{
	if (!req->preallocated)
		fuse_request_free(req);
	else {
		spin_lock(&fuse_lock);
		list_add(&req->list, &fc->unused_list);
		spin_unlock(&fuse_lock);
		up(&fc->unused_sem);
	}
}

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

/* Called with fuse_lock, unlocks it */
static void request_end(struct fuse_conn *fc, struct fuse_req *req)
{
	int putback;
	req->finished = 1;
	putback = atomic_dec_and_test(&req->count);
	spin_unlock(&fuse_lock);
	wake_up(&req->waitq);
	if (putback)
		fuse_putback_request(fc, req);
}

static int request_wait_answer_nonint(struct fuse_req *req)
{
	int err;
	sigset_t oldset;
	block_sigs(&oldset);
	err = wait_event_interruptible(req->waitq, req->finished);
	restore_sigs(&oldset);
	return err;
}

/* Called with fuse_lock held.  Releases, and then reaquires it. */
static void request_wait_answer(struct fuse_req *req, int interruptible,
				int background)
{
	int intr;

	spin_unlock(&fuse_lock);
	if (interruptible)
		intr = wait_event_interruptible(req->waitq, req->finished);
	else
		intr = request_wait_answer_nonint(req);
	spin_lock(&fuse_lock);
	if (intr && interruptible && req->sent) {
		/* If request is already in userspace, only allow KILL
		   signal to interrupt */
		spin_unlock(&fuse_lock);
		intr = request_wait_answer_nonint(req);
		spin_lock(&fuse_lock);
	}
	if (!intr)
		return;

	if (background && !req->sent) {
		req->isreply = 0;
		return;
	}
	req->out.h.error = -ERESTARTNOINTR;
	req->interrupted = 1;
	if (req->locked) {
		/* This is uninterruptible sleep, because data is
		   being copied to/from the buffers of req.  During
		   locked state, there musn't be any filesystem
		   operation (e.g. page fault), since that could lead
		   to deadlock */
		spin_unlock(&fuse_lock);
		wait_event(req->waitq, !req->locked);
		spin_lock(&fuse_lock);
	}
	if (!list_empty(&req->list)) {
		/* request is still on one of the lists */
		list_del(&req->list);
		__fuse_put_request(req);
	}
}

static void request_send_wait(struct fuse_conn *fc, struct fuse_req *req,
			      int interruptible, int background)
{
	req->isreply = 1;
	spin_lock(&fuse_lock);
	req->out.h.error = -ENOTCONN;
	if (fc->file) {
		req->in.h.unique = get_unique(fc);
		list_add_tail(&req->list, &fc->pending);
		wake_up(&fc->waitq);
		/* acquire extra reference, since request is still needed
		   after request_end() */
		__fuse_get_request(req);

		request_wait_answer(req, interruptible, background);
	}
	spin_unlock(&fuse_lock);
}

void request_send(struct fuse_conn *fc, struct fuse_req *req)
{
	request_send_wait(fc, req, 1, 0);
}

void request_send_nonint(struct fuse_conn *fc, struct fuse_req *req,
			 int background)
{
	request_send_wait(fc, req, 0, background);
}

void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req)
{
	req->isreply = 0;
	spin_lock(&fuse_lock);
	if (fc->file) {
		list_add_tail(&req->list, &fc->pending);
		wake_up(&fc->waitq);
		spin_unlock(&fuse_lock);
	} else {
		req->out.h.error = -ENOTCONN;
		request_end(fc, req);
	}
}

static inline int lock_request(struct fuse_req *req)
{
	int err = 0;
	if (req) {
		spin_lock(&fuse_lock);
		if (req->interrupted)
			err = -ENOENT;
		else
			req->locked = 1;
		spin_unlock(&fuse_lock);
	}
	return err;
}

static inline void unlock_request(struct fuse_req *req)
{
	if (req) {
		spin_lock(&fuse_lock);
		req->locked = 0;
		if (req->interrupted)
			wake_up(&req->waitq);
		spin_unlock(&fuse_lock);
	}
}

struct fuse_copy_state {
	int write;
	struct fuse_req *req;
	const struct iovec *iov;
	unsigned long nr_segs;
	unsigned long seglen;
	unsigned long addr;
	struct page *pg;
	void *mapaddr;
	void *buf;
	unsigned len;
};

static unsigned fuse_copy_init(struct fuse_copy_state *cs, int write,
			       struct fuse_req *req, const struct iovec *iov,
			       unsigned long nr_segs)
{
	unsigned i;
	unsigned nbytes;

	memset(cs, 0, sizeof(*cs));
	cs->write = write;
	cs->req = req;
	cs->iov = iov;
	cs->nr_segs = nr_segs;

	nbytes = 0;
	for (i = 0; i < nr_segs; i++)
		nbytes += iov[i].iov_len;

	return nbytes;
}

static inline void fuse_copy_finish(struct fuse_copy_state *cs)
{
	if (cs->mapaddr) {
		kunmap_atomic(cs->mapaddr, KM_USER0);
		if (cs->write) {
			flush_dcache_page(cs->pg);
			set_page_dirty_lock(cs->pg);
		}
		put_page(cs->pg);
		cs->mapaddr = NULL;
	}
}

static int fuse_copy_fill(struct fuse_copy_state *cs)
{
	unsigned long offset;
	int err;

	unlock_request(cs->req);
	fuse_copy_finish(cs);
	if (!cs->seglen) {
		BUG_ON(!cs->nr_segs);
		cs->seglen = cs->iov[0].iov_len;
		cs->addr = (unsigned long) cs->iov[0].iov_base;
		cs->iov ++;
		cs->nr_segs --;
	}
	down_read(&current->mm->mmap_sem);
	err = get_user_pages(current, current->mm, cs->addr, 1, cs->write, 0,
			     &cs->pg, NULL);
	up_read(&current->mm->mmap_sem);
	if (err < 0)
		return err;
	BUG_ON(err != 1);
	offset = cs->addr % PAGE_SIZE;
	cs->mapaddr = kmap_atomic(cs->pg, KM_USER0);
	cs->buf = cs->mapaddr + offset;
	cs->len = min(PAGE_SIZE - offset, cs->seglen);
	cs->seglen -= cs->len;
	cs->addr += cs->len;

	return lock_request(cs->req);
}

static inline int fuse_copy_do(struct fuse_copy_state *cs, void **val,
			       unsigned *size)
{
	unsigned ncpy = min(*size, cs->len);
	if (val) {
		if (cs->write)
			memcpy(cs->buf, *val, ncpy);
		else
			memcpy(*val, cs->buf, ncpy);
		*val += ncpy;
	}
	*size -= ncpy;
	cs->len -= ncpy;
	cs->buf += ncpy;
	return ncpy;
}

static inline int fuse_copy_page(struct fuse_copy_state *cs, struct page *page,
				 unsigned offset, unsigned count, int zeroing)
{
	if (page && zeroing && count < PAGE_SIZE) {
		void *mapaddr = kmap_atomic(page, KM_USER1);
		memset(mapaddr, 0, PAGE_SIZE);
		kunmap_atomic(mapaddr, KM_USER1);
	}
	while (count) {
		int err;
		if (!cs->len && (err = fuse_copy_fill(cs)))
			return err;
		if (page) {
			void *mapaddr = kmap_atomic(page, KM_USER1);
			void *buf = mapaddr + offset;
			offset += fuse_copy_do(cs, &buf, &count);
			kunmap_atomic(mapaddr, KM_USER1);
		} else
			offset += fuse_copy_do(cs, NULL, &count);
	}
	if (page && !cs->write)
		flush_dcache_page(page);
	return 0;
}

static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
			   int zeroing)
{
	unsigned i;
	struct fuse_req *req = cs->req;
	unsigned offset = req->page_offset;
	unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset);

	for (i = 0; i < req->num_pages && nbytes; i++) {
		struct page *page = req->pages[i];
		int err = fuse_copy_page(cs, page, offset, count, zeroing);
		if (err)
			return err;

		nbytes -= count;
		count = min(nbytes, (unsigned) PAGE_SIZE);
		offset = 0;
	}
	return 0;
}

static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size)
{
	while (size) {
		int err;
		if (!cs->len && (err = fuse_copy_fill(cs)))
			return err;
		fuse_copy_do(cs, &val, &size);
	}
	return 0;
}

static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
			  unsigned argpages, struct fuse_arg *args,
			  int zeroing)
{
	int err = 0;
	unsigned i;

	for (i = 0; !err && i < numargs; i++)  {
		struct fuse_arg *arg = &args[i];
		if (i == numargs - 1 && argpages)
			err = fuse_copy_pages(cs, arg->size, zeroing);
		else
			err = fuse_copy_one(cs, arg->value, arg->size);
	}
	return err;
}

static unsigned len_args(unsigned numargs, struct fuse_arg *args)
{
	unsigned nbytes = 0;
	unsigned i;

	for (i = 0; i < numargs; i++)
		nbytes += args[i].size;

	return nbytes;
}

static void request_wait(struct fuse_conn *fc)
{
	DECLARE_WAITQUEUE(wait, current);

	add_wait_queue_exclusive(&fc->waitq, &wait);
	while (fc->sb && list_empty(&fc->pending)) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (signal_pending(current))
			break;

		spin_unlock(&fuse_lock);
		schedule();
		spin_lock(&fuse_lock);
	}
	set_current_state(TASK_RUNNING);
	remove_wait_queue(&fc->waitq, &wait);
}

static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov,
			      unsigned long nr_segs, loff_t *off)
{
	int err;
	struct fuse_conn *fc;
	struct fuse_req *req;
	struct fuse_in *in;
	struct fuse_copy_state cs;
	unsigned nbytes;
	unsigned reqsize;

	spin_lock(&fuse_lock);
	fc = file->private_data;
	err = -EPERM;
	if (!fc)
		goto err_unlock;
	request_wait(fc);
	err = -ENODEV;
	if (!fc->sb)
		goto err_unlock;
	err = -EINTR;
	if (list_empty(&fc->pending))
		goto err_unlock;

	req = list_entry(fc->pending.next, struct fuse_req, list);
	list_del_init(&req->list);
	spin_unlock(&fuse_lock);

	in = &req->in;
	reqsize = sizeof(struct fuse_in_header);
	reqsize += len_args(in->numargs, (struct fuse_arg *) in->args);
	nbytes = fuse_copy_init(&cs, 1, req, iov, nr_segs);
	err = -EINVAL;
	if (nbytes >= reqsize) {
		err = fuse_copy_one(&cs, &in->h, sizeof(in->h));
		if (!err)
			err = fuse_copy_args(&cs, in->numargs, in->argpages,
					     (struct fuse_arg *) in->args, 0);
	}
	fuse_copy_finish(&cs);

	spin_lock(&fuse_lock);
	req->locked = 0;
	if (!err && req->interrupted)
		err = -ENOENT;
	if (err) {
		if (!req->interrupted)
			req->out.h.error = -EIO;
		request_end(fc, req);
		return err;
	}
	if (!req->isreply)
		request_end(fc, req);
	else {
		req->sent = 1;
		list_add_tail(&req->list, &fc->processing);
		spin_unlock(&fuse_lock);
	}
	return reqsize;

 err_unlock:
	spin_unlock(&fuse_lock);
	return err;
}

static ssize_t fuse_dev_read(struct file *file, char __user *buf,
			     size_t nbytes, loff_t *off)
{
	struct iovec iov;
	iov.iov_len = nbytes;
	iov.iov_base = buf;
	return fuse_dev_readv(file, &iov, 1, off);
}

static struct fuse_req *request_find(struct fuse_conn *fc, unsigned unique)
{
	struct list_head *entry;

	list_for_each(entry, &fc->processing) {
		struct fuse_req *req;
		req = list_entry(entry, struct fuse_req, list);
		if (req->in.h.unique == unique)
			return req;
	}
	return NULL;
}

/* fget() needs to be done in this context */
static void process_getdir(struct fuse_req *req)
{
	struct fuse_getdir_out_i *arg = req->out.args[0].value;
	arg->file = fget(arg->fd);
}

static int copy_out_args(struct fuse_copy_state *cs, struct fuse_out *out,
			 unsigned nbytes)
{
	unsigned reqsize = sizeof(struct fuse_out_header);

	if (out->h.error)
		return nbytes != reqsize ? -EINVAL : 0;

	reqsize += len_args(out->numargs, out->args);

	if (reqsize < nbytes || (reqsize > nbytes && !out->argvar))
		return -EINVAL;
	else if (reqsize > nbytes) {
		struct fuse_arg *lastarg = &out->args[out->numargs-1];
		unsigned diffsize = reqsize - nbytes;
		if (diffsize > lastarg->size)
			return -EINVAL;
		lastarg->size -= diffsize;
	}
	return fuse_copy_args(cs, out->numargs, out->argpages, out->args,
			      out->page_zeroing);
}

static ssize_t fuse_dev_writev(struct file *file, const struct iovec *iov,
			       unsigned long nr_segs, loff_t *off)
{
	int err;
	unsigned nbytes;
	struct fuse_req *req;
	struct fuse_out_header oh;
	struct fuse_copy_state cs;
	struct fuse_conn *fc = fuse_get_conn(file);
	if (!fc)
		return -ENODEV;

	nbytes = fuse_copy_init(&cs, 0, NULL, iov, nr_segs);
	if (nbytes < sizeof(struct fuse_out_header))
		return -EINVAL;

	err = fuse_copy_one(&cs, &oh, sizeof(oh));
	if (err)
		goto err_finish;
	err = -EINVAL;
	if (!oh.unique || oh.error <= -1000 || oh.error > 0)
		goto err_finish;

	spin_lock(&fuse_lock);
	req = request_find(fc, oh.unique);
	err = -ENOENT;
	if (!req)
		goto err_unlock;

	list_del_init(&req->list);
	req->out.h = oh;
	req->locked = 1;
	cs.req = req;
	spin_unlock(&fuse_lock);

	err = copy_out_args(&cs, &req->out, nbytes);
	fuse_copy_finish(&cs);

	spin_lock(&fuse_lock);
	req->locked = 0;
	if (!err) {
		if (req->interrupted)
			err = -ENOENT;
		else if (req->in.h.opcode == FUSE_GETDIR && !oh.error)
			process_getdir(req);
	} else if (!req->interrupted)
		req->out.h.error = -EIO;
	request_end(fc, req);

	return err ? err : nbytes;

 err_unlock:
	spin_unlock(&fuse_lock);
 err_finish:
	fuse_copy_finish(&cs);
	return err;
}

static ssize_t fuse_dev_write(struct file *file, const char __user *buf,
			      size_t nbytes, loff_t *off)
{
	struct iovec iov;
	iov.iov_len = nbytes;
	iov.iov_base = (char __user *) buf;
	return fuse_dev_writev(file, &iov, 1, off);
}

static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
{
	struct fuse_conn *fc = fuse_get_conn(file);
	unsigned mask = POLLOUT | POLLWRNORM;

	if (!fc)
		return -ENODEV;

	poll_wait(file, &fc->waitq, wait);

	spin_lock(&fuse_lock);
	if (!list_empty(&fc->pending))
                mask |= POLLIN | POLLRDNORM;
	spin_unlock(&fuse_lock);

	return mask;
}

static void end_requests(struct fuse_conn *fc, struct list_head *head)
{
	while (!list_empty(head)) {
		struct fuse_req *req;
		req = list_entry(head->next, struct fuse_req, list);
		list_del_init(&req->list);
		req->out.h.error = -ECONNABORTED;
		request_end(fc, req);
		spin_lock(&fuse_lock);
	}
}

static int fuse_dev_release(struct inode *inode, struct file *file)
{
	struct fuse_conn *fc;

	spin_lock(&fuse_lock);
	fc = file->private_data;
	if (fc) {
		fc->file = NULL;
		end_requests(fc, &fc->pending);
		end_requests(fc, &fc->processing);
		fuse_release_conn(fc);
	}
	spin_unlock(&fuse_lock);
	return 0;
}

struct file_operations fuse_dev_operations = {
	.owner		= THIS_MODULE,
	.read		= fuse_dev_read,
	.readv		= fuse_dev_readv,
	.write		= fuse_dev_write,
	.writev		= fuse_dev_writev,
	.poll		= fuse_dev_poll,
	.release	= fuse_dev_release,
};

#ifdef KERNEL_2_6
#ifndef HAVE_FS_SUBSYS
static decl_subsys(fs, NULL, NULL);
#endif
static decl_subsys(fuse, NULL, NULL);

static ssize_t version_show(struct subsystem *subsys, char *buf)
{
	return sprintf(buf, "%i.%i\n", FUSE_KERNEL_VERSION,
		       FUSE_KERNEL_MINOR_VERSION);
}
static struct subsys_attribute fuse_attr_version = __ATTR_RO(version);

static int __init fuse_version_init(void)
{
	int err;

#ifndef HAVE_FS_SUBSYS
	subsystem_register(&fs_subsys);
#endif
	kset_set_kset_s(&fuse_subsys, fs_subsys);
	err = subsystem_register(&fuse_subsys);
	if (err)
		return err;
	err = subsys_create_file(&fuse_subsys, &fuse_attr_version);
	if (err) {
		subsystem_unregister(&fuse_subsys);
#ifndef HAVE_FS_SUBSYS
		subsystem_unregister(&fs_subsys);
#endif
		return err;
	}
	return 0;
}

static void fuse_version_clean(void)
{
	subsys_remove_file(&fuse_subsys, &fuse_attr_version);
	subsystem_unregister(&fuse_subsys);
#ifndef HAVE_FS_SUBSYS
	subsystem_unregister(&fs_subsys);
#endif
}
#else
static struct proc_dir_entry *proc_fs_fuse;

static int read_version(char *page, char **start, off_t off, int count,
			int *eof, void *data)
{
	char *s = page;
	s += sprintf(s, "%i.%i\n", FUSE_KERNEL_VERSION,
		     FUSE_KERNEL_MINOR_VERSION);
	return s - page;
}

static int fuse_version_init(void)
{
	proc_fs_fuse = proc_mkdir("fuse", proc_root_fs);
	if (proc_fs_fuse) {
		struct proc_dir_entry *de;

		de = create_proc_entry("version", S_IFREG | 0444, proc_fs_fuse);
		if (de) {
			de->owner = THIS_MODULE;
			de->read_proc = read_version;
		}
	}
	return 0;
}

static void fuse_version_clean(void)
{
	if (proc_fs_fuse) {
		remove_proc_entry("version", proc_fs_fuse);
		remove_proc_entry("fuse", proc_root_fs);
	}
}
#endif

static struct miscdevice fuse_miscdevice = {
	.minor = FUSE_MINOR,
	.name  = "fuse",
	.fops = &fuse_dev_operations,
};

int __init fuse_dev_init(void)
{
	int err;
	err = fuse_version_init();
	if (err)
		goto out;

	err = -ENOMEM;
	fuse_req_cachep = kmem_cache_create("fuser_request",
					    sizeof(struct fuse_req),
					    0, 0, NULL, NULL);
	if (!fuse_req_cachep)
		goto out_version_clean;

	err = misc_register(&fuse_miscdevice);
	if (err)
		goto out_cache_clean;

	return 0;

 out_cache_clean:
	kmem_cache_destroy(fuse_req_cachep);
 out_version_clean:
	fuse_version_clean();
 out:
	return err;
}

void fuse_dev_cleanup(void)
{
	misc_deregister(&fuse_miscdevice);
	kmem_cache_destroy(fuse_req_cachep);
	fuse_version_clean();
}