text: /*
    FUSE: Filesystem in Userspace
    Copyright (C) 2001-2008  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>
  #include <linux/pipe_fs_i.h>
  #include <linux/swap.h>
  #include <linux/splice.h>
  
  MODULE_ALIAS_MISCDEV(FUSE_MINOR);
  MODULE_ALIAS("devname:fuse");
  
  static struct kmem_cache *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_LIST_HEAD(&req->intr_entry);
  	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, GFP_KERNEL);
  	if (req)
  		fuse_request_init(req);
  	return req;
  }
  EXPORT_SYMBOL_GPL(fuse_request_alloc);
  
  struct fuse_req *fuse_request_alloc_nofs(void)
  {
  	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_NOFS);
  	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);
  }
  
  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 void fuse_req_init_context(struct fuse_req *req)
  {
  	req->in.h.uid = current_fsuid();
  	req->in.h.gid = current_fsgid();
  	req->in.h.pid = current->pid;
  }
  
  struct fuse_req *fuse_get_req(struct fuse_conn *fc)
  {
  	struct fuse_req *req;
  	sigset_t oldset;
  	int intr;
  	int err;
  
  	atomic_inc(&fc->num_waiting);
  	block_sigs(&oldset);
  	intr = wait_event_interruptible(fc->blocked_waitq, !fc->blocked);
  	restore_sigs(&oldset);
  	err = -EINTR;
  	if (intr)
  		goto out;
  
  	err = -ENOTCONN;
  	if (!fc->connected)
  		goto out;
  
  	req = fuse_request_alloc();
  	err = -ENOMEM;
  	if (!req)
  		goto out;
  
  	fuse_req_init_context(req);
  	req->waiting = 1;
  	return req;
  
   out:
  	atomic_dec(&fc->num_waiting);
  	return ERR_PTR(err);
  }
  EXPORT_SYMBOL_GPL(fuse_get_req);
  
  /*
   * Return request in fuse_file->reserved_req.  However that may
   * currently be in use.  If that is the case, wait for it to become
   * available.
   */
  static struct fuse_req *get_reserved_req(struct fuse_conn *fc,
  					 struct file *file)
  {
  	struct fuse_req *req = NULL;
  	struct fuse_file *ff = file->private_data;
  
  	do {
  		wait_event(fc->reserved_req_waitq, ff->reserved_req);
  		spin_lock(&fc->lock);
  		if (ff->reserved_req) {
  			req = ff->reserved_req;
  			ff->reserved_req = NULL;
  			get_file(file);
  			req->stolen_file = file;
  		}
  		spin_unlock(&fc->lock);
  	} while (!req);
  
  	return req;
  }
  
  /*
   * Put stolen request back into fuse_file->reserved_req
   */
  static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
  {
  	struct file *file = req->stolen_file;
  	struct fuse_file *ff = file->private_data;
  
  	spin_lock(&fc->lock);
  	fuse_request_init(req);
  	BUG_ON(ff->reserved_req);
  	ff->reserved_req = req;
  	wake_up_all(&fc->reserved_req_waitq);
  	spin_unlock(&fc->lock);
  	fput(file);
  }
  
  /*
   * Gets a requests for a file operation, always succeeds
   *
   * This is used for sending the FLUSH request, which must get to
   * userspace, due to POSIX locks which may need to be unlocked.
   *
   * If allocation fails due to OOM, use the reserved request in
   * fuse_file.
   *
   * This is very unlikely to deadlock accidentally, since the
   * filesystem should not have it's own file open.  If deadlock is
   * intentional, it can still be broken by "aborting" the filesystem.
   */
  struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
  {
  	struct fuse_req *req;
  
  	atomic_inc(&fc->num_waiting);
  	wait_event(fc->blocked_waitq, !fc->blocked);
  	req = fuse_request_alloc();
  	if (!req)
  		req = get_reserved_req(fc, file);
  
  	fuse_req_init_context(req);
  	req->waiting = 1;
  	return req;
  }
  
  void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
  {
  	if (atomic_dec_and_test(&req->count)) {
  		if (req->waiting)
  			atomic_dec(&fc->num_waiting);
  
  		if (req->stolen_file)
  			put_reserved_req(fc, req);
  		else
  			fuse_request_free(req);
  	}
  }
  EXPORT_SYMBOL_GPL(fuse_put_request);
  
  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 u64 fuse_get_unique(struct fuse_conn *fc)
  {
  	fc->reqctr++;
  	/* zero is special */
  	if (fc->reqctr == 0)
  		fc->reqctr = 1;
  
  	return fc->reqctr;
  }
  
  static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
  {
  	req->in.h.len = sizeof(struct fuse_in_header) +
  		len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
  	list_add_tail(&req->list, &fc->pending);
  	req->state = FUSE_REQ_PENDING;
  	if (!req->waiting) {
  		req->waiting = 1;
  		atomic_inc(&fc->num_waiting);
  	}
  	wake_up(&fc->waitq);
  	kill_fasync(&fc->fasync, SIGIO, POLL_IN);
  }
  
  static void flush_bg_queue(struct fuse_conn *fc)
  {
  	while (fc->active_background < fc->max_background &&
  	       !list_empty(&fc->bg_queue)) {
  		struct fuse_req *req;
  
  		req = list_entry(fc->bg_queue.next, struct fuse_req, list);
  		list_del(&req->list);
  		fc->active_background++;
  		req->in.h.unique = fuse_get_unique(fc);
  		queue_request(fc, req);
  	}
  }
  
  /*
   * This function is called when a request is finished.  Either a reply
   * has arrived or it was aborted (and not yet sent) or some error
   * occurred during communication with userspace, or the device file
   * was closed.  The requester thread is woken up (if still waiting),
   * the 'end' callback is called if given, else the reference to the
   * request is released
   *
   * Called with fc->lock, unlocks it
   */
  static void request_end(struct fuse_conn *fc, struct fuse_req *req)
  __releases(fc->lock)
  {
  	void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
  	req->end = NULL;
  	list_del(&req->list);
  	list_del(&req->intr_entry);
  	req->state = FUSE_REQ_FINISHED;
  	if (req->background) {
  		if (fc->num_background == fc->max_background) {
  			fc->blocked = 0;
  			wake_up_all(&fc->blocked_waitq);
  		}
  		if (fc->num_background == fc->congestion_threshold &&
  		    fc->connected && fc->bdi_initialized) {
  			clear_bdi_congested(&fc->bdi, BLK_RW_SYNC);
  			clear_bdi_congested(&fc->bdi, BLK_RW_ASYNC);
  		}
  		fc->num_background--;
  		fc->active_background--;
  		flush_bg_queue(fc);
  	}
  	spin_unlock(&fc->lock);
  	wake_up(&req->waitq);
  	if (end)
  		end(fc, req);
  	fuse_put_request(fc, req);
  }
  
  static void wait_answer_interruptible(struct fuse_conn *fc,
  				      struct fuse_req *req)
  __releases(fc->lock)
  __acquires(fc->lock)
  {
  	if (signal_pending(current))
  		return;
  
  	spin_unlock(&fc->lock);
  	wait_event_interruptible(req->waitq, req->state == FUSE_REQ_FINISHED);
  	spin_lock(&fc->lock);
  }
  
  static void queue_interrupt(struct fuse_conn *fc, struct fuse_req *req)
  {
  	list_add_tail(&req->intr_entry, &fc->interrupts);
  	wake_up(&fc->waitq);
  	kill_fasync(&fc->fasync, SIGIO, POLL_IN);
  }
  
  static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
  __releases(fc->lock)
  __acquires(fc->lock)
  {
  	if (!fc->no_interrupt) {
  		/* Any signal may interrupt this */
  		wait_answer_interruptible(fc, req);
  
  		if (req->aborted)
  			goto aborted;
  		if (req->state == FUSE_REQ_FINISHED)
  			return;
  
  		req->interrupted = 1;
  		if (req->state == FUSE_REQ_SENT)
  			queue_interrupt(fc, req);
  	}
  
  	if (!req->force) {
  		sigset_t oldset;
  
  		/* Only fatal signals may interrupt this */
  		block_sigs(&oldset);
  		wait_answer_interruptible(fc, req);
  		restore_sigs(&oldset);
  
  		if (req->aborted)
  			goto aborted;
  		if (req->state == FUSE_REQ_FINISHED)
  			return;
  
  		/* Request is not yet in userspace, bail out */
  		if (req->state == FUSE_REQ_PENDING) {
  			list_del(&req->list);
  			__fuse_put_request(req);
  			req->out.h.error = -EINTR;
  			return;
  		}
  	}
  
  	/*
  	 * Either request is already in userspace, or it was forced.
  	 * Wait it out.
  	 */
  	spin_unlock(&fc->lock);
  	wait_event(req->waitq, req->state == FUSE_REQ_FINISHED);
  	spin_lock(&fc->lock);
  
  	if (!req->aborted)
  		return;
  
   aborted:
  	BUG_ON(req->state != FUSE_REQ_FINISHED);
  	if (req->locked) {
  		/* This is uninterruptible sleep, because data is
  		   being copied to/from the buffers of req.  During
  		   locked state, there mustn't be any filesystem
  		   operation (e.g. page fault), since that could lead
  		   to deadlock */
  		spin_unlock(&fc->lock);
  		wait_event(req->waitq, !req->locked);
  		spin_lock(&fc->lock);
  	}
  }
  
  void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
  {
  	req->isreply = 1;
  	spin_lock(&fc->lock);
  	if (!fc->connected)
  		req->out.h.error = -ENOTCONN;
  	else if (fc->conn_error)
  		req->out.h.error = -ECONNREFUSED;
  	else {
  		req->in.h.unique = fuse_get_unique(fc);
  		queue_request(fc, req);
  		/* acquire extra reference, since request is still needed
  		   after request_end() */
  		__fuse_get_request(req);
  
  		request_wait_answer(fc, req);
  	}
  	spin_unlock(&fc->lock);
  }
  EXPORT_SYMBOL_GPL(fuse_request_send);
  
  static void fuse_request_send_nowait_locked(struct fuse_conn *fc,
  					    struct fuse_req *req)
  {
  	req->background = 1;
  	fc->num_background++;
  	if (fc->num_background == fc->max_background)
  		fc->blocked = 1;
  	if (fc->num_background == fc->congestion_threshold &&
  	    fc->bdi_initialized) {
  		set_bdi_congested(&fc->bdi, BLK_RW_SYNC);
  		set_bdi_congested(&fc->bdi, BLK_RW_ASYNC);
  	}
  	list_add_tail(&req->list, &fc->bg_queue);
  	flush_bg_queue(fc);
  }
  
  static void fuse_request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
  {
  	spin_lock(&fc->lock);
  	if (fc->connected) {
  		fuse_request_send_nowait_locked(fc, req);
  		spin_unlock(&fc->lock);
  	} else {
  		req->out.h.error = -ENOTCONN;
  		request_end(fc, req);
  	}
  }
  
  void fuse_request_send_noreply(struct fuse_conn *fc, struct fuse_req *req)
  {
  	req->isreply = 0;
  	fuse_request_send_nowait(fc, req);
  }
  
  void fuse_request_send_background(struct fuse_conn *fc, struct fuse_req *req)
  {
  	req->isreply = 1;
  	fuse_request_send_nowait(fc, req);
  }
  EXPORT_SYMBOL_GPL(fuse_request_send_background);
  
  static int fuse_request_send_notify_reply(struct fuse_conn *fc,
  					  struct fuse_req *req, u64 unique)
  {
  	int err = -ENODEV;
  
  	req->isreply = 0;
  	req->in.h.unique = unique;
  	spin_lock(&fc->lock);
  	if (fc->connected) {
  		queue_request(fc, req);
  		err = 0;
  	}
  	spin_unlock(&fc->lock);
  
  	return err;
  }
  
  /*
   * Called under fc->lock
   *
   * fc->connected must have been checked previously
   */
  void fuse_request_send_background_locked(struct fuse_conn *fc,
  					 struct fuse_req *req)
  {
  	req->isreply = 1;
  	fuse_request_send_nowait_locked(fc, req);
  }
  
  /*
   * Lock the request.  Up to the next unlock_request() there mustn't be
   * anything that could cause a page-fault.  If the request was already
   * aborted bail out.
   */
  static int lock_request(struct fuse_conn *fc, struct fuse_req *req)
  {
  	int err = 0;
  	if (req) {
  		spin_lock(&fc->lock);
  		if (req->aborted)
  			err = -ENOENT;
  		else
  			req->locked = 1;
  		spin_unlock(&fc->lock);
  	}
  	return err;
  }
  
  /*
   * Unlock request.  If it was aborted during being locked, the
   * requester thread is currently waiting for it to be unlocked, so
   * wake it up.
   */
  static void unlock_request(struct fuse_conn *fc, struct fuse_req *req)
  {
  	if (req) {
  		spin_lock(&fc->lock);
  		req->locked = 0;
  		if (req->aborted)
  			wake_up(&req->waitq);
  		spin_unlock(&fc->lock);
  	}
  }
  
  struct fuse_copy_state {
  	struct fuse_conn *fc;
  	int write;
  	struct fuse_req *req;
  	const struct iovec *iov;
  	struct pipe_buffer *pipebufs;
  	struct pipe_buffer *currbuf;
  	struct pipe_inode_info *pipe;
  	unsigned long nr_segs;
  	unsigned long seglen;
  	unsigned long addr;
  	struct page *pg;
  	void *mapaddr;
  	void *buf;
  	unsigned len;
  	unsigned move_pages:1;
  };
  
  static void fuse_copy_init(struct fuse_copy_state *cs, struct fuse_conn *fc,
  			   int write,
  			   const struct iovec *iov, unsigned long nr_segs)
  {
  	memset(cs, 0, sizeof(*cs));
  	cs->fc = fc;
  	cs->write = write;
  	cs->iov = iov;
  	cs->nr_segs = nr_segs;
  }
  
  /* Unmap and put previous page of userspace buffer */
  static void fuse_copy_finish(struct fuse_copy_state *cs)
  {
  	if (cs->currbuf) {
  		struct pipe_buffer *buf = cs->currbuf;
  
  		if (!cs->write) {
  			buf->ops->unmap(cs->pipe, buf, cs->mapaddr);
  		} else {
  			kunmap(buf->page);
  			buf->len = PAGE_SIZE - cs->len;
  		}
  		cs->currbuf = NULL;
  		cs->mapaddr = NULL;
  	} else if (cs->mapaddr) {
  		kunmap(cs->pg);
  		if (cs->write) {
  			flush_dcache_page(cs->pg);
  			set_page_dirty_lock(cs->pg);
  		}
  		put_page(cs->pg);
  		cs->mapaddr = NULL;
  	}
  }
  
  /*
   * Get another pagefull of userspace buffer, and map it to kernel
   * address space, and lock request
   */
  static int fuse_copy_fill(struct fuse_copy_state *cs)
  {
  	unsigned long offset;
  	int err;
  
  	unlock_request(cs->fc, cs->req);
  	fuse_copy_finish(cs);
  	if (cs->pipebufs) {
  		struct pipe_buffer *buf = cs->pipebufs;
  
  		if (!cs->write) {
  			err = buf->ops->confirm(cs->pipe, buf);
  			if (err)
  				return err;
  
  			BUG_ON(!cs->nr_segs);
  			cs->currbuf = buf;
  			cs->mapaddr = buf->ops->map(cs->pipe, buf, 0);
  			cs->len = buf->len;
  			cs->buf = cs->mapaddr + buf->offset;
  			cs->pipebufs++;
  			cs->nr_segs--;
  		} else {
  			struct page *page;
  
  			if (cs->nr_segs == cs->pipe->buffers)
  				return -EIO;
  
  			page = alloc_page(GFP_HIGHUSER);
  			if (!page)
  				return -ENOMEM;
  
  			buf->page = page;
  			buf->offset = 0;
  			buf->len = 0;
  
  			cs->currbuf = buf;
  			cs->mapaddr = kmap(page);
  			cs->buf = cs->mapaddr;
  			cs->len = PAGE_SIZE;
  			cs->pipebufs++;
  			cs->nr_segs++;
  		}
  	} else {
  		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--;
  		}
  		err = get_user_pages_fast(cs->addr, 1, cs->write, &cs->pg);
  		if (err < 0)
  			return err;
  		BUG_ON(err != 1);
  		offset = cs->addr % PAGE_SIZE;
  		cs->mapaddr = kmap(cs->pg);
  		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->fc, cs->req);
  }
  
  /* Do as much copy to/from userspace buffer as we can */
  static 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 int fuse_check_page(struct page *page)
  {
  	if (page_mapcount(page) ||
  	    page->mapping != NULL ||
  	    page_count(page) != 1 ||
  	    (page->flags & PAGE_FLAGS_CHECK_AT_PREP &
  	     ~(1 << PG_locked |
  	       1 << PG_referenced |
  	       1 << PG_uptodate |
  	       1 << PG_lru |
  	       1 << PG_active |
  	       1 << PG_reclaim))) {
  		printk(KERN_WARNING "fuse: trying to steal weird page\n");
  		printk(KERN_WARNING "  page=%p index=%li flags=%08lx, count=%i, mapcount=%i, mapping=%p\n", page, page->index, page->flags, page_count(page), page_mapcount(page), page->mapping);
  		return 1;
  	}
  	return 0;
  }
  
  static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
  {
  	int err;
  	struct page *oldpage = *pagep;
  	struct page *newpage;
  	struct pipe_buffer *buf = cs->pipebufs;
  	struct address_space *mapping;
  	pgoff_t index;
  
  	unlock_request(cs->fc, cs->req);
  	fuse_copy_finish(cs);
  
  	err = buf->ops->confirm(cs->pipe, buf);
  	if (err)
  		return err;
  
  	BUG_ON(!cs->nr_segs);
  	cs->currbuf = buf;
  	cs->len = buf->len;
  	cs->pipebufs++;
  	cs->nr_segs--;
  
  	if (cs->len != PAGE_SIZE)
  		goto out_fallback;
  
  	if (buf->ops->steal(cs->pipe, buf) != 0)
  		goto out_fallback;
  
  	newpage = buf->page;
  
  	if (WARN_ON(!PageUptodate(newpage)))
  		return -EIO;
  
  	ClearPageMappedToDisk(newpage);
  
  	if (fuse_check_page(newpage) != 0)
  		goto out_fallback_unlock;
  
  	mapping = oldpage->mapping;
  	index = oldpage->index;
  
  	/*
  	 * This is a new and locked page, it shouldn't be mapped or
  	 * have any special flags on it
  	 */
  	if (WARN_ON(page_mapped(oldpage)))
  		goto out_fallback_unlock;
  	if (WARN_ON(page_has_private(oldpage)))
  		goto out_fallback_unlock;
  	if (WARN_ON(PageDirty(oldpage) || PageWriteback(oldpage)))
  		goto out_fallback_unlock;
  	if (WARN_ON(PageMlocked(oldpage)))
  		goto out_fallback_unlock;
  
  	remove_from_page_cache(oldpage);
  	page_cache_release(oldpage);
  
  	err = add_to_page_cache_locked(newpage, mapping, index, GFP_KERNEL);
  	if (err) {
  		printk(KERN_WARNING "fuse_try_move_page: failed to add page");
  		goto out_fallback_unlock;
  	}
  	page_cache_get(newpage);
  
  	if (!(buf->flags & PIPE_BUF_FLAG_LRU))
  		lru_cache_add_file(newpage);
  
  	err = 0;
  	spin_lock(&cs->fc->lock);
  	if (cs->req->aborted)
  		err = -ENOENT;
  	else
  		*pagep = newpage;
  	spin_unlock(&cs->fc->lock);
  
  	if (err) {
  		unlock_page(newpage);
  		page_cache_release(newpage);
  		return err;
  	}
  
  	unlock_page(oldpage);
  	page_cache_release(oldpage);
  	cs->len = 0;
  
  	return 0;
  
  out_fallback_unlock:
  	unlock_page(newpage);
  out_fallback:
  	cs->mapaddr = buf->ops->map(cs->pipe, buf, 1);
  	cs->buf = cs->mapaddr + buf->offset;
  
  	err = lock_request(cs->fc, cs->req);
  	if (err)
  		return err;
  
  	return 1;
  }
  
  static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page,
  			 unsigned offset, unsigned count)
  {
  	struct pipe_buffer *buf;
  
  	if (cs->nr_segs == cs->pipe->buffers)
  		return -EIO;
  
  	unlock_request(cs->fc, cs->req);
  	fuse_copy_finish(cs);
  
  	buf = cs->pipebufs;
  	page_cache_get(page);
  	buf->page = page;
  	buf->offset = offset;
  	buf->len = count;
  
  	cs->pipebufs++;
  	cs->nr_segs++;
  	cs->len = 0;
  
  	return 0;
  }
  
  /*
   * Copy a page in the request to/from the userspace buffer.  Must be
   * done atomically
   */
  static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
  			  unsigned offset, unsigned count, int zeroing)
  {
  	int err;
  	struct page *page = *pagep;
  
  	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) {
  		if (cs->write && cs->pipebufs && page) {
  			return fuse_ref_page(cs, page, offset, count);
  		} else if (!cs->len) {
  			if (cs->move_pages && page &&
  			    offset == 0 && count == PAGE_SIZE) {
  				err = fuse_try_move_page(cs, pagep);
  				if (err <= 0)
  					return err;
  			} else {
  				err = fuse_copy_fill(cs);
  				if (err)
  					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;
  }
  
  /* Copy pages in the request to/from userspace buffer */
  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 || zeroing); i++) {
  		int err;
  
  		err = fuse_copy_page(cs, &req->pages[i], offset, count,
  				     zeroing);
  		if (err)
  			return err;
  
  		nbytes -= count;
  		count = min(nbytes, (unsigned) PAGE_SIZE);
  		offset = 0;
  	}
  	return 0;
  }
  
  /* Copy a single argument in the request to/from userspace buffer */
  static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size)
  {
  	while (size) {
  		if (!cs->len) {
  			int err = fuse_copy_fill(cs);
  			if (err)
  				return err;
  		}
  		fuse_copy_do(cs, &val, &size);
  	}
  	return 0;
  }
  
  /* Copy request arguments to/from userspace buffer */
  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 int request_pending(struct fuse_conn *fc)
  {
  	return !list_empty(&fc->pending) || !list_empty(&fc->interrupts);
  }
  
  /* Wait until a request is available on the pending list */
  static void request_wait(struct fuse_conn *fc)
  __releases(fc->lock)
  __acquires(fc->lock)
  {
  	DECLARE_WAITQUEUE(wait, current);
  
  	add_wait_queue_exclusive(&fc->waitq, &wait);
  	while (fc->connected && !request_pending(fc)) {
  		set_current_state(TASK_INTERRUPTIBLE);
  		if (signal_pending(current))
  			break;
  
  		spin_unlock(&fc->lock);
  		schedule();
  		spin_lock(&fc->lock);
  	}
  	set_current_state(TASK_RUNNING);
  	remove_wait_queue(&fc->waitq, &wait);
  }
  
  /*
   * Transfer an interrupt request to userspace
   *
   * Unlike other requests this is assembled on demand, without a need
   * to allocate a separate fuse_req structure.
   *
   * Called with fc->lock held, releases it
   */
  static int fuse_read_interrupt(struct fuse_conn *fc, struct fuse_copy_state *cs,
  			       size_t nbytes, struct fuse_req *req)
  __releases(fc->lock)
  {
  	struct fuse_in_header ih;
  	struct fuse_interrupt_in arg;
  	unsigned reqsize = sizeof(ih) + sizeof(arg);
  	int err;
  
  	list_del_init(&req->intr_entry);
  	req->intr_unique = fuse_get_unique(fc);
  	memset(&ih, 0, sizeof(ih));
  	memset(&arg, 0, sizeof(arg));
  	ih.len = reqsize;
  	ih.opcode = FUSE_INTERRUPT;
  	ih.unique = req->intr_unique;
  	arg.unique = req->in.h.unique;
  
  	spin_unlock(&fc->lock);
  	if (nbytes < reqsize)
  		return -EINVAL;
  
  	err = fuse_copy_one(cs, &ih, sizeof(ih));
  	if (!err)
  		err = fuse_copy_one(cs, &arg, sizeof(arg));
  	fuse_copy_finish(cs);
  
  	return err ? err : reqsize;
  }
  
  /*
   * Read a single request into the userspace filesystem's buffer.  This
   * function waits until a request is available, then removes it from
   * the pending list and copies request data to userspace buffer.  If
   * no reply is needed (FORGET) or request has been aborted or there
   * was an error during the copying then it's finished by calling
   * request_end().  Otherwise add it to the processing list, and set
   * the 'sent' flag.
   */
  static ssize_t fuse_dev_do_read(struct fuse_conn *fc, struct file *file,
  				struct fuse_copy_state *cs, size_t nbytes)
  {
  	int err;
  	struct fuse_req *req;
  	struct fuse_in *in;
  	unsigned reqsize;
  
   restart:
  	spin_lock(&fc->lock);
  	err = -EAGAIN;
  	if ((file->f_flags & O_NONBLOCK) && fc->connected &&
  	    !request_pending(fc))
  		goto err_unlock;
  
  	request_wait(fc);
  	err = -ENODEV;
  	if (!fc->connected)
  		goto err_unlock;
  	err = -ERESTARTSYS;
  	if (!request_pending(fc))
  		goto err_unlock;
  
  	if (!list_empty(&fc->interrupts)) {
  		req = list_entry(fc->interrupts.next, struct fuse_req,
  				 intr_entry);
  		return fuse_read_interrupt(fc, cs, nbytes, req);
  	}
  
  	req = list_entry(fc->pending.next, struct fuse_req, list);
  	req->state = FUSE_REQ_READING;
  	list_move(&req->list, &fc->io);
  
  	in = &req->in;
  	reqsize = in->h.len;
  	/* If request is too large, reply with an error and restart the read */
  	if (nbytes < reqsize) {
  		req->out.h.error = -EIO;
  		/* SETXATTR is special, since it may contain too large data */
  		if (in->h.opcode == FUSE_SETXATTR)
  			req->out.h.error = -E2BIG;
  		request_end(fc, req);
  		goto restart;
  	}
  	spin_unlock(&fc->lock);
  	cs->req = req;
  	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(&fc->lock);
  	req->locked = 0;
  	if (req->aborted) {
  		request_end(fc, req);
  		return -ENODEV;
  	}
  	if (err) {
  		req->out.h.error = -EIO;
  		request_end(fc, req);
  		return err;
  	}
  	if (!req->isreply)
  		request_end(fc, req);
  	else {
  		req->state = FUSE_REQ_SENT;
  		list_move_tail(&req->list, &fc->processing);
  		if (req->interrupted)
  			queue_interrupt(fc, req);
  		spin_unlock(&fc->lock);
  	}
  	return reqsize;
  
   err_unlock:
  	spin_unlock(&fc->lock);
  	return err;
  }
  
  static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
  			      unsigned long nr_segs, loff_t pos)
  {
  	struct fuse_copy_state cs;
  	struct file *file = iocb->ki_filp;
  	struct fuse_conn *fc = fuse_get_conn(file);
  	if (!fc)
  		return -EPERM;
  
  	fuse_copy_init(&cs, fc, 1, iov, nr_segs);
  
  	return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
  }
  
  static int fuse_dev_pipe_buf_steal(struct pipe_inode_info *pipe,
  				   struct pipe_buffer *buf)
  {
  	return 1;
  }
  
  static const struct pipe_buf_operations fuse_dev_pipe_buf_ops = {
  	.can_merge = 0,
  	.map = generic_pipe_buf_map,
  	.unmap = generic_pipe_buf_unmap,
  	.confirm = generic_pipe_buf_confirm,
  	.release = generic_pipe_buf_release,
  	.steal = fuse_dev_pipe_buf_steal,
  	.get = generic_pipe_buf_get,
  };
  
  static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
  				    struct pipe_inode_info *pipe,
  				    size_t len, unsigned int flags)
  {
  	int ret;
  	int page_nr = 0;
  	int do_wakeup = 0;
  	struct pipe_buffer *bufs;
  	struct fuse_copy_state cs;
  	struct fuse_conn *fc = fuse_get_conn(in);
  	if (!fc)
  		return -EPERM;
  
  	bufs = kmalloc(pipe->buffers * sizeof (struct pipe_buffer), GFP_KERNEL);
  	if (!bufs)
  		return -ENOMEM;
  
  	fuse_copy_init(&cs, fc, 1, NULL, 0);
  	cs.pipebufs = bufs;
  	cs.pipe = pipe;
  	ret = fuse_dev_do_read(fc, in, &cs, len);
  	if (ret < 0)
  		goto out;
  
  	ret = 0;
  	pipe_lock(pipe);
  
  	if (!pipe->readers) {
  		send_sig(SIGPIPE, current, 0);
  		if (!ret)
  			ret = -EPIPE;
  		goto out_unlock;
  	}
  
  	if (pipe->nrbufs + cs.nr_segs > pipe->buffers) {
  		ret = -EIO;
  		goto out_unlock;
  	}
  
  	while (page_nr < cs.nr_segs) {
  		int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
  		struct pipe_buffer *buf = pipe->bufs + newbuf;
  
  		buf->page = bufs[page_nr].page;
  		buf->offset = bufs[page_nr].offset;
  		buf->len = bufs[page_nr].len;
  		buf->ops = &fuse_dev_pipe_buf_ops;
  
  		pipe->nrbufs++;
  		page_nr++;
  		ret += buf->len;
  
  		if (pipe->inode)
  			do_wakeup = 1;
  	}
  
  out_unlock:
  	pipe_unlock(pipe);
  
  	if (do_wakeup) {
  		smp_mb();
  		if (waitqueue_active(&pipe->wait))
  			wake_up_interruptible(&pipe->wait);
  		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
  	}
  
  out:
  	for (; page_nr < cs.nr_segs; page_nr++)
  		page_cache_release(bufs[page_nr].page);
  
  	kfree(bufs);
  	return ret;
  }
  
  static int fuse_notify_poll(struct fuse_conn *fc, unsigned int size,
  			    struct fuse_copy_state *cs)
  {
  	struct fuse_notify_poll_wakeup_out outarg;
  	int err = -EINVAL;
  
  	if (size != sizeof(outarg))
  		goto err;
  
  	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
  	if (err)
  		goto err;
  
  	fuse_copy_finish(cs);
  	return fuse_notify_poll_wakeup(fc, &outarg);
  
  err:
  	fuse_copy_finish(cs);
  	return err;
  }
  
  static int fuse_notify_inval_inode(struct fuse_conn *fc, unsigned int size,
  				   struct fuse_copy_state *cs)
  {
  	struct fuse_notify_inval_inode_out outarg;
  	int err = -EINVAL;
  
  	if (size != sizeof(outarg))
  		goto err;
  
  	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
  	if (err)
  		goto err;
  	fuse_copy_finish(cs);
  
  	down_read(&fc->killsb);
  	err = -ENOENT;
  	if (fc->sb) {
  		err = fuse_reverse_inval_inode(fc->sb, outarg.ino,
  					       outarg.off, outarg.len);
  	}
  	up_read(&fc->killsb);
  	return err;
  
  err:
  	fuse_copy_finish(cs);
  	return err;
  }
  
  static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size,
  				   struct fuse_copy_state *cs)
  {
  	struct fuse_notify_inval_entry_out outarg;
  	int err = -ENOMEM;
  	char *buf;
  	struct qstr name;
  
  	buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
  	if (!buf)
  		goto err;
  
  	err = -EINVAL;
  	if (size < sizeof(outarg))
  		goto err;
  
  	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
  	if (err)
  		goto err;
  
  	err = -ENAMETOOLONG;
  	if (outarg.namelen > FUSE_NAME_MAX)
  		goto err;
  
  	name.name = buf;
  	name.len = outarg.namelen;
  	err = fuse_copy_one(cs, buf, outarg.namelen + 1);
  	if (err)
  		goto err;
  	fuse_copy_finish(cs);
  	buf[outarg.namelen] = 0;
  	name.hash = full_name_hash(name.name, name.len);
  
  	down_read(&fc->killsb);
  	err = -ENOENT;
  	if (fc->sb)
  		err = fuse_reverse_inval_entry(fc->sb, outarg.parent, &name);
  	up_read(&fc->killsb);
  	kfree(buf);
  	return err;
  
  err:
  	kfree(buf);
  	fuse_copy_finish(cs);
  	return err;
  }
  
  static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
  			     struct fuse_copy_state *cs)
  {
  	struct fuse_notify_store_out outarg;
  	struct inode *inode;
  	struct address_space *mapping;
  	u64 nodeid;
  	int err;
  	pgoff_t index;
  	unsigned int offset;
  	unsigned int num;
  	loff_t file_size;
  	loff_t end;
  
  	err = -EINVAL;
  	if (size < sizeof(outarg))
  		goto out_finish;
  
  	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
  	if (err)
  		goto out_finish;
  
  	err = -EINVAL;
  	if (size - sizeof(outarg) != outarg.size)
  		goto out_finish;
  
  	nodeid = outarg.nodeid;
  
  	down_read(&fc->killsb);
  
  	err = -ENOENT;
  	if (!fc->sb)
  		goto out_up_killsb;
  
  	inode = ilookup5(fc->sb, nodeid, fuse_inode_eq, &nodeid);
  	if (!inode)
  		goto out_up_killsb;
  
  	mapping = inode->i_mapping;
  	index = outarg.offset >> PAGE_CACHE_SHIFT;
  	offset = outarg.offset & ~PAGE_CACHE_MASK;
  	file_size = i_size_read(inode);
  	end = outarg.offset + outarg.size;
  	if (end > file_size) {
  		file_size = end;
  		fuse_write_update_size(inode, file_size);
  	}
  
  	num = outarg.size;
  	while (num) {
  		struct page *page;
  		unsigned int this_num;
  
  		err = -ENOMEM;
  		page = find_or_create_page(mapping, index,
  					   mapping_gfp_mask(mapping));
  		if (!page)
  			goto out_iput;
  
  		this_num = min_t(unsigned, num, PAGE_CACHE_SIZE - offset);
  		err = fuse_copy_page(cs, &page, offset, this_num, 0);
  		if (!err && offset == 0 && (num != 0 || file_size == end))
  			SetPageUptodate(page);
  		unlock_page(page);
  		page_cache_release(page);
  
  		if (err)
  			goto out_iput;
  
  		num -= this_num;
  		offset = 0;
  		index++;
  	}
  
  	err = 0;
  
  out_iput:
  	iput(inode);
  out_up_killsb:
  	up_read(&fc->killsb);
  out_finish:
  	fuse_copy_finish(cs);
  	return err;
  }
  
  static void fuse_retrieve_end(struct fuse_conn *fc, struct fuse_req *req)
  {
  	int i;
  
  	for (i = 0; i < req->num_pages; i++) {
  		struct page *page = req->pages[i];
  		page_cache_release(page);
  	}
  }
  
  static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
  			 struct fuse_notify_retrieve_out *outarg)
  {
  	int err;
  	struct address_space *mapping = inode->i_mapping;
  	struct fuse_req *req;
  	pgoff_t index;
  	loff_t file_size;
  	unsigned int num;
  	unsigned int offset;
  	size_t total_len = 0;
  
  	req = fuse_get_req(fc);
  	if (IS_ERR(req))
  		return PTR_ERR(req);
  
  	offset = outarg->offset & ~PAGE_CACHE_MASK;
  
  	req->in.h.opcode = FUSE_NOTIFY_REPLY;
  	req->in.h.nodeid = outarg->nodeid;
  	req->in.numargs = 2;
  	req->in.argpages = 1;
  	req->page_offset = offset;
  	req->end = fuse_retrieve_end;
  
  	index = outarg->offset >> PAGE_CACHE_SHIFT;
  	file_size = i_size_read(inode);
  	num = outarg->size;
  	if (outarg->offset > file_size)
  		num = 0;
  	else if (outarg->offset + num > file_size)
  		num = file_size - outarg->offset;
  
  	while (num) {
  		struct page *page;
  		unsigned int this_num;
  
  		page = find_get_page(mapping, index);
  		if (!page)
  			break;
  
  		this_num = min_t(unsigned, num, PAGE_CACHE_SIZE - offset);
  		req->pages[req->num_pages] = page;
  		req->num_pages++;
  
  		num -= this_num;
  		total_len += this_num;
  	}
  	req->misc.retrieve_in.offset = outarg->offset;
  	req->misc.retrieve_in.size = total_len;
  	req->in.args[0].size = sizeof(req->misc.retrieve_in);
  	req->in.args[0].value = &req->misc.retrieve_in;
  	req->in.args[1].size = total_len;
  
  	err = fuse_request_send_notify_reply(fc, req, outarg->notify_unique);
  	if (err)
  		fuse_retrieve_end(fc, req);
  
  	return err;
  }
  
  static int fuse_notify_retrieve(struct fuse_conn *fc, unsigned int size,
  				struct fuse_copy_state *cs)
  {
  	struct fuse_notify_retrieve_out outarg;
  	struct inode *inode;
  	int err;
  
  	err = -EINVAL;
  	if (size != sizeof(outarg))
  		goto copy_finish;
  
  	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
  	if (err)
  		goto copy_finish;
  
  	fuse_copy_finish(cs);
  
  	down_read(&fc->killsb);
  	err = -ENOENT;
  	if (fc->sb) {
  		u64 nodeid = outarg.nodeid;
  
  		inode = ilookup5(fc->sb, nodeid, fuse_inode_eq, &nodeid);
  		if (inode) {
  			err = fuse_retrieve(fc, inode, &outarg);
  			iput(inode);
  		}
  	}
  	up_read(&fc->killsb);
  
  	return err;
  
  copy_finish:
  	fuse_copy_finish(cs);
  	return err;
  }
  
  static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
  		       unsigned int size, struct fuse_copy_state *cs)
  {
  	switch (code) {
  	case FUSE_NOTIFY_POLL:
  		return fuse_notify_poll(fc, size, cs);
  
  	case FUSE_NOTIFY_INVAL_INODE:
  		return fuse_notify_inval_inode(fc, size, cs);
  
  	case FUSE_NOTIFY_INVAL_ENTRY:
  		return fuse_notify_inval_entry(fc, size, cs);
  
  	case FUSE_NOTIFY_STORE:
  		return fuse_notify_store(fc, size, cs);
  
  	case FUSE_NOTIFY_RETRIEVE:
  		return fuse_notify_retrieve(fc, size, cs);
  
  	default:
  		fuse_copy_finish(cs);
  		return -EINVAL;
  	}
  }
  
  /* Look up request on processing list by unique ID */
  static struct fuse_req *request_find(struct fuse_conn *fc, u64 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 || req->intr_unique == unique)
  			return req;
  	}
  	return NULL;
  }
  
  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);
  }
  
  /*
   * Write a single reply to a request.  First the header is copied from
   * the write buffer.  The request is then searched on the processing
   * list by the unique ID found in the header.  If found, then remove
   * it from the list and copy the rest of the buffer to the request.
   * The request is finished by calling request_end()
   */
  static ssize_t fuse_dev_do_write(struct fuse_conn *fc,
  				 struct fuse_copy_state *cs, size_t nbytes)
  {
  	int err;
  	struct fuse_req *req;
  	struct fuse_out_header oh;
  
  	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.len != nbytes)
  		goto err_finish;
  
  	/*
  	 * Zero oh.unique indicates unsolicited notification message
  	 * and error contains notification code.
  	 */
  	if (!oh.unique) {
  		err = fuse_notify(fc, oh.error, nbytes - sizeof(oh), cs);
  		return err ? err : nbytes;
  	}
  
  	err = -EINVAL;
  	if (oh.error <= -1000 || oh.error > 0)
  		goto err_finish;
  
  	spin_lock(&fc->lock);
  	err = -ENOENT;
  	if (!fc->connected)
  		goto err_unlock;
  
  	req = request_find(fc, oh.unique);
  	if (!req)
  		goto err_unlock;
  
  	if (req->aborted) {
  		spin_unlock(&fc->lock);
  		fuse_copy_finish(cs);
  		spin_lock(&fc->lock);
  		request_end(fc, req);
  		return -ENOENT;
  	}
  	/* Is it an interrupt reply? */
  	if (req->intr_unique == oh.unique) {
  		err = -EINVAL;
  		if (nbytes != sizeof(struct fuse_out_header))
  			goto err_unlock;
  
  		if (oh.error == -ENOSYS)
  			fc->no_interrupt = 1;
  		else if (oh.error == -EAGAIN)
  			queue_interrupt(fc, req);
  
  		spin_unlock(&fc->lock);
  		fuse_copy_finish(cs);
  		return nbytes;
  	}
  
  	req->state = FUSE_REQ_WRITING;
  	list_move(&req->list, &fc->io);
  	req->out.h = oh;
  	req->locked = 1;
  	cs->req = req;
  	if (!req->out.page_replace)
  		cs->move_pages = 0;
  	spin_unlock(&fc->lock);
  
  	err = copy_out_args(cs, &req->out, nbytes);
  	fuse_copy_finish(cs);
  
  	spin_lock(&fc->lock);
  	req->locked = 0;
  	if (!err) {
  		if (req->aborted)
  			err = -ENOENT;
  	} else if (!req->aborted)
  		req->out.h.error = -EIO;
  	request_end(fc, req);
  
  	return err ? err : nbytes;
  
   err_unlock:
  	spin_unlock(&fc->lock);
   err_finish:
  	fuse_copy_finish(cs);
  	return err;
  }
  
  static ssize_t fuse_dev_write(struct kiocb *iocb, const struct iovec *iov,
  			      unsigned long nr_segs, loff_t pos)
  {
  	struct fuse_copy_state cs;
  	struct fuse_conn *fc = fuse_get_conn(iocb->ki_filp);
  	if (!fc)
  		return -EPERM;
  
  	fuse_copy_init(&cs, fc, 0, iov, nr_segs);
  
  	return fuse_dev_do_write(fc, &cs, iov_length(iov, nr_segs));
  }
  
  static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
  				     struct file *out, loff_t *ppos,
  				     size_t len, unsigned int flags)
  {
  	unsigned nbuf;
  	unsigned idx;
  	struct pipe_buffer *bufs;
  	struct fuse_copy_state cs;
  	struct fuse_conn *fc;
  	size_t rem;
  	ssize_t ret;
  
  	fc = fuse_get_conn(out);
  	if (!fc)
  		return -EPERM;
  
  	bufs = kmalloc(pipe->buffers * sizeof (struct pipe_buffer), GFP_KERNEL);
  	if (!bufs)
  		return -ENOMEM;
  
  	pipe_lock(pipe);
  	nbuf = 0;
  	rem = 0;
  	for (idx = 0; idx < pipe->nrbufs && rem < len; idx++)
  		rem += pipe->bufs[(pipe->curbuf + idx) & (pipe->buffers - 1)].len;
  
  	ret = -EINVAL;
  	if (rem < len) {
  		pipe_unlock(pipe);
  		goto out;
  	}
  
  	rem = len;
  	while (rem) {
  		struct pipe_buffer *ibuf;
  		struct pipe_buffer *obuf;
  
  		BUG_ON(nbuf >= pipe->buffers);
  		BUG_ON(!pipe->nrbufs);
  		ibuf = &pipe->bufs[pipe->curbuf];
  		obuf = &bufs[nbuf];
  
  		if (rem >= ibuf->len) {
  			*obuf = *ibuf;
  			ibuf->ops = NULL;
  			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
  			pipe->nrbufs--;
  		} else {
  			ibuf->ops->get(pipe, ibuf);
  			*obuf = *ibuf;
  			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
  			obuf->len = rem;
  			ibuf->offset += obuf->len;
  			ibuf->len -= obuf->len;
  		}
  		nbuf++;
  		rem -= obuf->len;
  	}
  	pipe_unlock(pipe);
  
  	fuse_copy_init(&cs, fc, 0, NULL, nbuf);
  	cs.pipebufs = bufs;
  	cs.pipe = pipe;
  
  	if (flags & SPLICE_F_MOVE)
  		cs.move_pages = 1;
  
  	ret = fuse_dev_do_write(fc, &cs, len);
  
  	for (idx = 0; idx < nbuf; idx++) {
  		struct pipe_buffer *buf = &bufs[idx];
  		buf->ops->release(pipe, buf);
  	}
  out:
  	kfree(bufs);
  	return ret;
  }
  
  static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
  {
  	unsigned mask = POLLOUT | POLLWRNORM;
  	struct fuse_conn *fc = fuse_get_conn(file);
  	if (!fc)
  		return POLLERR;
  
  	poll_wait(file, &fc->waitq, wait);
  
  	spin_lock(&fc->lock);
  	if (!fc->connected)
  		mask = POLLERR;
  	else if (request_pending(fc))
  		mask |= POLLIN | POLLRDNORM;
  	spin_unlock(&fc->lock);
  
  	return mask;
  }
  
  /*
   * Abort all requests on the given list (pending or processing)
   *
   * This function releases and reacquires fc->lock
   */
  static void end_requests(struct fuse_conn *fc, struct list_head *head)
  __releases(fc->lock)
  __acquires(fc->lock)
  {
  	while (!list_empty(head)) {
  		struct fuse_req *req;
  		req = list_entry(head->next, struct fuse_req, list);
  		req->out.h.error = -ECONNABORTED;
  		request_end(fc, req);
  		spin_lock(&fc->lock);
  	}
  }
  
  /*
   * Abort requests under I/O
   *
   * The requests are set to aborted and finished, and the request
   * waiter is woken up.  This will make request_wait_answer() wait
   * until the request is unlocked and then return.
   *
   * If the request is asynchronous, then the end function needs to be
   * called after waiting for the request to be unlocked (if it was
   * locked).
   */
  static void end_io_requests(struct fuse_conn *fc)
  __releases(fc->lock)
  __acquires(fc->lock)
  {
  	while (!list_empty(&fc->io)) {
  		struct fuse_req *req =
  			list_entry(fc->io.next, struct fuse_req, list);
  		void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
  
  		req->aborted = 1;
  		req->out.h.error = -ECONNABORTED;
  		req->state = FUSE_REQ_FINISHED;
  		list_del_init(&req->list);
  		wake_up(&req->waitq);
  		if (end) {
  			req->end = NULL;
  			__fuse_get_request(req);
  			spin_unlock(&fc->lock);
  			wait_event(req->waitq, !req->locked);
  			end(fc, req);
  			fuse_put_request(fc, req);
  			spin_lock(&fc->lock);
  		}
  	}
  }
  
  static void end_queued_requests(struct fuse_conn *fc)
  __releases(fc->lock)
  __acquires(fc->lock)
  {
  	fc->max_background = UINT_MAX;
  	flush_bg_queue(fc);
  	end_requests(fc, &fc->pending);
  	end_requests(fc, &fc->processing);
  }
  
  /*
   * Abort all requests.
   *
   * Emergency exit in case of a malicious or accidental deadlock, or
   * just a hung filesystem.
   *
   * The same effect is usually achievable through killing the
   * filesystem daemon and all users of the filesystem.  The exception
   * is the combination of an asynchronous request and the tricky
   * deadlock (see Documentation/filesystems/fuse.txt).
   *
   * During the aborting, progression of requests from the pending and
   * processing lists onto the io list, and progression of new requests
   * onto the pending list is prevented by req->connected being false.
   *
   * Progression of requests under I/O to the processing list is
   * prevented by the req->aborted flag being true for these requests.
   * For this reason requests on the io list must be aborted first.
   */
  void fuse_abort_conn(struct fuse_conn *fc)
  {
  	spin_lock(&fc->lock);
  	if (fc->connected) {
  		fc->connected = 0;
  		fc->blocked = 0;
  		end_io_requests(fc);
  		end_queued_requests(fc);
  		wake_up_all(&fc->waitq);
  		wake_up_all(&fc->blocked_waitq);
  		kill_fasync(&fc->fasync, SIGIO, POLL_IN);
  	}
  	spin_unlock(&fc->lock);
  }
  EXPORT_SYMBOL_GPL(fuse_abort_conn);
  
  int fuse_dev_release(struct inode *inode, struct file *file)
  {
  	struct fuse_conn *fc = fuse_get_conn(file);
  	if (fc) {
  		spin_lock(&fc->lock);
  		fc->connected = 0;
  		fc->blocked = 0;
  		end_queued_requests(fc);
  		wake_up_all(&fc->blocked_waitq);
  		spin_unlock(&fc->lock);
  		fuse_conn_put(fc);
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(fuse_dev_release);
  
  static int fuse_dev_fasync(int fd, struct file *file, int on)
  {
  	struct fuse_conn *fc = fuse_get_conn(file);
  	if (!fc)
  		return -EPERM;
  
  	/* No locking - fasync_helper does its own locking */
  	return fasync_helper(fd, file, on, &fc->fasync);
  }
  
  const struct file_operations fuse_dev_operations = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.read		= do_sync_read,
  	.aio_read	= fuse_dev_read,
  	.splice_read	= fuse_dev_splice_read,
  	.write		= do_sync_write,
  	.aio_write	= fuse_dev_write,
  	.splice_write	= fuse_dev_splice_write,
  	.poll		= fuse_dev_poll,
  	.release	= fuse_dev_release,
  	.fasync		= fuse_dev_fasync,
  };
  EXPORT_SYMBOL_GPL(fuse_dev_operations);
  
  static struct miscdevice fuse_miscdevice = {
  	.minor = FUSE_MINOR,
  	.name  = "fuse",
  	.fops = &fuse_dev_operations,
  };
  
  int __init fuse_dev_init(void)
  {
  	int err = -ENOMEM;
  	fuse_req_cachep = kmem_cache_create("fuse_request",
  					    sizeof(struct fuse_req),
  					    0, 0, NULL);
  	if (!fuse_req_cachep)
  		goto out;
  
  	err = misc_register(&fuse_miscdevice);
  	if (err)
  		goto out_cache_clean;
  
  	return 0;
  
   out_cache_clean:
  	kmem_cache_destroy(fuse_req_cachep);
   out:
  	return err;
  }
  
  void fuse_dev_cleanup(void)
  {
  	misc_deregister(&fuse_miscdevice);
  	kmem_cache_destroy(fuse_req_cachep);
  }
  