/*
   *  linux/fs/read_write.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */
  
  #include <linux/slab.h> 
  #include <linux/stat.h>
  #include <linux/fcntl.h>
  #include <linux/file.h>
  #include <linux/uio.h>

  #include <linux/aio.h>

  #include <linux/fsnotify.h>

  #include <linux/security.h>

  #include <linux/export.h>

  #include <linux/syscalls.h>

  #include <linux/pagemap.h>

  #include <linux/splice.h>

  #include <linux/compat.h>

  #include "internal.h"

  
  #include <asm/uaccess.h>
  #include <asm/unistd.h>

  typedef ssize_t (*io_fn_t)(struct file *, char __user *, size_t, loff_t *);
  typedef ssize_t (*iov_fn_t)(struct kiocb *, const struct iovec *,
  		unsigned long, loff_t);

  typedef ssize_t (*iter_fn_t)(struct kiocb *, struct iov_iter *);

  const struct file_operations generic_ro_fops = {

  	.llseek		= generic_file_llseek,

  	.read		= new_sync_read,
  	.read_iter	= generic_file_read_iter,

  	.mmap		= generic_file_readonly_mmap,

  	.splice_read	= generic_file_splice_read,

  };
  
  EXPORT_SYMBOL(generic_ro_fops);

  static inline int unsigned_offsets(struct file *file)

  {

  	return file->f_mode & FMODE_UNSIGNED_OFFSET;

  }

  /**
   * vfs_setpos - update the file offset for lseek
   * @file:	file structure in question
   * @offset:	file offset to seek to
   * @maxsize:	maximum file size
   *
   * This is a low-level filesystem helper for updating the file offset to
   * the value specified by @offset if the given offset is valid and it is
   * not equal to the current file offset.
   *
   * Return the specified offset on success and -EINVAL on invalid offset.
   */
  loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize)

  {
  	if (offset < 0 && !unsigned_offsets(file))
  		return -EINVAL;
  	if (offset > maxsize)
  		return -EINVAL;
  
  	if (offset != file->f_pos) {
  		file->f_pos = offset;
  		file->f_version = 0;
  	}
  	return offset;
  }

  EXPORT_SYMBOL(vfs_setpos);

  /**

   * generic_file_llseek_size - generic llseek implementation for regular files

   * @file:	file structure to seek on
   * @offset:	file offset to seek to

   * @whence:	type of seek

   * @size:	max size of this file in file system
   * @eof:	offset used for SEEK_END position

   *

   * This is a variant of generic_file_llseek that allows passing in a custom

   * maximum file size and a custom EOF position, for e.g. hashed directories

   *
   * Synchronization:

   * SEEK_SET and SEEK_END are unsynchronized (but atomic on 64bit platforms)

   * SEEK_CUR is synchronized against other SEEK_CURs, but not read/writes.
   * read/writes behave like SEEK_SET against seeks.

   */

  loff_t

  generic_file_llseek_size(struct file *file, loff_t offset, int whence,

  		loff_t maxsize, loff_t eof)

  {

  	switch (whence) {

  	case SEEK_END:

  		offset += eof;

  		break;
  	case SEEK_CUR:

  		/*
  		 * Here we special-case the lseek(fd, 0, SEEK_CUR)
  		 * position-querying operation.  Avoid rewriting the "same"
  		 * f_pos value back to the file because a concurrent read(),
  		 * write() or lseek() might have altered it
  		 */
  		if (offset == 0)
  			return file->f_pos;

  		/*
  		 * f_lock protects against read/modify/write race with other
  		 * SEEK_CURs. Note that parallel writes and reads behave
  		 * like SEEK_SET.
  		 */
  		spin_lock(&file->f_lock);

  		offset = vfs_setpos(file, file->f_pos + offset, maxsize);

  		spin_unlock(&file->f_lock);
  		return offset;

  	case SEEK_DATA:
  		/*
  		 * In the generic case the entire file is data, so as long as
  		 * offset isn't at the end of the file then the offset is data.
  		 */

  		if (offset >= eof)

  			return -ENXIO;
  		break;
  	case SEEK_HOLE:
  		/*
  		 * There is a virtual hole at the end of the file, so as long as
  		 * offset isn't i_size or larger, return i_size.
  		 */

  		if (offset >= eof)

  			return -ENXIO;

  		offset = eof;

  		break;

  	}

  	return vfs_setpos(file, offset, maxsize);

  }
  EXPORT_SYMBOL(generic_file_llseek_size);
  
  /**
   * generic_file_llseek - generic llseek implementation for regular files
   * @file:	file structure to seek on
   * @offset:	file offset to seek to

   * @whence:	type of seek

   *
   * This is a generic implemenation of ->llseek useable for all normal local
   * filesystems.  It just updates the file offset to the value specified by

   * @offset and @whence.

   */

  loff_t generic_file_llseek(struct file *file, loff_t offset, int whence)

  {
  	struct inode *inode = file->f_mapping->host;

  	return generic_file_llseek_size(file, offset, whence,

  					inode->i_sb->s_maxbytes,
  					i_size_read(inode));

  }

  EXPORT_SYMBOL(generic_file_llseek);

  /**

   * fixed_size_llseek - llseek implementation for fixed-sized devices
   * @file:	file structure to seek on
   * @offset:	file offset to seek to
   * @whence:	type of seek
   * @size:	size of the file
   *
   */
  loff_t fixed_size_llseek(struct file *file, loff_t offset, int whence, loff_t size)
  {
  	switch (whence) {
  	case SEEK_SET: case SEEK_CUR: case SEEK_END:
  		return generic_file_llseek_size(file, offset, whence,
  						size, size);
  	default:
  		return -EINVAL;
  	}
  }
  EXPORT_SYMBOL(fixed_size_llseek);
  
  /**

   * noop_llseek - No Operation Performed llseek implementation
   * @file:	file structure to seek on
   * @offset:	file offset to seek to

   * @whence:	type of seek

   *
   * This is an implementation of ->llseek useable for the rare special case when
   * userspace expects the seek to succeed but the (device) file is actually not
   * able to perform the seek. In this case you use noop_llseek() instead of
   * falling back to the default implementation of ->llseek.
   */

  loff_t noop_llseek(struct file *file, loff_t offset, int whence)

  {
  	return file->f_pos;
  }
  EXPORT_SYMBOL(noop_llseek);

  loff_t no_llseek(struct file *file, loff_t offset, int whence)

  {
  	return -ESPIPE;
  }
  EXPORT_SYMBOL(no_llseek);

  loff_t default_llseek(struct file *file, loff_t offset, int whence)

  {

  	struct inode *inode = file_inode(file);

  	loff_t retval;

  	mutex_lock(&inode->i_mutex);

  	switch (whence) {

  		case SEEK_END:

  			offset += i_size_read(inode);

  			break;

  		case SEEK_CUR:

  			if (offset == 0) {
  				retval = file->f_pos;
  				goto out;
  			}

  			offset += file->f_pos;

  			break;
  		case SEEK_DATA:
  			/*
  			 * In the generic case the entire file is data, so as
  			 * long as offset isn't at the end of the file then the
  			 * offset is data.
  			 */

  			if (offset >= inode->i_size) {
  				retval = -ENXIO;
  				goto out;
  			}

  			break;
  		case SEEK_HOLE:
  			/*
  			 * There is a virtual hole at the end of the file, so
  			 * as long as offset isn't i_size or larger, return
  			 * i_size.
  			 */

  			if (offset >= inode->i_size) {
  				retval = -ENXIO;
  				goto out;
  			}

  			offset = inode->i_size;
  			break;

  	}
  	retval = -EINVAL;

  	if (offset >= 0 || unsigned_offsets(file)) {

  		if (offset != file->f_pos) {
  			file->f_pos = offset;
  			file->f_version = 0;
  		}
  		retval = offset;
  	}

  out:

  	mutex_unlock(&inode->i_mutex);

  	return retval;
  }
  EXPORT_SYMBOL(default_llseek);

  loff_t vfs_llseek(struct file *file, loff_t offset, int whence)

  {
  	loff_t (*fn)(struct file *, loff_t, int);
  
  	fn = no_llseek;
  	if (file->f_mode & FMODE_LSEEK) {

  		if (file->f_op->llseek)

  			fn = file->f_op->llseek;
  	}

  	return fn(file, offset, whence);

  }
  EXPORT_SYMBOL(vfs_llseek);

  static inline struct fd fdget_pos(int fd)
  {

  	return __to_fd(__fdget_pos(fd));

  }
  
  static inline void fdput_pos(struct fd f)
  {
  	if (f.flags & FDPUT_POS_UNLOCK)
  		mutex_unlock(&f.file->f_pos_lock);
  	fdput(f);
  }

  SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence)

  {
  	off_t retval;

  	struct fd f = fdget_pos(fd);

  	if (!f.file)
  		return -EBADF;

  
  	retval = -EINVAL;

  	if (whence <= SEEK_MAX) {
  		loff_t res = vfs_llseek(f.file, offset, whence);

  		retval = res;
  		if (res != (loff_t)retval)
  			retval = -EOVERFLOW;	/* LFS: should only happen on 32 bit platforms */
  	}

  	fdput_pos(f);

  	return retval;
  }

  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE3(lseek, unsigned int, fd, compat_off_t, offset, unsigned int, whence)
  {
  	return sys_lseek(fd, offset, whence);
  }
  #endif

  #ifdef __ARCH_WANT_SYS_LLSEEK

  SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned long, offset_high,
  		unsigned long, offset_low, loff_t __user *, result,

  		unsigned int, whence)

  {
  	int retval;

  	struct fd f = fdget_pos(fd);

  	loff_t offset;

  	if (!f.file)
  		return -EBADF;

  
  	retval = -EINVAL;

  	if (whence > SEEK_MAX)

  		goto out_putf;

  	offset = vfs_llseek(f.file, ((loff_t) offset_high << 32) | offset_low,

  			whence);

  
  	retval = (int)offset;
  	if (offset >= 0) {
  		retval = -EFAULT;
  		if (!copy_to_user(result, &offset, sizeof(offset)))
  			retval = 0;
  	}
  out_putf:

  	fdput_pos(f);

  	return retval;
  }
  #endif

  /*
   * rw_verify_area doesn't like huge counts. We limit
   * them to something that fits in "int" so that others
   * won't have to do range checks all the time.
   */

  int rw_verify_area(int read_write, struct file *file, const loff_t *ppos, size_t count)

  {
  	struct inode *inode;
  	loff_t pos;

  	int retval = -EINVAL;

  	inode = file_inode(file);

  	if (unlikely((ssize_t) count < 0))

  		return retval;

  	pos = *ppos;

  	if (unlikely(pos < 0)) {
  		if (!unsigned_offsets(file))
  			return retval;
  		if (count >= -pos) /* both values are in 0..LLONG_MAX */
  			return -EOVERFLOW;
  	} else if (unlikely((loff_t) (pos + count) < 0)) {
  		if (!unsigned_offsets(file))

  			return retval;
  	}

  	if (unlikely(inode->i_flock && mandatory_lock(inode))) {

  		retval = locks_mandatory_area(

  			read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE,
  			inode, file, pos, count);
  		if (retval < 0)
  			return retval;
  	}

  	retval = security_file_permission(file,
  				read_write == READ ? MAY_READ : MAY_WRITE);
  	if (retval)
  		return retval;

  	return count > MAX_RW_COUNT ? MAX_RW_COUNT : count;

  }
  
  ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
  {

  	struct iovec iov = { .iov_base = buf, .iov_len = len };

  	struct kiocb kiocb;
  	ssize_t ret;
  
  	init_sync_kiocb(&kiocb, filp);
  	kiocb.ki_pos = *ppos;

  	kiocb.ki_nbytes = len;

  	ret = filp->f_op->aio_read(&kiocb, &iov, 1, kiocb.ki_pos);

  	if (-EIOCBQUEUED == ret)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  
  EXPORT_SYMBOL(do_sync_read);

  ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
  {
  	struct iovec iov = { .iov_base = buf, .iov_len = len };
  	struct kiocb kiocb;
  	struct iov_iter iter;
  	ssize_t ret;
  
  	init_sync_kiocb(&kiocb, filp);
  	kiocb.ki_pos = *ppos;
  	kiocb.ki_nbytes = len;
  	iov_iter_init(&iter, READ, &iov, 1, len);
  
  	ret = filp->f_op->read_iter(&kiocb, &iter);
  	if (-EIOCBQUEUED == ret)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  
  EXPORT_SYMBOL(new_sync_read);

  ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
  {
  	ssize_t ret;
  
  	if (!(file->f_mode & FMODE_READ))
  		return -EBADF;

  	if (!(file->f_mode & FMODE_CAN_READ))

  		return -EINVAL;
  	if (unlikely(!access_ok(VERIFY_WRITE, buf, count)))
  		return -EFAULT;
  
  	ret = rw_verify_area(READ, file, pos, count);

  	if (ret >= 0) {
  		count = ret;

  		if (file->f_op->read)
  			ret = file->f_op->read(file, buf, count, pos);

  		else if (file->f_op->aio_read)

  			ret = do_sync_read(file, buf, count, pos);

  		else
  			ret = new_sync_read(file, buf, count, pos);

  		if (ret > 0) {

  			fsnotify_access(file);

  			add_rchar(current, ret);

  		}

  		inc_syscr(current);

  	}
  
  	return ret;
  }
  
  EXPORT_SYMBOL(vfs_read);
  
  ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
  {

  	struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = len };

  	struct kiocb kiocb;
  	ssize_t ret;
  
  	init_sync_kiocb(&kiocb, filp);
  	kiocb.ki_pos = *ppos;

  	kiocb.ki_nbytes = len;

  	ret = filp->f_op->aio_write(&kiocb, &iov, 1, kiocb.ki_pos);

  	if (-EIOCBQUEUED == ret)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  
  EXPORT_SYMBOL(do_sync_write);

  ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
  {
  	struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = len };
  	struct kiocb kiocb;
  	struct iov_iter iter;
  	ssize_t ret;
  
  	init_sync_kiocb(&kiocb, filp);
  	kiocb.ki_pos = *ppos;
  	kiocb.ki_nbytes = len;
  	iov_iter_init(&iter, WRITE, &iov, 1, len);
  
  	ret = filp->f_op->write_iter(&kiocb, &iter);
  	if (-EIOCBQUEUED == ret)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  
  EXPORT_SYMBOL(new_sync_write);

  ssize_t __kernel_write(struct file *file, const char *buf, size_t count, loff_t *pos)
  {
  	mm_segment_t old_fs;
  	const char __user *p;
  	ssize_t ret;

  	if (!(file->f_mode & FMODE_CAN_WRITE))

  		return -EINVAL;

  	old_fs = get_fs();
  	set_fs(get_ds());
  	p = (__force const char __user *)buf;
  	if (count > MAX_RW_COUNT)
  		count =  MAX_RW_COUNT;
  	if (file->f_op->write)
  		ret = file->f_op->write(file, p, count, pos);

  	else if (file->f_op->aio_write)

  		ret = do_sync_write(file, p, count, pos);

  	else
  		ret = new_sync_write(file, p, count, pos);

  	set_fs(old_fs);
  	if (ret > 0) {
  		fsnotify_modify(file);
  		add_wchar(current, ret);
  	}
  	inc_syscw(current);
  	return ret;
  }

  EXPORT_SYMBOL(__kernel_write);

  ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
  {
  	ssize_t ret;
  
  	if (!(file->f_mode & FMODE_WRITE))
  		return -EBADF;

  	if (!(file->f_mode & FMODE_CAN_WRITE))

  		return -EINVAL;
  	if (unlikely(!access_ok(VERIFY_READ, buf, count)))
  		return -EFAULT;
  
  	ret = rw_verify_area(WRITE, file, pos, count);

  	if (ret >= 0) {
  		count = ret;

  		file_start_write(file);

  		if (file->f_op->write)
  			ret = file->f_op->write(file, buf, count, pos);

  		else if (file->f_op->aio_write)

  			ret = do_sync_write(file, buf, count, pos);

  		else
  			ret = new_sync_write(file, buf, count, pos);

  		if (ret > 0) {

  			fsnotify_modify(file);

  			add_wchar(current, ret);

  		}

  		inc_syscw(current);

  		file_end_write(file);

  	}
  
  	return ret;
  }
  
  EXPORT_SYMBOL(vfs_write);
  
  static inline loff_t file_pos_read(struct file *file)
  {
  	return file->f_pos;
  }
  
  static inline void file_pos_write(struct file *file, loff_t pos)
  {
  	file->f_pos = pos;
  }

  SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count)

  {

  	struct fd f = fdget_pos(fd);

  	ssize_t ret = -EBADF;

  	if (f.file) {
  		loff_t pos = file_pos_read(f.file);
  		ret = vfs_read(f.file, buf, count, &pos);

  		if (ret >= 0)
  			file_pos_write(f.file, pos);

  		fdput_pos(f);

  	}

  	return ret;
  }

  SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
  		size_t, count)

  {

  	struct fd f = fdget_pos(fd);

  	ssize_t ret = -EBADF;

  	if (f.file) {
  		loff_t pos = file_pos_read(f.file);
  		ret = vfs_write(f.file, buf, count, &pos);

  		if (ret >= 0)
  			file_pos_write(f.file, pos);

  		fdput_pos(f);

  	}
  
  	return ret;
  }

  SYSCALL_DEFINE4(pread64, unsigned int, fd, char __user *, buf,
  			size_t, count, loff_t, pos)

  {

  	struct fd f;

  	ssize_t ret = -EBADF;

  
  	if (pos < 0)
  		return -EINVAL;

  	f = fdget(fd);
  	if (f.file) {

  		ret = -ESPIPE;

  		if (f.file->f_mode & FMODE_PREAD)
  			ret = vfs_read(f.file, buf, count, &pos);
  		fdput(f);

  	}
  
  	return ret;
  }

  SYSCALL_DEFINE4(pwrite64, unsigned int, fd, const char __user *, buf,
  			 size_t, count, loff_t, pos)

  {

  	struct fd f;

  	ssize_t ret = -EBADF;

  
  	if (pos < 0)
  		return -EINVAL;

  	f = fdget(fd);
  	if (f.file) {

  		ret = -ESPIPE;

  		if (f.file->f_mode & FMODE_PWRITE)  
  			ret = vfs_write(f.file, buf, count, &pos);
  		fdput(f);

  	}
  
  	return ret;
  }
  
  /*
   * Reduce an iovec's length in-place.  Return the resulting number of segments
   */
  unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to)
  {
  	unsigned long seg = 0;
  	size_t len = 0;
  
  	while (seg < nr_segs) {
  		seg++;
  		if (len + iov->iov_len >= to) {
  			iov->iov_len = to - len;
  			break;
  		}
  		len += iov->iov_len;
  		iov++;
  	}
  	return seg;
  }

  EXPORT_SYMBOL(iov_shorten);

  static ssize_t do_iter_readv_writev(struct file *filp, int rw, const struct iovec *iov,
  		unsigned long nr_segs, size_t len, loff_t *ppos, iter_fn_t fn)
  {
  	struct kiocb kiocb;
  	struct iov_iter iter;
  	ssize_t ret;
  
  	init_sync_kiocb(&kiocb, filp);
  	kiocb.ki_pos = *ppos;
  	kiocb.ki_nbytes = len;
  
  	iov_iter_init(&iter, rw, iov, nr_segs, len);
  	ret = fn(&kiocb, &iter);
  	if (ret == -EIOCBQUEUED)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }

  static ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,

  		unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn)
  {
  	struct kiocb kiocb;
  	ssize_t ret;
  
  	init_sync_kiocb(&kiocb, filp);
  	kiocb.ki_pos = *ppos;

  	kiocb.ki_nbytes = len;

  	ret = fn(&kiocb, iov, nr_segs, kiocb.ki_pos);

  	if (ret == -EIOCBQUEUED)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  
  /* Do it by hand, with file-ops */

  static ssize_t do_loop_readv_writev(struct file *filp, struct iovec *iov,

  		unsigned long nr_segs, loff_t *ppos, io_fn_t fn)
  {
  	struct iovec *vector = iov;
  	ssize_t ret = 0;
  
  	while (nr_segs > 0) {
  		void __user *base;
  		size_t len;
  		ssize_t nr;
  
  		base = vector->iov_base;
  		len = vector->iov_len;
  		vector++;
  		nr_segs--;
  
  		nr = fn(filp, base, len, ppos);
  
  		if (nr < 0) {
  			if (!ret)
  				ret = nr;
  			break;
  		}
  		ret += nr;
  		if (nr != len)
  			break;
  	}
  
  	return ret;
  }

  /* A write operation does a read from user space and vice versa */
  #define vrfy_dir(type) ((type) == READ ? VERIFY_WRITE : VERIFY_READ)

  ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
  			      unsigned long nr_segs, unsigned long fast_segs,
  			      struct iovec *fast_pointer,

  			      struct iovec **ret_pointer)

  {

  	unsigned long seg;

  	ssize_t ret;

  	struct iovec *iov = fast_pointer;

  	/*
  	 * SuS says "The readv() function *may* fail if the iovcnt argument
  	 * was less than or equal to 0, or greater than {IOV_MAX}.  Linux has
  	 * traditionally returned zero for zero segments, so...
  	 */

  	if (nr_segs == 0) {
  		ret = 0;

  		goto out;

  	}

  	/*
  	 * First get the "struct iovec" from user memory and
  	 * verify all the pointers
  	 */

  	if (nr_segs > UIO_MAXIOV) {
  		ret = -EINVAL;

  		goto out;

  	}
  	if (nr_segs > fast_segs) {

  		iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);

  		if (iov == NULL) {
  			ret = -ENOMEM;

  			goto out;

  		}

  	}

  	if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) {
  		ret = -EFAULT;

  		goto out;

  	}

  	/*

  	 * According to the Single Unix Specification we should return EINVAL
  	 * if an element length is < 0 when cast to ssize_t or if the
  	 * total length would overflow the ssize_t return value of the
  	 * system call.

  	 *
  	 * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
  	 * overflow case.
  	 */

  	ret = 0;

  	for (seg = 0; seg < nr_segs; seg++) {
  		void __user *buf = iov[seg].iov_base;
  		ssize_t len = (ssize_t)iov[seg].iov_len;

  
  		/* see if we we're about to use an invalid len or if
  		 * it's about to overflow ssize_t */

  		if (len < 0) {

  			ret = -EINVAL;

  			goto out;

  		}

  		if (type >= 0

  		    && unlikely(!access_ok(vrfy_dir(type), buf, len))) {

  			ret = -EFAULT;

  			goto out;
  		}
  		if (len > MAX_RW_COUNT - ret) {
  			len = MAX_RW_COUNT - ret;
  			iov[seg].iov_len = len;

  		}

  		ret += len;

  	}

  out:
  	*ret_pointer = iov;
  	return ret;
  }

  static ssize_t do_readv_writev(int type, struct file *file,
  			       const struct iovec __user * uvector,
  			       unsigned long nr_segs, loff_t *pos)
  {

  	size_t tot_len;
  	struct iovec iovstack[UIO_FASTIOV];

  	struct iovec *iov = iovstack;

  	ssize_t ret;

  	io_fn_t fn;
  	iov_fn_t fnv;

  	iter_fn_t iter_fn;

  	ret = rw_copy_check_uvector(type, uvector, nr_segs,

  				    ARRAY_SIZE(iovstack), iovstack, &iov);

  	if (ret <= 0)

  		goto out;

  	tot_len = ret;

  	ret = rw_verify_area(type, file, pos, tot_len);

  	if (ret < 0)

  		goto out;
  
  	fnv = NULL;
  	if (type == READ) {
  		fn = file->f_op->read;

  		fnv = file->f_op->aio_read;

  		iter_fn = file->f_op->read_iter;

  	} else {
  		fn = (io_fn_t)file->f_op->write;

  		fnv = file->f_op->aio_write;

  		iter_fn = file->f_op->write_iter;

  		file_start_write(file);

  	}

  	if (iter_fn)
  		ret = do_iter_readv_writev(file, type, iov, nr_segs, tot_len,
  						pos, iter_fn);
  	else if (fnv)

  		ret = do_sync_readv_writev(file, iov, nr_segs, tot_len,
  						pos, fnv);
  	else
  		ret = do_loop_readv_writev(file, iov, nr_segs, pos, fn);

  	if (type != READ)
  		file_end_write(file);

  out:
  	if (iov != iovstack)
  		kfree(iov);

  	if ((ret + (type == READ)) > 0) {
  		if (type == READ)

  			fsnotify_access(file);

  		else

  			fsnotify_modify(file);

  	}

  	return ret;

  }
  
  ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
  		  unsigned long vlen, loff_t *pos)
  {
  	if (!(file->f_mode & FMODE_READ))
  		return -EBADF;

  	if (!(file->f_mode & FMODE_CAN_READ))

  		return -EINVAL;
  
  	return do_readv_writev(READ, file, vec, vlen, pos);
  }
  
  EXPORT_SYMBOL(vfs_readv);
  
  ssize_t vfs_writev(struct file *file, const struct iovec __user *vec,
  		   unsigned long vlen, loff_t *pos)
  {
  	if (!(file->f_mode & FMODE_WRITE))
  		return -EBADF;

  	if (!(file->f_mode & FMODE_CAN_WRITE))

  		return -EINVAL;
  
  	return do_readv_writev(WRITE, file, vec, vlen, pos);
  }
  
  EXPORT_SYMBOL(vfs_writev);

  SYSCALL_DEFINE3(readv, unsigned long, fd, const struct iovec __user *, vec,
  		unsigned long, vlen)

  {

  	struct fd f = fdget_pos(fd);

  	ssize_t ret = -EBADF;

  	if (f.file) {
  		loff_t pos = file_pos_read(f.file);
  		ret = vfs_readv(f.file, vec, vlen, &pos);

  		if (ret >= 0)
  			file_pos_write(f.file, pos);

  		fdput_pos(f);

  	}
  
  	if (ret > 0)

  		add_rchar(current, ret);
  	inc_syscr(current);

  	return ret;
  }

  SYSCALL_DEFINE3(writev, unsigned long, fd, const struct iovec __user *, vec,
  		unsigned long, vlen)

  {

  	struct fd f = fdget_pos(fd);

  	ssize_t ret = -EBADF;

  	if (f.file) {
  		loff_t pos = file_pos_read(f.file);
  		ret = vfs_writev(f.file, vec, vlen, &pos);

  		if (ret >= 0)
  			file_pos_write(f.file, pos);

  		fdput_pos(f);

  	}
  
  	if (ret > 0)

  		add_wchar(current, ret);
  	inc_syscw(current);

  	return ret;
  }

  static inline loff_t pos_from_hilo(unsigned long high, unsigned long low)
  {
  #define HALF_LONG_BITS (BITS_PER_LONG / 2)
  	return (((loff_t)high << HALF_LONG_BITS) << HALF_LONG_BITS) | low;
  }

  SYSCALL_DEFINE5(preadv, unsigned long, fd, const struct iovec __user *, vec,

  		unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h)

  {

  	loff_t pos = pos_from_hilo(pos_h, pos_l);

  	struct fd f;

  	ssize_t ret = -EBADF;

  
  	if (pos < 0)
  		return -EINVAL;

  	f = fdget(fd);
  	if (f.file) {

  		ret = -ESPIPE;

  		if (f.file->f_mode & FMODE_PREAD)
  			ret = vfs_readv(f.file, vec, vlen, &pos);
  		fdput(f);

  	}
  
  	if (ret > 0)
  		add_rchar(current, ret);
  	inc_syscr(current);
  	return ret;
  }
  
  SYSCALL_DEFINE5(pwritev, unsigned long, fd, const struct iovec __user *, vec,

  		unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h)

  {

  	loff_t pos = pos_from_hilo(pos_h, pos_l);

  	struct fd f;

  	ssize_t ret = -EBADF;

  
  	if (pos < 0)
  		return -EINVAL;

  	f = fdget(fd);
  	if (f.file) {

  		ret = -ESPIPE;

  		if (f.file->f_mode & FMODE_PWRITE)
  			ret = vfs_writev(f.file, vec, vlen, &pos);
  		fdput(f);

  	}
  
  	if (ret > 0)
  		add_wchar(current, ret);
  	inc_syscw(current);
  	return ret;
  }

  #ifdef CONFIG_COMPAT
  
  static ssize_t compat_do_readv_writev(int type, struct file *file,
  			       const struct compat_iovec __user *uvector,
  			       unsigned long nr_segs, loff_t *pos)
  {
  	compat_ssize_t tot_len;
  	struct iovec iovstack[UIO_FASTIOV];
  	struct iovec *iov = iovstack;
  	ssize_t ret;
  	io_fn_t fn;
  	iov_fn_t fnv;

  	iter_fn_t iter_fn;

  	ret = compat_rw_copy_check_uvector(type, uvector, nr_segs,
  					       UIO_FASTIOV, iovstack, &iov);
  	if (ret <= 0)
  		goto out;
  
  	tot_len = ret;
  	ret = rw_verify_area(type, file, pos, tot_len);
  	if (ret < 0)
  		goto out;
  
  	fnv = NULL;
  	if (type == READ) {
  		fn = file->f_op->read;
  		fnv = file->f_op->aio_read;

  		iter_fn = file->f_op->read_iter;

  	} else {
  		fn = (io_fn_t)file->f_op->write;
  		fnv = file->f_op->aio_write;

  		iter_fn = file->f_op->write_iter;

  		file_start_write(file);

  	}

  	if (iter_fn)
  		ret = do_iter_readv_writev(file, type, iov, nr_segs, tot_len,
  						pos, iter_fn);
  	else if (fnv)

  		ret = do_sync_readv_writev(file, iov, nr_segs, tot_len,
  						pos, fnv);

  	else

  		ret = do_loop_readv_writev(file, iov, nr_segs, pos, fn);

  	if (type != READ)
  		file_end_write(file);

  out:
  	if (iov != iovstack)
  		kfree(iov);
  	if ((ret + (type == READ)) > 0) {
  		if (type == READ)
  			fsnotify_access(file);
  		else
  			fsnotify_modify(file);
  	}
  	return ret;
  }
  
  static size_t compat_readv(struct file *file,
  			   const struct compat_iovec __user *vec,
  			   unsigned long vlen, loff_t *pos)
  {
  	ssize_t ret = -EBADF;
  
  	if (!(file->f_mode & FMODE_READ))
  		goto out;
  
  	ret = -EINVAL;

  	if (!(file->f_mode & FMODE_CAN_READ))

  		goto out;
  
  	ret = compat_do_readv_writev(READ, file, vec, vlen, pos);
  
  out:
  	if (ret > 0)
  		add_rchar(current, ret);
  	inc_syscr(current);
  	return ret;
  }

  COMPAT_SYSCALL_DEFINE3(readv, compat_ulong_t, fd,

  		const struct compat_iovec __user *,vec,

  		compat_ulong_t, vlen)

  {

  	struct fd f = fdget_pos(fd);

  	ssize_t ret;
  	loff_t pos;
  
  	if (!f.file)
  		return -EBADF;
  	pos = f.file->f_pos;
  	ret = compat_readv(f.file, vec, vlen, &pos);

  	if (ret >= 0)
  		f.file->f_pos = pos;

  	fdput_pos(f);

  	return ret;
  }

  static long __compat_sys_preadv64(unsigned long fd,
  				  const struct compat_iovec __user *vec,
  				  unsigned long vlen, loff_t pos)

  {
  	struct fd f;
  	ssize_t ret;
  
  	if (pos < 0)
  		return -EINVAL;
  	f = fdget(fd);
  	if (!f.file)
  		return -EBADF;
  	ret = -ESPIPE;
  	if (f.file->f_mode & FMODE_PREAD)
  		ret = compat_readv(f.file, vec, vlen, &pos);
  	fdput(f);
  	return ret;
  }

  #ifdef __ARCH_WANT_COMPAT_SYS_PREADV64
  COMPAT_SYSCALL_DEFINE4(preadv64, unsigned long, fd,
  		const struct compat_iovec __user *,vec,
  		unsigned long, vlen, loff_t, pos)
  {
  	return __compat_sys_preadv64(fd, vec, vlen, pos);
  }
  #endif

  COMPAT_SYSCALL_DEFINE5(preadv, compat_ulong_t, fd,

  		const struct compat_iovec __user *,vec,

  		compat_ulong_t, vlen, u32, pos_low, u32, pos_high)

  {
  	loff_t pos = ((loff_t)pos_high << 32) | pos_low;

  
  	return __compat_sys_preadv64(fd, vec, vlen, pos);

  }
  
  static size_t compat_writev(struct file *file,
  			    const struct compat_iovec __user *vec,
  			    unsigned long vlen, loff_t *pos)
  {
  	ssize_t ret = -EBADF;
  
  	if (!(file->f_mode & FMODE_WRITE))
  		goto out;
  
  	ret = -EINVAL;

  	if (!(file->f_mode & FMODE_CAN_WRITE))

  		goto out;
  
  	ret = compat_do_readv_writev(WRITE, file, vec, vlen, pos);
  
  out:
  	if (ret > 0)
  		add_wchar(current, ret);
  	inc_syscw(current);
  	return ret;
  }

  COMPAT_SYSCALL_DEFINE3(writev, compat_ulong_t, fd,

  		const struct compat_iovec __user *, vec,

  		compat_ulong_t, vlen)

  {

  	struct fd f = fdget_pos(fd);

  	ssize_t ret;
  	loff_t pos;
  
  	if (!f.file)
  		return -EBADF;
  	pos = f.file->f_pos;
  	ret = compat_writev(f.file, vec, vlen, &pos);

  	if (ret >= 0)
  		f.file->f_pos = pos;

  	fdput_pos(f);

  	return ret;
  }

  static long __compat_sys_pwritev64(unsigned long fd,
  				   const struct compat_iovec __user *vec,
  				   unsigned long vlen, loff_t pos)

  {
  	struct fd f;
  	ssize_t ret;
  
  	if (pos < 0)
  		return -EINVAL;
  	f = fdget(fd);
  	if (!f.file)
  		return -EBADF;
  	ret = -ESPIPE;
  	if (f.file->f_mode & FMODE_PWRITE)
  		ret = compat_writev(f.file, vec, vlen, &pos);
  	fdput(f);
  	return ret;
  }

  #ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64
  COMPAT_SYSCALL_DEFINE4(pwritev64, unsigned long, fd,
  		const struct compat_iovec __user *,vec,
  		unsigned long, vlen, loff_t, pos)
  {
  	return __compat_sys_pwritev64(fd, vec, vlen, pos);
  }
  #endif

  COMPAT_SYSCALL_DEFINE5(pwritev, compat_ulong_t, fd,

  		const struct compat_iovec __user *,vec,

  		compat_ulong_t, vlen, u32, pos_low, u32, pos_high)

  {
  	loff_t pos = ((loff_t)pos_high << 32) | pos_low;

  
  	return __compat_sys_pwritev64(fd, vec, vlen, pos);

  }
  #endif

  static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
  		  	   size_t count, loff_t max)

  {

  	struct fd in, out;
  	struct inode *in_inode, *out_inode;

  	loff_t pos;

  	loff_t out_pos;

  	ssize_t retval;

  	int fl;

  
  	/*
  	 * Get input file, and verify that it is ok..
  	 */
  	retval = -EBADF;

  	in = fdget(in_fd);
  	if (!in.file)

  		goto out;

  	if (!(in.file->f_mode & FMODE_READ))

  		goto fput_in;

  	retval = -ESPIPE;

  	if (!ppos) {
  		pos = in.file->f_pos;
  	} else {
  		pos = *ppos;

  		if (!(in.file->f_mode & FMODE_PREAD))

  			goto fput_in;

  	}
  	retval = rw_verify_area(READ, in.file, &pos, count);

  	if (retval < 0)

  		goto fput_in;

  	count = retval;

  	/*
  	 * Get output file, and verify that it is ok..
  	 */
  	retval = -EBADF;

  	out = fdget(out_fd);
  	if (!out.file)

  		goto fput_in;

  	if (!(out.file->f_mode & FMODE_WRITE))

  		goto fput_out;
  	retval = -EINVAL;

  	in_inode = file_inode(in.file);
  	out_inode = file_inode(out.file);

  	out_pos = out.file->f_pos;
  	retval = rw_verify_area(WRITE, out.file, &out_pos, count);

  	if (retval < 0)

  		goto fput_out;

  	count = retval;

  	if (!max)
  		max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);

  	if (unlikely(pos + count > max)) {
  		retval = -EOVERFLOW;
  		if (pos >= max)
  			goto fput_out;
  		count = max - pos;
  	}

  	fl = 0;

  #if 0

  	/*
  	 * We need to debate whether we can enable this or not. The
  	 * man page documents EAGAIN return for the output at least,
  	 * and the application is arguably buggy if it doesn't expect
  	 * EAGAIN on a non-blocking file descriptor.
  	 */

  	if (in.file->f_flags & O_NONBLOCK)

  		fl = SPLICE_F_NONBLOCK;

  #endif

  	file_start_write(out.file);

  	retval = do_splice_direct(in.file, &pos, out.file, &out_pos, count, fl);

  	file_end_write(out.file);

  
  	if (retval > 0) {

  		add_rchar(current, retval);
  		add_wchar(current, retval);

  		fsnotify_access(in.file);
  		fsnotify_modify(out.file);

  		out.file->f_pos = out_pos;
  		if (ppos)
  			*ppos = pos;
  		else
  			in.file->f_pos = pos;

  	}

  	inc_syscr(current);
  	inc_syscw(current);

  	if (pos > max)

  		retval = -EOVERFLOW;
  
  fput_out:

  	fdput(out);

  fput_in:

  	fdput(in);

  out:
  	return retval;
  }

  SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd, off_t __user *, offset, size_t, count)

  {
  	loff_t pos;
  	off_t off;
  	ssize_t ret;
  
  	if (offset) {
  		if (unlikely(get_user(off, offset)))
  			return -EFAULT;
  		pos = off;
  		ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
  		if (unlikely(put_user(pos, offset)))
  			return -EFAULT;
  		return ret;
  	}
  
  	return do_sendfile(out_fd, in_fd, NULL, count, 0);
  }

  SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd, loff_t __user *, offset, size_t, count)

  {
  	loff_t pos;
  	ssize_t ret;
  
  	if (offset) {
  		if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
  			return -EFAULT;
  		ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
  		if (unlikely(put_user(pos, offset)))
  			return -EFAULT;
  		return ret;
  	}
  
  	return do_sendfile(out_fd, in_fd, NULL, count, 0);
  }

  
  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd,
  		compat_off_t __user *, offset, compat_size_t, count)
  {
  	loff_t pos;
  	off_t off;
  	ssize_t ret;
  
  	if (offset) {
  		if (unlikely(get_user(off, offset)))
  			return -EFAULT;
  		pos = off;
  		ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
  		if (unlikely(put_user(pos, offset)))
  			return -EFAULT;
  		return ret;
  	}
  
  	return do_sendfile(out_fd, in_fd, NULL, count, 0);
  }
  
  COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
  		compat_loff_t __user *, offset, compat_size_t, count)
  {
  	loff_t pos;
  	ssize_t ret;
  
  	if (offset) {
  		if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
  			return -EFAULT;
  		ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
  		if (unlikely(put_user(pos, offset)))
  			return -EFAULT;
  		return ret;
  	}
  
  	return do_sendfile(out_fd, in_fd, NULL, count, 0);
  }
  #endif