/*
   *  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/smp_lock.h>

  #include <linux/fsnotify.h>

  #include <linux/security.h>
  #include <linux/module.h>
  #include <linux/syscalls.h>

  #include <linux/pagemap.h>

  #include <linux/splice.h>

  #include "read_write.h"

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

  const struct file_operations generic_ro_fops = {

  	.llseek		= generic_file_llseek,

  	.read		= do_sync_read,
  	.aio_read	= generic_file_aio_read,

  	.mmap		= generic_file_readonly_mmap,

  	.splice_read	= generic_file_splice_read,

  };
  
  EXPORT_SYMBOL(generic_ro_fops);

  loff_t
  generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)

  {

  	loff_t retval;

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

  	switch (origin) {

  		case SEEK_END:

  			offset += inode->i_size;
  			break;

  		case SEEK_CUR:

  			offset += file->f_pos;
  	}
  	retval = -EINVAL;
  	if (offset>=0 && offset<=inode->i_sb->s_maxbytes) {

  		/* Special lock needed here? */

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

  	return retval;
  }

  EXPORT_SYMBOL(generic_file_llseek_unlocked);

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

  {

  	loff_t n;
  	mutex_lock(&file->f_dentry->d_inode->i_mutex);
  	n = generic_file_llseek_unlocked(file, offset, origin);
  	mutex_unlock(&file->f_dentry->d_inode->i_mutex);
  	return n;

  }

  EXPORT_SYMBOL(generic_file_llseek);

  
  loff_t no_llseek(struct file *file, loff_t offset, int origin)
  {
  	return -ESPIPE;
  }
  EXPORT_SYMBOL(no_llseek);
  
  loff_t default_llseek(struct file *file, loff_t offset, int origin)
  {

  	loff_t retval;

  
  	lock_kernel();
  	switch (origin) {

  		case SEEK_END:

  			offset += i_size_read(file->f_path.dentry->d_inode);

  			break;

  		case SEEK_CUR:

  			offset += file->f_pos;
  	}
  	retval = -EINVAL;
  	if (offset >= 0) {
  		if (offset != file->f_pos) {
  			file->f_pos = offset;
  			file->f_version = 0;
  		}
  		retval = offset;
  	}
  	unlock_kernel();
  	return retval;
  }
  EXPORT_SYMBOL(default_llseek);
  
  loff_t vfs_llseek(struct file *file, loff_t offset, int origin)
  {
  	loff_t (*fn)(struct file *, loff_t, int);
  
  	fn = no_llseek;
  	if (file->f_mode & FMODE_LSEEK) {
  		fn = default_llseek;
  		if (file->f_op && file->f_op->llseek)
  			fn = file->f_op->llseek;
  	}
  	return fn(file, offset, origin);
  }
  EXPORT_SYMBOL(vfs_llseek);
  
  asmlinkage off_t sys_lseek(unsigned int fd, off_t offset, unsigned int origin)
  {
  	off_t retval;
  	struct file * file;
  	int fput_needed;
  
  	retval = -EBADF;
  	file = fget_light(fd, &fput_needed);
  	if (!file)
  		goto bad;
  
  	retval = -EINVAL;

  	if (origin <= SEEK_MAX) {

  		loff_t res = vfs_llseek(file, offset, origin);
  		retval = res;
  		if (res != (loff_t)retval)
  			retval = -EOVERFLOW;	/* LFS: should only happen on 32 bit platforms */
  	}
  	fput_light(file, fput_needed);
  bad:
  	return retval;
  }
  
  #ifdef __ARCH_WANT_SYS_LLSEEK
  asmlinkage long sys_llseek(unsigned int fd, unsigned long offset_high,
  			   unsigned long offset_low, loff_t __user * result,
  			   unsigned int origin)
  {
  	int retval;
  	struct file * file;
  	loff_t offset;
  	int fput_needed;
  
  	retval = -EBADF;
  	file = fget_light(fd, &fput_needed);
  	if (!file)
  		goto bad;
  
  	retval = -EINVAL;

  	if (origin > SEEK_MAX)

  		goto out_putf;
  
  	offset = vfs_llseek(file, ((loff_t) offset_high << 32) | offset_low,
  			origin);
  
  	retval = (int)offset;
  	if (offset >= 0) {
  		retval = -EFAULT;
  		if (!copy_to_user(result, &offset, sizeof(offset)))
  			retval = 0;
  	}
  out_putf:
  	fput_light(file, fput_needed);
  bad:
  	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.
   */
  #define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK)

  
  int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count)
  {
  	struct inode *inode;
  	loff_t pos;

  	int retval = -EINVAL;

  	inode = file->f_path.dentry->d_inode;

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

  		return retval;

  	pos = *ppos;
  	if (unlikely((pos < 0) || (loff_t) (pos + count) < 0))

  		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;

  }

  static void wait_on_retry_sync_kiocb(struct kiocb *iocb)
  {
  	set_current_state(TASK_UNINTERRUPTIBLE);
  	if (!kiocbIsKicked(iocb))
  		schedule();
  	else
  		kiocbClearKicked(iocb);
  	__set_current_state(TASK_RUNNING);
  }

  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_left = len;
  
  	for (;;) {
  		ret = filp->f_op->aio_read(&kiocb, &iov, 1, kiocb.ki_pos);
  		if (ret != -EIOCBRETRY)
  			break;

  		wait_on_retry_sync_kiocb(&kiocb);

  	}

  	if (-EIOCBQUEUED == ret)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  
  EXPORT_SYMBOL(do_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_op || (!file->f_op->read && !file->f_op->aio_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
  			ret = do_sync_read(file, buf, count, pos);
  		if (ret > 0) {
  			fsnotify_access(file->f_path.dentry);
  			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_left = len;
  
  	for (;;) {
  		ret = filp->f_op->aio_write(&kiocb, &iov, 1, kiocb.ki_pos);
  		if (ret != -EIOCBRETRY)
  			break;

  		wait_on_retry_sync_kiocb(&kiocb);

  	}

  	if (-EIOCBQUEUED == ret)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  
  EXPORT_SYMBOL(do_sync_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_op || (!file->f_op->write && !file->f_op->aio_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;

  		if (file->f_op->write)
  			ret = file->f_op->write(file, buf, count, pos);
  		else
  			ret = do_sync_write(file, buf, count, pos);
  		if (ret > 0) {
  			fsnotify_modify(file->f_path.dentry);
  			add_wchar(current, ret);

  		}

  		inc_syscw(current);

  	}
  
  	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;
  }
  
  asmlinkage ssize_t sys_read(unsigned int fd, char __user * buf, size_t count)
  {
  	struct file *file;
  	ssize_t ret = -EBADF;
  	int fput_needed;
  
  	file = fget_light(fd, &fput_needed);
  	if (file) {
  		loff_t pos = file_pos_read(file);
  		ret = vfs_read(file, buf, count, &pos);
  		file_pos_write(file, pos);
  		fput_light(file, fput_needed);
  	}
  
  	return ret;
  }

  
  asmlinkage ssize_t sys_write(unsigned int fd, const char __user * buf, size_t count)
  {
  	struct file *file;
  	ssize_t ret = -EBADF;
  	int fput_needed;
  
  	file = fget_light(fd, &fput_needed);
  	if (file) {
  		loff_t pos = file_pos_read(file);
  		ret = vfs_write(file, buf, count, &pos);
  		file_pos_write(file, pos);
  		fput_light(file, fput_needed);
  	}
  
  	return ret;
  }
  
  asmlinkage ssize_t sys_pread64(unsigned int fd, char __user *buf,
  			     size_t count, loff_t pos)
  {
  	struct file *file;
  	ssize_t ret = -EBADF;
  	int fput_needed;
  
  	if (pos < 0)
  		return -EINVAL;
  
  	file = fget_light(fd, &fput_needed);
  	if (file) {
  		ret = -ESPIPE;
  		if (file->f_mode & FMODE_PREAD)
  			ret = vfs_read(file, buf, count, &pos);
  		fput_light(file, fput_needed);
  	}
  
  	return ret;
  }
  
  asmlinkage ssize_t sys_pwrite64(unsigned int fd, const char __user *buf,
  			      size_t count, loff_t pos)
  {
  	struct file *file;
  	ssize_t ret = -EBADF;
  	int fput_needed;
  
  	if (pos < 0)
  		return -EINVAL;
  
  	file = fget_light(fd, &fput_needed);
  	if (file) {
  		ret = -ESPIPE;
  		if (file->f_mode & FMODE_PWRITE)  
  			ret = vfs_write(file, buf, count, &pos);
  		fput_light(file, fput_needed);
  	}
  
  	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);

  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_left = len;
  	kiocb.ki_nbytes = len;
  
  	for (;;) {
  		ret = fn(&kiocb, iov, nr_segs, kiocb.ki_pos);
  		if (ret != -EIOCBRETRY)
  			break;
  		wait_on_retry_sync_kiocb(&kiocb);
  	}
  
  	if (ret == -EIOCBQUEUED)
  		ret = wait_on_sync_kiocb(&kiocb);
  	*ppos = kiocb.ki_pos;
  	return ret;
  }
  
  /* Do it by hand, with file-ops */
  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.
    	 */
  	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 + len < ret)) {
  			ret = -EINVAL;
    			goto out;
  		}
  		if (unlikely(!access_ok(vrfy_dir(type), buf, len))) {
  			ret = -EFAULT;
    			goto out;
  		}
  
  		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;

  	if (!file->f_op) {
  		ret = -EINVAL;

  		goto out;

  	}

  	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;

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

  		fnv = file->f_op->aio_write;

  	}

  	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);

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

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

  			fsnotify_access(file->f_path.dentry);

  		else

  			fsnotify_modify(file->f_path.dentry);

  	}

  	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_op || (!file->f_op->aio_read && !file->f_op->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_op || (!file->f_op->aio_write && !file->f_op->write))

  		return -EINVAL;
  
  	return do_readv_writev(WRITE, file, vec, vlen, pos);
  }
  
  EXPORT_SYMBOL(vfs_writev);
  
  asmlinkage ssize_t
  sys_readv(unsigned long fd, const struct iovec __user *vec, unsigned long vlen)
  {
  	struct file *file;
  	ssize_t ret = -EBADF;
  	int fput_needed;
  
  	file = fget_light(fd, &fput_needed);
  	if (file) {
  		loff_t pos = file_pos_read(file);
  		ret = vfs_readv(file, vec, vlen, &pos);
  		file_pos_write(file, pos);
  		fput_light(file, fput_needed);
  	}
  
  	if (ret > 0)

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

  	return ret;
  }
  
  asmlinkage ssize_t
  sys_writev(unsigned long fd, const struct iovec __user *vec, unsigned long vlen)
  {
  	struct file *file;
  	ssize_t ret = -EBADF;
  	int fput_needed;
  
  	file = fget_light(fd, &fput_needed);
  	if (file) {
  		loff_t pos = file_pos_read(file);
  		ret = vfs_writev(file, vec, vlen, &pos);
  		file_pos_write(file, pos);
  		fput_light(file, fput_needed);
  	}
  
  	if (ret > 0)

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

  	return ret;
  }
  
  static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
  			   size_t count, loff_t max)
  {
  	struct file * in_file, * out_file;
  	struct inode * in_inode, * out_inode;
  	loff_t pos;
  	ssize_t retval;

  	int fput_needed_in, fput_needed_out, fl;

  
  	/*
  	 * Get input file, and verify that it is ok..
  	 */
  	retval = -EBADF;
  	in_file = fget_light(in_fd, &fput_needed_in);
  	if (!in_file)
  		goto out;
  	if (!(in_file->f_mode & FMODE_READ))
  		goto fput_in;
  	retval = -EINVAL;

  	in_inode = in_file->f_path.dentry->d_inode;

  	if (!in_inode)
  		goto fput_in;

  	if (!in_file->f_op || !in_file->f_op->splice_read)

  		goto fput_in;
  	retval = -ESPIPE;
  	if (!ppos)
  		ppos = &in_file->f_pos;
  	else
  		if (!(in_file->f_mode & FMODE_PREAD))
  			goto fput_in;
  	retval = rw_verify_area(READ, in_file, ppos, count);

  	if (retval < 0)

  		goto fput_in;

  	count = retval;

  	/*
  	 * Get output file, and verify that it is ok..
  	 */
  	retval = -EBADF;
  	out_file = fget_light(out_fd, &fput_needed_out);
  	if (!out_file)
  		goto fput_in;
  	if (!(out_file->f_mode & FMODE_WRITE))
  		goto fput_out;
  	retval = -EINVAL;
  	if (!out_file->f_op || !out_file->f_op->sendpage)
  		goto fput_out;

  	out_inode = out_file->f_path.dentry->d_inode;

  	retval = rw_verify_area(WRITE, out_file, &out_file->f_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);
  
  	pos = *ppos;
  	retval = -EINVAL;
  	if (unlikely(pos < 0))
  		goto fput_out;
  	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

  	retval = do_splice_direct(in_file, ppos, out_file, count, fl);

  
  	if (retval > 0) {

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

  	}

  	inc_syscr(current);
  	inc_syscw(current);

  	if (*ppos > max)
  		retval = -EOVERFLOW;
  
  fput_out:
  	fput_light(out_file, fput_needed_out);
  fput_in:
  	fput_light(in_file, fput_needed_in);
  out:
  	return retval;
  }
  
  asmlinkage ssize_t sys_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);
  }
  
  asmlinkage ssize_t sys_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);
  }