// SPDX-License-Identifier: GPL-2.0

  /*
   *  linux/fs/read_write.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */

  #include <linux/slab.h>

  #include <linux/stat.h>

  #include <linux/sched/xacct.h>

  #include <linux/fcntl.h>
  #include <linux/file.h>
  #include <linux/uio.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 <linux/mount.h>

  #include <linux/fs.h>

  #include "internal.h"

  #include <linux/uaccess.h>

  #include <asm/unistd.h>

  const struct file_operations generic_ro_fops = {

  	.llseek		= generic_file_llseek,

  	.read_iter	= generic_file_read_iter,

  	.mmap		= generic_file_readonly_mmap,

  	.splice_read	= generic_file_splice_read,

  };
  
  EXPORT_SYMBOL(generic_ro_fops);

  static inline bool 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 ((unsigned long long)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 ((unsigned long long)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);
  
  /**

   * no_seek_end_llseek - llseek implementation for fixed-sized devices
   * @file:	file structure to seek on
   * @offset:	file offset to seek to
   * @whence:	type of seek
   *
   */
  loff_t no_seek_end_llseek(struct file *file, loff_t offset, int whence)
  {
  	switch (whence) {
  	case SEEK_SET: case SEEK_CUR:
  		return generic_file_llseek_size(file, offset, whence,

  						OFFSET_MAX, 0);

  	default:
  		return -EINVAL;
  	}
  }
  EXPORT_SYMBOL(no_seek_end_llseek);
  
  /**
   * no_seek_end_llseek_size - llseek implementation for fixed-sized devices
   * @file:	file structure to seek on
   * @offset:	file offset to seek to
   * @whence:	type of seek
   * @size:	maximal offset allowed
   *
   */
  loff_t no_seek_end_llseek_size(struct file *file, loff_t offset, int whence, loff_t size)
  {
  	switch (whence) {
  	case SEEK_SET: case SEEK_CUR:
  		return generic_file_llseek_size(file, offset, whence,
  						size, 0);
  	default:
  		return -EINVAL;
  	}
  }
  EXPORT_SYMBOL(no_seek_end_llseek_size);
  
  /**

   * 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;

  	inode_lock(inode);

  	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:

  	inode_unlock(inode);

  	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 off_t ksys_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;
  }

  SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence)
  {
  	return ksys_lseek(fd, offset, whence);
  }

  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE3(lseek, unsigned int, fd, compat_off_t, offset, unsigned int, whence)
  {

  	return ksys_lseek(fd, offset, whence);

  }
  #endif

  #if !defined(CONFIG_64BIT) || defined(CONFIG_COMPAT) || \
  	defined(__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

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

  {
  	struct inode *inode;

  	int retval = -EINVAL;

  	inode = file_inode(file);

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

  		return retval;

  	/*
  	 * ranged mandatory locking does not apply to streams - it makes sense
  	 * only for files where position has a meaning.
  	 */
  	if (ppos) {
  		loff_t 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_flctx && mandatory_lock(inode))) {
  			retval = locks_mandatory_area(inode, file, pos, pos + count - 1,
  					read_write == READ ? F_RDLCK : F_WRLCK);
  			if (retval < 0)
  				return retval;
  		}

  	}

  	return security_file_permission(file,

  				read_write == READ ? MAY_READ : MAY_WRITE);

  }

  static 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 ? *ppos : 0);

  	iov_iter_init(&iter, READ, &iov, 1, len);

  	ret = call_read_iter(filp, &kiocb, &iter);

  	BUG_ON(ret == -EIOCBQUEUED);

  	if (ppos)
  		*ppos = kiocb.ki_pos;

  	return ret;
  }

  static int warn_unsupported(struct file *file, const char *op)
  {
  	pr_warn_ratelimited(
  		"kernel %s not supported for file %pD4 (pid: %d comm: %.20s)
  ",
  		op, file, current->pid, current->comm);
  	return -EINVAL;
  }

  ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
  {

  	struct kvec iov = {
  		.iov_base	= buf,
  		.iov_len	= min_t(size_t, count, MAX_RW_COUNT),
  	};
  	struct kiocb kiocb;
  	struct iov_iter iter;

  	ssize_t ret;
  
  	if (WARN_ON_ONCE(!(file->f_mode & FMODE_READ)))
  		return -EINVAL;
  	if (!(file->f_mode & FMODE_CAN_READ))
  		return -EINVAL;

  	/*
  	 * Also fail if ->read_iter and ->read are both wired up as that
  	 * implies very convoluted semantics.
  	 */
  	if (unlikely(!file->f_op->read_iter || file->f_op->read))
  		return warn_unsupported(file, "read");

  	init_sync_kiocb(&kiocb, file);

  	kiocb.ki_pos = pos ? *pos : 0;

  	iov_iter_kvec(&iter, READ, &iov, 1, iov.iov_len);
  	ret = file->f_op->read_iter(&kiocb, &iter);

  	if (ret > 0) {

  		if (pos)
  			*pos = kiocb.ki_pos;

  		fsnotify_access(file);
  		add_rchar(current, ret);
  	}
  	inc_syscr(current);
  	return ret;
  }

  ssize_t kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)

  {

  	ssize_t ret;

  	ret = rw_verify_area(READ, file, pos, count);
  	if (ret)
  		return ret;
  	return __kernel_read(file, buf, count, pos);

  }
  EXPORT_SYMBOL(kernel_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(buf, count)))

  		return -EFAULT;
  
  	ret = rw_verify_area(READ, file, pos, count);

  	if (ret)
  		return ret;
  	if (count > MAX_RW_COUNT)
  		count =  MAX_RW_COUNT;

  	if (file->f_op->read)
  		ret = file->f_op->read(file, buf, count, pos);
  	else if (file->f_op->read_iter)
  		ret = new_sync_read(file, buf, count, pos);
  	else
  		ret = -EINVAL;
  	if (ret > 0) {
  		fsnotify_access(file);
  		add_rchar(current, ret);
  	}
  	inc_syscr(current);

  	return ret;
  }

  static 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 ? *ppos : 0);

  	iov_iter_init(&iter, WRITE, &iov, 1, len);

  	ret = call_write_iter(filp, &kiocb, &iter);

  	BUG_ON(ret == -EIOCBQUEUED);

  	if (ret > 0 && ppos)

  		*ppos = kiocb.ki_pos;

  	return ret;
  }

  /* caller is responsible for file_start_write/file_end_write */

  ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)

  {

  	struct kvec iov = {
  		.iov_base	= (void *)buf,
  		.iov_len	= min_t(size_t, count, MAX_RW_COUNT),
  	};
  	struct kiocb kiocb;
  	struct iov_iter iter;

  	ssize_t ret;

  	if (WARN_ON_ONCE(!(file->f_mode & FMODE_WRITE)))
  		return -EBADF;

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

  		return -EINVAL;

  	/*
  	 * Also fail if ->write_iter and ->write are both wired up as that
  	 * implies very convoluted semantics.
  	 */
  	if (unlikely(!file->f_op->write_iter || file->f_op->write))
  		return warn_unsupported(file, "write");

  	init_sync_kiocb(&kiocb, file);

  	kiocb.ki_pos = pos ? *pos : 0;

  	iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
  	ret = file->f_op->write_iter(&kiocb, &iter);

  	if (ret > 0) {

  		if (pos)
  			*pos = kiocb.ki_pos;

  		fsnotify_modify(file);
  		add_wchar(current, ret);
  	}
  	inc_syscw(current);
  	return ret;
  }

  /*
   * This "EXPORT_SYMBOL_GPL()" is more of a "EXPORT_SYMBOL_DONTUSE()",
   * but autofs is one of the few internal kernel users that actually
   * wants this _and_ can be built as a module. So we need to export
   * this symbol for autofs, even though it really isn't appropriate
   * for any other kernel modules.
   */
  EXPORT_SYMBOL_GPL(__kernel_write);

  ssize_t kernel_write(struct file *file, const void *buf, size_t count,
  			    loff_t *pos)

  {

  	ssize_t ret;

  	ret = rw_verify_area(WRITE, file, pos, count);
  	if (ret)
  		return ret;

  	file_start_write(file);
  	ret =  __kernel_write(file, buf, count, pos);
  	file_end_write(file);
  	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(buf, count)))

  		return -EFAULT;
  
  	ret = rw_verify_area(WRITE, file, pos, count);

  	if (ret)
  		return ret;
  	if (count > MAX_RW_COUNT)
  		count =  MAX_RW_COUNT;
  	file_start_write(file);
  	if (file->f_op->write)
  		ret = file->f_op->write(file, buf, count, pos);
  	else if (file->f_op->write_iter)
  		ret = new_sync_write(file, buf, count, pos);
  	else
  		ret = -EINVAL;
  	if (ret > 0) {
  		fsnotify_modify(file);
  		add_wchar(current, ret);

  	}

  	inc_syscw(current);
  	file_end_write(file);

  	return ret;
  }

  /* file_ppos returns &file->f_pos or NULL if file is stream */
  static inline loff_t *file_ppos(struct file *file)

  {

  	return file->f_mode & FMODE_STREAM ? NULL : &file->f_pos;

  }

  ssize_t ksys_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, *ppos = file_ppos(f.file);
  		if (ppos) {
  			pos = *ppos;
  			ppos = &pos;
  		}
  		ret = vfs_read(f.file, buf, count, ppos);
  		if (ret >= 0 && ppos)
  			f.file->f_pos = pos;

  		fdput_pos(f);

  	}

  	return ret;
  }

  SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count)
  {
  	return ksys_read(fd, buf, count);
  }

  ssize_t ksys_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, *ppos = file_ppos(f.file);
  		if (ppos) {
  			pos = *ppos;
  			ppos = &pos;
  		}
  		ret = vfs_write(f.file, buf, count, ppos);
  		if (ret >= 0 && ppos)
  			f.file->f_pos = pos;

  		fdput_pos(f);

  	}
  
  	return ret;
  }

  SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
  		size_t, count)
  {
  	return ksys_write(fd, buf, count);
  }

  ssize_t ksys_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(pread64, unsigned int, fd, char __user *, buf,
  			size_t, count, loff_t, pos)
  {
  	return ksys_pread64(fd, buf, count, pos);
  }
  
  ssize_t ksys_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;
  }

  SYSCALL_DEFINE4(pwrite64, unsigned int, fd, const char __user *, buf,
  			 size_t, count, loff_t, pos)
  {
  	return ksys_pwrite64(fd, buf, count, pos);
  }

  static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,

  		loff_t *ppos, int type, rwf_t flags)

  {
  	struct kiocb kiocb;

  	ssize_t ret;
  
  	init_sync_kiocb(&kiocb, filp);

  	ret = kiocb_set_rw_flags(&kiocb, flags);
  	if (ret)
  		return ret;

  	kiocb.ki_pos = (ppos ? *ppos : 0);

  	if (type == READ)

  		ret = call_read_iter(filp, &kiocb, iter);

  	else

  		ret = call_write_iter(filp, &kiocb, iter);

  	BUG_ON(ret == -EIOCBQUEUED);

  	if (ppos)
  		*ppos = kiocb.ki_pos;

  	return ret;
  }

  /* Do it by hand, with file-ops */

  static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,

  		loff_t *ppos, int type, rwf_t flags)

  {

  	ssize_t ret = 0;

  	if (flags & ~RWF_HIPRI)

  		return -EOPNOTSUPP;

  	while (iov_iter_count(iter)) {
  		struct iovec iovec = iov_iter_iovec(iter);

  		ssize_t nr;

  		if (type == READ) {
  			nr = filp->f_op->read(filp, iovec.iov_base,
  					      iovec.iov_len, ppos);
  		} else {
  			nr = filp->f_op->write(filp, iovec.iov_base,
  					       iovec.iov_len, ppos);
  		}

  
  		if (nr < 0) {
  			if (!ret)
  				ret = nr;
  			break;
  		}
  		ret += nr;

  		if (nr != iovec.iov_len)

  			break;

  		iov_iter_advance(iter, nr);

  	}
  
  	return ret;
  }

  static ssize_t do_iter_read(struct file *file, struct iov_iter *iter,

  		loff_t *pos, rwf_t flags)

  {

  	size_t tot_len;

  	ssize_t ret = 0;

  	if (!(file->f_mode & FMODE_READ))
  		return -EBADF;
  	if (!(file->f_mode & FMODE_CAN_READ))
  		return -EINVAL;

  	tot_len = iov_iter_count(iter);

  	if (!tot_len)
  		goto out;

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

  	if (ret < 0)

  		return ret;

  	if (file->f_op->read_iter)
  		ret = do_iter_readv_writev(file, iter, pos, READ, flags);

  	else

  		ret = do_loop_readv_writev(file, iter, pos, READ, flags);

  out:

  	if (ret >= 0)
  		fsnotify_access(file);

  	return ret;

  }

  ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
  			   struct iov_iter *iter)
  {
  	size_t tot_len;
  	ssize_t ret = 0;
  
  	if (!file->f_op->read_iter)
  		return -EINVAL;
  	if (!(file->f_mode & FMODE_READ))
  		return -EBADF;
  	if (!(file->f_mode & FMODE_CAN_READ))
  		return -EINVAL;
  
  	tot_len = iov_iter_count(iter);
  	if (!tot_len)
  		goto out;
  	ret = rw_verify_area(READ, file, &iocb->ki_pos, tot_len);
  	if (ret < 0)
  		return ret;
  
  	ret = call_read_iter(file, iocb, iter);
  out:
  	if (ret >= 0)
  		fsnotify_access(file);
  	return ret;
  }
  EXPORT_SYMBOL(vfs_iocb_iter_read);

  ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,

  		rwf_t flags)

  {

  	if (!file->f_op->read_iter)
  		return -EINVAL;
  	return do_iter_read(file, iter, ppos, flags);
  }
  EXPORT_SYMBOL(vfs_iter_read);

  static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,

  		loff_t *pos, rwf_t flags)

  {
  	size_t tot_len;
  	ssize_t ret = 0;

  	if (!(file->f_mode & FMODE_WRITE))
  		return -EBADF;
  	if (!(file->f_mode & FMODE_CAN_WRITE))
  		return -EINVAL;

  	tot_len = iov_iter_count(iter);
  	if (!tot_len)
  		return 0;
  	ret = rw_verify_area(WRITE, file, pos, tot_len);

  	if (ret < 0)
  		return ret;

  	if (file->f_op->write_iter)
  		ret = do_iter_readv_writev(file, iter, pos, WRITE, flags);
  	else
  		ret = do_loop_readv_writev(file, iter, pos, WRITE, flags);

  	if (ret > 0)
  		fsnotify_modify(file);

  	return ret;
  }

  ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
  			    struct iov_iter *iter)
  {
  	size_t tot_len;
  	ssize_t ret = 0;
  
  	if (!file->f_op->write_iter)
  		return -EINVAL;
  	if (!(file->f_mode & FMODE_WRITE))
  		return -EBADF;
  	if (!(file->f_mode & FMODE_CAN_WRITE))
  		return -EINVAL;
  
  	tot_len = iov_iter_count(iter);
  	if (!tot_len)
  		return 0;
  	ret = rw_verify_area(WRITE, file, &iocb->ki_pos, tot_len);
  	if (ret < 0)
  		return ret;
  
  	ret = call_write_iter(file, iocb, iter);
  	if (ret > 0)
  		fsnotify_modify(file);
  
  	return ret;
  }
  EXPORT_SYMBOL(vfs_iocb_iter_write);

  ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,

  		rwf_t flags)

  {
  	if (!file->f_op->write_iter)
  		return -EINVAL;
  	return do_iter_write(file, iter, ppos, flags);
  }
  EXPORT_SYMBOL(vfs_iter_write);

  static ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,

  		  unsigned long vlen, loff_t *pos, rwf_t flags)

  {

  	struct iovec iovstack[UIO_FASTIOV];
  	struct iovec *iov = iovstack;
  	struct iov_iter iter;
  	ssize_t ret;

  	ret = import_iovec(READ, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);

  	if (ret >= 0) {
  		ret = do_iter_read(file, &iter, pos, flags);
  		kfree(iov);
  	}

  	return ret;
  }

  static ssize_t vfs_writev(struct file *file, const struct iovec __user *vec,

  		   unsigned long vlen, loff_t *pos, rwf_t flags)

  {

  	struct iovec iovstack[UIO_FASTIOV];
  	struct iovec *iov = iovstack;
  	struct iov_iter iter;
  	ssize_t ret;

  	ret = import_iovec(WRITE, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);

  	if (ret >= 0) {

  		file_start_write(file);

  		ret = do_iter_write(file, &iter, pos, flags);

  		file_end_write(file);

  		kfree(iov);
  	}

  	return ret;

  }

  static ssize_t do_readv(unsigned long fd, const struct iovec __user *vec,

  			unsigned long vlen, rwf_t flags)

  {

  	struct fd f = fdget_pos(fd);

  	ssize_t ret = -EBADF;

  	if (f.file) {

  		loff_t pos, *ppos = file_ppos(f.file);
  		if (ppos) {
  			pos = *ppos;
  			ppos = &pos;
  		}
  		ret = vfs_readv(f.file, vec, vlen, ppos, flags);
  		if (ret >= 0 && ppos)
  			f.file->f_pos = pos;

  		fdput_pos(f);

  	}
  
  	if (ret > 0)

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

  	return ret;
  }

  static ssize_t do_writev(unsigned long fd, const struct iovec __user *vec,

  			 unsigned long vlen, rwf_t flags)

  {

  	struct fd f = fdget_pos(fd);

  	ssize_t ret = -EBADF;

  	if (f.file) {

  		loff_t pos, *ppos = file_ppos(f.file);
  		if (ppos) {
  			pos = *ppos;
  			ppos = &pos;
  		}
  		ret = vfs_writev(f.file, vec, vlen, ppos, flags);
  		if (ret >= 0 && ppos)
  			f.file->f_pos = 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;
  }

  static ssize_t do_preadv(unsigned long fd, const struct iovec __user *vec,

  			 unsigned long vlen, loff_t pos, rwf_t flags)

  {

  	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, flags);

  		fdput(f);

  	}
  
  	if (ret > 0)
  		add_rchar(current, ret);
  	inc_syscr(current);
  	return ret;
  }

  static ssize_t do_pwritev(unsigned long fd, const struct iovec __user *vec,

  			  unsigned long vlen, loff_t pos, rwf_t flags)

  {

  	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, flags);

  		fdput(f);

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

  SYSCALL_DEFINE3(readv, unsigned long, fd, const struct iovec __user *, vec,
  		unsigned long, vlen)
  {
  	return do_readv(fd, vec, vlen, 0);
  }
  
  SYSCALL_DEFINE3(writev, unsigned long, fd, const struct iovec __user *, vec,
  		unsigned long, vlen)
  {
  	return do_writev(fd, vec, vlen, 0);
  }
  
  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);
  
  	return do_preadv(fd, vec, vlen, pos, 0);
  }
  
  SYSCALL_DEFINE6(preadv2, unsigned long, fd, const struct iovec __user *, vec,
  		unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h,

  		rwf_t, flags)

  {
  	loff_t pos = pos_from_hilo(pos_h, pos_l);
  
  	if (pos == -1)
  		return do_readv(fd, vec, vlen, flags);
  
  	return do_preadv(fd, vec, vlen, pos, flags);
  }
  
  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);
  
  	return do_pwritev(fd, vec, vlen, pos, 0);
  }
  
  SYSCALL_DEFINE6(pwritev2, unsigned long, fd, const struct iovec __user *, vec,
  		unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h,

  		rwf_t, flags)

  {
  	loff_t pos = pos_from_hilo(pos_h, pos_l);
  
  	if (pos == -1)
  		return do_writev(fd, vec, vlen, flags);
  
  	return do_pwritev(fd, vec, vlen, pos, flags);
  }

  /*
   * Various compat syscalls.  Note that they all pretend to take a native
   * iovec - import_iovec will properly treat those as compat_iovecs based on
   * in_compat_syscall().
   */

  #ifdef CONFIG_COMPAT

  #ifdef __ARCH_WANT_COMPAT_SYS_PREADV64
  COMPAT_SYSCALL_DEFINE4(preadv64, unsigned long, fd,

  		const struct iovec __user *, vec,

  		unsigned long, vlen, loff_t, pos)
  {

  	return do_preadv(fd, vec, vlen, pos, 0);

  }
  #endif

  COMPAT_SYSCALL_DEFINE5(preadv, compat_ulong_t, fd,

  		const struct iovec __user *, vec,

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

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

  	return do_preadv(fd, vec, vlen, pos, 0);

  }

  #ifdef __ARCH_WANT_COMPAT_SYS_PREADV64V2
  COMPAT_SYSCALL_DEFINE5(preadv64v2, unsigned long, fd,

  		const struct iovec __user *, vec,

  		unsigned long, vlen, loff_t, pos, rwf_t, flags)

  {

  	if (pos == -1)

  		return do_readv(fd, vec, vlen, flags);
  	return do_preadv(fd, vec, vlen, pos, flags);

  }
  #endif

  COMPAT_SYSCALL_DEFINE6(preadv2, compat_ulong_t, fd,

  		const struct iovec __user *, vec,

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

  		rwf_t, flags)

  {
  	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
  
  	if (pos == -1)

  		return do_readv(fd, vec, vlen, flags);
  	return do_preadv(fd, vec, vlen, pos, flags);

  }

  #ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64
  COMPAT_SYSCALL_DEFINE4(pwritev64, unsigned long, fd,

  		const struct iovec __user *, vec,

  		unsigned long, vlen, loff_t, pos)
  {

  	return do_pwritev(fd, vec, vlen, pos, 0);

  }
  #endif

  COMPAT_SYSCALL_DEFINE5(pwritev, compat_ulong_t, fd,

  		const struct iovec __user *,vec,

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

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

  	return do_pwritev(fd, vec, vlen, pos, 0);

  }

  #ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64V2
  COMPAT_SYSCALL_DEFINE5(pwritev64v2, unsigned long, fd,

  		const struct iovec __user *, vec,

  		unsigned long, vlen, loff_t, pos, rwf_t, flags)

  {

  	if (pos == -1)

  		return do_writev(fd, vec, vlen, flags);
  	return do_pwritev(fd, vec, vlen, pos, flags);

  }
  #endif

  COMPAT_SYSCALL_DEFINE6(pwritev2, compat_ulong_t, fd,

  		const struct iovec __user *,vec,

  		compat_ulong_t, vlen, u32, pos_low, u32, pos_high, rwf_t, flags)

  {
  	loff_t pos = ((loff_t)pos_high << 32) | pos_low;
  
  	if (pos == -1)

  		return do_writev(fd, vec, vlen, flags);
  	return do_pwritev(fd, vec, vlen, pos, flags);

  }

  #endif /* CONFIG_COMPAT */

  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;

  	if (count > MAX_RW_COUNT)
  		count =  MAX_RW_COUNT;

  	/*
  	 * 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;

  	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;

  	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

  /**
   * generic_copy_file_range - copy data between two files
   * @file_in:	file structure to read from
   * @pos_in:	file offset to read from
   * @file_out:	file structure to write data to
   * @pos_out:	file offset to write data to
   * @len:	amount of data to copy
   * @flags:	copy flags
   *
   * This is a generic filesystem helper to copy data from one file to another.
   * It has no constraints on the source or destination file owners - the files
   * can belong to different superblocks and different filesystem types. Short
   * copies are allowed.
   *
   * This should be called from the @file_out filesystem, as per the
   * ->copy_file_range() method.
   *
   * Returns the number of bytes copied or a negative error indicating the
   * failure.
   */
  
  ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
  				struct file *file_out, loff_t pos_out,
  				size_t len, unsigned int flags)
  {
  	return do_splice_direct(file_in, &pos_in, file_out, &pos_out,
  				len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
  }
  EXPORT_SYMBOL(generic_copy_file_range);

  static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
  				  struct file *file_out, loff_t pos_out,
  				  size_t len, unsigned int flags)
  {

  	/*
  	 * Although we now allow filesystems to handle cross sb copy, passing
  	 * a file of the wrong filesystem type to filesystem driver can result
  	 * in an attempt to dereference the wrong type of ->private_data, so
  	 * avoid doing that until we really have a good reason.  NFS defines
  	 * several different file_system_type structures, but they all end up
  	 * using the same ->copy_file_range() function pointer.
  	 */
  	if (file_out->f_op->copy_file_range &&
  	    file_out->f_op->copy_file_range == file_in->f_op->copy_file_range)

  		return file_out->f_op->copy_file_range(file_in, pos_in,
  						       file_out, pos_out,
  						       len, flags);
  
  	return generic_copy_file_range(file_in, pos_in, file_out, pos_out, len,
  				       flags);
  }

  /*

   * Performs necessary checks before doing a file copy
   *
   * Can adjust amount of bytes to copy via @req_count argument.
   * Returns appropriate error code that caller should return or
   * zero in case the copy should be allowed.
   */
  static int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
  				    struct file *file_out, loff_t pos_out,
  				    size_t *req_count, unsigned int flags)
  {
  	struct inode *inode_in = file_inode(file_in);
  	struct inode *inode_out = file_inode(file_out);
  	uint64_t count = *req_count;
  	loff_t size_in;
  	int ret;
  
  	ret = generic_file_rw_checks(file_in, file_out);
  	if (ret)
  		return ret;
  
  	/* Don't touch certain kinds of inodes */
  	if (IS_IMMUTABLE(inode_out))
  		return -EPERM;
  
  	if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
  		return -ETXTBSY;
  
  	/* Ensure offsets don't wrap. */
  	if (pos_in + count < pos_in || pos_out + count < pos_out)
  		return -EOVERFLOW;
  
  	/* Shorten the copy to EOF */
  	size_in = i_size_read(inode_in);
  	if (pos_in >= size_in)
  		count = 0;
  	else
  		count = min(count, size_in - (uint64_t)pos_in);
  
  	ret = generic_write_check_limits(file_out, pos_out, &count);
  	if (ret)
  		return ret;
  
  	/* Don't allow overlapped copying within the same file. */
  	if (inode_in == inode_out &&
  	    pos_out + count > pos_in &&
  	    pos_out < pos_in + count)
  		return -EINVAL;
  
  	*req_count = count;
  	return 0;
  }
  
  /*

   * copy_file_range() differs from regular file read and write in that it
   * specifically allows return partial success.  When it does so is up to
   * the copy_file_range method.
   */
  ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
  			    struct file *file_out, loff_t pos_out,
  			    size_t len, unsigned int flags)
  {

  	ssize_t ret;
  
  	if (flags != 0)
  		return -EINVAL;

  	ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len,
  				       flags);

  	if (unlikely(ret))
  		return ret;

  	ret = rw_verify_area(READ, file_in, &pos_in, len);

  	if (unlikely(ret))
  		return ret;
  
  	ret = rw_verify_area(WRITE, file_out, &pos_out, len);
  	if (unlikely(ret))

  		return ret;

  	if (len == 0)
  		return 0;

  	file_start_write(file_out);

  	/*
  	 * Try cloning first, this is supported by more file systems, and
  	 * more efficient if both clone and copy are supported (e.g. NFS).
  	 */

  	if (file_in->f_op->remap_file_range &&
  	    file_inode(file_in)->i_sb == file_inode(file_out)->i_sb) {

  		loff_t cloned;
  
  		cloned = file_in->f_op->remap_file_range(file_in, pos_in,
  				file_out, pos_out,

  				min_t(loff_t, MAX_RW_COUNT, len),
  				REMAP_FILE_CAN_SHORTEN);

  		if (cloned > 0) {
  			ret = cloned;

  			goto done;
  		}
  	}

  	ret = do_copy_file_range(file_in, pos_in, file_out, pos_out, len,
  				flags);
  	WARN_ON_ONCE(ret == -EOPNOTSUPP);

  done:

  	if (ret > 0) {
  		fsnotify_access(file_in);
  		add_rchar(current, ret);
  		fsnotify_modify(file_out);
  		add_wchar(current, ret);
  	}

  	inc_syscr(current);
  	inc_syscw(current);

  	file_end_write(file_out);

  
  	return ret;
  }
  EXPORT_SYMBOL(vfs_copy_file_range);
  
  SYSCALL_DEFINE6(copy_file_range, int, fd_in, loff_t __user *, off_in,
  		int, fd_out, loff_t __user *, off_out,
  		size_t, len, unsigned int, flags)
  {
  	loff_t pos_in;
  	loff_t pos_out;
  	struct fd f_in;
  	struct fd f_out;
  	ssize_t ret = -EBADF;
  
  	f_in = fdget(fd_in);
  	if (!f_in.file)
  		goto out2;
  
  	f_out = fdget(fd_out);
  	if (!f_out.file)
  		goto out1;
  
  	ret = -EFAULT;
  	if (off_in) {
  		if (copy_from_user(&pos_in, off_in, sizeof(loff_t)))
  			goto out;
  	} else {
  		pos_in = f_in.file->f_pos;
  	}
  
  	if (off_out) {
  		if (copy_from_user(&pos_out, off_out, sizeof(loff_t)))
  			goto out;
  	} else {
  		pos_out = f_out.file->f_pos;
  	}
  
  	ret = vfs_copy_file_range(f_in.file, pos_in, f_out.file, pos_out, len,
  				  flags);
  	if (ret > 0) {
  		pos_in += ret;
  		pos_out += ret;
  
  		if (off_in) {
  			if (copy_to_user(off_in, &pos_in, sizeof(loff_t)))
  				ret = -EFAULT;
  		} else {
  			f_in.file->f_pos = pos_in;
  		}
  
  		if (off_out) {
  			if (copy_to_user(off_out, &pos_out, sizeof(loff_t)))
  				ret = -EFAULT;
  		} else {
  			f_out.file->f_pos = pos_out;
  		}
  	}
  
  out:
  	fdput(f_out);
  out1:
  	fdput(f_in);
  out2:
  	return ret;
  }

  /*

   * Don't operate on ranges the page cache doesn't support, and don't exceed the
   * LFS limits.  If pos is under the limit it becomes a short access.  If it
   * exceeds the limit we return -EFBIG.

   */

  int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)

  {

  	struct inode *inode = file->f_mapping->host;
  	loff_t max_size = inode->i_sb->s_maxbytes;
  	loff_t limit = rlimit(RLIMIT_FSIZE);

  	if (limit != RLIM_INFINITY) {
  		if (pos >= limit) {
  			send_sig(SIGXFSZ, current, 0);
  			return -EFBIG;

  		}

  		*count = min(*count, limit - pos);
  	}

  	if (!(file->f_flags & O_LARGEFILE))
  		max_size = MAX_NON_LFS;

  	if (unlikely(pos >= max_size))
  		return -EFBIG;

  	*count = min(*count, max_size - pos);

  	return 0;

  }

  /*

   * Performs necessary checks before doing a write

   *

   * Can adjust writing position or amount of bytes to write.
   * Returns appropriate error code that caller should return or
   * zero in case that write should be allowed.

   */

  ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)

  {

  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file->f_mapping->host;
  	loff_t count;

  	int ret;

  	if (IS_SWAPFILE(inode))

  		return -ETXTBSY;

  	if (!iov_iter_count(from))
  		return 0;

  	/* FIXME: this is for backwards compatibility with 2.4 */
  	if (iocb->ki_flags & IOCB_APPEND)
  		iocb->ki_pos = i_size_read(inode);

  	if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
  		return -EINVAL;

  	count = iov_iter_count(from);
  	ret = generic_write_check_limits(file, iocb->ki_pos, &count);

  	if (ret)
  		return ret;

  	iov_iter_truncate(from, count);
  	return iov_iter_count(from);

  }

  EXPORT_SYMBOL(generic_write_checks);

  /*
   * Performs common checks before doing a file copy/clone
   * from @file_in to @file_out.
   */
  int generic_file_rw_checks(struct file *file_in, struct file *file_out)

  {

  	struct inode *inode_in = file_inode(file_in);
  	struct inode *inode_out = file_inode(file_out);

  	/* Don't copy dirs, pipes, sockets... */
  	if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))

  		return -EISDIR;

  	if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))

  		return -EINVAL;

  	if (!(file_in->f_mode & FMODE_READ) ||
  	    !(file_out->f_mode & FMODE_WRITE) ||
  	    (file_out->f_flags & O_APPEND))
  		return -EBADF;

  	return 0;

  }