/*
   *	linux/mm/filemap.h
   *
   * Copyright (C) 1994-1999  Linus Torvalds
   */
  
  #ifndef __FILEMAP_H
  #define __FILEMAP_H
  
  #include <linux/types.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/highmem.h>
  #include <linux/uio.h>

  #include <linux/uaccess.h>

  size_t

  __filemap_copy_from_user_iovec_inatomic(char *vaddr,
  					const struct iovec *iov,
  					size_t base,
  					size_t bytes);

  
  /*
   * Copy as much as we can into the page and return the number of bytes which
   * were sucessfully copied.  If a fault is encountered then clear the page
   * out to (offset+bytes) and return the number of bytes which were copied.

   *
   * NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache
   * to *NOT* zero any tail of the buffer that it failed to copy.  If it does,
   * and if the following non-atomic copy succeeds, then there is a small window
   * where the target page contains neither the data before the write, nor the
   * data after the write (it contains zero).  A read at this time will see
   * data that is inconsistent with any ordering of the read and the write.
   * (This has been detected in practice).

   */
  static inline size_t
  filemap_copy_from_user(struct page *page, unsigned long offset,
  			const char __user *buf, unsigned bytes)
  {
  	char *kaddr;
  	int left;
  
  	kaddr = kmap_atomic(page, KM_USER0);

  	left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);

  	kunmap_atomic(kaddr, KM_USER0);
  
  	if (left != 0) {
  		/* Do it the slow way */
  		kaddr = kmap(page);

  		left = __copy_from_user_nocache(kaddr + offset, buf, bytes);

  		kunmap(page);
  	}
  	return bytes - left;
  }
  
  /*
   * This has the same sideeffects and return value as filemap_copy_from_user().
   * The difference is that on a fault we need to memset the remainder of the
   * page (out to offset+bytes), to emulate filemap_copy_from_user()'s
   * single-segment behaviour.
   */
  static inline size_t
  filemap_copy_from_user_iovec(struct page *page, unsigned long offset,
  			const struct iovec *iov, size_t base, size_t bytes)
  {
  	char *kaddr;
  	size_t copied;
  
  	kaddr = kmap_atomic(page, KM_USER0);

  	copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
  							 base, bytes);

  	kunmap_atomic(kaddr, KM_USER0);
  	if (copied != bytes) {
  		kaddr = kmap(page);

  		copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
  								 base, bytes);
  		if (bytes - copied)
  			memset(kaddr + offset + copied, 0, bytes - copied);

  		kunmap(page);
  	}
  	return copied;
  }
  
  static inline void
  filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
  {
  	const struct iovec *iov = *iovp;
  	size_t base = *basep;

  	do {

  		int copy = min(bytes, iov->iov_len - base);
  
  		bytes -= copy;
  		base += copy;
  		if (iov->iov_len == base) {
  			iov++;
  			base = 0;
  		}

  	} while (bytes);

  	*iovp = iov;
  	*basep = base;
  }
  #endif