NFS: Allow nfs_updatepage to extend a write under additional circumstances

	return PageUptodate(page) != 0;

}

/* If we know the page is up to date, and we're not using byte range locks (or

 * if we have the whole file locked for writing), it may be more efficient to

 * extend the write to cover the entire page in order to avoid fragmentation

 * inefficiencies.

 *

 * If the file is opened for synchronous writes or if we have a write delegation

 * from the server then we can just skip the rest of the checks.

 */

static int nfs_can_extend_write(struct file *file, struct page *page, struct inode *inode)

{

	if (file->f_flags & O_DSYNC)

		return 0;

	if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))

		return 1;

	if (nfs_write_pageuptodate(page, inode) && (inode->i_flock == NULL ||

			(inode->i_flock->fl_start == 0 &&

			inode->i_flock->fl_end == OFFSET_MAX &&

			inode->i_flock->fl_type != F_RDLCK)))

		return 1;

	return 0;

}

/*

 * Update and possibly write a cached page of an NFS file.

 *

		file->f_path.dentry->d_name.name, count,

		(long long)(page_file_offset(page) + offset));

	/* If we're not using byte range locks, and we know the page

	 * is up to date, it may be more efficient to extend the write

	 * to cover the entire page in order to avoid fragmentation

	 * inefficiencies.

	 */

	if (nfs_write_pageuptodate(page, inode) &&

			inode->i_flock == NULL &&

			!(file->f_flags & O_DSYNC)) {

	if (nfs_can_extend_write(file, page, inode)) {

		count = max(count + offset, nfs_page_length(page));

		offset = 0;

	}