/*
 *  linux/fs/9p/vfs_addr.c
 *
 * This file contians vfs address (mmap) ops for 9P2000.
 *
 *  Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com>
 *  Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/inet.h>
#include <linux/pagemap.h>
#include <linux/idr.h>
#include <linux/sched.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>

#include "v9fs.h"
#include "v9fs_vfs.h"
#include "cache.h"

/**
 * v9fs_vfs_readpage - read an entire page in from 9P
 *
 * @filp: file being read
 * @page: structure to page
 *
 */

static int v9fs_vfs_readpage(struct file *filp, struct page *page)
{
	int retval;
	loff_t offset;
	char *buffer;
	struct inode *inode;

	inode = page->mapping->host;
	P9_DPRINTK(P9_DEBUG_VFS, "\n");

	BUG_ON(!PageLocked(page));

	retval = v9fs_readpage_from_fscache(inode, page);
	if (retval == 0)
		return retval;

	buffer = kmap(page);
	offset = page_offset(page);

	retval = v9fs_file_readn(filp, buffer, NULL, PAGE_CACHE_SIZE, offset);
	if (retval < 0) {
		v9fs_uncache_page(inode, page);
		goto done;
	}

	memset(buffer + retval, 0, PAGE_CACHE_SIZE - retval);
	flush_dcache_page(page);
	SetPageUptodate(page);

	v9fs_readpage_to_fscache(inode, page);
	retval = 0;

done:
	kunmap(page);
	unlock_page(page);
	return retval;
}

/**
 * v9fs_vfs_readpages - read a set of pages from 9P
 *
 * @filp: file being read
 * @mapping: the address space
 * @pages: list of pages to read
 * @nr_pages: count of pages to read
 *
 */

static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
			     struct list_head *pages, unsigned nr_pages)
{
	int ret = 0;
	struct inode *inode;

	inode = mapping->host;
	P9_DPRINTK(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);

	ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
	if (ret == 0)
		return ret;

	ret = read_cache_pages(mapping, pages, (void *)v9fs_vfs_readpage, filp);
	P9_DPRINTK(P9_DEBUG_VFS, "  = %d\n", ret);
	return ret;
}

/**
 * v9fs_release_page - release the private state associated with a page
 *
 * Returns 1 if the page can be released, false otherwise.
 */

static int v9fs_release_page(struct page *page, gfp_t gfp)
{
	if (PagePrivate(page))
		return 0;

	return v9fs_fscache_release_page(page, gfp);
}

/**
 * v9fs_invalidate_page - Invalidate a page completely or partially
 *
 * @page: structure to page
 * @offset: offset in the page
 */

static void v9fs_invalidate_page(struct page *page, unsigned long offset)
{
	if (offset == 0)
		v9fs_fscache_invalidate_page(page);
}

/**
 * v9fs_launder_page - Writeback a dirty page
 * Since the writes go directly to the server, we simply return a 0
 * here to indicate success.
 *
 * Returns 0 on success.
 */

static int v9fs_launder_page(struct page *page)
{
	return 0;
}

/**
 * v9fs_direct_IO - 9P address space operation for direct I/O
 * @rw: direction (read or write)
 * @iocb: target I/O control block
 * @iov: array of vectors that define I/O buffer
 * @pos: offset in file to begin the operation
 * @nr_segs: size of iovec array
 *
 * The presence of v9fs_direct_IO() in the address space ops vector
 * allowes open() O_DIRECT flags which would have failed otherwise.
 *
 * In the non-cached mode, we shunt off direct read and write requests before
 * the VFS gets them, so this method should never be called.
 *
 * Direct IO is not 'yet' supported in the cached mode. Hence when
 * this routine is called through generic_file_aio_read(), the read/write fails
 * with an error.
 *
 */
ssize_t v9fs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
		loff_t pos, unsigned long nr_segs)
{
	P9_DPRINTK(P9_DEBUG_VFS, "v9fs_direct_IO: v9fs_direct_IO (%s) "
			"off/no(%lld/%lu) EINVAL\n",
			iocb->ki_filp->f_path.dentry->d_name.name,
			(long long) pos, nr_segs);

	return -EINVAL;
}
const struct address_space_operations v9fs_addr_operations = {
      .readpage = v9fs_vfs_readpage,
      .readpages = v9fs_vfs_readpages,
      .releasepage = v9fs_release_page,
      .invalidatepage = v9fs_invalidate_page,
      .launder_page = v9fs_launder_page,
      .direct_IO = v9fs_direct_IO,
};