/* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * mmap.c
   *
   * Code to deal with the mess that is clustered mmap.
   *
   * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * 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 the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */
  
  #include <linux/fs.h>
  #include <linux/types.h>

  #include <linux/highmem.h>
  #include <linux/pagemap.h>
  #include <linux/uio.h>
  #include <linux/signal.h>
  #include <linux/rbtree.h>

  #include <cluster/masklog.h>
  
  #include "ocfs2.h"

  #include "aops.h"

  #include "dlmglue.h"
  #include "file.h"
  #include "inode.h"
  #include "mmap.h"

  #include "super.h"

  #include "ocfs2_trace.h"

  static int ocfs2_fault(struct vm_fault *vmf)

  {

  	struct vm_area_struct *vma = vmf->vma;

  	sigset_t oldset;
  	int ret;

  	ocfs2_block_signals(&oldset);

  	ret = filemap_fault(vmf);

  	ocfs2_unblock_signals(&oldset);

  	trace_ocfs2_fault(OCFS2_I(vma->vm_file->f_mapping->host)->ip_blkno,
  			  vma, vmf->page, vmf->pgoff);

  	return ret;

  }

  static int __ocfs2_page_mkwrite(struct file *file, struct buffer_head *di_bh,

  				struct page *page)
  {

  	int ret = VM_FAULT_NOPAGE;

  	struct inode *inode = file_inode(file);

  	struct address_space *mapping = inode->i_mapping;

  	loff_t pos = page_offset(page);

  	unsigned int len = PAGE_SIZE;

  	pgoff_t last_index;
  	struct page *locked_page = NULL;
  	void *fsdata;
  	loff_t size = i_size_read(inode);

  	last_index = (size - 1) >> PAGE_SHIFT;

  
  	/*

  	 * There are cases that lead to the page no longer bebongs to the
  	 * mapping.
  	 * 1) pagecache truncates locally due to memory pressure.
  	 * 2) pagecache truncates when another is taking EX lock against 
  	 * inode lock. see ocfs2_data_convert_worker.
  	 * 
  	 * The i_size check doesn't catch the case where nodes truncated and
  	 * then re-extended the file. We'll re-check the page mapping after
  	 * taking the page lock inside of ocfs2_write_begin_nolock().
  	 *
  	 * Let VM retry with these cases.

  	 */

  	if ((page->mapping != inode->i_mapping) ||
  	    (!PageUptodate(page)) ||
  	    (page_offset(page) >= size))

  		goto out;

  
  	/*
  	 * Call ocfs2_write_begin() and ocfs2_write_end() to take
  	 * advantage of the allocation code there. We pass a write
  	 * length of the whole page (chopped to i_size) to make sure
  	 * the whole thing is allocated.
  	 *
  	 * Since we know the page is up to date, we don't have to
  	 * worry about ocfs2_write_begin() skipping some buffer reads
  	 * because the "write" would invalidate their data.
  	 */
  	if (page->index == last_index)

  		len = ((size - 1) & ~PAGE_MASK) + 1;

  	ret = ocfs2_write_begin_nolock(mapping, pos, len, OCFS2_WRITE_MMAP,
  				       &locked_page, &fsdata, di_bh, page);

  	if (ret) {
  		if (ret != -ENOSPC)
  			mlog_errno(ret);

  		if (ret == -ENOMEM)
  			ret = VM_FAULT_OOM;
  		else
  			ret = VM_FAULT_SIGBUS;

  		goto out;
  	}

  	if (!locked_page) {
  		ret = VM_FAULT_NOPAGE;

  		goto out;
  	}

  	ret = ocfs2_write_end_nolock(mapping, pos, len, len, fsdata);

  	BUG_ON(ret != len);

  	ret = VM_FAULT_LOCKED;

  out:
  	return ret;
  }

  static int ocfs2_page_mkwrite(struct vm_fault *vmf)

  {

  	struct page *page = vmf->page;

  	struct inode *inode = file_inode(vmf->vma->vm_file);

  	struct buffer_head *di_bh = NULL;

  	sigset_t oldset;
  	int ret;

  	sb_start_pagefault(inode->i_sb);

  	ocfs2_block_signals(&oldset);

  
  	/*
  	 * The cluster locks taken will block a truncate from another
  	 * node. Taking the data lock will also ensure that we don't
  	 * attempt page truncation as part of a downconvert.
  	 */

  	ret = ocfs2_inode_lock(inode, &di_bh, 1);

  	if (ret < 0) {
  		mlog_errno(ret);

  		if (ret == -ENOMEM)
  			ret = VM_FAULT_OOM;
  		else
  			ret = VM_FAULT_SIGBUS;

  		goto out;
  	}

  	/*

  	 * The alloc sem should be enough to serialize with
  	 * ocfs2_truncate_file() changing i_size as well as any thread
  	 * modifying the inode btree.

  	 */

  	down_write(&OCFS2_I(inode)->ip_alloc_sem);

  	ret = __ocfs2_page_mkwrite(vmf->vma->vm_file, di_bh, page);

  	up_write(&OCFS2_I(inode)->ip_alloc_sem);
  
  	brelse(di_bh);

  	ocfs2_inode_unlock(inode, 1);

  
  out:

  	ocfs2_unblock_signals(&oldset);

  	sb_end_pagefault(inode->i_sb);

  	return ret;
  }

  static const struct vm_operations_struct ocfs2_file_vm_ops = {

  	.fault		= ocfs2_fault,

  	.page_mkwrite	= ocfs2_page_mkwrite,
  };
  
  int ocfs2_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	int ret = 0, lock_level = 0;

  	ret = ocfs2_inode_lock_atime(file_inode(file),

  				    file->f_path.mnt, &lock_level);

  	if (ret < 0) {
  		mlog_errno(ret);
  		goto out;
  	}

  	ocfs2_inode_unlock(file_inode(file), lock_level);

  out:

  	vma->vm_ops = &ocfs2_file_vm_ops;
  	return 0;
  }