/* -*- 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_area_struct *area, struct vm_fault *vmf)
{
        sigset_t oldset;
        int ret;

        ocfs2_block_signals(&oldset);
        ret = filemap_fault(area, vmf);
        ocfs2_unblock_signals(&oldset);

        trace_ocfs2_fault(OCFS2_I(area->vm_file->f_mapping->host)->ip_blkno,
                          area, 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_CACHE_SIZE;
        pgoff_t last_index;
        struct page *locked_page = NULL;
        void *fsdata;
        loff_t size = i_size_read(inode);

        last_index = (size - 1) >> PAGE_CACHE_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_CACHE_MASK) + 1;

        ret = ocfs2_write_begin_nolock(file, mapping, pos, len, 0, &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, locked_page,
                                     fsdata);
        BUG_ON(ret != len);
        ret = VM_FAULT_LOCKED;
out:
        return ret;
}

static int ocfs2_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct page *page = vmf->page;
        struct inode *inode = file_inode(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);
                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(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,
        .remap_pages    = generic_file_remap_pages,
};

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;
}