/*
   * gcinode.c - dummy inodes to buffer blocks for garbage collection
   *
   * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
   *
   * 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   *
   * Written by Seiji Kihara <kihara@osrg.net>, Amagai Yoshiji <amagai@osrg.net>,
   *            and Ryusuke Konishi <ryusuke@osrg.net>.
   * Revised by Ryusuke Konishi <ryusuke@osrg.net>.
   *
   */
  /*
   * This file adds the cache of on-disk blocks to be moved in garbage
   * collection.  The disk blocks are held with dummy inodes (called
   * gcinodes), and this file provides lookup function of the dummy
   * inodes and their buffer read function.
   *
   * Buffers and pages held by the dummy inodes will be released each
   * time after they are copied to a new log.  Dirty blocks made on the
   * current generation and the blocks to be moved by GC never overlap
   * because the dirty blocks make a new generation; they rather must be
   * written individually.
   */
  
  #include <linux/buffer_head.h>
  #include <linux/mpage.h>
  #include <linux/hash.h>
  #include <linux/slab.h>
  #include <linux/swap.h>
  #include "nilfs.h"
  #include "btree.h"
  #include "btnode.h"
  #include "page.h"
  #include "mdt.h"
  #include "dat.h"
  #include "ifile.h"
  
  /*
   * nilfs_gccache_submit_read_data() - add data buffer and submit read request
   * @inode - gc inode
   * @blkoff - dummy offset treated as the key for the page cache
   * @pbn - physical block number of the block
   * @vbn - virtual block number of the block, 0 for non-virtual block
   * @out_bh - indirect pointer to a buffer_head struct to receive the results
   *
   * Description: nilfs_gccache_submit_read_data() registers the data buffer
   * specified by @pbn to the GC pagecache with the key @blkoff.
   * This function sets @vbn (@pbn if @vbn is zero) in b_blocknr of the buffer.
   *
   * Return Value: On success, 0 is returned. On Error, one of the following
   * negative error code is returned.
   *
   * %-EIO - I/O error.
   *
   * %-ENOMEM - Insufficient amount of memory available.
   *
   * %-ENOENT - The block specified with @pbn does not exist.
   */
  int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
  				   sector_t pbn, __u64 vbn,
  				   struct buffer_head **out_bh)
  {
  	struct buffer_head *bh;
  	int err;
  
  	bh = nilfs_grab_buffer(inode, inode->i_mapping, blkoff, 0);
  	if (unlikely(!bh))
  		return -ENOMEM;
  
  	if (buffer_uptodate(bh))
  		goto out;
  
  	if (pbn == 0) {
  		struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
  
  		err = nilfs_dat_translate(nilfs->ns_dat, vbn, &pbn);
  		if (unlikely(err)) { /* -EIO, -ENOMEM, -ENOENT */
  			brelse(bh);
  			goto failed;
  		}
  	}
  
  	lock_buffer(bh);
  	if (buffer_uptodate(bh)) {
  		unlock_buffer(bh);
  		goto out;
  	}
  
  	if (!buffer_mapped(bh)) {
  		bh->b_bdev = inode->i_sb->s_bdev;
  		set_buffer_mapped(bh);
  	}
  	bh->b_blocknr = pbn;
  	bh->b_end_io = end_buffer_read_sync;
  	get_bh(bh);
  	submit_bh(READ, bh);
  	if (vbn)
  		bh->b_blocknr = vbn;
   out:
  	err = 0;
  	*out_bh = bh;
  
   failed:
  	unlock_page(bh->b_page);
  	page_cache_release(bh->b_page);
  	return err;
  }
  
  /*
   * nilfs_gccache_submit_read_node() - add node buffer and submit read request
   * @inode - gc inode
   * @pbn - physical block number for the block
   * @vbn - virtual block number for the block
   * @out_bh - indirect pointer to a buffer_head struct to receive the results
   *
   * Description: nilfs_gccache_submit_read_node() registers the node buffer
   * specified by @vbn to the GC pagecache.  @pbn can be supplied by the
   * caller to avoid translation of the disk block address.
   *
   * Return Value: On success, 0 is returned. On Error, one of the following
   * negative error code is returned.
   *
   * %-EIO - I/O error.
   *
   * %-ENOMEM - Insufficient amount of memory available.
   */
  int nilfs_gccache_submit_read_node(struct inode *inode, sector_t pbn,
  				   __u64 vbn, struct buffer_head **out_bh)
  {
  	int ret;
  
  	ret = nilfs_btnode_submit_block(&NILFS_I(inode)->i_btnode_cache,
  					vbn ? : pbn, pbn, READ, out_bh, &pbn);
  	if (ret == -EEXIST) /* internal code (cache hit) */
  		ret = 0;
  	return ret;
  }
  
  int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *bh)
  {
  	wait_on_buffer(bh);
  	if (!buffer_uptodate(bh))
  		return -EIO;
  	if (buffer_dirty(bh))
  		return -EEXIST;
  
  	if (buffer_nilfs_node(bh) && nilfs_btree_broken_node_block(bh)) {
  		clear_buffer_uptodate(bh);
  		return -EIO;
  	}
  	mark_buffer_dirty(bh);
  	return 0;
  }
  
  int nilfs_init_gcinode(struct inode *inode)
  {
  	struct nilfs_inode_info *ii = NILFS_I(inode);
  
  	inode->i_mode = S_IFREG;
  	mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
  	inode->i_mapping->a_ops = &empty_aops;
  	inode->i_mapping->backing_dev_info = inode->i_sb->s_bdi;
  
  	ii->i_flags = 0;
  	nilfs_bmap_init_gc(ii->i_bmap);
  
  	return 0;
  }
  
  /**
   * nilfs_remove_all_gcinodes() - remove all unprocessed gc inodes
   */
  void nilfs_remove_all_gcinodes(struct the_nilfs *nilfs)
  {
  	struct list_head *head = &nilfs->ns_gc_inodes;
  	struct nilfs_inode_info *ii;
  
  	while (!list_empty(head)) {
  		ii = list_first_entry(head, struct nilfs_inode_info, i_dirty);
  		list_del_init(&ii->i_dirty);
  		truncate_inode_pages(&ii->vfs_inode.i_data, 0);
  		nilfs_btnode_cache_clear(&ii->i_btnode_cache);
  		iput(&ii->vfs_inode);
  	}
  }