/*
   * mdt.c - meta data file for NILFS
   *
   * 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 Ryusuke Konishi <ryusuke@osrg.net>
   */
  
  #include <linux/buffer_head.h>
  #include <linux/mpage.h>
  #include <linux/mm.h>
  #include <linux/writeback.h>
  #include <linux/backing-dev.h>
  #include <linux/swap.h>

  #include <linux/slab.h>

  #include "nilfs.h"

  #include "btnode.h"

  #include "segment.h"
  #include "page.h"
  #include "mdt.h"
  
  
  #define NILFS_MDT_MAX_RA_BLOCKS		(16 - 1)

  
  static int
  nilfs_mdt_insert_new_block(struct inode *inode, unsigned long block,
  			   struct buffer_head *bh,
  			   void (*init_block)(struct inode *,
  					      struct buffer_head *, void *))
  {
  	struct nilfs_inode_info *ii = NILFS_I(inode);
  	void *kaddr;
  	int ret;
  
  	/* Caller exclude read accesses using page lock */
  
  	/* set_buffer_new(bh); */
  	bh->b_blocknr = 0;
  
  	ret = nilfs_bmap_insert(ii->i_bmap, block, (unsigned long)bh);
  	if (unlikely(ret))
  		return ret;
  
  	set_buffer_mapped(bh);
  
  	kaddr = kmap_atomic(bh->b_page, KM_USER0);
  	memset(kaddr + bh_offset(bh), 0, 1 << inode->i_blkbits);
  	if (init_block)
  		init_block(inode, bh, kaddr);
  	flush_dcache_page(bh->b_page);
  	kunmap_atomic(kaddr, KM_USER0);
  
  	set_buffer_uptodate(bh);

  	mark_buffer_dirty(bh);

  	nilfs_mdt_mark_dirty(inode);
  	return 0;
  }
  
  static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
  				  struct buffer_head **out_bh,
  				  void (*init_block)(struct inode *,
  						     struct buffer_head *,
  						     void *))
  {

  	struct super_block *sb = inode->i_sb;
  	struct nilfs_transaction_info ti;
  	struct buffer_head *bh;
  	int err;

  	nilfs_transaction_begin(sb, &ti, 0);
  
  	err = -ENOMEM;
  	bh = nilfs_grab_buffer(inode, inode->i_mapping, block, 0);
  	if (unlikely(!bh))
  		goto failed_unlock;
  
  	err = -EEXIST;

  	if (buffer_uptodate(bh))

  		goto failed_bh;

  	wait_on_buffer(bh);
  	if (buffer_uptodate(bh))
  		goto failed_bh;

  	bh->b_bdev = sb->s_bdev;

  	err = nilfs_mdt_insert_new_block(inode, block, bh, init_block);
  	if (likely(!err)) {
  		get_bh(bh);
  		*out_bh = bh;
  	}
  
   failed_bh:
  	unlock_page(bh->b_page);
  	page_cache_release(bh->b_page);
  	brelse(bh);
  
   failed_unlock:

  	if (likely(!err))
  		err = nilfs_transaction_commit(sb);
  	else
  		nilfs_transaction_abort(sb);

  	return err;
  }
  
  static int
  nilfs_mdt_submit_block(struct inode *inode, unsigned long blkoff,
  		       int mode, struct buffer_head **out_bh)
  {
  	struct buffer_head *bh;

  	__u64 blknum = 0;

  	int ret = -ENOMEM;
  
  	bh = nilfs_grab_buffer(inode, inode->i_mapping, blkoff, 0);
  	if (unlikely(!bh))
  		goto failed;
  
  	ret = -EEXIST; /* internal code */
  	if (buffer_uptodate(bh))
  		goto out;
  
  	if (mode == READA) {
  		if (!trylock_buffer(bh)) {
  			ret = -EBUSY;
  			goto failed_bh;
  		}

  	} else /* mode == READ */

  		lock_buffer(bh);

  
  	if (buffer_uptodate(bh)) {
  		unlock_buffer(bh);
  		goto out;
  	}

  
  	ret = nilfs_bmap_lookup(NILFS_I(inode)->i_bmap, blkoff, &blknum);
  	if (unlikely(ret)) {
  		unlock_buffer(bh);
  		goto failed_bh;

  	}

  	map_bh(bh, inode->i_sb, (sector_t)blknum);

  
  	bh->b_end_io = end_buffer_read_sync;
  	get_bh(bh);
  	submit_bh(mode, bh);
  	ret = 0;
   out:
  	get_bh(bh);
  	*out_bh = bh;
  
   failed_bh:
  	unlock_page(bh->b_page);
  	page_cache_release(bh->b_page);
  	brelse(bh);
   failed:
  	return ret;
  }
  
  static int nilfs_mdt_read_block(struct inode *inode, unsigned long block,

  				int readahead, struct buffer_head **out_bh)

  {
  	struct buffer_head *first_bh, *bh;
  	unsigned long blkoff;
  	int i, nr_ra_blocks = NILFS_MDT_MAX_RA_BLOCKS;
  	int err;
  
  	err = nilfs_mdt_submit_block(inode, block, READ, &first_bh);
  	if (err == -EEXIST) /* internal code */
  		goto out;
  
  	if (unlikely(err))
  		goto failed;

  	if (readahead) {
  		blkoff = block + 1;
  		for (i = 0; i < nr_ra_blocks; i++, blkoff++) {
  			err = nilfs_mdt_submit_block(inode, blkoff, READA, &bh);
  			if (likely(!err || err == -EEXIST))
  				brelse(bh);
  			else if (err != -EBUSY)
  				break;
  				/* abort readahead if bmap lookup failed */
  			if (!buffer_locked(first_bh))
  				goto out_no_wait;
  		}

  	}
  
  	wait_on_buffer(first_bh);
  
   out_no_wait:
  	err = -EIO;
  	if (!buffer_uptodate(first_bh))
  		goto failed_bh;
   out:
  	*out_bh = first_bh;
  	return 0;
  
   failed_bh:
  	brelse(first_bh);
   failed:
  	return err;
  }
  
  /**
   * nilfs_mdt_get_block - read or create a buffer on meta data file.
   * @inode: inode of the meta data file
   * @blkoff: block offset
   * @create: create flag
   * @init_block: initializer used for newly allocated block
   * @out_bh: output of a pointer to the buffer_head
   *
   * nilfs_mdt_get_block() looks up the specified buffer and tries to create
   * a new buffer if @create is not zero.  On success, the returned buffer is
   * assured to be either existing or formatted using a buffer lock on success.
   * @out_bh is substituted only when zero is returned.
   *
   * Return Value: On success, it returns 0. On error, the following negative
   * error code is returned.
   *
   * %-ENOMEM - Insufficient memory available.
   *
   * %-EIO - I/O error
   *
   * %-ENOENT - the specified block does not exist (hole block)
   *

   * %-EROFS - Read only filesystem (for create mode)
   */
  int nilfs_mdt_get_block(struct inode *inode, unsigned long blkoff, int create,
  			void (*init_block)(struct inode *,
  					   struct buffer_head *, void *),
  			struct buffer_head **out_bh)
  {
  	int ret;
  
  	/* Should be rewritten with merging nilfs_mdt_read_block() */
   retry:

  	ret = nilfs_mdt_read_block(inode, blkoff, !create, out_bh);

  	if (!create || ret != -ENOENT)
  		return ret;
  
  	ret = nilfs_mdt_create_block(inode, blkoff, out_bh, init_block);
  	if (unlikely(ret == -EEXIST)) {
  		/* create = 0; */  /* limit read-create loop retries */
  		goto retry;
  	}
  	return ret;
  }
  
  /**
   * nilfs_mdt_delete_block - make a hole on the meta data file.
   * @inode: inode of the meta data file
   * @block: block offset
   *
   * Return Value: On success, zero is returned.
   * On error, one of the following negative error code is returned.
   *
   * %-ENOMEM - Insufficient memory available.
   *
   * %-EIO - I/O error

   */
  int nilfs_mdt_delete_block(struct inode *inode, unsigned long block)
  {
  	struct nilfs_inode_info *ii = NILFS_I(inode);
  	int err;
  
  	err = nilfs_bmap_delete(ii->i_bmap, block);

  	if (!err || err == -ENOENT) {

  		nilfs_mdt_mark_dirty(inode);
  		nilfs_mdt_forget_block(inode, block);
  	}
  	return err;
  }
  
  /**
   * nilfs_mdt_forget_block - discard dirty state and try to remove the page
   * @inode: inode of the meta data file
   * @block: block offset
   *
   * nilfs_mdt_forget_block() clears a dirty flag of the specified buffer, and
   * tries to release the page including the buffer from a page cache.
   *
   * Return Value: On success, 0 is returned. On error, one of the following
   * negative error code is returned.
   *
   * %-EBUSY - page has an active buffer.
   *
   * %-ENOENT - page cache has no page addressed by the offset.
   */
  int nilfs_mdt_forget_block(struct inode *inode, unsigned long block)
  {
  	pgoff_t index = (pgoff_t)block >>
  		(PAGE_CACHE_SHIFT - inode->i_blkbits);
  	struct page *page;
  	unsigned long first_block;
  	int ret = 0;
  	int still_dirty;
  
  	page = find_lock_page(inode->i_mapping, index);
  	if (!page)
  		return -ENOENT;
  
  	wait_on_page_writeback(page);
  
  	first_block = (unsigned long)index <<
  		(PAGE_CACHE_SHIFT - inode->i_blkbits);
  	if (page_has_buffers(page)) {
  		struct buffer_head *bh;
  
  		bh = nilfs_page_get_nth_block(page, block - first_block);
  		nilfs_forget_buffer(bh);
  	}
  	still_dirty = PageDirty(page);
  	unlock_page(page);
  	page_cache_release(page);
  
  	if (still_dirty ||
  	    invalidate_inode_pages2_range(inode->i_mapping, index, index) != 0)
  		ret = -EBUSY;
  	return ret;
  }
  
  /**
   * nilfs_mdt_mark_block_dirty - mark a block on the meta data file dirty.
   * @inode: inode of the meta data file
   * @block: block offset
   *
   * Return Value: On success, it returns 0. On error, the following negative
   * error code is returned.
   *
   * %-ENOMEM - Insufficient memory available.
   *
   * %-EIO - I/O error
   *
   * %-ENOENT - the specified block does not exist (hole block)

   */
  int nilfs_mdt_mark_block_dirty(struct inode *inode, unsigned long block)
  {
  	struct buffer_head *bh;
  	int err;

  	err = nilfs_mdt_read_block(inode, block, 0, &bh);

  	if (unlikely(err))
  		return err;

  	mark_buffer_dirty(bh);

  	nilfs_mdt_mark_dirty(inode);
  	brelse(bh);
  	return 0;
  }
  
  int nilfs_mdt_fetch_dirty(struct inode *inode)
  {
  	struct nilfs_inode_info *ii = NILFS_I(inode);
  
  	if (nilfs_bmap_test_and_clear_dirty(ii->i_bmap)) {
  		set_bit(NILFS_I_DIRTY, &ii->i_state);
  		return 1;
  	}
  	return test_bit(NILFS_I_DIRTY, &ii->i_state);
  }
  
  static int
  nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
  {

  	struct inode *inode;
  	struct super_block *sb;

  	int err = 0;
  
  	redirty_page_for_writepage(wbc, page);
  	unlock_page(page);

  	inode = page->mapping->host;
  	if (!inode)
  		return 0;
  
  	sb = inode->i_sb;

  
  	if (wbc->sync_mode == WB_SYNC_ALL)
  		err = nilfs_construct_segment(sb);
  	else if (wbc->for_reclaim)
  		nilfs_flush_segment(sb, inode->i_ino);

  	return err;
  }

  static const struct address_space_operations def_mdt_aops = {

  	.writepage		= nilfs_mdt_write_page,
  };

  static const struct inode_operations def_mdt_iops;

  static const struct file_operations def_mdt_fops;

  int nilfs_mdt_init(struct inode *inode, gfp_t gfp_mask, size_t objsz)

  {
  	struct nilfs_mdt_info *mi;
  
  	mi = kzalloc(max(sizeof(*mi), objsz), GFP_NOFS);
  	if (!mi)
  		return -ENOMEM;

  	init_rwsem(&mi->mi_sem);
  	inode->i_private = mi;
  
  	inode->i_mode = S_IFREG;
  	mapping_set_gfp_mask(inode->i_mapping, gfp_mask);

  	inode->i_mapping->backing_dev_info = inode->i_sb->s_bdi;
  
  	inode->i_op = &def_mdt_iops;
  	inode->i_fop = &def_mdt_fops;
  	inode->i_mapping->a_ops = &def_mdt_aops;

  
  	return 0;
  }

  void nilfs_mdt_set_entry_size(struct inode *inode, unsigned entry_size,
  			      unsigned header_size)
  {
  	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
  
  	mi->mi_entry_size = entry_size;
  	mi->mi_entries_per_block = (1 << inode->i_blkbits) / entry_size;
  	mi->mi_first_entry_offset = DIV_ROUND_UP(header_size, entry_size);
  }

  /**
   * nilfs_mdt_setup_shadow_map - setup shadow map and bind it to metadata file
   * @inode: inode of the metadata file
   * @shadow: shadow mapping
   */
  int nilfs_mdt_setup_shadow_map(struct inode *inode,
  			       struct nilfs_shadow_map *shadow)
  {
  	struct nilfs_mdt_info *mi = NILFS_MDT(inode);

  	struct backing_dev_info *bdi = inode->i_sb->s_bdi;

  
  	INIT_LIST_HEAD(&shadow->frozen_buffers);

  	address_space_init_once(&shadow->frozen_data);

  	nilfs_mapping_init(&shadow->frozen_data, inode, bdi);

  	address_space_init_once(&shadow->frozen_btnodes);

  	nilfs_mapping_init(&shadow->frozen_btnodes, inode, bdi);

  	mi->mi_shadow = shadow;
  	return 0;
  }
  
  /**
   * nilfs_mdt_save_to_shadow_map - copy bmap and dirty pages to shadow map
   * @inode: inode of the metadata file
   */
  int nilfs_mdt_save_to_shadow_map(struct inode *inode)
  {
  	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
  	struct nilfs_inode_info *ii = NILFS_I(inode);
  	struct nilfs_shadow_map *shadow = mi->mi_shadow;
  	int ret;
  
  	ret = nilfs_copy_dirty_pages(&shadow->frozen_data, inode->i_mapping);
  	if (ret)
  		goto out;
  
  	ret = nilfs_copy_dirty_pages(&shadow->frozen_btnodes,
  				     &ii->i_btnode_cache);
  	if (ret)
  		goto out;
  
  	nilfs_bmap_save(ii->i_bmap, &shadow->bmap_store);
   out:
  	return ret;
  }

  int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh)
  {
  	struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
  	struct buffer_head *bh_frozen;
  	struct page *page;
  	int blkbits = inode->i_blkbits;

  
  	page = grab_cache_page(&shadow->frozen_data, bh->b_page->index);
  	if (!page)

  		return -ENOMEM;

  
  	if (!page_has_buffers(page))
  		create_empty_buffers(page, 1 << blkbits, 0);
  
  	bh_frozen = nilfs_page_get_nth_block(page, bh_offset(bh) >> blkbits);

  
  	if (!buffer_uptodate(bh_frozen))
  		nilfs_copy_buffer(bh_frozen, bh);
  	if (list_empty(&bh_frozen->b_assoc_buffers)) {
  		list_add_tail(&bh_frozen->b_assoc_buffers,
  			      &shadow->frozen_buffers);
  		set_buffer_nilfs_redirected(bh);
  	} else {
  		brelse(bh_frozen); /* already frozen */

  	}

  	unlock_page(page);
  	page_cache_release(page);

  	return 0;

  }
  
  struct buffer_head *
  nilfs_mdt_get_frozen_buffer(struct inode *inode, struct buffer_head *bh)
  {
  	struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
  	struct buffer_head *bh_frozen = NULL;
  	struct page *page;
  	int n;
  
  	page = find_lock_page(&shadow->frozen_data, bh->b_page->index);
  	if (page) {
  		if (page_has_buffers(page)) {
  			n = bh_offset(bh) >> inode->i_blkbits;
  			bh_frozen = nilfs_page_get_nth_block(page, n);
  		}
  		unlock_page(page);
  		page_cache_release(page);
  	}
  	return bh_frozen;
  }
  
  static void nilfs_release_frozen_buffers(struct nilfs_shadow_map *shadow)
  {
  	struct list_head *head = &shadow->frozen_buffers;
  	struct buffer_head *bh;
  
  	while (!list_empty(head)) {
  		bh = list_first_entry(head, struct buffer_head,
  				      b_assoc_buffers);
  		list_del_init(&bh->b_assoc_buffers);
  		brelse(bh); /* drop ref-count to make it releasable */
  	}
  }

  /**
   * nilfs_mdt_restore_from_shadow_map - restore dirty pages and bmap state
   * @inode: inode of the metadata file
   */
  void nilfs_mdt_restore_from_shadow_map(struct inode *inode)
  {
  	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
  	struct nilfs_inode_info *ii = NILFS_I(inode);
  	struct nilfs_shadow_map *shadow = mi->mi_shadow;
  
  	down_write(&mi->mi_sem);
  
  	if (mi->mi_palloc_cache)
  		nilfs_palloc_clear_cache(inode);
  
  	nilfs_clear_dirty_pages(inode->i_mapping);
  	nilfs_copy_back_pages(inode->i_mapping, &shadow->frozen_data);
  
  	nilfs_clear_dirty_pages(&ii->i_btnode_cache);
  	nilfs_copy_back_pages(&ii->i_btnode_cache, &shadow->frozen_btnodes);
  
  	nilfs_bmap_restore(ii->i_bmap, &shadow->bmap_store);
  
  	up_write(&mi->mi_sem);
  }
  
  /**
   * nilfs_mdt_clear_shadow_map - truncate pages in shadow map caches
   * @inode: inode of the metadata file
   */
  void nilfs_mdt_clear_shadow_map(struct inode *inode)
  {
  	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
  	struct nilfs_shadow_map *shadow = mi->mi_shadow;
  
  	down_write(&mi->mi_sem);

  	nilfs_release_frozen_buffers(shadow);

  	truncate_inode_pages(&shadow->frozen_data, 0);
  	truncate_inode_pages(&shadow->frozen_btnodes, 0);
  	up_write(&mi->mi_sem);
  }