/*
   * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.

   * Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.

   *
   * This copyrighted material is made available to anyone wishing to use,
   * modify, copy, or redistribute it subject to the terms and conditions

   * of the GNU General Public License version 2.

   */
  
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/completion.h>
  #include <linux/buffer_head.h>
  #include <linux/pagemap.h>

  #include <linux/pagevec.h>

  #include <linux/mpage.h>

  #include <linux/fs.h>

  #include <linux/writeback.h>

  #include <linux/swap.h>

  #include <linux/gfs2_ondisk.h>

  #include <linux/backing-dev.h>

  
  #include "gfs2.h"

  #include "incore.h"

  #include "bmap.h"
  #include "glock.h"
  #include "inode.h"

  #include "log.h"
  #include "meta_io.h"

  #include "quota.h"
  #include "trans.h"

  #include "rgrp.h"

  #include "super.h"

  #include "util.h"

  #include "glops.h"

  void gfs2_page_add_databufs(struct gfs2_inode *ip, struct page *page,
  			    unsigned int from, unsigned int to)

  {
  	struct buffer_head *head = page_buffers(page);
  	unsigned int bsize = head->b_size;
  	struct buffer_head *bh;
  	unsigned int start, end;
  
  	for (bh = head, start = 0; bh != head || !start;
  	     bh = bh->b_this_page, start = end) {
  		end = start + bsize;
  		if (end <= from || start >= to)
  			continue;

  		if (gfs2_is_jdata(ip))
  			set_buffer_uptodate(bh);

  		gfs2_trans_add_bh(ip->i_gl, bh, 0);
  	}
  }

  /**

   * gfs2_get_block_noalloc - Fills in a buffer head with details about a block

   * @inode: The inode
   * @lblock: The block number to look up
   * @bh_result: The buffer head to return the result in
   * @create: Non-zero if we may add block to the file
   *
   * Returns: errno
   */

  static int gfs2_get_block_noalloc(struct inode *inode, sector_t lblock,
  				  struct buffer_head *bh_result, int create)

  {

  	int error;

  	error = gfs2_block_map(inode, lblock, bh_result, 0);

  	if (error)
  		return error;

  	if (!buffer_mapped(bh_result))

  		return -EIO;
  	return 0;

  }

  static int gfs2_get_block_direct(struct inode *inode, sector_t lblock,
  				 struct buffer_head *bh_result, int create)

  {

  	return gfs2_block_map(inode, lblock, bh_result, 0);

  }

  /**

   * gfs2_writepage_common - Common bits of writepage
   * @page: The page to be written
   * @wbc: The writeback control

   *

   * Returns: 1 if writepage is ok, otherwise an error code or zero if no error.

   */

  static int gfs2_writepage_common(struct page *page,
  				 struct writeback_control *wbc)

  {

  	struct inode *inode = page->mapping->host;

  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);

  	loff_t i_size = i_size_read(inode);
  	pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
  	unsigned offset;

  	if (gfs2_assert_withdraw(sdp, gfs2_glock_is_held_excl(ip->i_gl)))
  		goto out;

  	if (current->journal_info)

  		goto redirty;

  	/* Is the page fully outside i_size? (truncate in progress) */

  	offset = i_size & (PAGE_CACHE_SIZE-1);

  	if (page->index > end_index || (page->index == end_index && !offset)) {

  		page->mapping->a_ops->invalidatepage(page, 0);

  		goto out;

  	}

  	return 1;
  redirty:
  	redirty_page_for_writepage(wbc, page);
  out:
  	unlock_page(page);
  	return 0;
  }
  
  /**
   * gfs2_writeback_writepage - Write page for writeback mappings
   * @page: The page
   * @wbc: The writeback control
   *
   */
  
  static int gfs2_writeback_writepage(struct page *page,
  				    struct writeback_control *wbc)
  {
  	int ret;
  
  	ret = gfs2_writepage_common(page, wbc);
  	if (ret <= 0)
  		return ret;

  	return nobh_writepage(page, gfs2_get_block_noalloc, wbc);

  }
  
  /**
   * gfs2_ordered_writepage - Write page for ordered data files
   * @page: The page to write
   * @wbc: The writeback control
   *
   */
  
  static int gfs2_ordered_writepage(struct page *page,
  				  struct writeback_control *wbc)
  {
  	struct inode *inode = page->mapping->host;
  	struct gfs2_inode *ip = GFS2_I(inode);
  	int ret;
  
  	ret = gfs2_writepage_common(page, wbc);
  	if (ret <= 0)
  		return ret;
  
  	if (!page_has_buffers(page)) {
  		create_empty_buffers(page, inode->i_sb->s_blocksize,
  				     (1 << BH_Dirty)|(1 << BH_Uptodate));
  	}
  	gfs2_page_add_databufs(ip, page, 0, inode->i_sb->s_blocksize-1);
  	return block_write_full_page(page, gfs2_get_block_noalloc, wbc);
  }
  
  /**

   * __gfs2_jdata_writepage - The core of jdata writepage
   * @page: The page to write
   * @wbc: The writeback control
   *
   * This is shared between writepage and writepages and implements the
   * core of the writepage operation. If a transaction is required then
   * PageChecked will have been set and the transaction will have
   * already been started before this is called.
   */
  
  static int __gfs2_jdata_writepage(struct page *page, struct writeback_control *wbc)
  {
  	struct inode *inode = page->mapping->host;
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  
  	if (PageChecked(page)) {
  		ClearPageChecked(page);
  		if (!page_has_buffers(page)) {
  			create_empty_buffers(page, inode->i_sb->s_blocksize,
  					     (1 << BH_Dirty)|(1 << BH_Uptodate));
  		}
  		gfs2_page_add_databufs(ip, page, 0, sdp->sd_vfs->s_blocksize-1);
  	}
  	return block_write_full_page(page, gfs2_get_block_noalloc, wbc);
  }
  
  /**

   * gfs2_jdata_writepage - Write complete page
   * @page: Page to write
   *
   * Returns: errno
   *
   */
  
  static int gfs2_jdata_writepage(struct page *page, struct writeback_control *wbc)
  {
  	struct inode *inode = page->mapping->host;

  	struct gfs2_sbd *sdp = GFS2_SB(inode);

  	int ret;

  	int done_trans = 0;

  	if (PageChecked(page)) {

  		if (wbc->sync_mode != WB_SYNC_ALL)
  			goto out_ignore;

  		ret = gfs2_trans_begin(sdp, RES_DINODE + 1, 0);
  		if (ret)

  			goto out_ignore;

  		done_trans = 1;
  	}

  	ret = gfs2_writepage_common(page, wbc);
  	if (ret > 0)
  		ret = __gfs2_jdata_writepage(page, wbc);

  	if (done_trans)
  		gfs2_trans_end(sdp);

  	return ret;

  
  out_ignore:
  	redirty_page_for_writepage(wbc, page);
  	unlock_page(page);
  	return 0;

  }
  
  /**

   * gfs2_writeback_writepages - Write a bunch of dirty pages back to disk

   * @mapping: The mapping to write
   * @wbc: Write-back control
   *

   * For the data=writeback case we can already ignore buffer heads

   * and write whole extents at once. This is a big reduction in the
   * number of I/O requests we send and the bmap calls we make in this case.
   */

  static int gfs2_writeback_writepages(struct address_space *mapping,
  				     struct writeback_control *wbc)

  {

  	return mpage_writepages(mapping, wbc, gfs2_get_block_noalloc);

  }
  
  /**

   * gfs2_write_jdata_pagevec - Write back a pagevec's worth of pages
   * @mapping: The mapping
   * @wbc: The writeback control
   * @writepage: The writepage function to call for each page
   * @pvec: The vector of pages
   * @nr_pages: The number of pages to write
   *
   * Returns: non-zero if loop should terminate, zero otherwise
   */
  
  static int gfs2_write_jdata_pagevec(struct address_space *mapping,
  				    struct writeback_control *wbc,
  				    struct pagevec *pvec,
  				    int nr_pages, pgoff_t end)
  {
  	struct inode *inode = mapping->host;
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  	loff_t i_size = i_size_read(inode);
  	pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
  	unsigned offset = i_size & (PAGE_CACHE_SIZE-1);
  	unsigned nrblocks = nr_pages * (PAGE_CACHE_SIZE/inode->i_sb->s_blocksize);

  	int i;
  	int ret;

  	ret = gfs2_trans_begin(sdp, nrblocks, nrblocks);

  	if (ret < 0)
  		return ret;
  
  	for(i = 0; i < nr_pages; i++) {
  		struct page *page = pvec->pages[i];
  
  		lock_page(page);
  
  		if (unlikely(page->mapping != mapping)) {
  			unlock_page(page);
  			continue;
  		}
  
  		if (!wbc->range_cyclic && page->index > end) {
  			ret = 1;
  			unlock_page(page);
  			continue;
  		}
  
  		if (wbc->sync_mode != WB_SYNC_NONE)
  			wait_on_page_writeback(page);
  
  		if (PageWriteback(page) ||
  		    !clear_page_dirty_for_io(page)) {
  			unlock_page(page);
  			continue;
  		}
  
  		/* Is the page fully outside i_size? (truncate in progress) */
  		if (page->index > end_index || (page->index == end_index && !offset)) {
  			page->mapping->a_ops->invalidatepage(page, 0);
  			unlock_page(page);
  			continue;
  		}
  
  		ret = __gfs2_jdata_writepage(page, wbc);
  
  		if (ret || (--(wbc->nr_to_write) <= 0))
  			ret = 1;

  	}
  	gfs2_trans_end(sdp);
  	return ret;
  }
  
  /**
   * gfs2_write_cache_jdata - Like write_cache_pages but different
   * @mapping: The mapping to write
   * @wbc: The writeback control
   * @writepage: The writepage function to call
   * @data: The data to pass to writepage
   *
   * The reason that we use our own function here is that we need to
   * start transactions before we grab page locks. This allows us
   * to get the ordering right.
   */
  
  static int gfs2_write_cache_jdata(struct address_space *mapping,
  				  struct writeback_control *wbc)
  {

  	int ret = 0;
  	int done = 0;
  	struct pagevec pvec;
  	int nr_pages;
  	pgoff_t index;
  	pgoff_t end;
  	int scanned = 0;
  	int range_whole = 0;

  	pagevec_init(&pvec, 0);
  	if (wbc->range_cyclic) {
  		index = mapping->writeback_index; /* Start from prev offset */
  		end = -1;
  	} else {
  		index = wbc->range_start >> PAGE_CACHE_SHIFT;
  		end = wbc->range_end >> PAGE_CACHE_SHIFT;
  		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
  			range_whole = 1;
  		scanned = 1;
  	}
  
  retry:
  	 while (!done && (index <= end) &&
  		(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
  					       PAGECACHE_TAG_DIRTY,
  					       min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
  		scanned = 1;
  		ret = gfs2_write_jdata_pagevec(mapping, wbc, &pvec, nr_pages, end);
  		if (ret)
  			done = 1;
  		if (ret > 0)
  			ret = 0;
  
  		pagevec_release(&pvec);
  		cond_resched();
  	}
  
  	if (!scanned && !done) {
  		/*
  		 * We hit the last page and there is more work to be done: wrap
  		 * back to the start of the file
  		 */
  		scanned = 1;
  		index = 0;
  		goto retry;
  	}
  
  	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
  		mapping->writeback_index = index;
  	return ret;
  }
  
  
  /**
   * gfs2_jdata_writepages - Write a bunch of dirty pages back to disk
   * @mapping: The mapping to write
   * @wbc: The writeback control
   * 
   */
  
  static int gfs2_jdata_writepages(struct address_space *mapping,
  				 struct writeback_control *wbc)
  {
  	struct gfs2_inode *ip = GFS2_I(mapping->host);
  	struct gfs2_sbd *sdp = GFS2_SB(mapping->host);
  	int ret;
  
  	ret = gfs2_write_cache_jdata(mapping, wbc);
  	if (ret == 0 && wbc->sync_mode == WB_SYNC_ALL) {
  		gfs2_log_flush(sdp, ip->i_gl);
  		ret = gfs2_write_cache_jdata(mapping, wbc);
  	}
  	return ret;
  }
  
  /**

   * stuffed_readpage - Fill in a Linux page with stuffed file data
   * @ip: the inode
   * @page: the page
   *
   * Returns: errno
   */
  
  static int stuffed_readpage(struct gfs2_inode *ip, struct page *page)
  {
  	struct buffer_head *dibh;

  	u64 dsize = i_size_read(&ip->i_inode);

  	void *kaddr;
  	int error;

  	/*

  	 * Due to the order of unstuffing files and ->fault(), we can be

  	 * asked for a zero page in the case of a stuffed file being extended,
  	 * so we need to supply one here. It doesn't happen often.
  	 */
  	if (unlikely(page->index)) {

  		zero_user(page, 0, PAGE_CACHE_SIZE);

  		SetPageUptodate(page);

  		return 0;
  	}

  	error = gfs2_meta_inode_buffer(ip, &dibh);
  	if (error)
  		return error;

  	kaddr = kmap_atomic(page, KM_USER0);

  	if (dsize > (dibh->b_size - sizeof(struct gfs2_dinode)))
  		dsize = (dibh->b_size - sizeof(struct gfs2_dinode));
  	memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode), dsize);
  	memset(kaddr + dsize, 0, PAGE_CACHE_SIZE - dsize);

  	kunmap_atomic(kaddr, KM_USER0);

  	flush_dcache_page(page);

  	brelse(dibh);

  	SetPageUptodate(page);
  
  	return 0;
  }

  
  /**

   * __gfs2_readpage - readpage
   * @file: The file to read a page for

   * @page: The page to read
   *

   * This is the core of gfs2's readpage. Its used by the internal file
   * reading code as in that case we already hold the glock. Also its
   * called by gfs2_readpage() once the required lock has been granted.
   *

   */

  static int __gfs2_readpage(void *file, struct page *page)

  {

  	struct gfs2_inode *ip = GFS2_I(page->mapping->host);
  	struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host);

  	int error;

  	if (gfs2_is_stuffed(ip)) {

  		error = stuffed_readpage(ip, page);
  		unlock_page(page);

  	} else {

  		error = mpage_readpage(page, gfs2_block_map);

  	}

  
  	if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))

  		return -EIO;

  	return error;
  }
  
  /**
   * gfs2_readpage - read a page of a file
   * @file: The file to read
   * @page: The page of the file
   *

   * This deals with the locking required. We have to unlock and
   * relock the page in order to get the locking in the right
   * order.

   */
  
  static int gfs2_readpage(struct file *file, struct page *page)
  {

  	struct address_space *mapping = page->mapping;
  	struct gfs2_inode *ip = GFS2_I(mapping->host);

  	struct gfs2_holder gh;

  	int error;

  	unlock_page(page);

  	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
  	error = gfs2_glock_nq(&gh);

  	if (unlikely(error))

  		goto out;

  	error = AOP_TRUNCATED_PAGE;
  	lock_page(page);
  	if (page->mapping == mapping && !PageUptodate(page))
  		error = __gfs2_readpage(file, page);
  	else
  		unlock_page(page);

  	gfs2_glock_dq(&gh);

  out:

  	gfs2_holder_uninit(&gh);

  	if (error && error != AOP_TRUNCATED_PAGE)
  		lock_page(page);

  	return error;
  }
  
  /**
   * gfs2_internal_read - read an internal file
   * @ip: The gfs2 inode
   * @ra_state: The readahead state (or NULL for no readahead)
   * @buf: The buffer to fill
   * @pos: The file position
   * @size: The amount to read
   *
   */
  
  int gfs2_internal_read(struct gfs2_inode *ip, struct file_ra_state *ra_state,
                         char *buf, loff_t *pos, unsigned size)
  {
  	struct address_space *mapping = ip->i_inode.i_mapping;
  	unsigned long index = *pos / PAGE_CACHE_SIZE;
  	unsigned offset = *pos & (PAGE_CACHE_SIZE - 1);
  	unsigned copied = 0;
  	unsigned amt;
  	struct page *page;
  	void *p;
  
  	do {
  		amt = size - copied;
  		if (offset + size > PAGE_CACHE_SIZE)
  			amt = PAGE_CACHE_SIZE - offset;
  		page = read_cache_page(mapping, index, __gfs2_readpage, NULL);
  		if (IS_ERR(page))
  			return PTR_ERR(page);
  		p = kmap_atomic(page, KM_USER0);
  		memcpy(buf + copied, p + offset, amt);
  		kunmap_atomic(p, KM_USER0);
  		mark_page_accessed(page);
  		page_cache_release(page);
  		copied += amt;
  		index++;
  		offset = 0;
  	} while(copied < size);
  	(*pos) += size;
  	return size;

  }

  /**
   * gfs2_readpages - Read a bunch of pages at once
   *
   * Some notes:
   * 1. This is only for readahead, so we can simply ignore any things
   *    which are slightly inconvenient (such as locking conflicts between
   *    the page lock and the glock) and return having done no I/O. Its
   *    obviously not something we'd want to do on too regular a basis.
   *    Any I/O we ignore at this time will be done via readpage later.

   * 2. We don't handle stuffed files here we let readpage do the honours.

   * 3. mpage_readpages() does most of the heavy lifting in the common case.

   * 4. gfs2_block_map() is relied upon to set BH_Boundary in the right places.

   */

  static int gfs2_readpages(struct file *file, struct address_space *mapping,
  			  struct list_head *pages, unsigned nr_pages)
  {
  	struct inode *inode = mapping->host;

  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);

  	struct gfs2_holder gh;

  	int ret;

  	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
  	ret = gfs2_glock_nq(&gh);

  	if (unlikely(ret))

  		goto out_uninit;

  	if (!gfs2_is_stuffed(ip))

  		ret = mpage_readpages(mapping, pages, nr_pages, gfs2_block_map);

  	gfs2_glock_dq(&gh);
  out_uninit:
  	gfs2_holder_uninit(&gh);

  	if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
  		ret = -EIO;
  	return ret;

  }
  
  /**

   * gfs2_write_begin - Begin to write to a file

   * @file: The file to write to

   * @mapping: The mapping in which to write
   * @pos: The file offset at which to start writing
   * @len: Length of the write
   * @flags: Various flags
   * @pagep: Pointer to return the page
   * @fsdata: Pointer to return fs data (unused by GFS2)

   *
   * Returns: errno
   */

  static int gfs2_write_begin(struct file *file, struct address_space *mapping,
  			    loff_t pos, unsigned len, unsigned flags,
  			    struct page **pagep, void **fsdata)

  {

  	struct gfs2_inode *ip = GFS2_I(mapping->host);
  	struct gfs2_sbd *sdp = GFS2_SB(mapping->host);

  	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);

  	unsigned int data_blocks = 0, ind_blocks = 0, rblocks;

  	int alloc_required;

  	int error = 0;

  	struct gfs2_qadata *qa = NULL;

  	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
  	unsigned from = pos & (PAGE_CACHE_SIZE - 1);

  	struct page *page;

  	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &ip->i_gh);
  	error = gfs2_glock_nq(&ip->i_gh);

  	if (unlikely(error))

  		goto out_uninit;

  	if (&ip->i_inode == sdp->sd_rindex) {
  		error = gfs2_glock_nq_init(m_ip->i_gl, LM_ST_EXCLUSIVE,
  					   GL_NOCACHE, &m_ip->i_gh);
  		if (unlikely(error)) {
  			gfs2_glock_dq(&ip->i_gh);
  			goto out_uninit;
  		}
  	}

  	alloc_required = gfs2_write_alloc_required(ip, pos, len);

  	if (alloc_required || gfs2_is_jdata(ip))
  		gfs2_write_calc_reserv(ip, len, &data_blocks, &ind_blocks);

  	if (alloc_required) {

  		qa = gfs2_qadata_get(ip);
  		if (!qa) {

  			error = -ENOMEM;
  			goto out_unlock;
  		}

  		error = gfs2_quota_lock_check(ip);

  		if (error)
  			goto out_alloc_put;

  		error = gfs2_inplace_reserve(ip, data_blocks + ind_blocks);

  		if (error)
  			goto out_qunlock;
  	}
  
  	rblocks = RES_DINODE + ind_blocks;
  	if (gfs2_is_jdata(ip))
  		rblocks += data_blocks ? data_blocks : 1;
  	if (ind_blocks || data_blocks)
  		rblocks += RES_STATFS + RES_QUOTA;

  	if (&ip->i_inode == sdp->sd_rindex)
  		rblocks += 2 * RES_STATFS;

  	if (alloc_required)

  		rblocks += gfs2_rg_blocks(ip);

  	error = gfs2_trans_begin(sdp, rblocks,
  				 PAGE_CACHE_SIZE/sdp->sd_sb.sb_bsize);

  	if (error)

  		goto out_trans_fail;

  	error = -ENOMEM;

  	flags |= AOP_FLAG_NOFS;

  	page = grab_cache_page_write_begin(mapping, index, flags);

  	*pagep = page;
  	if (unlikely(!page))
  		goto out_endtrans;

  	if (gfs2_is_stuffed(ip)) {

  		error = 0;

  		if (pos + len > sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode)) {

  			error = gfs2_unstuff_dinode(ip, page);

  			if (error == 0)
  				goto prepare_write;

  		} else if (!PageUptodate(page)) {

  			error = stuffed_readpage(ip, page);

  		}

  		goto out;

  	}

  prepare_write:

  	error = __block_write_begin(page, from, len, gfs2_block_map);

  out:

  	if (error == 0)
  		return 0;

  	unlock_page(page);

  	page_cache_release(page);

  	gfs2_trans_end(sdp);

  	if (pos + len > ip->i_inode.i_size)

  		gfs2_trim_blocks(&ip->i_inode);
  	goto out_trans_fail;

  out_endtrans:
  	gfs2_trans_end(sdp);

  out_trans_fail:

  	if (alloc_required) {
  		gfs2_inplace_release(ip);

  out_qunlock:

  		gfs2_quota_unlock(ip);

  out_alloc_put:

  		gfs2_qadata_put(ip);

  	}

  out_unlock:

  	if (&ip->i_inode == sdp->sd_rindex) {
  		gfs2_glock_dq(&m_ip->i_gh);
  		gfs2_holder_uninit(&m_ip->i_gh);
  	}

  	gfs2_glock_dq(&ip->i_gh);

  out_uninit:

  	gfs2_holder_uninit(&ip->i_gh);

  	return error;
  }
  
  /**

   * adjust_fs_space - Adjusts the free space available due to gfs2_grow
   * @inode: the rindex inode
   */
  static void adjust_fs_space(struct inode *inode)
  {
  	struct gfs2_sbd *sdp = inode->i_sb->s_fs_info;

  	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
  	struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);

  	struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
  	struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;

  	struct buffer_head *m_bh, *l_bh;

  	u64 fs_total, new_free;
  
  	/* Total up the file system space, according to the latest rindex. */
  	fs_total = gfs2_ri_total(sdp);

  	if (gfs2_meta_inode_buffer(m_ip, &m_bh) != 0)
  		return;

  
  	spin_lock(&sdp->sd_statfs_spin);

  	gfs2_statfs_change_in(m_sc, m_bh->b_data +
  			      sizeof(struct gfs2_dinode));

  	if (fs_total > (m_sc->sc_total + l_sc->sc_total))
  		new_free = fs_total - (m_sc->sc_total + l_sc->sc_total);
  	else
  		new_free = 0;
  	spin_unlock(&sdp->sd_statfs_spin);

  	fs_warn(sdp, "File system extended by %llu blocks.
  ",
  		(unsigned long long)new_free);

  	gfs2_statfs_change(sdp, new_free, new_free, 0);

  
  	if (gfs2_meta_inode_buffer(l_ip, &l_bh) != 0)
  		goto out;
  	update_statfs(sdp, m_bh, l_bh);
  	brelse(l_bh);
  out:
  	brelse(m_bh);

  }
  
  /**

   * gfs2_stuffed_write_end - Write end for stuffed files
   * @inode: The inode
   * @dibh: The buffer_head containing the on-disk inode
   * @pos: The file position
   * @len: The length of the write
   * @copied: How much was actually copied by the VFS
   * @page: The page
   *
   * This copies the data from the page into the inode block after
   * the inode data structure itself.
   *
   * Returns: errno
   */
  static int gfs2_stuffed_write_end(struct inode *inode, struct buffer_head *dibh,
  				  loff_t pos, unsigned len, unsigned copied,
  				  struct page *page)
  {
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);

  	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);

  	u64 to = pos + copied;
  	void *kaddr;
  	unsigned char *buf = dibh->b_data + sizeof(struct gfs2_dinode);

  
  	BUG_ON((pos + len) > (dibh->b_size - sizeof(struct gfs2_dinode)));
  	kaddr = kmap_atomic(page, KM_USER0);
  	memcpy(buf + pos, kaddr + pos, copied);
  	memset(kaddr + pos + copied, 0, len - copied);
  	flush_dcache_page(page);
  	kunmap_atomic(kaddr, KM_USER0);
  
  	if (!PageUptodate(page))
  		SetPageUptodate(page);
  	unlock_page(page);
  	page_cache_release(page);

  	if (copied) {

  		if (inode->i_size < to)

  			i_size_write(inode, to);

  		mark_inode_dirty(inode);
  	}

  	if (inode == sdp->sd_rindex) {

  		adjust_fs_space(inode);

  		ip->i_gh.gh_flags |= GL_NOCACHE;
  	}

  
  	brelse(dibh);
  	gfs2_trans_end(sdp);

  	if (inode == sdp->sd_rindex) {
  		gfs2_glock_dq(&m_ip->i_gh);
  		gfs2_holder_uninit(&m_ip->i_gh);
  	}

  	gfs2_glock_dq(&ip->i_gh);
  	gfs2_holder_uninit(&ip->i_gh);
  	return copied;
  }
  
  /**
   * gfs2_write_end

   * @file: The file to write to

   * @mapping: The address space to write to
   * @pos: The file position
   * @len: The length of the data
   * @copied:
   * @page: The page that has been written
   * @fsdata: The fsdata (unused in GFS2)
   *
   * The main write_end function for GFS2. We have a separate one for
   * stuffed files as they are slightly different, otherwise we just
   * put our locking around the VFS provided functions.

   *
   * Returns: errno
   */

  static int gfs2_write_end(struct file *file, struct address_space *mapping,
  			  loff_t pos, unsigned len, unsigned copied,
  			  struct page *page, void *fsdata)

  {
  	struct inode *inode = page->mapping->host;

  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);

  	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);

  	struct buffer_head *dibh;

  	struct gfs2_qadata *qa = ip->i_qadata;

  	unsigned int from = pos & (PAGE_CACHE_SIZE - 1);
  	unsigned int to = from + len;
  	int ret;

  	BUG_ON(gfs2_glock_is_locked_by_me(ip->i_gl) == NULL);

  	ret = gfs2_meta_inode_buffer(ip, &dibh);
  	if (unlikely(ret)) {
  		unlock_page(page);
  		page_cache_release(page);
  		goto failed;
  	}

  
  	gfs2_trans_add_bh(ip->i_gl, dibh, 1);

  	if (gfs2_is_stuffed(ip))
  		return gfs2_stuffed_write_end(inode, dibh, pos, len, copied, page);

  	if (!gfs2_is_writeback(ip))

  		gfs2_page_add_databufs(ip, page, from, to);

  	ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);

  	if (inode == sdp->sd_rindex) {

  		adjust_fs_space(inode);

  		ip->i_gh.gh_flags |= GL_NOCACHE;
  	}

  	brelse(dibh);

  failed:

  	gfs2_trans_end(sdp);

  	if (ip->i_res)

  		gfs2_inplace_release(ip);

  	if (qa) {

  		gfs2_quota_unlock(ip);

  		gfs2_qadata_put(ip);

  	}

  	if (inode == sdp->sd_rindex) {
  		gfs2_glock_dq(&m_ip->i_gh);
  		gfs2_holder_uninit(&m_ip->i_gh);
  	}

  	gfs2_glock_dq(&ip->i_gh);

  	gfs2_holder_uninit(&ip->i_gh);

  	return ret;

  }
  
  /**

   * gfs2_set_page_dirty - Page dirtying function
   * @page: The page to dirty
   *
   * Returns: 1 if it dirtyed the page, or 0 otherwise
   */
   
  static int gfs2_set_page_dirty(struct page *page)
  {

  	SetPageChecked(page);

  	return __set_page_dirty_buffers(page);
  }
  
  /**

   * gfs2_bmap - Block map function
   * @mapping: Address space info
   * @lblock: The block to map
   *
   * Returns: The disk address for the block or 0 on hole or error
   */
  
  static sector_t gfs2_bmap(struct address_space *mapping, sector_t lblock)
  {

  	struct gfs2_inode *ip = GFS2_I(mapping->host);

  	struct gfs2_holder i_gh;
  	sector_t dblock = 0;
  	int error;

  	error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
  	if (error)
  		return 0;
  
  	if (!gfs2_is_stuffed(ip))

  		dblock = generic_block_bmap(mapping, lblock, gfs2_block_map);

  
  	gfs2_glock_dq_uninit(&i_gh);
  
  	return dblock;
  }

  static void gfs2_discard(struct gfs2_sbd *sdp, struct buffer_head *bh)
  {
  	struct gfs2_bufdata *bd;
  
  	lock_buffer(bh);
  	gfs2_log_lock(sdp);
  	clear_buffer_dirty(bh);
  	bd = bh->b_private;
  	if (bd) {

  		if (!list_empty(&bd->bd_le.le_list) && !buffer_pinned(bh))
  			list_del_init(&bd->bd_le.le_list);
  		else
  			gfs2_remove_from_journal(bh, current->journal_info, 0);

  	}
  	bh->b_bdev = NULL;
  	clear_buffer_mapped(bh);
  	clear_buffer_req(bh);
  	clear_buffer_new(bh);
  	gfs2_log_unlock(sdp);
  	unlock_buffer(bh);
  }

  static void gfs2_invalidatepage(struct page *page, unsigned long offset)

  {

  	struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host);
  	struct buffer_head *bh, *head;
  	unsigned long pos = 0;

  	BUG_ON(!PageLocked(page));

  	if (offset == 0)
  		ClearPageChecked(page);

  	if (!page_has_buffers(page))
  		goto out;

  	bh = head = page_buffers(page);
  	do {
  		if (offset <= pos)
  			gfs2_discard(sdp, bh);
  		pos += bh->b_size;
  		bh = bh->b_this_page;
  	} while (bh != head);
  out:
  	if (offset == 0)
  		try_to_release_page(page, 0);

  }

  /**
   * gfs2_ok_for_dio - check that dio is valid on this file
   * @ip: The inode
   * @rw: READ or WRITE
   * @offset: The offset at which we are reading or writing
   *
   * Returns: 0 (to ignore the i/o request and thus fall back to buffered i/o)
   *          1 (to accept the i/o request)
   */
  static int gfs2_ok_for_dio(struct gfs2_inode *ip, int rw, loff_t offset)
  {
  	/*
  	 * Should we return an error here? I can't see that O_DIRECT for

  	 * a stuffed file makes any sense. For now we'll silently fall
  	 * back to buffered I/O

  	 */

  	if (gfs2_is_stuffed(ip))
  		return 0;

  	if (offset >= i_size_read(&ip->i_inode))

  		return 0;
  	return 1;
  }

  static ssize_t gfs2_direct_IO(int rw, struct kiocb *iocb,
  			      const struct iovec *iov, loff_t offset,
  			      unsigned long nr_segs)

  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file->f_mapping->host;

  	struct gfs2_inode *ip = GFS2_I(inode);

  	struct gfs2_holder gh;
  	int rv;
  
  	/*

  	 * Deferred lock, even if its a write, since we do no allocation
  	 * on this path. All we need change is atime, and this lock mode
  	 * ensures that other nodes have flushed their buffered read caches
  	 * (i.e. their page cache entries for this inode). We do not,
  	 * unfortunately have the option of only flushing a range like
  	 * the VFS does.

  	 */

  	gfs2_holder_init(ip->i_gl, LM_ST_DEFERRED, 0, &gh);
  	rv = gfs2_glock_nq(&gh);

  	if (rv)

  		return rv;
  	rv = gfs2_ok_for_dio(ip, rw, offset);
  	if (rv != 1)
  		goto out; /* dio not valid, fall back to buffered i/o */

  	rv = __blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
  				  offset, nr_segs, gfs2_get_block_direct,
  				  NULL, NULL, 0);

  out:
  	gfs2_glock_dq_m(1, &gh);
  	gfs2_holder_uninit(&gh);

  	return rv;
  }
  
  /**

   * gfs2_releasepage - free the metadata associated with a page

   * @page: the page that's being released
   * @gfp_mask: passed from Linux VFS, ignored by us
   *
   * Call try_to_free_buffers() if the buffers in this page can be
   * released.
   *
   * Returns: 0
   */
  
  int gfs2_releasepage(struct page *page, gfp_t gfp_mask)
  {

  	struct address_space *mapping = page->mapping;
  	struct gfs2_sbd *sdp = gfs2_mapping2sbd(mapping);

  	struct buffer_head *bh, *head;
  	struct gfs2_bufdata *bd;

  
  	if (!page_has_buffers(page))

  		return 0;

  	gfs2_log_lock(sdp);

  	spin_lock(&sdp->sd_ail_lock);

  	head = bh = page_buffers(page);
  	do {

  		if (atomic_read(&bh->b_count))
  			goto cannot_release;
  		bd = bh->b_private;
  		if (bd && bd->bd_ail)
  			goto cannot_release;

  		if (buffer_pinned(bh) || buffer_dirty(bh))
  			goto not_possible;

  		bh = bh->b_this_page;
  	} while(bh != head);

  	spin_unlock(&sdp->sd_ail_lock);

  	gfs2_log_unlock(sdp);

  	head = bh = page_buffers(page);
  	do {

  		gfs2_log_lock(sdp);

  		bd = bh->b_private;
  		if (bd) {
  			gfs2_assert_warn(sdp, bd->bd_bh == bh);
  			gfs2_assert_warn(sdp, list_empty(&bd->bd_list_tr));

  			if (!list_empty(&bd->bd_le.le_list)) {
  				if (!buffer_pinned(bh))
  					list_del_init(&bd->bd_le.le_list);
  				else
  					bd = NULL;
  			}
  			if (bd)
  				bd->bd_bh = NULL;

  			bh->b_private = NULL;
  		}

  		gfs2_log_unlock(sdp);
  		if (bd)
  			kmem_cache_free(gfs2_bufdata_cachep, bd);

  
  		bh = bh->b_this_page;

  	} while (bh != head);

  	return try_to_free_buffers(page);

  
  not_possible: /* Should never happen */
  	WARN_ON(buffer_dirty(bh));
  	WARN_ON(buffer_pinned(bh));

  cannot_release:

  	spin_unlock(&sdp->sd_ail_lock);

  	gfs2_log_unlock(sdp);
  	return 0;

  }

  static const struct address_space_operations gfs2_writeback_aops = {

  	.writepage = gfs2_writeback_writepage,

  	.writepages = gfs2_writeback_writepages,
  	.readpage = gfs2_readpage,
  	.readpages = gfs2_readpages,

  	.write_begin = gfs2_write_begin,
  	.write_end = gfs2_write_end,
  	.bmap = gfs2_bmap,
  	.invalidatepage = gfs2_invalidatepage,
  	.releasepage = gfs2_releasepage,
  	.direct_IO = gfs2_direct_IO,

  	.migratepage = buffer_migrate_page,

  	.is_partially_uptodate = block_is_partially_uptodate,

  	.error_remove_page = generic_error_remove_page,

  };
  
  static const struct address_space_operations gfs2_ordered_aops = {

  	.writepage = gfs2_ordered_writepage,

  	.readpage = gfs2_readpage,

  	.readpages = gfs2_readpages,

  	.write_begin = gfs2_write_begin,
  	.write_end = gfs2_write_end,

  	.set_page_dirty = gfs2_set_page_dirty,

  	.bmap = gfs2_bmap,
  	.invalidatepage = gfs2_invalidatepage,

  	.releasepage = gfs2_releasepage,

  	.direct_IO = gfs2_direct_IO,

  	.migratepage = buffer_migrate_page,

  	.is_partially_uptodate = block_is_partially_uptodate,

  	.error_remove_page = generic_error_remove_page,

  };

  static const struct address_space_operations gfs2_jdata_aops = {

  	.writepage = gfs2_jdata_writepage,

  	.writepages = gfs2_jdata_writepages,

  	.readpage = gfs2_readpage,
  	.readpages = gfs2_readpages,

  	.write_begin = gfs2_write_begin,
  	.write_end = gfs2_write_end,
  	.set_page_dirty = gfs2_set_page_dirty,
  	.bmap = gfs2_bmap,
  	.invalidatepage = gfs2_invalidatepage,
  	.releasepage = gfs2_releasepage,

  	.is_partially_uptodate = block_is_partially_uptodate,

  	.error_remove_page = generic_error_remove_page,

  };
  
  void gfs2_set_aops(struct inode *inode)
  {
  	struct gfs2_inode *ip = GFS2_I(inode);
  
  	if (gfs2_is_writeback(ip))
  		inode->i_mapping->a_ops = &gfs2_writeback_aops;
  	else if (gfs2_is_ordered(ip))
  		inode->i_mapping->a_ops = &gfs2_ordered_aops;
  	else if (gfs2_is_jdata(ip))
  		inode->i_mapping->a_ops = &gfs2_jdata_aops;
  	else
  		BUG();
  }