file.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * file.c
 *
 * File open, close, extend, truncate
 *
 * 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/capability.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/uio.h>
#include <linux/sched.h>
#include <linux/splice.h>
#include <linux/mount.h>
#include <linux/writeback.h>

#define MLOG_MASK_PREFIX ML_INODE
#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "aops.h"
#include "dir.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "file.h"
#include "sysfile.h"
#include "inode.h"
#include "ioctl.h"
#include "journal.h"
#include "mmap.h"
#include "suballoc.h"
#include "super.h"

#include "buffer_head_io.h"

static int ocfs2_sync_inode(struct inode *inode)
{
	filemap_fdatawrite(inode->i_mapping);
	return sync_mapping_buffers(inode->i_mapping);
}

static int ocfs2_file_open(struct inode *inode, struct file *file)
{
	int status;
	int mode = file->f_flags;
	struct ocfs2_inode_info *oi = OCFS2_I(inode);

	mlog_entry("(0x%p, 0x%p, '%.*s')\n", inode, file,
		   file->f_path.dentry->d_name.len, file->f_path.dentry->d_name.name);

	spin_lock(&oi->ip_lock);

	/* Check that the inode hasn't been wiped from disk by another
	 * node. If it hasn't then we're safe as long as we hold the
	 * spin lock until our increment of open count. */
	if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_DELETED) {
		spin_unlock(&oi->ip_lock);

		status = -ENOENT;
		goto leave;
	}

	if (mode & O_DIRECT)
		oi->ip_flags |= OCFS2_INODE_OPEN_DIRECT;

	oi->ip_open_count++;
	spin_unlock(&oi->ip_lock);
	status = 0;
leave:
	mlog_exit(status);
	return status;
}

static int ocfs2_file_release(struct inode *inode, struct file *file)
{
	struct ocfs2_inode_info *oi = OCFS2_I(inode);

	mlog_entry("(0x%p, 0x%p, '%.*s')\n", inode, file,
		       file->f_path.dentry->d_name.len,
		       file->f_path.dentry->d_name.name);

	spin_lock(&oi->ip_lock);
	if (!--oi->ip_open_count)
		oi->ip_flags &= ~OCFS2_INODE_OPEN_DIRECT;
	spin_unlock(&oi->ip_lock);

	mlog_exit(0);

	return 0;
}

static int ocfs2_sync_file(struct file *file,
			   struct dentry *dentry,
			   int datasync)
{
	int err = 0;
	journal_t *journal;
	struct inode *inode = dentry->d_inode;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

	mlog_entry("(0x%p, 0x%p, %d, '%.*s')\n", file, dentry, datasync,
		   dentry->d_name.len, dentry->d_name.name);

	err = ocfs2_sync_inode(dentry->d_inode);
	if (err)
		goto bail;

	journal = osb->journal->j_journal;
	err = journal_force_commit(journal);

bail:
	mlog_exit(err);

	return (err < 0) ? -EIO : 0;
}

int ocfs2_should_update_atime(struct inode *inode,
			      struct vfsmount *vfsmnt)
{
	struct timespec now;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

	if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb))
		return 0;

	if ((inode->i_flags & S_NOATIME) ||
	    ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode)))
		return 0;

	/*
	 * We can be called with no vfsmnt structure - NFSD will
	 * sometimes do this.
	 *
	 * Note that our action here is different than touch_atime() -
	 * if we can't tell whether this is a noatime mount, then we
	 * don't know whether to trust the value of s_atime_quantum.
	 */
	if (vfsmnt == NULL)
		return 0;

	if ((vfsmnt->mnt_flags & MNT_NOATIME) ||
	    ((vfsmnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode)))
		return 0;

	if (vfsmnt->mnt_flags & MNT_RELATIME) {
		if ((timespec_compare(&inode->i_atime, &inode->i_mtime) <= 0) ||
		    (timespec_compare(&inode->i_atime, &inode->i_ctime) <= 0))
			return 1;

		return 0;
	}

	now = CURRENT_TIME;
	if ((now.tv_sec - inode->i_atime.tv_sec <= osb->s_atime_quantum))
		return 0;
	else
		return 1;
}

int ocfs2_update_inode_atime(struct inode *inode,
			     struct buffer_head *bh)
{
	int ret;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
	handle_t *handle;

	mlog_entry_void();

	handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
	if (handle == NULL) {
		ret = -ENOMEM;
		mlog_errno(ret);
		goto out;
	}

	inode->i_atime = CURRENT_TIME;
	ret = ocfs2_mark_inode_dirty(handle, inode, bh);
	if (ret < 0)
		mlog_errno(ret);

	ocfs2_commit_trans(OCFS2_SB(inode->i_sb), handle);
out:
	mlog_exit(ret);
	return ret;
}

static int ocfs2_set_inode_size(handle_t *handle,
				struct inode *inode,
				struct buffer_head *fe_bh,
				u64 new_i_size)
{
	int status;

	mlog_entry_void();
	i_size_write(inode, new_i_size);
	inode->i_blocks = ocfs2_inode_sector_count(inode);
	inode->i_ctime = inode->i_mtime = CURRENT_TIME;

	status = ocfs2_mark_inode_dirty(handle, inode, fe_bh);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

bail:
	mlog_exit(status);
	return status;
}

static int ocfs2_simple_size_update(struct inode *inode,
				    struct buffer_head *di_bh,
				    u64 new_i_size)
{
	int ret;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
	handle_t *handle = NULL;

	handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
	if (handle == NULL) {
		ret = -ENOMEM;
		mlog_errno(ret);
		goto out;
	}

	ret = ocfs2_set_inode_size(handle, inode, di_bh,
				   new_i_size);
	if (ret < 0)
		mlog_errno(ret);

	ocfs2_commit_trans(osb, handle);
out:
	return ret;
}

static int ocfs2_orphan_for_truncate(struct ocfs2_super *osb,
				     struct inode *inode,
				     struct buffer_head *fe_bh,
				     u64 new_i_size)
{
	int status;
	handle_t *handle;
	struct ocfs2_dinode *di;

	mlog_entry_void();

	/* TODO: This needs to actually orphan the inode in this
	 * transaction. */

	handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
	if (IS_ERR(handle)) {
		status = PTR_ERR(handle);
		mlog_errno(status);
		goto out;
	}

	status = ocfs2_journal_access(handle, inode, fe_bh,
				      OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto out_commit;
	}

	/*
	 * Do this before setting i_size.
	 */
	status = ocfs2_zero_tail_for_truncate(inode, handle, new_i_size);
	if (status) {
		mlog_errno(status);
		goto out_commit;
	}

	i_size_write(inode, new_i_size);
	inode->i_blocks = ocfs2_align_bytes_to_sectors(new_i_size);
	inode->i_ctime = inode->i_mtime = CURRENT_TIME;

	di = (struct ocfs2_dinode *) fe_bh->b_data;
	di->i_size = cpu_to_le64(new_i_size);
	di->i_ctime = di->i_mtime = cpu_to_le64(inode->i_ctime.tv_sec);
	di->i_ctime_nsec = di->i_mtime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);

	status = ocfs2_journal_dirty(handle, fe_bh);
	if (status < 0)
		mlog_errno(status);

out_commit:
	ocfs2_commit_trans(osb, handle);
out:

	mlog_exit(status);
	return status;
}

static int ocfs2_truncate_file(struct inode *inode,
			       struct buffer_head *di_bh,
			       u64 new_i_size)
{
	int status = 0;
	struct ocfs2_dinode *fe = NULL;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
	struct ocfs2_truncate_context *tc = NULL;

	mlog_entry("(inode = %llu, new_i_size = %llu\n",
		   (unsigned long long)OCFS2_I(inode)->ip_blkno,
		   (unsigned long long)new_i_size);

	fe = (struct ocfs2_dinode *) di_bh->b_data;
	if (!OCFS2_IS_VALID_DINODE(fe)) {
		OCFS2_RO_ON_INVALID_DINODE(inode->i_sb, fe);
		status = -EIO;
		goto bail;
	}

	mlog_bug_on_msg(le64_to_cpu(fe->i_size) != i_size_read(inode),
			"Inode %llu, inode i_size = %lld != di "
			"i_size = %llu, i_flags = 0x%x\n",
			(unsigned long long)OCFS2_I(inode)->ip_blkno,
			i_size_read(inode),
			(unsigned long long)le64_to_cpu(fe->i_size),
			le32_to_cpu(fe->i_flags));

	if (new_i_size > le64_to_cpu(fe->i_size)) {
		mlog(0, "asked to truncate file with size (%llu) to size (%llu)!\n",
		     (unsigned long long)le64_to_cpu(fe->i_size),
		     (unsigned long long)new_i_size);
		status = -EINVAL;
		mlog_errno(status);
		goto bail;
	}

	mlog(0, "inode %llu, i_size = %llu, new_i_size = %llu\n",
	     (unsigned long long)le64_to_cpu(fe->i_blkno),
	     (unsigned long long)le64_to_cpu(fe->i_size),
	     (unsigned long long)new_i_size);

	/* lets handle the simple truncate cases before doing any more
	 * cluster locking. */
	if (new_i_size == le64_to_cpu(fe->i_size))
		goto bail;

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

	/* This forces other nodes to sync and drop their pages. Do
	 * this even if we have a truncate without allocation change -
	 * ocfs2 cluster sizes can be much greater than page size, so
	 * we have to truncate them anyway.  */
	status = ocfs2_data_lock(inode, 1);
	if (status < 0) {
		up_write(&OCFS2_I(inode)->ip_alloc_sem);

		mlog_errno(status);
		goto bail;
	}

	unmap_mapping_range(inode->i_mapping, new_i_size + PAGE_SIZE - 1, 0, 1);
	truncate_inode_pages(inode->i_mapping, new_i_size);

	/* alright, we're going to need to do a full blown alloc size
	 * change. Orphan the inode so that recovery can complete the
	 * truncate if necessary. This does the task of marking
	 * i_size. */
	status = ocfs2_orphan_for_truncate(osb, inode, di_bh, new_i_size);
	if (status < 0) {
		mlog_errno(status);
		goto bail_unlock_data;
	}

	status = ocfs2_prepare_truncate(osb, inode, di_bh, &tc);
	if (status < 0) {
		mlog_errno(status);
		goto bail_unlock_data;
	}

	status = ocfs2_commit_truncate(osb, inode, di_bh, tc);
	if (status < 0) {
		mlog_errno(status);
		goto bail_unlock_data;
	}

	/* TODO: orphan dir cleanup here. */
bail_unlock_data:
	ocfs2_data_unlock(inode, 1);

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

bail:

	mlog_exit(status);
	return status;
}

/*
 * extend allocation only here.
 * we'll update all the disk stuff, and oip->alloc_size
 *
 * expect stuff to be locked, a transaction started and enough data /
 * metadata reservations in the contexts.
 *
 * Will return -EAGAIN, and a reason if a restart is needed.
 * If passed in, *reason will always be set, even in error.
 */
int ocfs2_do_extend_allocation(struct ocfs2_super *osb,
			       struct inode *inode,
			       u32 *logical_offset,
			       u32 clusters_to_add,
			       int mark_unwritten,
			       struct buffer_head *fe_bh,
			       handle_t *handle,
			       struct ocfs2_alloc_context *data_ac,
			       struct ocfs2_alloc_context *meta_ac,
			       enum ocfs2_alloc_restarted *reason_ret)
{
	int status = 0;
	int free_extents;
	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) fe_bh->b_data;
	enum ocfs2_alloc_restarted reason = RESTART_NONE;
	u32 bit_off, num_bits;
	u64 block;
	u8 flags = 0;

	BUG_ON(!clusters_to_add);

	if (mark_unwritten)
		flags = OCFS2_EXT_UNWRITTEN;

	free_extents = ocfs2_num_free_extents(osb, inode, fe);
	if (free_extents < 0) {
		status = free_extents;
		mlog_errno(status);
		goto leave;
	}

	/* there are two cases which could cause us to EAGAIN in the
	 * we-need-more-metadata case:
	 * 1) we haven't reserved *any*
	 * 2) we are so fragmented, we've needed to add metadata too
	 *    many times. */
	if (!free_extents && !meta_ac) {
		mlog(0, "we haven't reserved any metadata!\n");
		status = -EAGAIN;
		reason = RESTART_META;
		goto leave;
	} else if ((!free_extents)
		   && (ocfs2_alloc_context_bits_left(meta_ac)
		       < ocfs2_extend_meta_needed(fe))) {
		mlog(0, "filesystem is really fragmented...\n");
		status = -EAGAIN;
		reason = RESTART_META;
		goto leave;
	}

	status = ocfs2_claim_clusters(osb, handle, data_ac, 1,
				      &bit_off, &num_bits);
	if (status < 0) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto leave;
	}

	BUG_ON(num_bits > clusters_to_add);

	/* reserve our write early -- insert_extent may update the inode */
	status = ocfs2_journal_access(handle, inode, fe_bh,
				      OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto leave;
	}

	block = ocfs2_clusters_to_blocks(osb->sb, bit_off);
	mlog(0, "Allocating %u clusters at block %u for inode %llu\n",
	     num_bits, bit_off, (unsigned long long)OCFS2_I(inode)->ip_blkno);
	status = ocfs2_insert_extent(osb, handle, inode, fe_bh,
				     *logical_offset, block, num_bits,
				     flags, meta_ac);
	if (status < 0) {
		mlog_errno(status);
		goto leave;
	}

	status = ocfs2_journal_dirty(handle, fe_bh);
	if (status < 0) {
		mlog_errno(status);
		goto leave;
	}

	clusters_to_add -= num_bits;
	*logical_offset += num_bits;

	if (clusters_to_add) {
		mlog(0, "need to alloc once more, clusters = %u, wanted = "
		     "%u\n", fe->i_clusters, clusters_to_add);
		status = -EAGAIN;
		reason = RESTART_TRANS;
	}

leave:
	mlog_exit(status);
	if (reason_ret)
		*reason_ret = reason;
	return status;
}

/*
 * For a given allocation, determine which allocators will need to be
 * accessed, and lock them, reserving the appropriate number of bits.
 *
 * Sparse file systems call this from ocfs2_write_begin_nolock()
 * and ocfs2_allocate_unwritten_extents().
 *
 * File systems which don't support holes call this from
 * ocfs2_extend_allocation().
 */
int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
			  u32 clusters_to_add, u32 extents_to_split,
			  struct ocfs2_alloc_context **data_ac,
			  struct ocfs2_alloc_context **meta_ac)
{
	int ret, num_free_extents;
	unsigned int max_recs_needed = clusters_to_add + 2 * extents_to_split;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

	*meta_ac = NULL;
	*data_ac = NULL;

	mlog(0, "extend inode %llu, i_size = %lld, di->i_clusters = %u, "
	     "clusters_to_add = %u, extents_to_split = %u\n",
	     (unsigned long long)OCFS2_I(inode)->ip_blkno, i_size_read(inode),
	     le32_to_cpu(di->i_clusters), clusters_to_add, extents_to_split);

	num_free_extents = ocfs2_num_free_extents(osb, inode, di);
	if (num_free_extents < 0) {
		ret = num_free_extents;
		mlog_errno(ret);
		goto out;
	}

	/*
	 * Sparse allocation file systems need to be more conservative
	 * with reserving room for expansion - the actual allocation
	 * happens while we've got a journal handle open so re-taking
	 * a cluster lock (because we ran out of room for another
	 * extent) will violate ordering rules.
	 *
	 * Most of the time we'll only be seeing this 1 cluster at a time
	 * anyway.
	 *
	 * Always lock for any unwritten extents - we might want to
	 * add blocks during a split.
	 */
	if (!num_free_extents ||
	    (ocfs2_sparse_alloc(osb) && num_free_extents < max_recs_needed)) {
		ret = ocfs2_reserve_new_metadata(osb, di, meta_ac);
		if (ret < 0) {
			if (ret != -ENOSPC)
				mlog_errno(ret);
			goto out;
		}
	}

	ret = ocfs2_reserve_clusters(osb, clusters_to_add, data_ac);
	if (ret < 0) {
		if (ret != -ENOSPC)
			mlog_errno(ret);
		goto out;
	}

out:
	if (ret) {
		if (*meta_ac) {
			ocfs2_free_alloc_context(*meta_ac);
			*meta_ac = NULL;
		}

		/*
		 * We cannot have an error and a non null *data_ac.
		 */
	}

	return ret;
}

static int __ocfs2_extend_allocation(struct inode *inode, u32 logical_start,
				     u32 clusters_to_add, int mark_unwritten)
{
	int status = 0;
	int restart_func = 0;
	int credits;
	u32 prev_clusters;
	struct buffer_head *bh = NULL;
	struct ocfs2_dinode *fe = NULL;
	handle_t *handle = NULL;
	struct ocfs2_alloc_context *data_ac = NULL;
	struct ocfs2_alloc_context *meta_ac = NULL;
	enum ocfs2_alloc_restarted why;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

	mlog_entry("(clusters_to_add = %u)\n", clusters_to_add);

	/*
	 * This function only exists for file systems which don't
	 * support holes.
	 */
	BUG_ON(mark_unwritten && !ocfs2_sparse_alloc(osb));

	status = ocfs2_read_block(osb, OCFS2_I(inode)->ip_blkno, &bh,
				  OCFS2_BH_CACHED, inode);
	if (status < 0) {
		mlog_errno(status);
		goto leave;
	}

	fe = (struct ocfs2_dinode *) bh->b_data;
	if (!OCFS2_IS_VALID_DINODE(fe)) {
		OCFS2_RO_ON_INVALID_DINODE(inode->i_sb, fe);
		status = -EIO;
		goto leave;
	}

restart_all:
	BUG_ON(le32_to_cpu(fe->i_clusters) != OCFS2_I(inode)->ip_clusters);

	status = ocfs2_lock_allocators(inode, fe, clusters_to_add, 0, &data_ac,
				       &meta_ac);
	if (status) {
		mlog_errno(status);
		goto leave;
	}

	credits = ocfs2_calc_extend_credits(osb->sb, fe, clusters_to_add);
	handle = ocfs2_start_trans(osb, credits);
	if (IS_ERR(handle)) {
		status = PTR_ERR(handle);
		handle = NULL;
		mlog_errno(status);
		goto leave;
	}

restarted_transaction:
	/* reserve a write to the file entry early on - that we if we
	 * run out of credits in the allocation path, we can still
	 * update i_size. */
	status = ocfs2_journal_access(handle, inode, bh,
				      OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto leave;
	}

	prev_clusters = OCFS2_I(inode)->ip_clusters;

	status = ocfs2_do_extend_allocation(osb,
					    inode,
					    &logical_start,
					    clusters_to_add,
					    mark_unwritten,
					    bh,
					    handle,
					    data_ac,
					    meta_ac,
					    &why);
	if ((status < 0) && (status != -EAGAIN)) {
		if (status != -ENOSPC)
			mlog_errno(status);
		goto leave;
	}

	status = ocfs2_journal_dirty(handle, bh);
	if (status < 0) {
		mlog_errno(status);
		goto leave;
	}

	spin_lock(&OCFS2_I(inode)->ip_lock);
	clusters_to_add -= (OCFS2_I(inode)->ip_clusters - prev_clusters);
	spin_unlock(&OCFS2_I(inode)->ip_lock);

	if (why != RESTART_NONE && clusters_to_add) {
		if (why == RESTART_META) {
			mlog(0, "restarting function.\n");
			restart_func = 1;
		} else {
			BUG_ON(why != RESTART_TRANS);

			mlog(0, "restarting transaction.\n");
			/* TODO: This can be more intelligent. */
			credits = ocfs2_calc_extend_credits(osb->sb,
							    fe,
							    clusters_to_add);
			status = ocfs2_extend_trans(handle, credits);
			if (status < 0) {
				/* handle still has to be committed at
				 * this point. */
				status = -ENOMEM;
				mlog_errno(status);
				goto leave;
			}
			goto restarted_transaction;
		}
	}

	mlog(0, "fe: i_clusters = %u, i_size=%llu\n",
	     le32_to_cpu(fe->i_clusters),
	     (unsigned long long)le64_to_cpu(fe->i_size));
	mlog(0, "inode: ip_clusters=%u, i_size=%lld\n",
	     OCFS2_I(inode)->ip_clusters, i_size_read(inode));

leave:
	if (handle) {
		ocfs2_commit_trans(osb, handle);
		handle = NULL;
	}
	if (data_ac) {
		ocfs2_free_alloc_context(data_ac);
		data_ac = NULL;
	}
	if (meta_ac) {
		ocfs2_free_alloc_context(meta_ac);
		meta_ac = NULL;
	}
	if ((!status) && restart_func) {
		restart_func = 0;
		goto restart_all;
	}
	if (bh) {
		brelse(bh);
		bh = NULL;
	}

	mlog_exit(status);
	return status;
}

static int ocfs2_extend_allocation(struct inode *inode, u32 logical_start,
				   u32 clusters_to_add, int mark_unwritten)
{
	int ret;

	/*
	 * The alloc sem blocks peope in read/write from reading our
	 * allocation until we're done changing it. We depend on
	 * i_mutex to block other extend/truncate calls while we're
	 * here.
	 */
	down_write(&OCFS2_I(inode)->ip_alloc_sem);
	ret = __ocfs2_extend_allocation(inode, logical_start, clusters_to_add,
					mark_unwritten);
	up_write(&OCFS2_I(inode)->ip_alloc_sem);

	return ret;
}

/* Some parts of this taken from generic_cont_expand, which turned out
 * to be too fragile to do exactly what we need without us having to
 * worry about recursive locking in ->prepare_write() and
 * ->commit_write(). */
static int ocfs2_write_zero_page(struct inode *inode,
				 u64 size)
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;
	unsigned long index;
	unsigned int offset;
	handle_t *handle = NULL;
	int ret;

	offset = (size & (PAGE_CACHE_SIZE-1)); /* Within page */
	/* ugh.  in prepare/commit_write, if from==to==start of block, we 
	** skip the prepare.  make sure we never send an offset for the start
	** of a block
	*/
	if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
		offset++;
	}
	index = size >> PAGE_CACHE_SHIFT;

	page = grab_cache_page(mapping, index);
	if (!page) {
		ret = -ENOMEM;
		mlog_errno(ret);
		goto out;
	}

	ret = ocfs2_prepare_write_nolock(inode, page, offset, offset);
	if (ret < 0) {
		mlog_errno(ret);
		goto out_unlock;
	}

	if (ocfs2_should_order_data(inode)) {
		handle = ocfs2_start_walk_page_trans(inode, page, offset,
						     offset);
		if (IS_ERR(handle)) {
			ret = PTR_ERR(handle);
			handle = NULL;
			goto out_unlock;
		}
	}

	/* must not update i_size! */
	ret = block_commit_write(page, offset, offset);
	if (ret < 0)
		mlog_errno(ret);
	else
		ret = 0;

	if (handle)
		ocfs2_commit_trans(OCFS2_SB(inode->i_sb), handle);
out_unlock:
	unlock_page(page);
	page_cache_release(page);
out:
	return ret;
}

static int ocfs2_zero_extend(struct inode *inode,
			     u64 zero_to_size)
{
	int ret = 0;
	u64 start_off;
	struct super_block *sb = inode->i_sb;

	start_off = ocfs2_align_bytes_to_blocks(sb, i_size_read(inode));
	while (start_off < zero_to_size) {
		ret = ocfs2_write_zero_page(inode, start_off);
		if (ret < 0) {
			mlog_errno(ret);
			goto out;
		}

		start_off += sb->s_blocksize;

		/*
		 * Very large extends have the potential to lock up
		 * the cpu for extended periods of time.
		 */
		cond_resched();
	}

out:
	return ret;
}

/* 
 * A tail_to_skip value > 0 indicates that we're being called from
 * ocfs2_file_aio_write(). This has the following implications:
 *
 * - we don't want to update i_size
 * - di_bh will be NULL, which is fine because it's only used in the
 *   case where we want to update i_size.
 * - ocfs2_zero_extend() will then only be filling the hole created
 *   between i_size and the start of the write.
 */
static int ocfs2_extend_file(struct inode *inode,
			     struct buffer_head *di_bh,
			     u64 new_i_size,
			     size_t tail_to_skip)
{
	int ret = 0;
	u32 clusters_to_add = 0;

	BUG_ON(!tail_to_skip && !di_bh);

	/* setattr sometimes calls us like this. */
	if (new_i_size == 0)
		goto out;

	if (i_size_read(inode) == new_i_size)
  		goto out;
	BUG_ON(new_i_size < i_size_read(inode));

	if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
		BUG_ON(tail_to_skip != 0);
		goto out_update_size;
	}

	clusters_to_add = ocfs2_clusters_for_bytes(inode->i_sb, new_i_size) - 
		OCFS2_I(inode)->ip_clusters;

	/* 
	 * protect the pages that ocfs2_zero_extend is going to be
	 * pulling into the page cache.. we do this before the
	 * metadata extend so that we don't get into the situation
	 * where we've extended the metadata but can't get the data
	 * lock to zero.
	 */
	ret = ocfs2_data_lock(inode, 1);
	if (ret < 0) {
		mlog_errno(ret);
		goto out;
	}

	if (clusters_to_add) {
		ret = ocfs2_extend_allocation(inode,
					      OCFS2_I(inode)->ip_clusters,
					      clusters_to_add, 0);
		if (ret < 0) {
			mlog_errno(ret);
			goto out_unlock;
		}
	}

	/*
	 * Call this even if we don't add any clusters to the tree. We
	 * still need to zero the area between the old i_size and the
	 * new i_size.
	 */
	ret = ocfs2_zero_extend(inode, (u64)new_i_size - tail_to_skip);
	if (ret < 0) {
		mlog_errno(ret);
		goto out_unlock;
	}

out_update_size:
	if (!tail_to_skip) {
		/* We're being called from ocfs2_setattr() which wants
		 * us to update i_size */
		ret = ocfs2_simple_size_update(inode, di_bh, new_i_size);
		if (ret < 0)
			mlog_errno(ret);
	}

out_unlock:
	if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
		ocfs2_data_unlock(inode, 1);

out:
	return ret;
}

int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
{
	int status = 0, size_change;
	struct inode *inode = dentry->d_inode;
	struct super_block *sb = inode->i_sb;
	struct ocfs2_super *osb = OCFS2_SB(sb);
	struct buffer_head *bh = NULL;
	handle_t *handle = NULL;

	mlog_entry("(0x%p, '%.*s')\n", dentry,
	           dentry->d_name.len, dentry->d_name.name);

	if (attr->ia_valid & ATTR_MODE)
		mlog(0, "mode change: %d\n", attr->ia_mode);
	if (attr->ia_valid & ATTR_UID)
		mlog(0, "uid change: %d\n", attr->ia_uid);
	if (attr->ia_valid & ATTR_GID)
		mlog(0, "gid change: %d\n", attr->ia_gid);
	if (attr->ia_valid & ATTR_SIZE)
		mlog(0, "size change...\n");
	if (attr->ia_valid & (ATTR_ATIME | ATTR_MTIME | ATTR_CTIME))
		mlog(0, "time change...\n");

#define OCFS2_VALID_ATTRS (ATTR_ATIME | ATTR_MTIME | ATTR_CTIME | ATTR_SIZE \
			   | ATTR_GID | ATTR_UID | ATTR_MODE)
	if (!(attr->ia_valid & OCFS2_VALID_ATTRS)) {
		mlog(0, "can't handle attrs: 0x%x\n", attr->ia_valid);
		return 0;
	}

	status = inode_change_ok(inode, attr);
	if (status)
		return status;

	size_change = S_ISREG(inode->i_mode) && attr->ia_valid & ATTR_SIZE;
	if (size_change) {
		status = ocfs2_rw_lock(inode, 1);
		if (status < 0) {
			mlog_errno(status);
			goto bail;
		}
	}

	status = ocfs2_meta_lock(inode, &bh, 1);
	if (status < 0) {
		if (status != -ENOENT)
			mlog_errno(status);
		goto bail_unlock_rw;
	}

	if (size_change && attr->ia_size != i_size_read(inode)) {
		if (i_size_read(inode) > attr->ia_size)
			status = ocfs2_truncate_file(inode, bh, attr->ia_size);
		else
			status = ocfs2_extend_file(inode, bh, attr->ia_size, 0);
		if (status < 0) {
			if (status != -ENOSPC)
				mlog_errno(status);
			status = -ENOSPC;
			goto bail_unlock;
		}
	}

	handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
	if (IS_ERR(handle)) {
		status = PTR_ERR(handle);
		mlog_errno(status);
		goto bail_unlock;
	}

	/*
	 * This will intentionally not wind up calling vmtruncate(),
	 * since all the work for a size change has been done above.
	 * Otherwise, we could get into problems with truncate as
	 * ip_alloc_sem is used there to protect against i_size
	 * changes.
	 */
	status = inode_setattr(inode, attr);
	if (status < 0) {
		mlog_errno(status);
		goto bail_commit;
	}

	status = ocfs2_mark_inode_dirty(handle, inode, bh);
	if (status < 0)
		mlog_errno(status);

bail_commit:
	ocfs2_commit_trans(osb, handle);
bail_unlock:
	ocfs2_meta_unlock(inode, 1);
bail_unlock_rw:
	if (size_change)
		ocfs2_rw_unlock(inode, 1);
bail:
	if (bh)
		brelse(bh);

	mlog_exit(status);
	return status;
}

int ocfs2_getattr(struct vfsmount *mnt,
		  struct dentry *dentry,
		  struct kstat *stat)
{
	struct inode *inode = dentry->d_inode;
	struct super_block *sb = dentry->d_inode->i_sb;
	struct ocfs2_super *osb = sb->s_fs_info;
	int err;

	mlog_entry_void();

	err = ocfs2_inode_revalidate(dentry);
	if (err) {
		if (err != -ENOENT)
			mlog_errno(err);
		goto bail;
	}

	generic_fillattr(inode, stat);

	/* We set the blksize from the cluster size for performance */
	stat->blksize = osb->s_clustersize;

bail:
	mlog_exit(err);

	return err;
}

int ocfs2_permission(struct inode *inode, int mask, struct nameidata *nd)
{
	int ret;

	mlog_entry_void();

	ret = ocfs2_meta_lock(inode, NULL, 0);
	if (ret) {
		if (ret != -ENOENT)
			mlog_errno(ret);
		goto out;
	}

	ret = generic_permission(inode, mask, NULL);

	ocfs2_meta_unlock(inode, 0);
out:
	mlog_exit(ret);
	return ret;
}

static int ocfs2_write_remove_suid(struct inode *inode)
{
	int ret;
	struct buffer_head *bh = NULL;
	struct ocfs2_inode_info *oi = OCFS2_I(inode);
	handle_t *handle;
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
	struct ocfs2_dinode *di;

	mlog_entry("(Inode %llu, mode 0%o)\n",
		   (unsigned long long)oi->ip_blkno, inode->i_mode);

	handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
	if (handle == NULL) {
		ret = -ENOMEM;
		mlog_errno(ret);
		goto out;
	}

	ret = ocfs2_read_block(osb, oi->ip_blkno, &bh, OCFS2_BH_CACHED, inode);
	if (ret < 0) {
		mlog_errno(ret);
		goto out_trans;
	}

	ret = ocfs2_journal_access(handle, inode, bh,
				   OCFS2_JOURNAL_ACCESS_WRITE);
	if (ret < 0) {
		mlog_errno(ret);
		goto out_bh;
	}

	inode->i_mode &= ~S_ISUID;
	if ((inode->i_mode & S_ISGID) && (inode->i_mode & S_IXGRP))
		inode->i_mode &= ~S_ISGID;

	di = (struct ocfs2_dinode *) bh->b_data;
	di->i_mode = cpu_to_le16(inode->i_mode);

	ret = ocfs2_journal_dirty(handle, bh);
	if (ret < 0)
		mlog_errno(ret);
out_bh:
	brelse(bh);
out_trans:
	ocfs2_commit_trans(osb, handle);
out:
	mlog_exit(ret);
	return ret;
}

/*
 * Will look for holes and unwritten extents in the range starting at
 * pos for count bytes (inclusive).
 */
static int ocfs2_check_range_for_holes(struct inode *inode, loff_t pos,
				       size_t count)
{
	int ret = 0;
	unsigned int extent_flags;
	u32 cpos, clusters, extent_len, phys_cpos;
	struct super_block *sb = inode->i_sb;

	cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
	clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;

	while (clusters) {
		ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
					 &extent_flags);
		if (ret < 0) {
			mlog_errno(ret);
			goto out;
		}

		if (phys_cpos == 0 || (extent_flags & OCFS2_EXT_UNWRITTEN)) {
			ret = 1;
			break;
		}

		if (extent_len > clusters)
			extent_len = clusters;

		clusters -= extent_len;
		cpos += extent_len;
	}
out:
	return ret;
}

/*
 * Allocate enough extents to cover the region starting at byte offset
 * start for len bytes. Existing extents are skipped, any extents
 * added are marked as "unwritten".
 */
static int ocfs2_allocate_unwritten_extents(struct inode *inode,
					    u64 start, u64 len)
{
	int ret;
	u32 cpos, phys_cpos, clusters, alloc_size;

	/*
	 * We consider both start and len to be inclusive.
	 */
	cpos = start >> OCFS2_SB(inode->i_sb)->s_clustersize_bits;
	clusters = ocfs2_clusters_for_bytes(inode->i_sb, start + len);
	clusters -= cpos;

	while (clusters) {
		ret = ocfs2_get_clusters(inode, cpos, &phys_cpos,
					 &alloc_size, NULL);
		if (ret) {
			mlog_errno(ret);
			goto out;
		}

		/*
		 * Hole or existing extent len can be arbitrary, so
		 * cap it to our own allocation request.
		 */
		if (alloc_size > clusters)
			alloc_size = clusters;

		if (phys_cpos) {
			/*
			 * We already have an allocation at this
			 * region so we can safely skip it.
			 */
			goto next;
		}

		ret = __ocfs2_extend_allocation(inode, cpos, alloc_size, 1);
		if (ret) {
			if (ret != -ENOSPC)
				mlog_errno(ret);
			goto out;
		}

next:
		cpos += alloc_size;
		clusters -= alloc_size;
	}

	ret = 0;
out:
	return ret;
}

static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
					 loff_t *ppos,
					 size_t count,
					 int appending,
					 int *direct_io)
{
	int ret = 0, meta_level = appending;
	struct inode *inode = dentry->d_inode;
	u32 clusters;
	loff_t newsize, saved_pos;

	/* 
	 * We sample i_size under a read level meta lock to see if our write
	 * is extending the file, if it is we back off and get a write level
	 * meta lock.
	 */
	for(;;) {
		ret = ocfs2_meta_lock(inode, NULL, meta_level);
		if (ret < 0) {
			meta_level = -1;
			mlog_errno(ret);
			goto out;
		}

		/* Clear suid / sgid if necessary. We do this here
		 * instead of later in the write path because
		 * remove_suid() calls ->setattr without any hint that
		 * we may have already done our cluster locking. Since
		 * ocfs2_setattr() *must* take cluster locks to
		 * proceeed, this will lead us to recursively lock the
		 * inode. There's also the dinode i_size state which
		 * can be lost via setattr during extending writes (we
		 * set inode->i_size at the end of a write. */
		if (should_remove_suid(dentry)) {
			if (meta_level == 0) {
				ocfs2_meta_unlock(inode, meta_level);
				meta_level = 1;
				continue;
			}

			ret = ocfs2_write_remove_suid(inode);
			if (ret < 0) {
				mlog_errno(ret);
				goto out_unlock;
			}
		}

		/* work on a copy of ppos until we're sure that we won't have
		 * to recalculate it due to relocking. */
		if (appending) {
			saved_pos = i_size_read(inode);
			mlog(0, "O_APPEND: inode->i_size=%llu\n", saved_pos);
		} else {
			saved_pos = *ppos;
		}

		if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
			loff_t end = saved_pos + count;

			/*
			 * Skip the O_DIRECT checks if we don't need
			 * them.
			 */
			if (!direct_io || !(*direct_io))
				break;

			/*
			 * Allowing concurrent direct writes means
			 * i_size changes wouldn't be synchronized, so
			 * one node could wind up truncating another
			 * nodes writes.
			 */
			if (end > i_size_read(inode)) {
				*direct_io = 0;
				break;
			}

			/*
			 * We don't fill holes during direct io, so
			 * check for them here. If any are found, the
			 * caller will have to retake some cluster
			 * locks and initiate the io as buffered.
			 */
			ret = ocfs2_check_range_for_holes(inode, saved_pos,
							  count);
			if (ret == 1) {
				*direct_io = 0;
				ret = 0;
			} else if (ret < 0)
				mlog_errno(ret);
			break;
		}

		/*
		 * The rest of this loop is concerned with legacy file
		 * systems which don't support sparse files.
		 */

		newsize = count + saved_pos;

		mlog(0, "pos=%lld newsize=%lld cursize=%lld\n",
		     (long long) saved_pos, (long long) newsize,
		     (long long) i_size_read(inode));

		/* No need for a higher level metadata lock if we're
		 * never going past i_size. */
		if (newsize <= i_size_read(inode))
			break;

		if (meta_level == 0) {
			ocfs2_meta_unlock(inode, meta_level);
			meta_level = 1;
			continue;
		}

		spin_lock(&OCFS2_I(inode)->ip_lock);
		clusters = ocfs2_clusters_for_bytes(inode->i_sb, newsize) -
			OCFS2_I(inode)->ip_clusters;
		spin_unlock(&OCFS2_I(inode)->ip_lock);

		mlog(0, "Writing at EOF, may need more allocation: "
		     "i_size = %lld, newsize = %lld, need %u clusters\n",
		     (long long) i_size_read(inode), (long long) newsize,
		     clusters);

		/* We only want to continue the rest of this loop if
		 * our extend will actually require more
		 * allocation. */
		if (!clusters)
			break;

		ret = ocfs2_extend_file(inode, NULL, newsize, count);
		if (ret < 0) {
			if (ret != -ENOSPC)
				mlog_errno(ret);
			goto out_unlock;
		}
		break;
	}

	if (appending)
		*ppos = saved_pos;

out_unlock:
	ocfs2_meta_unlock(inode, meta_level);

out:
	return ret;
}

static inline void
ocfs2_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
{
	const struct iovec *iov = *iovp;
	size_t base = *basep;

	do {
		int copy = min(bytes, iov->iov_len - base);

		bytes -= copy;
		base += copy;
		if (iov->iov_len == base) {
			iov++;
			base = 0;
		}
	} while (bytes);
	*iovp = iov;
	*basep = base;
}

static struct page * ocfs2_get_write_source(char **ret_src_buf,
					    const struct iovec *cur_iov,
					    size_t iov_offset)
{
	int ret;
	char *buf = cur_iov->iov_base + iov_offset;
	struct page *src_page = NULL;
	unsigned long off;

	off = (unsigned long)(buf) & ~PAGE_CACHE_MASK;

	if (!segment_eq(get_fs(), KERNEL_DS)) {
		/*
		 * Pull in the user page. We want to do this outside
		 * of the meta data locks in order to preserve locking
		 * order in case of page fault.
		 */
		ret = get_user_pages(current, current->mm,
				     (unsigned long)buf & PAGE_CACHE_MASK, 1,
				     0, 0, &src_page, NULL);
		if (ret == 1)
			*ret_src_buf = kmap(src_page) + off;
		else
			src_page = ERR_PTR(-EFAULT);
	} else {
		*ret_src_buf = buf;
	}

	return src_page;
}

static void ocfs2_put_write_source(struct page *page)
{
	if (page) {
		kunmap(page);
		page_cache_release(page);
	}
}

static ssize_t ocfs2_file_buffered_write(struct file *file, loff_t *ppos,
					 const struct iovec *iov,
					 unsigned long nr_segs,
					 size_t count,
					 ssize_t o_direct_written)
{
	int ret = 0;
	ssize_t copied, total = 0;
	size_t iov_offset = 0, bytes;
	loff_t pos;
	const struct iovec *cur_iov = iov;
	struct page *user_page, *page;
	char *buf, *dst;
	void *fsdata;

	/*
	 * handle partial DIO write.  Adjust cur_iov if needed.
	 */
	ocfs2_set_next_iovec(&cur_iov, &iov_offset, o_direct_written);

	do {
		pos = *ppos;

		user_page = ocfs2_get_write_source(&buf, cur_iov, iov_offset);
		if (IS_ERR(user_page)) {
			ret = PTR_ERR(user_page);
			goto out;
		}

		/* Stay within our page boundaries */
		bytes = min((PAGE_CACHE_SIZE - ((unsigned long)pos & ~PAGE_CACHE_MASK)),
			    (PAGE_CACHE_SIZE - ((unsigned long)buf & ~PAGE_CACHE_MASK)));
		/* Stay within the vector boundary */
		bytes = min_t(size_t, bytes, cur_iov->iov_len - iov_offset);
		/* Stay within count */
		bytes = min(bytes, count);

		page = NULL;
		ret = ocfs2_write_begin(file, file->f_mapping, pos, bytes, 0,
					&page, &fsdata);
		if (ret) {
			mlog_errno(ret);
			goto out;
		}

		dst = kmap_atomic(page, KM_USER0);
		memcpy(dst + (pos & (PAGE_CACHE_SIZE - 1)), buf, bytes);
		kunmap_atomic(dst, KM_USER0);
		flush_dcache_page(page);
		ocfs2_put_write_source(user_page);

		copied = ocfs2_write_end(file, file->f_mapping, pos, bytes,
					 bytes, page, fsdata);
		if (copied < 0) {
			mlog_errno(copied);
			ret = copied;
			goto out;
		}

		total += copied;
		*ppos = pos + copied;
		count -= copied;

		ocfs2_set_next_iovec(&cur_iov, &iov_offset, copied);
	} while(count);

out:
	return total ? total : ret;
}

static ssize_t ocfs2_file_aio_write(struct kiocb *iocb,
				    const struct iovec *iov,
				    unsigned long nr_segs,
				    loff_t pos)
{
	int ret, direct_io, appending, rw_level, have_alloc_sem  = 0;
	int can_do_direct, sync = 0;
	ssize_t written = 0;
	size_t ocount;		/* original count */
	size_t count;		/* after file limit checks */
	loff_t *ppos = &iocb->ki_pos;
	struct file *file = iocb->ki_filp;
	struct inode *inode = file->f_path.dentry->d_inode;

	mlog_entry("(0x%p, %u, '%.*s')\n", file,
		   (unsigned int)nr_segs,
		   file->f_path.dentry->d_name.len,
		   file->f_path.dentry->d_name.name);

	if (iocb->ki_left == 0)
		return 0;

	ret = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
	if (ret)
		return ret;

	count = ocount;

	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);

	appending = file->f_flags & O_APPEND ? 1 : 0;
	direct_io = file->f_flags & O_DIRECT ? 1 : 0;

	mutex_lock(&inode->i_mutex);

relock:
	/* to match setattr's i_mutex -> i_alloc_sem -> rw_lock ordering */
	if (direct_io) {
		down_read(&inode->i_alloc_sem);
		have_alloc_sem = 1;
	}

	/* concurrent O_DIRECT writes are allowed */
	rw_level = !direct_io;
	ret = ocfs2_rw_lock(inode, rw_level);
	if (ret < 0) {
		mlog_errno(ret);
		goto out_sems;
	}

	can_do_direct = direct_io;
	ret = ocfs2_prepare_inode_for_write(file->f_path.dentry, ppos,
					    iocb->ki_left, appending,
					    &can_do_direct);
	if (ret < 0) {
		mlog_errno(ret);
		goto out;
	}

	/*
	 * We can't complete the direct I/O as requested, fall back to
	 * buffered I/O.
	 */
	if (direct_io && !can_do_direct) {
		ocfs2_rw_unlock(inode, rw_level);
		up_read(&inode->i_alloc_sem);

		have_alloc_sem = 0;
		rw_level = -1;

		direct_io = 0;
		sync = 1;
		goto relock;
	}

	if (!sync && ((file->f_flags & O_SYNC) || IS_SYNC(inode)))
		sync = 1;

	/*
	 * XXX: Is it ok to execute these checks a second time?
	 */
	ret = generic_write_checks(file, ppos, &count, S_ISBLK(inode->i_mode));
	if (ret)
		goto out;

	/*
	 * Set pos so that sync_page_range_nolock() below understands
	 * where to start from. We might've moved it around via the
	 * calls above. The range we want to actually sync starts from
	 * *ppos here.
	 *
	 */
	pos = *ppos;

	/* communicate with ocfs2_dio_end_io */
	ocfs2_iocb_set_rw_locked(iocb, rw_level);

	if (direct_io) {
		written = generic_file_direct_write(iocb, iov, &nr_segs, *ppos,
						    ppos, count, ocount);
		if (written < 0) {
			ret = written;
			goto out_dio;
		}
	} else {
		written = ocfs2_file_buffered_write(file, ppos, iov, nr_segs,
						    count, written);
		if (written < 0) {
			ret = written;
			if (ret != -EFAULT || ret != -ENOSPC)
				mlog_errno(ret);
			goto out;
		}
	}

out_dio:
	/* buffered aio wouldn't have proper lock coverage today */
	BUG_ON(ret == -EIOCBQUEUED && !(file->f_flags & O_DIRECT));

	/* 
	 * deep in g_f_a_w_n()->ocfs2_direct_IO we pass in a ocfs2_dio_end_io
	 * function pointer which is called when o_direct io completes so that
	 * it can unlock our rw lock.  (it's the clustered equivalent of
	 * i_alloc_sem; protects truncate from racing with pending ios).
	 * Unfortunately there are error cases which call end_io and others
	 * that don't.  so we don't have to unlock the rw_lock if either an
	 * async dio is going to do it in the future or an end_io after an
	 * error has already done it.
	 */
	if (ret == -EIOCBQUEUED || !ocfs2_iocb_is_rw_locked(iocb)) {
		rw_level = -1;
		have_alloc_sem = 0;
	}

out:
	if (rw_level != -1)
		ocfs2_rw_unlock(inode, rw_level);

out_sems:
	if (have_alloc_sem)
		up_read(&inode->i_alloc_sem);

	if (written > 0 && sync) {
		ssize_t err;

		err = sync_page_range_nolock(inode, file->f_mapping, pos, count);
		if (err < 0)
			written = err;
	}

	mutex_unlock(&inode->i_mutex);

	mlog_exit(ret);
	return written ? written : ret;
}

static int ocfs2_splice_write_actor(struct pipe_inode_info *pipe,
				    struct pipe_buffer *buf,
				    struct splice_desc *sd)
{
	int ret, count;
	ssize_t copied = 0;
	struct file *file = sd->u.file;
	unsigned int offset;
	struct page *page = NULL;
	void *fsdata;
	char *src, *dst;

	ret = buf->ops->confirm(pipe, buf);
	if (ret)
		goto out;

	offset = sd->pos & ~PAGE_CACHE_MASK;
	count = sd->len;
	if (count + offset > PAGE_CACHE_SIZE)
		count = PAGE_CACHE_SIZE - offset;

	ret = ocfs2_write_begin(file, file->f_mapping, sd->pos, count, 0,
				&page, &fsdata);
	if (ret) {
		mlog_errno(ret);
		goto out;
	}

	src = buf->ops->map(pipe, buf, 1);
	dst = kmap_atomic(page, KM_USER1);
	memcpy(dst + offset, src + buf->offset, count);
	kunmap_atomic(page, KM_USER1);
	buf->ops->unmap(pipe, buf, src);

	copied = ocfs2_write_end(file, file->f_mapping, sd->pos, count, count,
				 page, fsdata);
	if (copied < 0) {
		mlog_errno(copied);
		ret = copied;
		goto out;
	}
out:

	return copied ? copied : ret;
}

static ssize_t __ocfs2_file_splice_write(struct pipe_inode_info *pipe,
					 struct file *out,
					 loff_t *ppos,
					 size_t len,
					 unsigned int flags)
{
	int ret, err;
	struct address_space *mapping = out->f_mapping;
	struct inode *inode = mapping->host;
	struct splice_desc sd = {
		.total_len = len,
		.flags = flags,
		.pos = *ppos,
		.u.file = out,
	};

	ret = __splice_from_pipe(pipe, &sd, ocfs2_splice_write_actor);
	if (ret > 0) {
		*ppos += ret;

		if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
			err = generic_osync_inode(inode, mapping,
						  OSYNC_METADATA|OSYNC_DATA);
			if (err)
				ret = err;
		}
	}

	return ret;
}

static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
				       struct file *out,
				       loff_t *ppos,
				       size_t len,
				       unsigned int flags)
{
	int ret;
	struct inode *inode = out->f_path.dentry->d_inode;

	mlog_entry("(0x%p, 0x%p, %u, '%.*s')\n", out, pipe,
		   (unsigned int)len,
		   out->f_path.dentry->d_name.len,
		   out->f_path.dentry->d_name.name);

	inode_double_lock(inode, pipe->inode);

	ret = ocfs2_rw_lock(inode, 1);
	if (ret < 0) {
		mlog_errno(ret);
		goto out;
	}

	ret = ocfs2_prepare_inode_for_write(out->f_path.dentry, ppos, len, 0,
					    NULL);
	if (ret < 0) {
		mlog_errno(ret);
		goto out_unlock;
	}

	/* ok, we're done with i_size and alloc work */
	ret = __ocfs2_file_splice_write(pipe, out, ppos, len, flags);

out_unlock:
	ocfs2_rw_unlock(inode, 1);
out:
	inode_double_unlock(inode, pipe->inode);

	mlog_exit(ret);
	return ret;
}

static ssize_t ocfs2_file_splice_read(struct file *in,
				      loff_t *ppos,
				      struct pipe_inode_info *pipe,
				      size_t len,
				      unsigned int flags)
{
	int ret = 0;
	struct inode *inode = in->f_path.dentry->d_inode;

	mlog_entry("(0x%p, 0x%p, %u, '%.*s')\n", in, pipe,
		   (unsigned int)len,
		   in->f_path.dentry->d_name.len,
		   in->f_path.dentry->d_name.name);

	/*
	 * See the comment in ocfs2_file_aio_read()
	 */
	ret = ocfs2_meta_lock(inode, NULL, 0);
	if (ret < 0) {
		mlog_errno(ret);
		goto bail;
	}
	ocfs2_meta_unlock(inode, 0);

	ret = generic_file_splice_read(in, ppos, pipe, len, flags);

bail:
	mlog_exit(ret);
	return ret;
}

static ssize_t ocfs2_file_aio_read(struct kiocb *iocb,
				   const struct iovec *iov,
				   unsigned long nr_segs,
				   loff_t pos)
{
	int ret = 0, rw_level = -1, have_alloc_sem = 0, lock_level = 0;
	struct file *filp = iocb->ki_filp;
	struct inode *inode = filp->f_path.dentry->d_inode;

	mlog_entry("(0x%p, %u, '%.*s')\n", filp,
		   (unsigned int)nr_segs,
		   filp->f_path.dentry->d_name.len,
		   filp->f_path.dentry->d_name.name);

	if (!inode) {
		ret = -EINVAL;
		mlog_errno(ret);
		goto bail;
	}

	/* 
	 * buffered reads protect themselves in ->readpage().  O_DIRECT reads
	 * need locks to protect pending reads from racing with truncate.
	 */
	if (filp->f_flags & O_DIRECT) {
		down_read(&inode->i_alloc_sem);
		have_alloc_sem = 1;

		ret = ocfs2_rw_lock(inode, 0);
		if (ret < 0) {
			mlog_errno(ret);
			goto bail;
		}
		rw_level = 0;
		/* communicate with ocfs2_dio_end_io */
		ocfs2_iocb_set_rw_locked(iocb, rw_level);
	}

	/*
	 * We're fine letting folks race truncates and extending
	 * writes with read across the cluster, just like they can
	 * locally. Hence no rw_lock during read.
	 * 
	 * Take and drop the meta data lock to update inode fields
	 * like i_size. This allows the checks down below
	 * generic_file_aio_read() a chance of actually working. 
	 */
	ret = ocfs2_meta_lock_atime(inode, filp->f_vfsmnt, &lock_level);
	if (ret < 0) {
		mlog_errno(ret);
		goto bail;
	}
	ocfs2_meta_unlock(inode, lock_level);

	ret = generic_file_aio_read(iocb, iov, nr_segs, iocb->ki_pos);
	if (ret == -EINVAL)
		mlog(ML_ERROR, "generic_file_aio_read returned -EINVAL\n");

	/* buffered aio wouldn't have proper lock coverage today */
	BUG_ON(ret == -EIOCBQUEUED && !(filp->f_flags & O_DIRECT));

	/* see ocfs2_file_aio_write */
	if (ret == -EIOCBQUEUED || !ocfs2_iocb_is_rw_locked(iocb)) {
		rw_level = -1;
		have_alloc_sem = 0;
	}

bail:
	if (have_alloc_sem)
		up_read(&inode->i_alloc_sem);
	if (rw_level != -1) 
		ocfs2_rw_unlock(inode, rw_level);
	mlog_exit(ret);

	return ret;
}

const struct inode_operations ocfs2_file_iops = {
	.setattr	= ocfs2_setattr,
	.getattr	= ocfs2_getattr,
	.permission	= ocfs2_permission,
};

const struct inode_operations ocfs2_special_file_iops = {
	.setattr	= ocfs2_setattr,
	.getattr	= ocfs2_getattr,
	.permission	= ocfs2_permission,
};

const struct file_operations ocfs2_fops = {
	.read		= do_sync_read,
	.write		= do_sync_write,
	.mmap		= ocfs2_mmap,
	.fsync		= ocfs2_sync_file,
	.release	= ocfs2_file_release,
	.open		= ocfs2_file_open,
	.aio_read	= ocfs2_file_aio_read,
	.aio_write	= ocfs2_file_aio_write,
	.ioctl		= ocfs2_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl   = ocfs2_compat_ioctl,
#endif
	.splice_read	= ocfs2_file_splice_read,
	.splice_write	= ocfs2_file_splice_write,
};

const struct file_operations ocfs2_dops = {
	.read		= generic_read_dir,
	.readdir	= ocfs2_readdir,
	.fsync		= ocfs2_sync_file,
	.ioctl		= ocfs2_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl   = ocfs2_compat_ioctl,
#endif
};