/*
   * Copyright (C) 2007 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 v2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */

  #include <linux/fs.h>

  #include <linux/slab.h>

  #include <linux/sched.h>

  #include <linux/writeback.h>

  #include <linux/pagemap.h>

  #include <linux/blkdev.h>

  #include "ctree.h"
  #include "disk-io.h"
  #include "transaction.h"

  #include "locking.h"

  #include "tree-log.h"

  #include "inode-map.h"

  #define BTRFS_ROOT_TRANS_TAG 0

  static noinline void put_transaction(struct btrfs_transaction *transaction)

  {

  	WARN_ON(atomic_read(&transaction->use_count) == 0);
  	if (atomic_dec_and_test(&transaction->use_count)) {

  		BUG_ON(!list_empty(&transaction->list));

  		memset(transaction, 0, sizeof(*transaction));
  		kmem_cache_free(btrfs_transaction_cachep, transaction);

  	}

  }

  static noinline void switch_commit_root(struct btrfs_root *root)
  {

  	free_extent_buffer(root->commit_root);
  	root->commit_root = btrfs_root_node(root);

  }

  /*
   * either allocate a new transaction or hop into the existing one
   */

  static noinline int join_transaction(struct btrfs_root *root, int nofail)

  {
  	struct btrfs_transaction *cur_trans;

  
  	spin_lock(&root->fs_info->trans_lock);

  loop:

  	if (root->fs_info->trans_no_join) {
  		if (!nofail) {
  			spin_unlock(&root->fs_info->trans_lock);
  			return -EBUSY;
  		}
  	}

  	cur_trans = root->fs_info->running_transaction;

  	if (cur_trans) {
  		atomic_inc(&cur_trans->use_count);

  		atomic_inc(&cur_trans->num_writers);

  		cur_trans->num_joined++;

  		spin_unlock(&root->fs_info->trans_lock);
  		return 0;

  	}

  	spin_unlock(&root->fs_info->trans_lock);
  
  	cur_trans = kmem_cache_alloc(btrfs_transaction_cachep, GFP_NOFS);
  	if (!cur_trans)
  		return -ENOMEM;

  	spin_lock(&root->fs_info->trans_lock);
  	if (root->fs_info->running_transaction) {

  		/*
  		 * someone started a transaction after we unlocked.  Make sure
  		 * to redo the trans_no_join checks above
  		 */

  		kmem_cache_free(btrfs_transaction_cachep, cur_trans);
  		cur_trans = root->fs_info->running_transaction;

  		goto loop;

  	}

  	atomic_set(&cur_trans->num_writers, 1);
  	cur_trans->num_joined = 0;
  	init_waitqueue_head(&cur_trans->writer_wait);
  	init_waitqueue_head(&cur_trans->commit_wait);
  	cur_trans->in_commit = 0;
  	cur_trans->blocked = 0;
  	/*
  	 * One for this trans handle, one so it will live on until we
  	 * commit the transaction.
  	 */
  	atomic_set(&cur_trans->use_count, 2);
  	cur_trans->commit_done = 0;
  	cur_trans->start_time = get_seconds();
  
  	cur_trans->delayed_refs.root = RB_ROOT;
  	cur_trans->delayed_refs.num_entries = 0;
  	cur_trans->delayed_refs.num_heads_ready = 0;
  	cur_trans->delayed_refs.num_heads = 0;
  	cur_trans->delayed_refs.flushing = 0;
  	cur_trans->delayed_refs.run_delayed_start = 0;
  	spin_lock_init(&cur_trans->commit_lock);
  	spin_lock_init(&cur_trans->delayed_refs.lock);
  
  	INIT_LIST_HEAD(&cur_trans->pending_snapshots);
  	list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
  	extent_io_tree_init(&cur_trans->dirty_pages,

  			     root->fs_info->btree_inode->i_mapping);

  	root->fs_info->generation++;
  	cur_trans->transid = root->fs_info->generation;
  	root->fs_info->running_transaction = cur_trans;
  	spin_unlock(&root->fs_info->trans_lock);

  	return 0;
  }

  /*

   * this does all the record keeping required to make sure that a reference
   * counted root is properly recorded in a given transaction.  This is required
   * to make sure the old root from before we joined the transaction is deleted
   * when the transaction commits

   */

  static int record_root_in_trans(struct btrfs_trans_handle *trans,

  			       struct btrfs_root *root)

  {

  	if (root->ref_cows && root->last_trans < trans->transid) {

  		WARN_ON(root == root->fs_info->extent_root);

  		WARN_ON(root->commit_root != root->node);

  		/*
  		 * see below for in_trans_setup usage rules
  		 * we have the reloc mutex held now, so there
  		 * is only one writer in this function
  		 */
  		root->in_trans_setup = 1;
  
  		/* make sure readers find in_trans_setup before
  		 * they find our root->last_trans update
  		 */
  		smp_wmb();

  		spin_lock(&root->fs_info->fs_roots_radix_lock);
  		if (root->last_trans == trans->transid) {
  			spin_unlock(&root->fs_info->fs_roots_radix_lock);
  			return 0;
  		}

  		radix_tree_tag_set(&root->fs_info->fs_roots_radix,
  			   (unsigned long)root->root_key.objectid,
  			   BTRFS_ROOT_TRANS_TAG);

  		spin_unlock(&root->fs_info->fs_roots_radix_lock);

  		root->last_trans = trans->transid;
  
  		/* this is pretty tricky.  We don't want to
  		 * take the relocation lock in btrfs_record_root_in_trans
  		 * unless we're really doing the first setup for this root in
  		 * this transaction.
  		 *
  		 * Normally we'd use root->last_trans as a flag to decide
  		 * if we want to take the expensive mutex.
  		 *
  		 * But, we have to set root->last_trans before we
  		 * init the relocation root, otherwise, we trip over warnings
  		 * in ctree.c.  The solution used here is to flag ourselves
  		 * with root->in_trans_setup.  When this is 1, we're still
  		 * fixing up the reloc trees and everyone must wait.
  		 *
  		 * When this is zero, they can trust root->last_trans and fly
  		 * through btrfs_record_root_in_trans without having to take the
  		 * lock.  smp_wmb() makes sure that all the writes above are
  		 * done before we pop in the zero below
  		 */

  		btrfs_init_reloc_root(trans, root);

  		smp_wmb();
  		root->in_trans_setup = 0;

  	}
  	return 0;
  }

  
  int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
  			       struct btrfs_root *root)
  {
  	if (!root->ref_cows)
  		return 0;
  
  	/*
  	 * see record_root_in_trans for comments about in_trans_setup usage
  	 * and barriers
  	 */
  	smp_rmb();
  	if (root->last_trans == trans->transid &&
  	    !root->in_trans_setup)
  		return 0;
  
  	mutex_lock(&root->fs_info->reloc_mutex);
  	record_root_in_trans(trans, root);
  	mutex_unlock(&root->fs_info->reloc_mutex);
  
  	return 0;
  }

  /* wait for commit against the current transaction to become unblocked
   * when this is done, it is safe to start a new transaction, but the current
   * transaction might not be fully on disk.
   */

  static void wait_current_trans(struct btrfs_root *root)

  {

  	struct btrfs_transaction *cur_trans;

  	spin_lock(&root->fs_info->trans_lock);

  	cur_trans = root->fs_info->running_transaction;

  	if (cur_trans && cur_trans->blocked) {

  		atomic_inc(&cur_trans->use_count);

  		spin_unlock(&root->fs_info->trans_lock);

  
  		wait_event(root->fs_info->transaction_wait,
  			   !cur_trans->blocked);

  		put_transaction(cur_trans);

  	} else {
  		spin_unlock(&root->fs_info->trans_lock);

  	}

  }

  enum btrfs_trans_type {
  	TRANS_START,
  	TRANS_JOIN,
  	TRANS_USERSPACE,

  	TRANS_JOIN_NOLOCK,

  };

  static int may_wait_transaction(struct btrfs_root *root, int type)
  {

  	if (root->fs_info->log_root_recovering)
  		return 0;
  
  	if (type == TRANS_USERSPACE)
  		return 1;
  
  	if (type == TRANS_START &&
  	    !atomic_read(&root->fs_info->open_ioctl_trans))

  		return 1;

  	return 0;
  }

  static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,

  						    u64 num_items, int type)

  {

  	struct btrfs_trans_handle *h;
  	struct btrfs_transaction *cur_trans;

  	u64 num_bytes = 0;

  	int ret;

  
  	if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
  		return ERR_PTR(-EROFS);

  
  	if (current->journal_info) {
  		WARN_ON(type != TRANS_JOIN && type != TRANS_JOIN_NOLOCK);
  		h = current->journal_info;
  		h->use_count++;
  		h->orig_rsv = h->block_rsv;
  		h->block_rsv = NULL;
  		goto got_it;
  	}

  
  	/*
  	 * Do the reservation before we join the transaction so we can do all
  	 * the appropriate flushing if need be.
  	 */
  	if (num_items > 0 && root != root->fs_info->chunk_root) {
  		num_bytes = btrfs_calc_trans_metadata_size(root, num_items);

  		ret = btrfs_block_rsv_add(root,

  					  &root->fs_info->trans_block_rsv,
  					  num_bytes);
  		if (ret)
  			return ERR_PTR(ret);
  	}

  again:
  	h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
  	if (!h)
  		return ERR_PTR(-ENOMEM);

  	if (may_wait_transaction(root, type))

  		wait_current_trans(root);

  	do {
  		ret = join_transaction(root, type == TRANS_JOIN_NOLOCK);
  		if (ret == -EBUSY)
  			wait_current_trans(root);
  	} while (ret == -EBUSY);

  	if (ret < 0) {

  		kmem_cache_free(btrfs_trans_handle_cachep, h);

  		return ERR_PTR(ret);
  	}

  	cur_trans = root->fs_info->running_transaction;

  
  	h->transid = cur_trans->transid;
  	h->transaction = cur_trans;

  	h->blocks_used = 0;

  	h->bytes_reserved = 0;

  	h->delayed_ref_updates = 0;

  	h->use_count = 1;

  	h->block_rsv = NULL;

  	h->orig_rsv = NULL;

  	smp_mb();
  	if (cur_trans->blocked && may_wait_transaction(root, type)) {
  		btrfs_commit_transaction(h, root);
  		goto again;
  	}

  	if (num_bytes) {
  		h->block_rsv = &root->fs_info->trans_block_rsv;
  		h->bytes_reserved = num_bytes;

  	}

  got_it:

  	btrfs_record_root_in_trans(h, root);

  
  	if (!current->journal_info && type != TRANS_USERSPACE)
  		current->journal_info = h;

  	return h;
  }

  struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,

  						   int num_items)

  {

  	return start_transaction(root, num_items, TRANS_START);

  }

  struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root)

  {

  	return start_transaction(root, 0, TRANS_JOIN);

  }

  struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root)

  {
  	return start_transaction(root, 0, TRANS_JOIN_NOLOCK);
  }

  struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *root)

  {

  	return start_transaction(root, 0, TRANS_USERSPACE);

  }

  /* wait for a transaction commit to be fully complete */

  static noinline void wait_for_commit(struct btrfs_root *root,

  				    struct btrfs_transaction *commit)
  {

  	wait_event(commit->commit_wait, commit->commit_done);

  }

  int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
  {
  	struct btrfs_transaction *cur_trans = NULL, *t;
  	int ret;

  	ret = 0;
  	if (transid) {
  		if (transid <= root->fs_info->last_trans_committed)

  			goto out;

  
  		/* find specified transaction */

  		spin_lock(&root->fs_info->trans_lock);

  		list_for_each_entry(t, &root->fs_info->trans_list, list) {
  			if (t->transid == transid) {
  				cur_trans = t;

  				atomic_inc(&cur_trans->use_count);

  				break;
  			}
  			if (t->transid > transid)
  				break;
  		}

  		spin_unlock(&root->fs_info->trans_lock);

  		ret = -EINVAL;
  		if (!cur_trans)

  			goto out;  /* bad transid */

  	} else {
  		/* find newest transaction that is committing | committed */

  		spin_lock(&root->fs_info->trans_lock);

  		list_for_each_entry_reverse(t, &root->fs_info->trans_list,
  					    list) {
  			if (t->in_commit) {
  				if (t->commit_done)

  					break;

  				cur_trans = t;

  				atomic_inc(&cur_trans->use_count);

  				break;
  			}
  		}

  		spin_unlock(&root->fs_info->trans_lock);

  		if (!cur_trans)

  			goto out;  /* nothing committing|committed */

  	}

  	wait_for_commit(root, cur_trans);

  	put_transaction(cur_trans);
  	ret = 0;

  out:

  	return ret;
  }

  void btrfs_throttle(struct btrfs_root *root)
  {

  	if (!atomic_read(&root->fs_info->open_ioctl_trans))

  		wait_current_trans(root);

  }

  static int should_end_transaction(struct btrfs_trans_handle *trans,
  				  struct btrfs_root *root)
  {
  	int ret;

  
  	ret = btrfs_block_rsv_check(root, &root->fs_info->global_block_rsv, 5);

  	return ret ? 1 : 0;
  }
  
  int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
  				 struct btrfs_root *root)
  {
  	struct btrfs_transaction *cur_trans = trans->transaction;

  	struct btrfs_block_rsv *rsv = trans->block_rsv;

  	int updates;

  	smp_mb();

  	if (cur_trans->blocked || cur_trans->delayed_refs.flushing)
  		return 1;

  	/*
  	 * We need to do this in case we're deleting csums so the global block
  	 * rsv get's used instead of the csum block rsv.
  	 */
  	trans->block_rsv = NULL;

  	updates = trans->delayed_ref_updates;
  	trans->delayed_ref_updates = 0;
  	if (updates)
  		btrfs_run_delayed_refs(trans, root, updates);

  	trans->block_rsv = rsv;

  	return should_end_transaction(trans, root);
  }

  static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,

  			  struct btrfs_root *root, int throttle, int lock)

  {

  	struct btrfs_transaction *cur_trans = trans->transaction;

  	struct btrfs_fs_info *info = root->fs_info;

  	int count = 0;

  	if (--trans->use_count) {
  		trans->block_rsv = trans->orig_rsv;
  		return 0;
  	}

  	btrfs_trans_release_metadata(trans, root);

  	trans->block_rsv = NULL;

  	while (count < 4) {
  		unsigned long cur = trans->delayed_ref_updates;
  		trans->delayed_ref_updates = 0;
  		if (cur &&
  		    trans->transaction->delayed_refs.num_heads_ready > 64) {
  			trans->delayed_ref_updates = 0;

  
  			/*
  			 * do a full flush if the transaction is trying
  			 * to close
  			 */
  			if (trans->transaction->delayed_refs.flushing)
  				cur = 0;

  			btrfs_run_delayed_refs(trans, root, cur);
  		} else {
  			break;
  		}
  		count++;

  	}

  	if (lock && !atomic_read(&root->fs_info->open_ioctl_trans) &&
  	    should_end_transaction(trans, root)) {

  		trans->transaction->blocked = 1;

  		smp_wmb();
  	}

  	if (lock && cur_trans->blocked && !cur_trans->in_commit) {

  		if (throttle) {
  			/*
  			 * We may race with somebody else here so end up having
  			 * to call end_transaction on ourselves again, so inc
  			 * our use_count.
  			 */
  			trans->use_count++;

  			return btrfs_commit_transaction(trans, root);

  		} else {

  			wake_up_process(info->transaction_kthread);

  		}

  	}

  	WARN_ON(cur_trans != info->running_transaction);

  	WARN_ON(atomic_read(&cur_trans->num_writers) < 1);
  	atomic_dec(&cur_trans->num_writers);

  	smp_mb();

  	if (waitqueue_active(&cur_trans->writer_wait))
  		wake_up(&cur_trans->writer_wait);

  	put_transaction(cur_trans);

  
  	if (current->journal_info == trans)
  		current->journal_info = NULL;

  	memset(trans, 0, sizeof(*trans));

  	kmem_cache_free(btrfs_trans_handle_cachep, trans);

  	if (throttle)
  		btrfs_run_delayed_iputs(root);

  	return 0;
  }

  int btrfs_end_transaction(struct btrfs_trans_handle *trans,
  			  struct btrfs_root *root)
  {

  	int ret;
  
  	ret = __btrfs_end_transaction(trans, root, 0, 1);
  	if (ret)
  		return ret;
  	return 0;

  }
  
  int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
  				   struct btrfs_root *root)
  {

  	int ret;
  
  	ret = __btrfs_end_transaction(trans, root, 1, 1);
  	if (ret)
  		return ret;
  	return 0;

  }
  
  int btrfs_end_transaction_nolock(struct btrfs_trans_handle *trans,
  				 struct btrfs_root *root)
  {

  	int ret;
  
  	ret = __btrfs_end_transaction(trans, root, 0, 0);
  	if (ret)
  		return ret;
  	return 0;
  }
  
  int btrfs_end_transaction_dmeta(struct btrfs_trans_handle *trans,
  				struct btrfs_root *root)
  {
  	return __btrfs_end_transaction(trans, root, 1, 1);

  }

  /*
   * when btree blocks are allocated, they have some corresponding bits set for
   * them in one of two extent_io trees.  This is used to make sure all of

   * those extents are sent to disk but does not wait on them

   */

  int btrfs_write_marked_extents(struct btrfs_root *root,

  			       struct extent_io_tree *dirty_pages, int mark)

  {

  	int err = 0;

  	int werr = 0;

  	struct address_space *mapping = root->fs_info->btree_inode->i_mapping;

  	u64 start = 0;

  	u64 end;

  	while (!find_first_extent_bit(dirty_pages, start, &start, &end,
  				      mark)) {
  		convert_extent_bit(dirty_pages, start, end, EXTENT_NEED_WAIT, mark,
  				   GFP_NOFS);
  		err = filemap_fdatawrite_range(mapping, start, end);
  		if (err)
  			werr = err;
  		cond_resched();
  		start = end + 1;

  	}

  	if (err)
  		werr = err;
  	return werr;
  }
  
  /*
   * when btree blocks are allocated, they have some corresponding bits set for
   * them in one of two extent_io trees.  This is used to make sure all of
   * those extents are on disk for transaction or log commit.  We wait
   * on all the pages and clear them from the dirty pages state tree
   */
  int btrfs_wait_marked_extents(struct btrfs_root *root,

  			      struct extent_io_tree *dirty_pages, int mark)

  {

  	int err = 0;
  	int werr = 0;

  	struct address_space *mapping = root->fs_info->btree_inode->i_mapping;

  	u64 start = 0;
  	u64 end;

  	while (!find_first_extent_bit(dirty_pages, start, &start, &end,
  				      EXTENT_NEED_WAIT)) {
  		clear_extent_bits(dirty_pages, start, end, EXTENT_NEED_WAIT, GFP_NOFS);
  		err = filemap_fdatawait_range(mapping, start, end);
  		if (err)
  			werr = err;
  		cond_resched();
  		start = end + 1;

  	}

  	if (err)
  		werr = err;
  	return werr;

  }

  /*
   * when btree blocks are allocated, they have some corresponding bits set for
   * them in one of two extent_io trees.  This is used to make sure all of
   * those extents are on disk for transaction or log commit
   */
  int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,

  				struct extent_io_tree *dirty_pages, int mark)

  {
  	int ret;
  	int ret2;

  	ret = btrfs_write_marked_extents(root, dirty_pages, mark);
  	ret2 = btrfs_wait_marked_extents(root, dirty_pages, mark);

  
  	if (ret)
  		return ret;
  	if (ret2)
  		return ret2;
  	return 0;

  }

  int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
  				     struct btrfs_root *root)
  {
  	if (!trans || !trans->transaction) {
  		struct inode *btree_inode;
  		btree_inode = root->fs_info->btree_inode;
  		return filemap_write_and_wait(btree_inode->i_mapping);
  	}
  	return btrfs_write_and_wait_marked_extents(root,

  					   &trans->transaction->dirty_pages,
  					   EXTENT_DIRTY);

  }

  /*
   * this is used to update the root pointer in the tree of tree roots.
   *
   * But, in the case of the extent allocation tree, updating the root
   * pointer may allocate blocks which may change the root of the extent
   * allocation tree.
   *
   * So, this loops and repeats and makes sure the cowonly root didn't
   * change while the root pointer was being updated in the metadata.
   */

  static int update_cowonly_root(struct btrfs_trans_handle *trans,
  			       struct btrfs_root *root)

  {
  	int ret;

  	u64 old_root_bytenr;

  	u64 old_root_used;

  	struct btrfs_root *tree_root = root->fs_info->tree_root;

  	old_root_used = btrfs_root_used(&root->root_item);

  	btrfs_write_dirty_block_groups(trans, root);

  	while (1) {

  		old_root_bytenr = btrfs_root_bytenr(&root->root_item);

  		if (old_root_bytenr == root->node->start &&
  		    old_root_used == btrfs_root_used(&root->root_item))

  			break;

  		btrfs_set_root_node(&root->root_item, root->node);

  		ret = btrfs_update_root(trans, tree_root,

  					&root->root_key,
  					&root->root_item);

  		BUG_ON(ret);

  		old_root_used = btrfs_root_used(&root->root_item);

  		ret = btrfs_write_dirty_block_groups(trans, root);

  		BUG_ON(ret);

  	}

  
  	if (root != root->fs_info->extent_root)
  		switch_commit_root(root);

  	return 0;
  }

  /*
   * update all the cowonly tree roots on disk
   */

  static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
  					 struct btrfs_root *root)

  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct list_head *next;

  	struct extent_buffer *eb;

  	int ret;

  	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
  	BUG_ON(ret);

  	eb = btrfs_lock_root_node(fs_info->tree_root);

  	btrfs_cow_block(trans, fs_info->tree_root, eb, NULL, 0, &eb);

  	btrfs_tree_unlock(eb);
  	free_extent_buffer(eb);

  	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
  	BUG_ON(ret);

  	while (!list_empty(&fs_info->dirty_cowonly_roots)) {

  		next = fs_info->dirty_cowonly_roots.next;
  		list_del_init(next);
  		root = list_entry(next, struct btrfs_root, dirty_list);

  		update_cowonly_root(trans, root);

  	}

  
  	down_write(&fs_info->extent_commit_sem);
  	switch_commit_root(fs_info->extent_root);
  	up_write(&fs_info->extent_commit_sem);

  	return 0;
  }

  /*
   * dead roots are old snapshots that need to be deleted.  This allocates
   * a dirty root struct and adds it into the list of dead roots that need to
   * be deleted
   */

  int btrfs_add_dead_root(struct btrfs_root *root)

  {

  	spin_lock(&root->fs_info->trans_lock);

  	list_add(&root->root_list, &root->fs_info->dead_roots);

  	spin_unlock(&root->fs_info->trans_lock);

  	return 0;
  }

  /*

   * update all the cowonly tree roots on disk

   */

  static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
  				    struct btrfs_root *root)

  {

  	struct btrfs_root *gang[8];

  	struct btrfs_fs_info *fs_info = root->fs_info;

  	int i;
  	int ret;

  	int err = 0;

  	spin_lock(&fs_info->fs_roots_radix_lock);

  	while (1) {

  		ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
  						 (void **)gang, 0,

  						 ARRAY_SIZE(gang),
  						 BTRFS_ROOT_TRANS_TAG);
  		if (ret == 0)
  			break;
  		for (i = 0; i < ret; i++) {
  			root = gang[i];

  			radix_tree_tag_clear(&fs_info->fs_roots_radix,
  					(unsigned long)root->root_key.objectid,
  					BTRFS_ROOT_TRANS_TAG);

  			spin_unlock(&fs_info->fs_roots_radix_lock);

  			btrfs_free_log(trans, root);

  			btrfs_update_reloc_root(trans, root);

  			btrfs_orphan_commit_root(trans, root);

  			btrfs_save_ino_cache(root, trans);

  			/* see comments in should_cow_block() */
  			root->force_cow = 0;
  			smp_wmb();

  			if (root->commit_root != root->node) {

  				mutex_lock(&root->fs_commit_mutex);

  				switch_commit_root(root);

  				btrfs_unpin_free_ino(root);
  				mutex_unlock(&root->fs_commit_mutex);

  				btrfs_set_root_node(&root->root_item,
  						    root->node);
  			}

  			err = btrfs_update_root(trans, fs_info->tree_root,

  						&root->root_key,
  						&root->root_item);

  			spin_lock(&fs_info->fs_roots_radix_lock);

  			if (err)
  				break;

  		}
  	}

  	spin_unlock(&fs_info->fs_roots_radix_lock);

  	return err;

  }

  /*
   * defrag a given btree.  If cacheonly == 1, this won't read from the disk,
   * otherwise every leaf in the btree is read and defragged.
   */

  int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
  {
  	struct btrfs_fs_info *info = root->fs_info;

  	struct btrfs_trans_handle *trans;

  	int ret;

  	unsigned long nr;

  	if (xchg(&root->defrag_running, 1))

  		return 0;

  	while (1) {

  		trans = btrfs_start_transaction(root, 0);
  		if (IS_ERR(trans))
  			return PTR_ERR(trans);

  		ret = btrfs_defrag_leaves(trans, root, cacheonly);

  		nr = trans->blocks_used;

  		btrfs_end_transaction(trans, root);

  		btrfs_btree_balance_dirty(info->tree_root, nr);

  		cond_resched();

  		if (btrfs_fs_closing(root->fs_info) || ret != -EAGAIN)

  			break;
  	}
  	root->defrag_running = 0;

  	return ret;

  }

  /*
   * new snapshots need to be created at a very specific time in the
   * transaction commit.  This does the actual creation
   */

  static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,

  				   struct btrfs_fs_info *fs_info,
  				   struct btrfs_pending_snapshot *pending)
  {
  	struct btrfs_key key;

  	struct btrfs_root_item *new_root_item;

  	struct btrfs_root *tree_root = fs_info->tree_root;
  	struct btrfs_root *root = pending->root;

  	struct btrfs_root *parent_root;

  	struct btrfs_block_rsv *rsv;

  	struct inode *parent_inode;

  	struct dentry *parent;

  	struct dentry *dentry;

  	struct extent_buffer *tmp;

  	struct extent_buffer *old;

  	int ret;

  	u64 to_reserve = 0;

  	u64 index = 0;

  	u64 objectid;

  	u64 root_flags;

  	rsv = trans->block_rsv;

  	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
  	if (!new_root_item) {

  		pending->error = -ENOMEM;

  		goto fail;
  	}

  	ret = btrfs_find_free_objectid(tree_root, &objectid);

  	if (ret) {
  		pending->error = ret;

  		goto fail;

  	}

  	btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);

  
  	if (to_reserve > 0) {

  		ret = btrfs_block_rsv_add_noflush(root, &pending->block_rsv,
  						  to_reserve);

  		if (ret) {
  			pending->error = ret;
  			goto fail;
  		}
  	}

  	key.objectid = objectid;

  	key.offset = (u64)-1;
  	key.type = BTRFS_ROOT_ITEM_KEY;

  	trans->block_rsv = &pending->block_rsv;

  	dentry = pending->dentry;

  	parent = dget_parent(dentry);
  	parent_inode = parent->d_inode;

  	parent_root = BTRFS_I(parent_inode)->root;

  	record_root_in_trans(trans, parent_root);

  	/*
  	 * insert the directory item
  	 */

  	ret = btrfs_set_inode_index(parent_inode, &index);

  	BUG_ON(ret);

  	ret = btrfs_insert_dir_item(trans, parent_root,

  				dentry->d_name.name, dentry->d_name.len,

  				parent_inode, &key,

  				BTRFS_FT_DIR, index);

  	BUG_ON(ret);

  	btrfs_i_size_write(parent_inode, parent_inode->i_size +
  					 dentry->d_name.len * 2);

  	ret = btrfs_update_inode(trans, parent_root, parent_inode);
  	BUG_ON(ret);

  	/*
  	 * pull in the delayed directory update
  	 * and the delayed inode item
  	 * otherwise we corrupt the FS during
  	 * snapshot
  	 */
  	ret = btrfs_run_delayed_items(trans, root);
  	BUG_ON(ret);

  	record_root_in_trans(trans, root);

  	btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
  	memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));

  	btrfs_check_and_init_root_item(new_root_item);

  	root_flags = btrfs_root_flags(new_root_item);
  	if (pending->readonly)
  		root_flags |= BTRFS_ROOT_SUBVOL_RDONLY;
  	else
  		root_flags &= ~BTRFS_ROOT_SUBVOL_RDONLY;
  	btrfs_set_root_flags(new_root_item, root_flags);

  	old = btrfs_lock_root_node(root);
  	btrfs_cow_block(trans, root, old, NULL, 0, &old);
  	btrfs_set_lock_blocking(old);
  
  	btrfs_copy_root(trans, root, old, &tmp, objectid);
  	btrfs_tree_unlock(old);
  	free_extent_buffer(old);

  	/* see comments in should_cow_block() */
  	root->force_cow = 1;
  	smp_wmb();

  	btrfs_set_root_node(new_root_item, tmp);

  	/* record when the snapshot was created in key.offset */
  	key.offset = trans->transid;
  	ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);

  	btrfs_tree_unlock(tmp);
  	free_extent_buffer(tmp);

  	BUG_ON(ret);

  	/*
  	 * insert root back/forward references
  	 */
  	ret = btrfs_add_root_ref(trans, tree_root, objectid,

  				 parent_root->root_key.objectid,

  				 btrfs_ino(parent_inode), index,

  				 dentry->d_name.name, dentry->d_name.len);

  	BUG_ON(ret);

  	dput(parent);

  	key.offset = (u64)-1;
  	pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
  	BUG_ON(IS_ERR(pending->snap));

  	btrfs_reloc_post_snapshot(trans, pending);

  fail:

  	kfree(new_root_item);

  	trans->block_rsv = rsv;

  	btrfs_block_rsv_release(root, &pending->block_rsv, (u64)-1);
  	return 0;

  }

  /*
   * create all the snapshots we've scheduled for creation
   */

  static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
  					     struct btrfs_fs_info *fs_info)

  {
  	struct btrfs_pending_snapshot *pending;
  	struct list_head *head = &trans->transaction->pending_snapshots;

  	int ret;

  	list_for_each_entry(pending, head, list) {

  		ret = create_pending_snapshot(trans, fs_info, pending);
  		BUG_ON(ret);
  	}
  	return 0;
  }

  static void update_super_roots(struct btrfs_root *root)
  {
  	struct btrfs_root_item *root_item;
  	struct btrfs_super_block *super;

  	super = root->fs_info->super_copy;

  
  	root_item = &root->fs_info->chunk_root->root_item;
  	super->chunk_root = root_item->bytenr;
  	super->chunk_root_generation = root_item->generation;
  	super->chunk_root_level = root_item->level;
  
  	root_item = &root->fs_info->tree_root->root_item;
  	super->root = root_item->bytenr;
  	super->generation = root_item->generation;
  	super->root_level = root_item->level;

  	if (btrfs_test_opt(root, SPACE_CACHE))

  		super->cache_generation = root_item->generation;

  }

  int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
  {
  	int ret = 0;

  	spin_lock(&info->trans_lock);

  	if (info->running_transaction)
  		ret = info->running_transaction->in_commit;

  	spin_unlock(&info->trans_lock);

  	return ret;
  }

  int btrfs_transaction_blocked(struct btrfs_fs_info *info)
  {
  	int ret = 0;

  	spin_lock(&info->trans_lock);

  	if (info->running_transaction)
  		ret = info->running_transaction->blocked;

  	spin_unlock(&info->trans_lock);

  	return ret;
  }

  /*
   * wait for the current transaction commit to start and block subsequent
   * transaction joins
   */
  static void wait_current_trans_commit_start(struct btrfs_root *root,
  					    struct btrfs_transaction *trans)
  {

  	wait_event(root->fs_info->transaction_blocked_wait, trans->in_commit);

  }
  
  /*
   * wait for the current transaction to start and then become unblocked.
   * caller holds ref.
   */
  static void wait_current_trans_commit_start_and_unblock(struct btrfs_root *root,
  					 struct btrfs_transaction *trans)
  {

  	wait_event(root->fs_info->transaction_wait,
  		   trans->commit_done || (trans->in_commit && !trans->blocked));

  }
  
  /*
   * commit transactions asynchronously. once btrfs_commit_transaction_async
   * returns, any subsequent transaction will not be allowed to join.
   */
  struct btrfs_async_commit {
  	struct btrfs_trans_handle *newtrans;
  	struct btrfs_root *root;
  	struct delayed_work work;
  };
  
  static void do_async_commit(struct work_struct *work)
  {
  	struct btrfs_async_commit *ac =
  		container_of(work, struct btrfs_async_commit, work.work);
  
  	btrfs_commit_transaction(ac->newtrans, ac->root);
  	kfree(ac);
  }
  
  int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
  				   struct btrfs_root *root,
  				   int wait_for_unblock)
  {
  	struct btrfs_async_commit *ac;
  	struct btrfs_transaction *cur_trans;
  
  	ac = kmalloc(sizeof(*ac), GFP_NOFS);

  	if (!ac)
  		return -ENOMEM;

  
  	INIT_DELAYED_WORK(&ac->work, do_async_commit);
  	ac->root = root;

  	ac->newtrans = btrfs_join_transaction(root);

  	if (IS_ERR(ac->newtrans)) {
  		int err = PTR_ERR(ac->newtrans);
  		kfree(ac);
  		return err;
  	}

  
  	/* take transaction reference */

  	cur_trans = trans->transaction;

  	atomic_inc(&cur_trans->use_count);

  
  	btrfs_end_transaction(trans, root);
  	schedule_delayed_work(&ac->work, 0);
  
  	/* wait for transaction to start and unblock */

  	if (wait_for_unblock)
  		wait_current_trans_commit_start_and_unblock(root, cur_trans);
  	else
  		wait_current_trans_commit_start(root, cur_trans);

  	if (current->journal_info == trans)
  		current->journal_info = NULL;
  
  	put_transaction(cur_trans);

  	return 0;
  }
  
  /*
   * btrfs_transaction state sequence:
   *    in_commit = 0, blocked = 0  (initial)
   *    in_commit = 1, blocked = 1
   *    blocked = 0
   *    commit_done = 1
   */

  int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
  			     struct btrfs_root *root)
  {

  	unsigned long joined = 0;

  	struct btrfs_transaction *cur_trans;

  	struct btrfs_transaction *prev_trans = NULL;

  	DEFINE_WAIT(wait);

  	int ret;

  	int should_grow = 0;
  	unsigned long now = get_seconds();

  	int flush_on_commit = btrfs_test_opt(root, FLUSHONCOMMIT);

  	btrfs_run_ordered_operations(root, 0);

  	btrfs_trans_release_metadata(trans, root);

  	trans->block_rsv = NULL;

  	/* make a pass through all the delayed refs we have so far
  	 * any runnings procs may add more while we are here
  	 */
  	ret = btrfs_run_delayed_refs(trans, root, 0);
  	BUG_ON(ret);

  	cur_trans = trans->transaction;

  	/*
  	 * set the flushing flag so procs in this transaction have to
  	 * start sending their work down.
  	 */

  	cur_trans->delayed_refs.flushing = 1;

  	ret = btrfs_run_delayed_refs(trans, root, 0);

  	BUG_ON(ret);

  	spin_lock(&cur_trans->commit_lock);

  	if (cur_trans->in_commit) {

  		spin_unlock(&cur_trans->commit_lock);

  		atomic_inc(&cur_trans->use_count);

  		btrfs_end_transaction(trans, root);

  		wait_for_commit(root, cur_trans);

  		put_transaction(cur_trans);

  		return 0;
  	}

  	trans->transaction->in_commit = 1;

  	trans->transaction->blocked = 1;

  	spin_unlock(&cur_trans->commit_lock);

  	wake_up(&root->fs_info->transaction_blocked_wait);

  	spin_lock(&root->fs_info->trans_lock);

  	if (cur_trans->list.prev != &root->fs_info->trans_list) {
  		prev_trans = list_entry(cur_trans->list.prev,
  					struct btrfs_transaction, list);
  		if (!prev_trans->commit_done) {

  			atomic_inc(&prev_trans->use_count);

  			spin_unlock(&root->fs_info->trans_lock);

  
  			wait_for_commit(root, prev_trans);

  			put_transaction(prev_trans);

  		} else {
  			spin_unlock(&root->fs_info->trans_lock);

  		}

  	} else {
  		spin_unlock(&root->fs_info->trans_lock);

  	}

  	if (now < cur_trans->start_time || now - cur_trans->start_time < 1)
  		should_grow = 1;

  	do {

  		int snap_pending = 0;

  		joined = cur_trans->num_joined;

  		if (!list_empty(&trans->transaction->pending_snapshots))
  			snap_pending = 1;

  		WARN_ON(cur_trans != trans->transaction);

  		if (flush_on_commit || snap_pending) {

  			btrfs_start_delalloc_inodes(root, 1);
  			ret = btrfs_wait_ordered_extents(root, 0, 1);

  			BUG_ON(ret);

  		}

  		ret = btrfs_run_delayed_items(trans, root);
  		BUG_ON(ret);

  		/*
  		 * rename don't use btrfs_join_transaction, so, once we
  		 * set the transaction to blocked above, we aren't going
  		 * to get any new ordered operations.  We can safely run
  		 * it here and no for sure that nothing new will be added
  		 * to the list
  		 */
  		btrfs_run_ordered_operations(root, 1);

  		prepare_to_wait(&cur_trans->writer_wait, &wait,
  				TASK_UNINTERRUPTIBLE);

  		if (atomic_read(&cur_trans->num_writers) > 1)

  			schedule_timeout(MAX_SCHEDULE_TIMEOUT);
  		else if (should_grow)
  			schedule_timeout(1);

  		finish_wait(&cur_trans->writer_wait, &wait);

  	} while (atomic_read(&cur_trans->num_writers) > 1 ||

  		 (should_grow && cur_trans->num_joined != joined));

  	/*

  	 * Ok now we need to make sure to block out any other joins while we
  	 * commit the transaction.  We could have started a join before setting
  	 * no_join so make sure to wait for num_writers to == 1 again.
  	 */
  	spin_lock(&root->fs_info->trans_lock);
  	root->fs_info->trans_no_join = 1;
  	spin_unlock(&root->fs_info->trans_lock);
  	wait_event(cur_trans->writer_wait,
  		   atomic_read(&cur_trans->num_writers) == 1);

  	/*

  	 * the reloc mutex makes sure that we stop
  	 * the balancing code from coming in and moving
  	 * extents around in the middle of the commit
  	 */
  	mutex_lock(&root->fs_info->reloc_mutex);

  	ret = btrfs_run_delayed_items(trans, root);

  	BUG_ON(ret);

  	ret = create_pending_snapshots(trans, root->fs_info);

  	BUG_ON(ret);

  	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
  	BUG_ON(ret);

  	/*
  	 * make sure none of the code above managed to slip in a
  	 * delayed item
  	 */
  	btrfs_assert_delayed_root_empty(root);

  	WARN_ON(cur_trans != trans->transaction);

  	btrfs_scrub_pause(root);

  	/* btrfs_commit_tree_roots is responsible for getting the
  	 * various roots consistent with each other.  Every pointer
  	 * in the tree of tree roots has to point to the most up to date
  	 * root for every subvolume and other tree.  So, we have to keep
  	 * the tree logging code from jumping in and changing any
  	 * of the trees.
  	 *
  	 * At this point in the commit, there can't be any tree-log
  	 * writers, but a little lower down we drop the trans mutex
  	 * and let new people in.  By holding the tree_log_mutex
  	 * from now until after the super is written, we avoid races
  	 * with the tree-log code.
  	 */
  	mutex_lock(&root->fs_info->tree_log_mutex);

  	ret = commit_fs_roots(trans, root);

  	BUG_ON(ret);

  	/* commit_fs_roots gets rid of all the tree log roots, it is now

  	 * safe to free the root of tree log roots
  	 */
  	btrfs_free_log_root_tree(trans, root->fs_info);

  	ret = commit_cowonly_roots(trans, root);

  	BUG_ON(ret);

  	btrfs_prepare_extent_commit(trans, root);

  	cur_trans = root->fs_info->running_transaction;

  
  	btrfs_set_root_node(&root->fs_info->tree_root->root_item,
  			    root->fs_info->tree_root->node);

  	switch_commit_root(root->fs_info->tree_root);

  
  	btrfs_set_root_node(&root->fs_info->chunk_root->root_item,
  			    root->fs_info->chunk_root->node);

  	switch_commit_root(root->fs_info->chunk_root);

  
  	update_super_roots(root);

  
  	if (!root->fs_info->log_root_recovering) {

  		btrfs_set_super_log_root(root->fs_info->super_copy, 0);
  		btrfs_set_super_log_root_level(root->fs_info->super_copy, 0);

  	}

  	memcpy(root->fs_info->super_for_commit, root->fs_info->super_copy,
  	       sizeof(*root->fs_info->super_copy));

  	trans->transaction->blocked = 0;

  	spin_lock(&root->fs_info->trans_lock);
  	root->fs_info->running_transaction = NULL;
  	root->fs_info->trans_no_join = 0;
  	spin_unlock(&root->fs_info->trans_lock);

  	mutex_unlock(&root->fs_info->reloc_mutex);

  	wake_up(&root->fs_info->transaction_wait);

  	ret = btrfs_write_and_wait_transaction(trans, root);
  	BUG_ON(ret);

  	write_ctree_super(trans, root, 0);

  	/*
  	 * the super is written, we can safely allow the tree-loggers
  	 * to go about their business
  	 */
  	mutex_unlock(&root->fs_info->tree_log_mutex);

  	btrfs_finish_extent_commit(trans, root);

  	cur_trans->commit_done = 1;

  	root->fs_info->last_trans_committed = cur_trans->transid;

  	wake_up(&cur_trans->commit_wait);

  	spin_lock(&root->fs_info->trans_lock);

  	list_del_init(&cur_trans->list);

  	spin_unlock(&root->fs_info->trans_lock);

  	put_transaction(cur_trans);

  	put_transaction(cur_trans);

  	trace_btrfs_transaction_commit(root);

  	btrfs_scrub_continue(root);

  	if (current->journal_info == trans)
  		current->journal_info = NULL;

  	kmem_cache_free(btrfs_trans_handle_cachep, trans);

  
  	if (current != root->fs_info->transaction_kthread)
  		btrfs_run_delayed_iputs(root);

  	return ret;
  }

  /*
   * interface function to delete all the snapshots we have scheduled for deletion
   */

  int btrfs_clean_old_snapshots(struct btrfs_root *root)
  {

  	LIST_HEAD(list);
  	struct btrfs_fs_info *fs_info = root->fs_info;

  	spin_lock(&fs_info->trans_lock);

  	list_splice_init(&fs_info->dead_roots, &list);

  	spin_unlock(&fs_info->trans_lock);

  	while (!list_empty(&list)) {
  		root = list_entry(list.next, struct btrfs_root, root_list);

  		list_del(&root->root_list);

  		btrfs_kill_all_delayed_nodes(root);

  		if (btrfs_header_backref_rev(root->node) <
  		    BTRFS_MIXED_BACKREF_REV)

  			btrfs_drop_snapshot(root, NULL, 0);

  		else

  			btrfs_drop_snapshot(root, NULL, 1);

  	}
  	return 0;
  }