fs/btrfs/transaction.c - LeafOS-Devices/android_kernel_realme_mt6785 - Gitiles

 /*
  * 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/sched.h>
 #include <linux/writeback.h>
 #include <linux/pagemap.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
 #include "locking.h"

 static int total_trans = 0;
 extern struct kmem_cache *btrfs_trans_handle_cachep;
 extern struct kmem_cache *btrfs_transaction_cachep;

 #define BTRFS_ROOT_TRANS_TAG 0

 static noinline void put_transaction(struct btrfs_transaction *transaction)
 {
 	WARN_ON(transaction->use_count == 0);
 	transaction->use_count--;
 	if (transaction->use_count == 0) {
 		WARN_ON(total_trans == 0);
 		total_trans--;
 		list_del_init(&transaction->list);
 		memset(transaction, 0, sizeof(*transaction));
 		kmem_cache_free(btrfs_transaction_cachep, transaction);
 	}
 }

 static noinline int join_transaction(struct btrfs_root *root)
 {
 	struct btrfs_transaction *cur_trans;
 	cur_trans = root->fs_info->running_transaction;
 	if (!cur_trans) {
 		cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
 					     GFP_NOFS);
 		total_trans++;
 		BUG_ON(!cur_trans);
 		root->fs_info->generation++;
 		root->fs_info->last_alloc = 0;
 		root->fs_info->last_data_alloc = 0;
 		cur_trans->num_writers = 1;
 		cur_trans->num_joined = 0;
 		cur_trans->transid = root->fs_info->generation;
 		init_waitqueue_head(&cur_trans->writer_wait);
 		init_waitqueue_head(&cur_trans->commit_wait);
 		cur_trans->in_commit = 0;
 		cur_trans->blocked = 0;
 		cur_trans->use_count = 1;
 		cur_trans->commit_done = 0;
 		cur_trans->start_time = get_seconds();
 		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,
 				     GFP_NOFS);
 		spin_lock(&root->fs_info->new_trans_lock);
 		root->fs_info->running_transaction = cur_trans;
 		spin_unlock(&root->fs_info->new_trans_lock);
 	} else {
 		cur_trans->num_writers++;
 		cur_trans->num_joined++;
 	}

 	return 0;
 }

 static noinline int record_root_in_trans(struct btrfs_root *root)
 {
 	u64 running_trans_id = root->fs_info->running_transaction->transid;
 	if (root->ref_cows && root->last_trans < running_trans_id) {
 		WARN_ON(root == root->fs_info->extent_root);
 		if (root->root_item.refs != 0) {
 			radix_tree_tag_set(&root->fs_info->fs_roots_radix,
 				   (unsigned long)root->root_key.objectid,
 				   BTRFS_ROOT_TRANS_TAG);
 			root->commit_root = btrfs_root_node(root);
 		} else {
 			WARN_ON(1);
 		}
 		root->last_trans = running_trans_id;
 	}
 	return 0;
 }

 struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
 					     int num_blocks, int join)
 {
 	struct btrfs_trans_handle *h =
 		kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
 	struct btrfs_transaction *cur_trans;
 	int ret;

 	mutex_lock(&root->fs_info->trans_mutex);
 	cur_trans = root->fs_info->running_transaction;
 	if (cur_trans && cur_trans->blocked && !join) {
 		DEFINE_WAIT(wait);
 		cur_trans->use_count++;
 		while(1) {
 			prepare_to_wait(&root->fs_info->transaction_wait, &wait,
 					TASK_UNINTERRUPTIBLE);
 			if (cur_trans->blocked) {
 				mutex_unlock(&root->fs_info->trans_mutex);
 				schedule();
 				mutex_lock(&root->fs_info->trans_mutex);
 				finish_wait(&root->fs_info->transaction_wait,
 					    &wait);
 			} else {
 				finish_wait(&root->fs_info->transaction_wait,
 					    &wait);
 				break;
 			}
 		}
 		put_transaction(cur_trans);
 	}
 	ret = join_transaction(root);
 	BUG_ON(ret);

 	record_root_in_trans(root);
 	h->transid = root->fs_info->running_transaction->transid;
 	h->transaction = root->fs_info->running_transaction;
 	h->blocks_reserved = num_blocks;
 	h->blocks_used = 0;
 	h->block_group = NULL;
 	h->alloc_exclude_nr = 0;
 	h->alloc_exclude_start = 0;
 	root->fs_info->running_transaction->use_count++;
 	mutex_unlock(&root->fs_info->trans_mutex);
 	return h;
 }

 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 						   int num_blocks)
 {
 	return start_transaction(root, num_blocks, 0);
 }
 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
 						   int num_blocks)
 {
 	return start_transaction(root, num_blocks, 1);
 }

 static noinline int wait_for_commit(struct btrfs_root *root,
 				    struct btrfs_transaction *commit)
 {
 	DEFINE_WAIT(wait);
 	mutex_lock(&root->fs_info->trans_mutex);
 	while(!commit->commit_done) {
 		prepare_to_wait(&commit->commit_wait, &wait,
 				TASK_UNINTERRUPTIBLE);
 		if (commit->commit_done)
 			break;
 		mutex_unlock(&root->fs_info->trans_mutex);
 		schedule();
 		mutex_lock(&root->fs_info->trans_mutex);
 	}
 	mutex_unlock(&root->fs_info->trans_mutex);
 	finish_wait(&commit->commit_wait, &wait);
 	return 0;
 }

 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root, int throttle)
 {
 	struct btrfs_transaction *cur_trans;

 	mutex_lock(&root->fs_info->trans_mutex);
 	cur_trans = root->fs_info->running_transaction;
 	WARN_ON(cur_trans != trans->transaction);
 	WARN_ON(cur_trans->num_writers < 1);
 	cur_trans->num_writers--;

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

 	if (0 && cur_trans->in_commit && throttle) {
 		DEFINE_WAIT(wait);
 		mutex_unlock(&root->fs_info->trans_mutex);
 		prepare_to_wait(&root->fs_info->transaction_throttle, &wait,
 				TASK_UNINTERRUPTIBLE);
 		schedule();
 		finish_wait(&root->fs_info->transaction_throttle, &wait);
 		mutex_lock(&root->fs_info->trans_mutex);
 	}

 	put_transaction(cur_trans);
 	mutex_unlock(&root->fs_info->trans_mutex);
 	memset(trans, 0, sizeof(*trans));
 	kmem_cache_free(btrfs_trans_handle_cachep, trans);
 	return 0;
 }

 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root)
 {
 	return __btrfs_end_transaction(trans, root, 0);
 }

 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
 				   struct btrfs_root *root)
 {
 	return __btrfs_end_transaction(trans, root, 1);
 }


 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
 				     struct btrfs_root *root)
 {
 	int ret;
 	int err;
 	int werr = 0;
 	struct extent_io_tree *dirty_pages;
 	struct page *page;
 	struct inode *btree_inode = root->fs_info->btree_inode;
 	u64 start;
 	u64 end;
 	unsigned long index;

 	if (!trans || !trans->transaction) {
 		return filemap_write_and_wait(btree_inode->i_mapping);
 	}
 	dirty_pages = &trans->transaction->dirty_pages;
 	while(1) {
 		ret = find_first_extent_bit(dirty_pages, 0, &start, &end,
 					    EXTENT_DIRTY);
 		if (ret)
 			break;
 		clear_extent_dirty(dirty_pages, start, end, GFP_NOFS);
 		while(start <= end) {
 			index = start >> PAGE_CACHE_SHIFT;
 			start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
 			page = find_lock_page(btree_inode->i_mapping, index);
 			if (!page)
 				continue;
 			if (PageWriteback(page)) {
 				if (PageDirty(page))
 					wait_on_page_writeback(page);
 				else {
 					unlock_page(page);
 					page_cache_release(page);
 					continue;
 				}
 			}
 			err = write_one_page(page, 0);
 			if (err)
 				werr = err;
 			page_cache_release(page);
 		}
 	}
 	err = filemap_fdatawait(btree_inode->i_mapping);
 	if (err)
 		werr = err;
 	return werr;
 }

 static int update_cowonly_root(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *root)
 {
 	int ret;
 	u64 old_root_bytenr;
 	struct btrfs_root *tree_root = root->fs_info->tree_root;

 	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)
 			break;
 		btrfs_set_root_bytenr(&root->root_item,
 				       root->node->start);
 		btrfs_set_root_level(&root->root_item,
 				     btrfs_header_level(root->node));
 		ret = btrfs_update_root(trans, tree_root,
 					&root->root_key,
 					&root->root_item);
 		BUG_ON(ret);
 		btrfs_write_dirty_block_groups(trans, root);
 	}
 	return 0;
 }

 int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
 			    struct btrfs_root *root)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct list_head *next;

 	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);
 	}
 	return 0;
 }

 struct dirty_root {
 	struct list_head list;
 	struct btrfs_root *root;
 	struct btrfs_root *latest_root;
 };

 int btrfs_add_dead_root(struct btrfs_root *root,
 			struct btrfs_root *latest,
 			struct list_head *dead_list)
 {
 	struct dirty_root *dirty;

 	dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 	if (!dirty)
 		return -ENOMEM;
 	dirty->root = root;
 	dirty->latest_root = latest;
 	list_add(&dirty->list, dead_list);
 	return 0;
 }

 static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 				    struct radix_tree_root *radix,
 				    struct list_head *list)
 {
 	struct dirty_root *dirty;
 	struct btrfs_root *gang[8];
 	struct btrfs_root *root;
 	int i;
 	int ret;
 	int err = 0;
 	u32 refs;

 	while(1) {
 		ret = radix_tree_gang_lookup_tag(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(radix,
 				     (unsigned long)root->root_key.objectid,
 				     BTRFS_ROOT_TRANS_TAG);
 			if (root->commit_root == root->node) {
 				WARN_ON(root->node->start !=
 					btrfs_root_bytenr(&root->root_item));
 				free_extent_buffer(root->commit_root);
 				root->commit_root = NULL;

 				/* make sure to update the root on disk
 				 * so we get any updates to the block used
 				 * counts
 				 */
 				err = btrfs_update_root(trans,
 						root->fs_info->tree_root,
 						&root->root_key,
 						&root->root_item);
 				continue;
 			}
 			dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 			BUG_ON(!dirty);
 			dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
 			BUG_ON(!dirty->root);

 			memset(&root->root_item.drop_progress, 0,
 			       sizeof(struct btrfs_disk_key));
 			root->root_item.drop_level = 0;

 			memcpy(dirty->root, root, sizeof(*root));
 			dirty->root->node = root->commit_root;
 			dirty->latest_root = root;
 			spin_lock_init(&dirty->root->node_lock);
 			mutex_init(&dirty->root->objectid_mutex);

 			root->commit_root = NULL;

 			root->root_key.offset = root->fs_info->generation;
 			btrfs_set_root_bytenr(&root->root_item,
 					      root->node->start);
 			btrfs_set_root_level(&root->root_item,
 					     btrfs_header_level(root->node));
 			err = btrfs_insert_root(trans, root->fs_info->tree_root,
 						&root->root_key,
 						&root->root_item);
 			if (err)
 				break;

 			refs = btrfs_root_refs(&dirty->root->root_item);
 			btrfs_set_root_refs(&dirty->root->root_item, refs - 1);
 			err = btrfs_update_root(trans, root->fs_info->tree_root,
 						&dirty->root->root_key,
 						&dirty->root->root_item);

 			BUG_ON(err);
 			if (refs == 1) {
 				list_add(&dirty->list, list);
 			} else {
 				WARN_ON(1);
 				kfree(dirty->root);
 				kfree(dirty);
 			}
 		}
 	}
 	return err;
 }

 int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
 {
 	struct btrfs_fs_info *info = root->fs_info;
 	int ret;
 	struct btrfs_trans_handle *trans;
 	unsigned long nr;

 	smp_mb();
 	if (root->defrag_running)
 		return 0;
 	trans = btrfs_start_transaction(root, 1);
 	while (1) {
 		root->defrag_running = 1;
 		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();

 		trans = btrfs_start_transaction(root, 1);
 		if (root->fs_info->closing || ret != -EAGAIN)
 			break;
 	}
 	root->defrag_running = 0;
 	smp_mb();
 	btrfs_end_transaction(trans, root);
 	return 0;
 }

 static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
 				     struct list_head *list)
 {
 	struct dirty_root *dirty;
 	struct btrfs_trans_handle *trans;
 	unsigned long nr;
 	u64 num_bytes;
 	u64 bytes_used;
 	int ret = 0;
 	int err;

 	while(!list_empty(list)) {
 		struct btrfs_root *root;

 		dirty = list_entry(list->next, struct dirty_root, list);
 		list_del_init(&dirty->list);

 		num_bytes = btrfs_root_used(&dirty->root->root_item);
 		root = dirty->latest_root;
 		atomic_inc(&root->fs_info->throttles);

 		mutex_lock(&root->fs_info->drop_mutex);
 		while(1) {
 			trans = btrfs_start_transaction(tree_root, 1);
 			ret = btrfs_drop_snapshot(trans, dirty->root);
 			if (ret != -EAGAIN) {
 				break;
 			}

 			err = btrfs_update_root(trans,
 					tree_root,
 					&dirty->root->root_key,
 					&dirty->root->root_item);
 			if (err)
 				ret = err;
 			nr = trans->blocks_used;
 			ret = btrfs_end_transaction_throttle(trans, tree_root);
 			BUG_ON(ret);

 			mutex_unlock(&root->fs_info->drop_mutex);
 			btrfs_btree_balance_dirty(tree_root, nr);
 			cond_resched();
 			mutex_lock(&root->fs_info->drop_mutex);
 		}
 		BUG_ON(ret);
 		atomic_dec(&root->fs_info->throttles);

 		mutex_lock(&root->fs_info->alloc_mutex);
 		num_bytes -= btrfs_root_used(&dirty->root->root_item);
 		bytes_used = btrfs_root_used(&root->root_item);
 		if (num_bytes) {
 			record_root_in_trans(root);
 			btrfs_set_root_used(&root->root_item,
 					    bytes_used - num_bytes);
 		}
 		mutex_unlock(&root->fs_info->alloc_mutex);

 		ret = btrfs_del_root(trans, tree_root, &dirty->root->root_key);
 		if (ret) {
 			BUG();
 			break;
 		}
 		mutex_unlock(&root->fs_info->drop_mutex);

 		nr = trans->blocks_used;
 		ret = btrfs_end_transaction(trans, tree_root);
 		BUG_ON(ret);

 		free_extent_buffer(dirty->root->node);
 		kfree(dirty->root);
 		kfree(dirty);

 		btrfs_btree_balance_dirty(tree_root, nr);
 		cond_resched();
 	}
 	return ret;
 }

 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 extent_buffer *tmp;
 	struct extent_buffer *old;
 	int ret;
 	int namelen;
 	u64 objectid;

 	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
 	if (!new_root_item) {
 		ret = -ENOMEM;
 		goto fail;
 	}
 	ret = btrfs_find_free_objectid(trans, tree_root, 0, &objectid);
 	if (ret)
 		goto fail;

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

 	key.objectid = objectid;
 	key.offset = 1;
 	btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);

 	old = btrfs_lock_root_node(root);
 	btrfs_cow_block(trans, root, old, NULL, 0, &old);

 	btrfs_copy_root(trans, root, old, &tmp, objectid);
 	btrfs_tree_unlock(old);
 	free_extent_buffer(old);

 	btrfs_set_root_bytenr(new_root_item, tmp->start);
 	btrfs_set_root_level(new_root_item, btrfs_header_level(tmp));
 	ret = btrfs_insert_root(trans, root->fs_info->tree_root, &key,
 				new_root_item);
 	btrfs_tree_unlock(tmp);
 	free_extent_buffer(tmp);
 	if (ret)
 		goto fail;

 	/*
 	 * insert the directory item
 	 */
 	key.offset = (u64)-1;
 	namelen = strlen(pending->name);
 	ret = btrfs_insert_dir_item(trans, root->fs_info->tree_root,
 				    pending->name, namelen,
 				    root->fs_info->sb->s_root->d_inode->i_ino,
 				    &key, BTRFS_FT_DIR, 0);

 	if (ret)
 		goto fail;

 	ret = btrfs_insert_inode_ref(trans, root->fs_info->tree_root,
 			     pending->name, strlen(pending->name), objectid,
 			     root->fs_info->sb->s_root->d_inode->i_ino, 0);

 	/* Invalidate existing dcache entry for new snapshot. */
 	btrfs_invalidate_dcache_root(root, pending->name, namelen);

 fail:
 	kfree(new_root_item);
 	return ret;
 }

 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;

 	while(!list_empty(head)) {
 		pending = list_entry(head->next,
 				     struct btrfs_pending_snapshot, list);
 		ret = create_pending_snapshot(trans, fs_info, pending);
 		BUG_ON(ret);
 		list_del(&pending->list);
 		kfree(pending->name);
 		kfree(pending);
 	}
 	return 0;
 }

 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root)
 {
 	unsigned long joined = 0;
 	unsigned long timeout = 1;
 	struct btrfs_transaction *cur_trans;
 	struct btrfs_transaction *prev_trans = NULL;
 	struct btrfs_root *chunk_root = root->fs_info->chunk_root;
 	struct list_head dirty_fs_roots;
 	struct extent_io_tree *pinned_copy;
 	DEFINE_WAIT(wait);
 	int ret;

 	INIT_LIST_HEAD(&dirty_fs_roots);

 	mutex_lock(&root->fs_info->trans_mutex);
 	if (trans->transaction->in_commit) {
 		cur_trans = trans->transaction;
 		trans->transaction->use_count++;
 		mutex_unlock(&root->fs_info->trans_mutex);
 		btrfs_end_transaction(trans, root);

 		ret = wait_for_commit(root, cur_trans);
 		BUG_ON(ret);

 		mutex_lock(&root->fs_info->trans_mutex);
 		put_transaction(cur_trans);
 		mutex_unlock(&root->fs_info->trans_mutex);

 		return 0;
 	}

 	pinned_copy = kmalloc(sizeof(*pinned_copy), GFP_NOFS);
 	if (!pinned_copy)
 		return -ENOMEM;

 	extent_io_tree_init(pinned_copy,
 			     root->fs_info->btree_inode->i_mapping, GFP_NOFS);

 	trans->transaction->in_commit = 1;
 	trans->transaction->blocked = 1;
 	cur_trans = trans->transaction;
 	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) {
 			prev_trans->use_count++;
 			mutex_unlock(&root->fs_info->trans_mutex);

 			wait_for_commit(root, prev_trans);

 			mutex_lock(&root->fs_info->trans_mutex);
 			put_transaction(prev_trans);
 		}
 	}

 	do {
 		joined = cur_trans->num_joined;
 		WARN_ON(cur_trans != trans->transaction);
 		prepare_to_wait(&cur_trans->writer_wait, &wait,
 				TASK_UNINTERRUPTIBLE);

 		if (cur_trans->num_writers > 1)
 			timeout = MAX_SCHEDULE_TIMEOUT;
 		else
 			timeout = 1;

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

 		schedule_timeout(timeout);

 		mutex_lock(&root->fs_info->trans_mutex);
 		finish_wait(&cur_trans->writer_wait, &wait);
 	} while (cur_trans->num_writers > 1 ||
 		 (cur_trans->num_joined != joined));

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

 	WARN_ON(cur_trans != trans->transaction);

 	ret = add_dirty_roots(trans, &root->fs_info->fs_roots_radix,
 			      &dirty_fs_roots);
 	BUG_ON(ret);

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

 	cur_trans = root->fs_info->running_transaction;
 	spin_lock(&root->fs_info->new_trans_lock);
 	root->fs_info->running_transaction = NULL;
 	spin_unlock(&root->fs_info->new_trans_lock);
 	btrfs_set_super_generation(&root->fs_info->super_copy,
 				   cur_trans->transid);
 	btrfs_set_super_root(&root->fs_info->super_copy,
 			     root->fs_info->tree_root->node->start);
 	btrfs_set_super_root_level(&root->fs_info->super_copy,
 			   btrfs_header_level(root->fs_info->tree_root->node));

 	btrfs_set_super_chunk_root(&root->fs_info->super_copy,
 				   chunk_root->node->start);
 	btrfs_set_super_chunk_root_level(&root->fs_info->super_copy,
 					 btrfs_header_level(chunk_root->node));
 	memcpy(&root->fs_info->super_for_commit, &root->fs_info->super_copy,
 	       sizeof(root->fs_info->super_copy));

 	btrfs_copy_pinned(root, pinned_copy);

 	trans->transaction->blocked = 0;
 	wake_up(&root->fs_info->transaction_throttle);
 	wake_up(&root->fs_info->transaction_wait);

 	mutex_unlock(&root->fs_info->trans_mutex);
 	ret = btrfs_write_and_wait_transaction(trans, root);
 	BUG_ON(ret);
 	write_ctree_super(trans, root);

 	btrfs_finish_extent_commit(trans, root, pinned_copy);
 	mutex_lock(&root->fs_info->trans_mutex);

 	kfree(pinned_copy);

 	cur_trans->commit_done = 1;
 	root->fs_info->last_trans_committed = cur_trans->transid;
 	wake_up(&cur_trans->commit_wait);
 	put_transaction(cur_trans);
 	put_transaction(cur_trans);

 	if (root->fs_info->closing)
 		list_splice_init(&root->fs_info->dead_roots, &dirty_fs_roots);
 	else
 		list_splice_init(&dirty_fs_roots, &root->fs_info->dead_roots);

 	mutex_unlock(&root->fs_info->trans_mutex);
 	kmem_cache_free(btrfs_trans_handle_cachep, trans);

 	if (root->fs_info->closing) {
 		drop_dirty_roots(root->fs_info->tree_root, &dirty_fs_roots);
 	}
 	return ret;
 }

 int btrfs_clean_old_snapshots(struct btrfs_root *root)
 {
 	struct list_head dirty_roots;
 	INIT_LIST_HEAD(&dirty_roots);
 again:
 	mutex_lock(&root->fs_info->trans_mutex);
 	list_splice_init(&root->fs_info->dead_roots, &dirty_roots);
 	mutex_unlock(&root->fs_info->trans_mutex);

 	if (!list_empty(&dirty_roots)) {
 		drop_dirty_roots(root, &dirty_roots);
 		goto again;
 	}
 	return 0;
 }
	/*
	* 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/sched.h>
	#include <linux/writeback.h>
	#include <linux/pagemap.h>
	#include "ctree.h"
	#include "disk-io.h"
	#include "transaction.h"
	#include "locking.h"

	static int total_trans = 0;
	extern struct kmem_cache *btrfs_trans_handle_cachep;
	extern struct kmem_cache *btrfs_transaction_cachep;

	#define BTRFS_ROOT_TRANS_TAG 0

	static noinline void put_transaction(struct btrfs_transaction *transaction)
	{
	WARN_ON(transaction->use_count == 0);
	transaction->use_count--;
	if (transaction->use_count == 0) {
	WARN_ON(total_trans == 0);
	total_trans--;
	list_del_init(&transaction->list);
	memset(transaction, 0, sizeof(*transaction));
	kmem_cache_free(btrfs_transaction_cachep, transaction);
	}
	}

	static noinline int join_transaction(struct btrfs_root *root)
	{
	struct btrfs_transaction *cur_trans;
	cur_trans = root->fs_info->running_transaction;
	if (!cur_trans) {
	cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
	GFP_NOFS);
	total_trans++;
	BUG_ON(!cur_trans);
	root->fs_info->generation++;
	root->fs_info->last_alloc = 0;
	root->fs_info->last_data_alloc = 0;
	cur_trans->num_writers = 1;
	cur_trans->num_joined = 0;
	cur_trans->transid = root->fs_info->generation;
	init_waitqueue_head(&cur_trans->writer_wait);
	init_waitqueue_head(&cur_trans->commit_wait);
	cur_trans->in_commit = 0;
	cur_trans->blocked = 0;
	cur_trans->use_count = 1;
	cur_trans->commit_done = 0;
	cur_trans->start_time = get_seconds();
	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,
	GFP_NOFS);
	spin_lock(&root->fs_info->new_trans_lock);
	root->fs_info->running_transaction = cur_trans;
	spin_unlock(&root->fs_info->new_trans_lock);
	} else {
	cur_trans->num_writers++;
	cur_trans->num_joined++;
	}

	return 0;
	}

	static noinline int record_root_in_trans(struct btrfs_root *root)
	{
	u64 running_trans_id = root->fs_info->running_transaction->transid;
	if (root->ref_cows && root->last_trans < running_trans_id) {
	WARN_ON(root == root->fs_info->extent_root);
	if (root->root_item.refs != 0) {
	radix_tree_tag_set(&root->fs_info->fs_roots_radix,
	(unsigned long)root->root_key.objectid,
	BTRFS_ROOT_TRANS_TAG);
	root->commit_root = btrfs_root_node(root);
	} else {
	WARN_ON(1);
	}
	root->last_trans = running_trans_id;
	}
	return 0;
	}

	struct btrfs_trans_handle start_transaction(struct btrfs_root root,
	int num_blocks, int join)
	{
	struct btrfs_trans_handle *h =
	kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
	struct btrfs_transaction *cur_trans;
	int ret;

	mutex_lock(&root->fs_info->trans_mutex);
	cur_trans = root->fs_info->running_transaction;
	if (cur_trans && cur_trans->blocked && !join) {
	DEFINE_WAIT(wait);
	cur_trans->use_count++;
	while(1) {
	prepare_to_wait(&root->fs_info->transaction_wait, &wait,
	TASK_UNINTERRUPTIBLE);
	if (cur_trans->blocked) {
	mutex_unlock(&root->fs_info->trans_mutex);
	schedule();
	mutex_lock(&root->fs_info->trans_mutex);
	finish_wait(&root->fs_info->transaction_wait,
	&wait);
	} else {
	finish_wait(&root->fs_info->transaction_wait,
	&wait);
	break;
	}
	}
	put_transaction(cur_trans);
	}
	ret = join_transaction(root);
	BUG_ON(ret);

	record_root_in_trans(root);
	h->transid = root->fs_info->running_transaction->transid;
	h->transaction = root->fs_info->running_transaction;
	h->blocks_reserved = num_blocks;
	h->blocks_used = 0;
	h->block_group = NULL;
	h->alloc_exclude_nr = 0;
	h->alloc_exclude_start = 0;
	root->fs_info->running_transaction->use_count++;
	mutex_unlock(&root->fs_info->trans_mutex);
	return h;
	}

	struct btrfs_trans_handle btrfs_start_transaction(struct btrfs_root root,
	int num_blocks)
	{
	return start_transaction(root, num_blocks, 0);
	}
	struct btrfs_trans_handle btrfs_join_transaction(struct btrfs_root root,
	int num_blocks)
	{
	return start_transaction(root, num_blocks, 1);
	}

	static noinline int wait_for_commit(struct btrfs_root *root,
	struct btrfs_transaction *commit)
	{
	DEFINE_WAIT(wait);
	mutex_lock(&root->fs_info->trans_mutex);
	while(!commit->commit_done) {
	prepare_to_wait(&commit->commit_wait, &wait,
	TASK_UNINTERRUPTIBLE);
	if (commit->commit_done)
	break;
	mutex_unlock(&root->fs_info->trans_mutex);
	schedule();
	mutex_lock(&root->fs_info->trans_mutex);
	}
	mutex_unlock(&root->fs_info->trans_mutex);
	finish_wait(&commit->commit_wait, &wait);
	return 0;
	}

	static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
	struct btrfs_root *root, int throttle)
	{
	struct btrfs_transaction *cur_trans;

	mutex_lock(&root->fs_info->trans_mutex);
	cur_trans = root->fs_info->running_transaction;
	WARN_ON(cur_trans != trans->transaction);
	WARN_ON(cur_trans->num_writers < 1);
	cur_trans->num_writers--;

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

	if (0 && cur_trans->in_commit && throttle) {
	DEFINE_WAIT(wait);
	mutex_unlock(&root->fs_info->trans_mutex);
	prepare_to_wait(&root->fs_info->transaction_throttle, &wait,
	TASK_UNINTERRUPTIBLE);
	schedule();
	finish_wait(&root->fs_info->transaction_throttle, &wait);
	mutex_lock(&root->fs_info->trans_mutex);
	}

	put_transaction(cur_trans);
	mutex_unlock(&root->fs_info->trans_mutex);
	memset(trans, 0, sizeof(*trans));
	kmem_cache_free(btrfs_trans_handle_cachep, trans);
	return 0;
	}

	int btrfs_end_transaction(struct btrfs_trans_handle *trans,
	struct btrfs_root *root)
	{
	return __btrfs_end_transaction(trans, root, 0);
	}

	int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
	struct btrfs_root *root)
	{
	return __btrfs_end_transaction(trans, root, 1);
	}


	int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
	struct btrfs_root *root)
	{
	int ret;
	int err;
	int werr = 0;
	struct extent_io_tree *dirty_pages;
	struct page *page;
	struct inode *btree_inode = root->fs_info->btree_inode;
	u64 start;
	u64 end;
	unsigned long index;

	if (!trans \|\| !trans->transaction) {
	return filemap_write_and_wait(btree_inode->i_mapping);
	}
	dirty_pages = &trans->transaction->dirty_pages;
	while(1) {
	ret = find_first_extent_bit(dirty_pages, 0, &start, &end,
	EXTENT_DIRTY);
	if (ret)
	break;
	clear_extent_dirty(dirty_pages, start, end, GFP_NOFS);
	while(start <= end) {
	index = start >> PAGE_CACHE_SHIFT;
	start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
	page = find_lock_page(btree_inode->i_mapping, index);
	if (!page)
	continue;
	if (PageWriteback(page)) {
	if (PageDirty(page))
	wait_on_page_writeback(page);
	else {
	unlock_page(page);
	page_cache_release(page);
	continue;
	}
	}
	err = write_one_page(page, 0);
	if (err)
	werr = err;
	page_cache_release(page);
	}
	}
	err = filemap_fdatawait(btree_inode->i_mapping);
	if (err)
	werr = err;
	return werr;
	}

	static int update_cowonly_root(struct btrfs_trans_handle *trans,
	struct btrfs_root *root)
	{
	int ret;
	u64 old_root_bytenr;
	struct btrfs_root *tree_root = root->fs_info->tree_root;

	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)
	break;
	btrfs_set_root_bytenr(&root->root_item,
	root->node->start);
	btrfs_set_root_level(&root->root_item,
	btrfs_header_level(root->node));
	ret = btrfs_update_root(trans, tree_root,
	&root->root_key,
	&root->root_item);
	BUG_ON(ret);
	btrfs_write_dirty_block_groups(trans, root);
	}
	return 0;
	}

	int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
	struct btrfs_root *root)
	{
	struct btrfs_fs_info *fs_info = root->fs_info;
	struct list_head *next;

	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);
	}
	return 0;
	}

	struct dirty_root {
	struct list_head list;
	struct btrfs_root *root;
	struct btrfs_root *latest_root;
	};

	int btrfs_add_dead_root(struct btrfs_root *root,
	struct btrfs_root *latest,
	struct list_head *dead_list)
	{
	struct dirty_root *dirty;

	dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
	if (!dirty)
	return -ENOMEM;
	dirty->root = root;
	dirty->latest_root = latest;
	list_add(&dirty->list, dead_list);
	return 0;
	}

	static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
	struct radix_tree_root *radix,
	struct list_head *list)
	{
	struct dirty_root *dirty;
	struct btrfs_root *gang[8];
	struct btrfs_root *root;
	int i;
	int ret;
	int err = 0;
	u32 refs;

	while(1) {
	ret = radix_tree_gang_lookup_tag(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(radix,
	(unsigned long)root->root_key.objectid,
	BTRFS_ROOT_TRANS_TAG);
	if (root->commit_root == root->node) {
	WARN_ON(root->node->start !=
	btrfs_root_bytenr(&root->root_item));
	free_extent_buffer(root->commit_root);
	root->commit_root = NULL;

	/* make sure to update the root on disk
	* so we get any updates to the block used
	* counts
	*/
	err = btrfs_update_root(trans,
	root->fs_info->tree_root,
	&root->root_key,
	&root->root_item);
	continue;
	}
	dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
	BUG_ON(!dirty);
	dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
	BUG_ON(!dirty->root);

	memset(&root->root_item.drop_progress, 0,
	sizeof(struct btrfs_disk_key));
	root->root_item.drop_level = 0;

	memcpy(dirty->root, root, sizeof(*root));
	dirty->root->node = root->commit_root;
	dirty->latest_root = root;
	spin_lock_init(&dirty->root->node_lock);
	mutex_init(&dirty->root->objectid_mutex);

	root->commit_root = NULL;

	root->root_key.offset = root->fs_info->generation;
	btrfs_set_root_bytenr(&root->root_item,
	root->node->start);
	btrfs_set_root_level(&root->root_item,
	btrfs_header_level(root->node));
	err = btrfs_insert_root(trans, root->fs_info->tree_root,
	&root->root_key,
	&root->root_item);
	if (err)
	break;

	refs = btrfs_root_refs(&dirty->root->root_item);
	btrfs_set_root_refs(&dirty->root->root_item, refs - 1);
	err = btrfs_update_root(trans, root->fs_info->tree_root,
	&dirty->root->root_key,
	&dirty->root->root_item);

	BUG_ON(err);
	if (refs == 1) {
	list_add(&dirty->list, list);
	} else {
	WARN_ON(1);
	kfree(dirty->root);
	kfree(dirty);
	}
	}
	}
	return err;
	}

	int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
	{
	struct btrfs_fs_info *info = root->fs_info;
	int ret;
	struct btrfs_trans_handle *trans;
	unsigned long nr;

	smp_mb();
	if (root->defrag_running)
	return 0;
	trans = btrfs_start_transaction(root, 1);
	while (1) {
	root->defrag_running = 1;
	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();

	trans = btrfs_start_transaction(root, 1);
	if (root->fs_info->closing \|\| ret != -EAGAIN)
	break;
	}
	root->defrag_running = 0;
	smp_mb();
	btrfs_end_transaction(trans, root);
	return 0;
	}

	static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
	struct list_head *list)
	{
	struct dirty_root *dirty;
	struct btrfs_trans_handle *trans;
	unsigned long nr;
	u64 num_bytes;
	u64 bytes_used;
	int ret = 0;
	int err;

	while(!list_empty(list)) {
	struct btrfs_root *root;

	dirty = list_entry(list->next, struct dirty_root, list);
	list_del_init(&dirty->list);

	num_bytes = btrfs_root_used(&dirty->root->root_item);
	root = dirty->latest_root;
	atomic_inc(&root->fs_info->throttles);

	mutex_lock(&root->fs_info->drop_mutex);
	while(1) {
	trans = btrfs_start_transaction(tree_root, 1);
	ret = btrfs_drop_snapshot(trans, dirty->root);
	if (ret != -EAGAIN) {
	break;
	}

	err = btrfs_update_root(trans,
	tree_root,
	&dirty->root->root_key,
	&dirty->root->root_item);
	if (err)
	ret = err;
	nr = trans->blocks_used;
	ret = btrfs_end_transaction_throttle(trans, tree_root);
	BUG_ON(ret);

	mutex_unlock(&root->fs_info->drop_mutex);
	btrfs_btree_balance_dirty(tree_root, nr);
	cond_resched();
	mutex_lock(&root->fs_info->drop_mutex);
	}
	BUG_ON(ret);
	atomic_dec(&root->fs_info->throttles);

	mutex_lock(&root->fs_info->alloc_mutex);
	num_bytes -= btrfs_root_used(&dirty->root->root_item);
	bytes_used = btrfs_root_used(&root->root_item);
	if (num_bytes) {
	record_root_in_trans(root);
	btrfs_set_root_used(&root->root_item,
	bytes_used - num_bytes);
	}
	mutex_unlock(&root->fs_info->alloc_mutex);

	ret = btrfs_del_root(trans, tree_root, &dirty->root->root_key);
	if (ret) {
	BUG();
	break;
	}
	mutex_unlock(&root->fs_info->drop_mutex);

	nr = trans->blocks_used;
	ret = btrfs_end_transaction(trans, tree_root);
	BUG_ON(ret);

	free_extent_buffer(dirty->root->node);
	kfree(dirty->root);
	kfree(dirty);

	btrfs_btree_balance_dirty(tree_root, nr);
	cond_resched();
	}
	return ret;
	}

	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 extent_buffer *tmp;
	struct extent_buffer *old;
	int ret;
	int namelen;
	u64 objectid;

	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
	if (!new_root_item) {
	ret = -ENOMEM;
	goto fail;
	}
	ret = btrfs_find_free_objectid(trans, tree_root, 0, &objectid);
	if (ret)
	goto fail;

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

	key.objectid = objectid;
	key.offset = 1;
	btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);

	old = btrfs_lock_root_node(root);
	btrfs_cow_block(trans, root, old, NULL, 0, &old);

	btrfs_copy_root(trans, root, old, &tmp, objectid);
	btrfs_tree_unlock(old);
	free_extent_buffer(old);

	btrfs_set_root_bytenr(new_root_item, tmp->start);
	btrfs_set_root_level(new_root_item, btrfs_header_level(tmp));
	ret = btrfs_insert_root(trans, root->fs_info->tree_root, &key,
	new_root_item);
	btrfs_tree_unlock(tmp);
	free_extent_buffer(tmp);
	if (ret)
	goto fail;

	/*
	* insert the directory item
	*/
	key.offset = (u64)-1;
	namelen = strlen(pending->name);
	ret = btrfs_insert_dir_item(trans, root->fs_info->tree_root,
	pending->name, namelen,
	root->fs_info->sb->s_root->d_inode->i_ino,
	&key, BTRFS_FT_DIR, 0);

	if (ret)
	goto fail;

	ret = btrfs_insert_inode_ref(trans, root->fs_info->tree_root,
	pending->name, strlen(pending->name), objectid,
	root->fs_info->sb->s_root->d_inode->i_ino, 0);

	/* Invalidate existing dcache entry for new snapshot. */
	btrfs_invalidate_dcache_root(root, pending->name, namelen);

	fail:
	kfree(new_root_item);
	return ret;
	}

	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;

	while(!list_empty(head)) {
	pending = list_entry(head->next,
	struct btrfs_pending_snapshot, list);
	ret = create_pending_snapshot(trans, fs_info, pending);
	BUG_ON(ret);
	list_del(&pending->list);
	kfree(pending->name);
	kfree(pending);
	}
	return 0;
	}

	int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
	struct btrfs_root *root)
	{
	unsigned long joined = 0;
	unsigned long timeout = 1;
	struct btrfs_transaction *cur_trans;
	struct btrfs_transaction *prev_trans = NULL;
	struct btrfs_root *chunk_root = root->fs_info->chunk_root;
	struct list_head dirty_fs_roots;
	struct extent_io_tree *pinned_copy;
	DEFINE_WAIT(wait);
	int ret;

	INIT_LIST_HEAD(&dirty_fs_roots);

	mutex_lock(&root->fs_info->trans_mutex);
	if (trans->transaction->in_commit) {
	cur_trans = trans->transaction;
	trans->transaction->use_count++;
	mutex_unlock(&root->fs_info->trans_mutex);
	btrfs_end_transaction(trans, root);

	ret = wait_for_commit(root, cur_trans);
	BUG_ON(ret);

	mutex_lock(&root->fs_info->trans_mutex);
	put_transaction(cur_trans);
	mutex_unlock(&root->fs_info->trans_mutex);

	return 0;
	}

	pinned_copy = kmalloc(sizeof(*pinned_copy), GFP_NOFS);
	if (!pinned_copy)
	return -ENOMEM;

	extent_io_tree_init(pinned_copy,
	root->fs_info->btree_inode->i_mapping, GFP_NOFS);

	trans->transaction->in_commit = 1;
	trans->transaction->blocked = 1;
	cur_trans = trans->transaction;
	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) {
	prev_trans->use_count++;
	mutex_unlock(&root->fs_info->trans_mutex);

	wait_for_commit(root, prev_trans);

	mutex_lock(&root->fs_info->trans_mutex);
	put_transaction(prev_trans);
	}
	}

	do {
	joined = cur_trans->num_joined;
	WARN_ON(cur_trans != trans->transaction);
	prepare_to_wait(&cur_trans->writer_wait, &wait,
	TASK_UNINTERRUPTIBLE);

	if (cur_trans->num_writers > 1)
	timeout = MAX_SCHEDULE_TIMEOUT;
	else
	timeout = 1;

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

	schedule_timeout(timeout);

	mutex_lock(&root->fs_info->trans_mutex);
	finish_wait(&cur_trans->writer_wait, &wait);
	} while (cur_trans->num_writers > 1 \|\|
	(cur_trans->num_joined != joined));

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

	WARN_ON(cur_trans != trans->transaction);

	ret = add_dirty_roots(trans, &root->fs_info->fs_roots_radix,
	&dirty_fs_roots);
	BUG_ON(ret);

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

	cur_trans = root->fs_info->running_transaction;
	spin_lock(&root->fs_info->new_trans_lock);
	root->fs_info->running_transaction = NULL;
	spin_unlock(&root->fs_info->new_trans_lock);
	btrfs_set_super_generation(&root->fs_info->super_copy,
	cur_trans->transid);
	btrfs_set_super_root(&root->fs_info->super_copy,
	root->fs_info->tree_root->node->start);
	btrfs_set_super_root_level(&root->fs_info->super_copy,
	btrfs_header_level(root->fs_info->tree_root->node));

	btrfs_set_super_chunk_root(&root->fs_info->super_copy,
	chunk_root->node->start);
	btrfs_set_super_chunk_root_level(&root->fs_info->super_copy,
	btrfs_header_level(chunk_root->node));
	memcpy(&root->fs_info->super_for_commit, &root->fs_info->super_copy,
	sizeof(root->fs_info->super_copy));

	btrfs_copy_pinned(root, pinned_copy);

	trans->transaction->blocked = 0;
	wake_up(&root->fs_info->transaction_throttle);
	wake_up(&root->fs_info->transaction_wait);

	mutex_unlock(&root->fs_info->trans_mutex);
	ret = btrfs_write_and_wait_transaction(trans, root);
	BUG_ON(ret);
	write_ctree_super(trans, root);

	btrfs_finish_extent_commit(trans, root, pinned_copy);
	mutex_lock(&root->fs_info->trans_mutex);

	kfree(pinned_copy);

	cur_trans->commit_done = 1;
	root->fs_info->last_trans_committed = cur_trans->transid;
	wake_up(&cur_trans->commit_wait);
	put_transaction(cur_trans);
	put_transaction(cur_trans);

	if (root->fs_info->closing)
	list_splice_init(&root->fs_info->dead_roots, &dirty_fs_roots);
	else
	list_splice_init(&dirty_fs_roots, &root->fs_info->dead_roots);

	mutex_unlock(&root->fs_info->trans_mutex);
	kmem_cache_free(btrfs_trans_handle_cachep, trans);

	if (root->fs_info->closing) {
	drop_dirty_roots(root->fs_info->tree_root, &dirty_fs_roots);
	}
	return ret;
	}

	int btrfs_clean_old_snapshots(struct btrfs_root *root)
	{
	struct list_head dirty_roots;
	INIT_LIST_HEAD(&dirty_roots);
	again:
	mutex_lock(&root->fs_info->trans_mutex);
	list_splice_init(&root->fs_info->dead_roots, &dirty_roots);
	mutex_unlock(&root->fs_info->trans_mutex);

	if (!list_empty(&dirty_roots)) {
	drop_dirty_roots(root, &dirty_roots);
	goto again;
	}
	return 0;
	}