transaction.c 36.7 KB
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/*
 * 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.
 */

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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/writeback.h>
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#include <linux/pagemap.h>
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#include <linux/blkdev.h>
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#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
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#include "locking.h"
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#include "tree-log.h"
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#define BTRFS_ROOT_TRANS_TAG 0

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

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static noinline void switch_commit_root(struct btrfs_root *root)
{
	free_extent_buffer(root->commit_root);
	root->commit_root = btrfs_root_node(root);
}

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/*
 * either allocate a new transaction or hop into the existing one
 */
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static noinline int join_transaction(struct btrfs_root *root)
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{
	struct btrfs_transaction *cur_trans;
	cur_trans = root->fs_info->running_transaction;
	if (!cur_trans) {
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		cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
					     GFP_NOFS);
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		BUG_ON(!cur_trans);
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		root->fs_info->generation++;
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		cur_trans->num_writers = 1;
		cur_trans->num_joined = 0;
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		cur_trans->transid = root->fs_info->generation;
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		init_waitqueue_head(&cur_trans->writer_wait);
		init_waitqueue_head(&cur_trans->commit_wait);
		cur_trans->in_commit = 0;
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		cur_trans->blocked = 0;
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		cur_trans->use_count = 1;
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		cur_trans->commit_done = 0;
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		cur_trans->start_time = get_seconds();
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		cur_trans->delayed_refs.root = RB_ROOT;
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		cur_trans->delayed_refs.num_entries = 0;
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		cur_trans->delayed_refs.num_heads_ready = 0;
		cur_trans->delayed_refs.num_heads = 0;
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		cur_trans->delayed_refs.flushing = 0;
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		cur_trans->delayed_refs.run_delayed_start = 0;
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		spin_lock_init(&cur_trans->delayed_refs.lock);

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		INIT_LIST_HEAD(&cur_trans->pending_snapshots);
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		list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
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		extent_io_tree_init(&cur_trans->dirty_pages,
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				     root->fs_info->btree_inode->i_mapping,
				     GFP_NOFS);
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		spin_lock(&root->fs_info->new_trans_lock);
		root->fs_info->running_transaction = cur_trans;
		spin_unlock(&root->fs_info->new_trans_lock);
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	} else {
		cur_trans->num_writers++;
		cur_trans->num_joined++;
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	}
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	return 0;
}

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/*
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 * 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
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 */
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static noinline int record_root_in_trans(struct btrfs_trans_handle *trans,
					 struct btrfs_root *root)
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{
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	if (root->ref_cows && root->last_trans < trans->transid) {
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		WARN_ON(root == root->fs_info->extent_root);
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		WARN_ON(root->commit_root != root->node);

		radix_tree_tag_set(&root->fs_info->fs_roots_radix,
			   (unsigned long)root->root_key.objectid,
			   BTRFS_ROOT_TRANS_TAG);
		root->last_trans = trans->transid;
		btrfs_init_reloc_root(trans, root);
	}
	return 0;
}
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int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
			       struct btrfs_root *root)
{
	if (!root->ref_cows)
		return 0;
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	mutex_lock(&root->fs_info->trans_mutex);
	if (root->last_trans == trans->transid) {
		mutex_unlock(&root->fs_info->trans_mutex);
		return 0;
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	}
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	record_root_in_trans(trans, root);
	mutex_unlock(&root->fs_info->trans_mutex);
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	return 0;
}

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/* 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.
 */
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static void wait_current_trans(struct btrfs_root *root)
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{
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	struct btrfs_transaction *cur_trans;
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	cur_trans = root->fs_info->running_transaction;
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	if (cur_trans && cur_trans->blocked) {
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		DEFINE_WAIT(wait);
		cur_trans->use_count++;
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		while (1) {
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			prepare_to_wait(&root->fs_info->transaction_wait, &wait,
					TASK_UNINTERRUPTIBLE);
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			if (!cur_trans->blocked)
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				break;
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			mutex_unlock(&root->fs_info->trans_mutex);
			schedule();
			mutex_lock(&root->fs_info->trans_mutex);
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		}
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		finish_wait(&root->fs_info->transaction_wait, &wait);
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		put_transaction(cur_trans);
	}
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}

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enum btrfs_trans_type {
	TRANS_START,
	TRANS_JOIN,
	TRANS_USERSPACE,
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	TRANS_JOIN_NOLOCK,
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};

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static int may_wait_transaction(struct btrfs_root *root, int type)
{
	if (!root->fs_info->log_root_recovering &&
	    ((type == TRANS_START && !root->fs_info->open_ioctl_trans) ||
	     type == TRANS_USERSPACE))
		return 1;
	return 0;
}

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static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
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						    u64 num_items, int type)
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{
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	struct btrfs_trans_handle *h;
	struct btrfs_transaction *cur_trans;
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	int ret;
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	if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
		return ERR_PTR(-EROFS);
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again:
	h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
	if (!h)
		return ERR_PTR(-ENOMEM);
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	if (type != TRANS_JOIN_NOLOCK)
		mutex_lock(&root->fs_info->trans_mutex);
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	if (may_wait_transaction(root, type))
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		wait_current_trans(root);
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	ret = join_transaction(root);
	BUG_ON(ret);
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	cur_trans = root->fs_info->running_transaction;
	cur_trans->use_count++;
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	if (type != TRANS_JOIN_NOLOCK)
		mutex_unlock(&root->fs_info->trans_mutex);
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	h->transid = cur_trans->transid;
	h->transaction = cur_trans;
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	h->blocks_used = 0;
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	h->block_group = 0;
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	h->bytes_reserved = 0;
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	h->delayed_ref_updates = 0;
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	h->block_rsv = NULL;
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	smp_mb();
	if (cur_trans->blocked && may_wait_transaction(root, type)) {
		btrfs_commit_transaction(h, root);
		goto again;
	}

	if (num_items > 0) {
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		ret = btrfs_trans_reserve_metadata(h, root, num_items);
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		if (ret == -EAGAIN) {
			btrfs_commit_transaction(h, root);
			goto again;
		}
		if (ret < 0) {
			btrfs_end_transaction(h, root);
			return ERR_PTR(ret);
		}
	}
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	if (type != TRANS_JOIN_NOLOCK)
		mutex_lock(&root->fs_info->trans_mutex);
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	record_root_in_trans(h, root);
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	if (type != TRANS_JOIN_NOLOCK)
		mutex_unlock(&root->fs_info->trans_mutex);
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	if (!current->journal_info && type != TRANS_USERSPACE)
		current->journal_info = h;
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	return h;
}

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

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struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root,
							  int num_blocks)
{
	return start_transaction(root, 0, TRANS_JOIN_NOLOCK);
}

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struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
							 int num_blocks)
{
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	return start_transaction(r, 0, TRANS_USERSPACE);
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}

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/* wait for a transaction commit to be fully complete */
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static noinline int wait_for_commit(struct btrfs_root *root,
				    struct btrfs_transaction *commit)
{
	DEFINE_WAIT(wait);
	mutex_lock(&root->fs_info->trans_mutex);
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	while (!commit->commit_done) {
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		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;
}

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

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

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

		/* find specified transaction */
		list_for_each_entry(t, &root->fs_info->trans_list, list) {
			if (t->transid == transid) {
				cur_trans = t;
				break;
			}
			if (t->transid > transid)
				break;
		}
		ret = -EINVAL;
		if (!cur_trans)
			goto out_unlock;  /* bad transid */
	} else {
		/* find newest transaction that is committing | committed */
		list_for_each_entry_reverse(t, &root->fs_info->trans_list,
					    list) {
			if (t->in_commit) {
				if (t->commit_done)
					goto out_unlock;
				cur_trans = t;
				break;
			}
		}
		if (!cur_trans)
			goto out_unlock;  /* nothing committing|committed */
	}

	cur_trans->use_count++;
	mutex_unlock(&root->fs_info->trans_mutex);

	wait_for_commit(root, cur_trans);

	mutex_lock(&root->fs_info->trans_mutex);
	put_transaction(cur_trans);
	ret = 0;
out_unlock:
	mutex_unlock(&root->fs_info->trans_mutex);
	return ret;
}

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#if 0
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/*
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 * rate limit against the drop_snapshot code.  This helps to slow down new
 * operations if the drop_snapshot code isn't able to keep up.
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 */
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static void throttle_on_drops(struct btrfs_root *root)
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{
	struct btrfs_fs_info *info = root->fs_info;
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	int harder_count = 0;
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harder:
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	if (atomic_read(&info->throttles)) {
		DEFINE_WAIT(wait);
		int thr;
		thr = atomic_read(&info->throttle_gen);

		do {
			prepare_to_wait(&info->transaction_throttle,
					&wait, TASK_UNINTERRUPTIBLE);
			if (!atomic_read(&info->throttles)) {
				finish_wait(&info->transaction_throttle, &wait);
				break;
			}
			schedule();
			finish_wait(&info->transaction_throttle, &wait);
		} while (thr == atomic_read(&info->throttle_gen));
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		harder_count++;

		if (root->fs_info->total_ref_cache_size > 1 * 1024 * 1024 &&
		    harder_count < 2)
			goto harder;

		if (root->fs_info->total_ref_cache_size > 5 * 1024 * 1024 &&
		    harder_count < 10)
			goto harder;

		if (root->fs_info->total_ref_cache_size > 10 * 1024 * 1024 &&
		    harder_count < 20)
			goto harder;
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	}
}
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#endif
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void btrfs_throttle(struct btrfs_root *root)
{
	mutex_lock(&root->fs_info->trans_mutex);
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	if (!root->fs_info->open_ioctl_trans)
		wait_current_trans(root);
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	mutex_unlock(&root->fs_info->trans_mutex);
}

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static int should_end_transaction(struct btrfs_trans_handle *trans,
				  struct btrfs_root *root)
{
	int ret;
	ret = btrfs_block_rsv_check(trans, root,
				    &root->fs_info->global_block_rsv, 0, 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;
	int updates;

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

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

	return should_end_transaction(trans, root);
}

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static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
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			  struct btrfs_root *root, int throttle, int lock)
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{
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	struct btrfs_transaction *cur_trans = trans->transaction;
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	struct btrfs_fs_info *info = root->fs_info;
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	int count = 0;

	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;
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			/*
			 * do a full flush if the transaction is trying
			 * to close
			 */
			if (trans->transaction->delayed_refs.flushing)
				cur = 0;
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			btrfs_run_delayed_refs(trans, root, cur);
		} else {
			break;
		}
		count++;
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	}

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	btrfs_trans_release_metadata(trans, root);

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	if (lock && !root->fs_info->open_ioctl_trans &&
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	    should_end_transaction(trans, root))
		trans->transaction->blocked = 1;

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	if (lock && cur_trans->blocked && !cur_trans->in_commit) {
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		if (throttle)
			return btrfs_commit_transaction(trans, root);
		else
			wake_up_process(info->transaction_kthread);
	}

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	if (lock)
		mutex_lock(&info->trans_mutex);
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	WARN_ON(cur_trans != info->running_transaction);
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	WARN_ON(cur_trans->num_writers < 1);
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	cur_trans->num_writers--;
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	smp_mb();
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	if (waitqueue_active(&cur_trans->writer_wait))
		wake_up(&cur_trans->writer_wait);
	put_transaction(cur_trans);
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	if (lock)
		mutex_unlock(&info->trans_mutex);
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	if (current->journal_info == trans)
		current->journal_info = NULL;
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	memset(trans, 0, sizeof(*trans));
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	kmem_cache_free(btrfs_trans_handle_cachep, trans);
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	if (throttle)
		btrfs_run_delayed_iputs(root);

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	return 0;
}

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int btrfs_end_transaction(struct btrfs_trans_handle *trans,
			  struct btrfs_root *root)
{
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	return __btrfs_end_transaction(trans, root, 0, 1);
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}

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

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

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/*
 * 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
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 * those extents are sent to disk but does not wait on them
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 */
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int btrfs_write_marked_extents(struct btrfs_root *root,
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			       struct extent_io_tree *dirty_pages, int mark)
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{
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	int ret;
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	int err = 0;
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	int werr = 0;
	struct page *page;
	struct inode *btree_inode = root->fs_info->btree_inode;
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	u64 start = 0;
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	u64 end;
	unsigned long index;
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	while (1) {
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		ret = find_first_extent_bit(dirty_pages, start, &start, &end,
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					    mark);
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		if (ret)
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			break;
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		while (start <= end) {
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			cond_resched();

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			index = start >> PAGE_CACHE_SHIFT;
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			start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
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			page = find_get_page(btree_inode->i_mapping, index);
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			if (!page)
				continue;
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			btree_lock_page_hook(page);
			if (!page->mapping) {
				unlock_page(page);
				page_cache_release(page);
				continue;
			}

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			if (PageWriteback(page)) {
				if (PageDirty(page))
					wait_on_page_writeback(page);
				else {
					unlock_page(page);
					page_cache_release(page);
					continue;
				}
			}
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			err = write_one_page(page, 0);
			if (err)
				werr = err;
			page_cache_release(page);
		}
	}
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	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,
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			      struct extent_io_tree *dirty_pages, int mark)
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{
	int ret;
	int err = 0;
	int werr = 0;
	struct page *page;
	struct inode *btree_inode = root->fs_info->btree_inode;
	u64 start = 0;
	u64 end;
	unsigned long index;

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	while (1) {
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		ret = find_first_extent_bit(dirty_pages, start, &start, &end,
					    mark);
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		if (ret)
			break;

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		clear_extent_bits(dirty_pages, start, end, mark, GFP_NOFS);
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		while (start <= end) {
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			index = start >> PAGE_CACHE_SHIFT;
			start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
			page = find_get_page(btree_inode->i_mapping, index);
			if (!page)
				continue;
			if (PageDirty(page)) {
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				btree_lock_page_hook(page);
				wait_on_page_writeback(page);
588 589 590 591
				err = write_one_page(page, 0);
				if (err)
					werr = err;
			}
592
			wait_on_page_writeback(page);
593 594 595 596
			page_cache_release(page);
			cond_resched();
		}
	}
597 598 599
	if (err)
		werr = err;
	return werr;
C
Chris Mason 已提交
600 601
}

602 603 604 605 606 607
/*
 * 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,
608
				struct extent_io_tree *dirty_pages, int mark)
609 610 611 612
{
	int ret;
	int ret2;

613 614
	ret = btrfs_write_marked_extents(root, dirty_pages, mark);
	ret2 = btrfs_wait_marked_extents(root, dirty_pages, mark);
615 616 617
	return ret || ret2;
}

618 619 620 621 622 623 624 625 626
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,
627 628
					   &trans->transaction->dirty_pages,
					   EXTENT_DIRTY);
629 630
}

C
Chris Mason 已提交
631 632 633 634 635 636 637 638 639 640
/*
 * 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.
 */
641 642
static int update_cowonly_root(struct btrfs_trans_handle *trans,
			       struct btrfs_root *root)
C
Chris Mason 已提交
643 644
{
	int ret;
645
	u64 old_root_bytenr;
646
	u64 old_root_used;
647
	struct btrfs_root *tree_root = root->fs_info->tree_root;
C
Chris Mason 已提交
648

649
	old_root_used = btrfs_root_used(&root->root_item);
650
	btrfs_write_dirty_block_groups(trans, root);
651

C
Chris Mason 已提交
652
	while (1) {
653
		old_root_bytenr = btrfs_root_bytenr(&root->root_item);
654 655
		if (old_root_bytenr == root->node->start &&
		    old_root_used == btrfs_root_used(&root->root_item))
C
Chris Mason 已提交
656
			break;
657

658
		btrfs_set_root_node(&root->root_item, root->node);
C
Chris Mason 已提交
659
		ret = btrfs_update_root(trans, tree_root,
660 661
					&root->root_key,
					&root->root_item);
C
Chris Mason 已提交
662
		BUG_ON(ret);
663

664
		old_root_used = btrfs_root_used(&root->root_item);
665
		ret = btrfs_write_dirty_block_groups(trans, root);
666
		BUG_ON(ret);
667
	}
668 669 670 671

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

672 673 674
	return 0;
}

C
Chris Mason 已提交
675 676 677
/*
 * update all the cowonly tree roots on disk
 */
678 679
static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
					 struct btrfs_root *root)
680 681 682
{
	struct btrfs_fs_info *fs_info = root->fs_info;
	struct list_head *next;
683
	struct extent_buffer *eb;
684
	int ret;
685

686 687
	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
	BUG_ON(ret);
688

689
	eb = btrfs_lock_root_node(fs_info->tree_root);
690
	btrfs_cow_block(trans, fs_info->tree_root, eb, NULL, 0, &eb);
691 692
	btrfs_tree_unlock(eb);
	free_extent_buffer(eb);
693

694 695
	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
	BUG_ON(ret);
696

C
Chris Mason 已提交
697
	while (!list_empty(&fs_info->dirty_cowonly_roots)) {
698 699 700
		next = fs_info->dirty_cowonly_roots.next;
		list_del_init(next);
		root = list_entry(next, struct btrfs_root, dirty_list);
701

702
		update_cowonly_root(trans, root);
C
Chris Mason 已提交
703
	}
704 705 706 707 708

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

C
Chris Mason 已提交
709 710 711
	return 0;
}

C
Chris Mason 已提交
712 713 714 715 716
/*
 * 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
 */
717
int btrfs_add_dead_root(struct btrfs_root *root)
718
{
Y
Yan Zheng 已提交
719
	mutex_lock(&root->fs_info->trans_mutex);
720
	list_add(&root->root_list, &root->fs_info->dead_roots);
Y
Yan Zheng 已提交
721
	mutex_unlock(&root->fs_info->trans_mutex);
722 723 724
	return 0;
}

C
Chris Mason 已提交
725
/*
726
 * update all the cowonly tree roots on disk
C
Chris Mason 已提交
727
 */
728 729
static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
				    struct btrfs_root *root)
730 731
{
	struct btrfs_root *gang[8];
732
	struct btrfs_fs_info *fs_info = root->fs_info;
733 734
	int i;
	int ret;
735 736
	int err = 0;

C
Chris Mason 已提交
737
	while (1) {
738 739
		ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
						 (void **)gang, 0,
740 741 742 743 744 745
						 ARRAY_SIZE(gang),
						 BTRFS_ROOT_TRANS_TAG);
		if (ret == 0)
			break;
		for (i = 0; i < ret; i++) {
			root = gang[i];
746 747 748
			radix_tree_tag_clear(&fs_info->fs_roots_radix,
					(unsigned long)root->root_key.objectid,
					BTRFS_ROOT_TRANS_TAG);
Y
Yan Zheng 已提交
749

750
			btrfs_free_log(trans, root);
751
			btrfs_update_reloc_root(trans, root);
752
			btrfs_orphan_commit_root(trans, root);
753

754
			if (root->commit_root != root->node) {
J
Josef Bacik 已提交
755
				switch_commit_root(root);
756 757 758
				btrfs_set_root_node(&root->root_item,
						    root->node);
			}
759 760

			err = btrfs_update_root(trans, fs_info->tree_root,
761 762
						&root->root_key,
						&root->root_item);
763 764
			if (err)
				break;
765 766
		}
	}
767
	return err;
768 769
}

C
Chris Mason 已提交
770 771 772 773
/*
 * defrag a given btree.  If cacheonly == 1, this won't read from the disk,
 * otherwise every leaf in the btree is read and defragged.
 */
774 775 776 777
int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
{
	struct btrfs_fs_info *info = root->fs_info;
	struct btrfs_trans_handle *trans;
778
	int ret;
779
	unsigned long nr;
780

781
	if (xchg(&root->defrag_running, 1))
782
		return 0;
783

784
	while (1) {
785 786 787 788
		trans = btrfs_start_transaction(root, 0);
		if (IS_ERR(trans))
			return PTR_ERR(trans);

789
		ret = btrfs_defrag_leaves(trans, root, cacheonly);
790

791
		nr = trans->blocks_used;
792
		btrfs_end_transaction(trans, root);
793
		btrfs_btree_balance_dirty(info->tree_root, nr);
794 795
		cond_resched();

796
		if (root->fs_info->closing || ret != -EAGAIN)
797 798 799
			break;
	}
	root->defrag_running = 0;
800
	return ret;
801 802
}

803
#if 0
804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820
/*
 * when dropping snapshots, we generate a ton of delayed refs, and it makes
 * sense not to join the transaction while it is trying to flush the current
 * queue of delayed refs out.
 *
 * This is used by the drop snapshot code only
 */
static noinline int wait_transaction_pre_flush(struct btrfs_fs_info *info)
{
	DEFINE_WAIT(wait);

	mutex_lock(&info->trans_mutex);
	while (info->running_transaction &&
	       info->running_transaction->delayed_refs.flushing) {
		prepare_to_wait(&info->transaction_wait, &wait,
				TASK_UNINTERRUPTIBLE);
		mutex_unlock(&info->trans_mutex);
821

822
		schedule();
823

824 825 826 827 828 829 830
		mutex_lock(&info->trans_mutex);
		finish_wait(&info->transaction_wait, &wait);
	}
	mutex_unlock(&info->trans_mutex);
	return 0;
}

C
Chris Mason 已提交
831 832 833 834
/*
 * Given a list of roots that need to be deleted, call btrfs_drop_snapshot on
 * all of them
 */
835
int btrfs_drop_dead_root(struct btrfs_root *root)
836 837
{
	struct btrfs_trans_handle *trans;
838
	struct btrfs_root *tree_root = root->fs_info->tree_root;
839
	unsigned long nr;
840
	int ret;
841

842 843 844 845 846 847 848
	while (1) {
		/*
		 * we don't want to jump in and create a bunch of
		 * delayed refs if the transaction is starting to close
		 */
		wait_transaction_pre_flush(tree_root->fs_info);
		trans = btrfs_start_transaction(tree_root, 1);
849

850 851 852 853 854 855 856
		/*
		 * we've joined a transaction, make sure it isn't
		 * closing right now
		 */
		if (trans->transaction->delayed_refs.flushing) {
			btrfs_end_transaction(trans, tree_root);
			continue;
857
		}
858

859 860 861
		ret = btrfs_drop_snapshot(trans, root);
		if (ret != -EAGAIN)
			break;
862

863 864 865 866
		ret = btrfs_update_root(trans, tree_root,
					&root->root_key,
					&root->root_item);
		if (ret)
867
			break;
868

869
		nr = trans->blocks_used;
870 871
		ret = btrfs_end_transaction(trans, tree_root);
		BUG_ON(ret);
872

873
		btrfs_btree_balance_dirty(tree_root, nr);
874
		cond_resched();
875
	}
876 877 878 879 880 881 882 883 884 885 886 887 888 889
	BUG_ON(ret);

	ret = btrfs_del_root(trans, tree_root, &root->root_key);
	BUG_ON(ret);

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

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

	btrfs_btree_balance_dirty(tree_root, nr);
890
	return ret;
891
}
892
#endif
893

C
Chris Mason 已提交
894 895 896 897
/*
 * new snapshots need to be created at a very specific time in the
 * transaction commit.  This does the actual creation
 */
898
static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
899 900 901 902
				   struct btrfs_fs_info *fs_info,
				   struct btrfs_pending_snapshot *pending)
{
	struct btrfs_key key;
903
	struct btrfs_root_item *new_root_item;
904 905
	struct btrfs_root *tree_root = fs_info->tree_root;
	struct btrfs_root *root = pending->root;
906 907
	struct btrfs_root *parent_root;
	struct inode *parent_inode;
908
	struct dentry *parent;
909
	struct dentry *dentry;
910
	struct extent_buffer *tmp;
911
	struct extent_buffer *old;
912
	int ret;
913
	u64 to_reserve = 0;
914
	u64 index = 0;
915
	u64 objectid;
L
Li Zefan 已提交
916
	u64 root_flags;
917

918 919
	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
	if (!new_root_item) {
920
		pending->error = -ENOMEM;
921 922
		goto fail;
	}
923

924
	ret = btrfs_find_free_objectid(trans, tree_root, 0, &objectid);
925 926
	if (ret) {
		pending->error = ret;
927
		goto fail;
928
	}
929

930
	btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
931 932 933 934
	btrfs_orphan_pre_snapshot(trans, pending, &to_reserve);

	if (to_reserve > 0) {
		ret = btrfs_block_rsv_add(trans, root, &pending->block_rsv,
935
					  to_reserve);
936 937 938 939 940 941
		if (ret) {
			pending->error = ret;
			goto fail;
		}
	}

942
	key.objectid = objectid;
943 944
	key.offset = (u64)-1;
	key.type = BTRFS_ROOT_ITEM_KEY;
945

946
	trans->block_rsv = &pending->block_rsv;
947

948
	dentry = pending->dentry;
949 950
	parent = dget_parent(dentry);
	parent_inode = parent->d_inode;
951
	parent_root = BTRFS_I(parent_inode)->root;
952
	record_root_in_trans(trans, parent_root);
953

954 955 956
	/*
	 * insert the directory item
	 */
957
	ret = btrfs_set_inode_index(parent_inode, &index);
958
	BUG_ON(ret);
959
	ret = btrfs_insert_dir_item(trans, parent_root,
960 961 962
				dentry->d_name.name, dentry->d_name.len,
				parent_inode->i_ino, &key,
				BTRFS_FT_DIR, index);
963
	BUG_ON(ret);
964

965 966
	btrfs_i_size_write(parent_inode, parent_inode->i_size +
					 dentry->d_name.len * 2);
967 968 969
	ret = btrfs_update_inode(trans, parent_root, parent_inode);
	BUG_ON(ret);

970 971 972 973
	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));

L
Li Zefan 已提交
974 975 976 977 978 979 980
	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);

981 982 983 984 985 986 987 988 989
	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);

	btrfs_set_root_node(new_root_item, tmp);
990 991 992
	/* record when the snapshot was created in key.offset */
	key.offset = trans->transid;
	ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);
993 994
	btrfs_tree_unlock(tmp);
	free_extent_buffer(tmp);
995
	BUG_ON(ret);
996

997 998 999 1000
	/*
	 * insert root back/forward references
	 */
	ret = btrfs_add_root_ref(trans, tree_root, objectid,
1001
				 parent_root->root_key.objectid,
1002 1003
				 parent_inode->i_ino, index,
				 dentry->d_name.name, dentry->d_name.len);
1004
	BUG_ON(ret);
1005
	dput(parent);
1006

1007 1008 1009
	key.offset = (u64)-1;
	pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
	BUG_ON(IS_ERR(pending->snap));
1010

1011
	btrfs_reloc_post_snapshot(trans, pending);
1012
	btrfs_orphan_post_snapshot(trans, pending);
1013
fail:
1014
	kfree(new_root_item);
1015 1016
	btrfs_block_rsv_release(root, &pending->block_rsv, (u64)-1);
	return 0;
1017 1018
}

C
Chris Mason 已提交
1019 1020 1021
/*
 * create all the snapshots we've scheduled for creation
 */
1022 1023
static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
					     struct btrfs_fs_info *fs_info)
1024 1025 1026 1027 1028
{
	struct btrfs_pending_snapshot *pending;
	struct list_head *head = &trans->transaction->pending_snapshots;
	int ret;

Q
Qinghuang Feng 已提交
1029
	list_for_each_entry(pending, head, list) {
1030 1031 1032 1033 1034 1035
		ret = create_pending_snapshot(trans, fs_info, pending);
		BUG_ON(ret);
	}
	return 0;
}

1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051
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;
1052 1053
	if (super->cache_generation != 0 || btrfs_test_opt(root, SPACE_CACHE))
		super->cache_generation = root_item->generation;
1054 1055
}

1056 1057 1058 1059 1060 1061 1062 1063 1064 1065
int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
{
	int ret = 0;
	spin_lock(&info->new_trans_lock);
	if (info->running_transaction)
		ret = info->running_transaction->in_commit;
	spin_unlock(&info->new_trans_lock);
	return ret;
}

1066 1067 1068 1069 1070 1071 1072 1073 1074 1075
int btrfs_transaction_blocked(struct btrfs_fs_info *info)
{
	int ret = 0;
	spin_lock(&info->new_trans_lock);
	if (info->running_transaction)
		ret = info->running_transaction->blocked;
	spin_unlock(&info->new_trans_lock);
	return ret;
}

S
Sage Weil 已提交
1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163
/*
 * 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)
{
	DEFINE_WAIT(wait);

	if (trans->in_commit)
		return;

	while (1) {
		prepare_to_wait(&root->fs_info->transaction_blocked_wait, &wait,
				TASK_UNINTERRUPTIBLE);
		if (trans->in_commit) {
			finish_wait(&root->fs_info->transaction_blocked_wait,
				    &wait);
			break;
		}
		mutex_unlock(&root->fs_info->trans_mutex);
		schedule();
		mutex_lock(&root->fs_info->trans_mutex);
		finish_wait(&root->fs_info->transaction_blocked_wait, &wait);
	}
}

/*
 * 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)
{
	DEFINE_WAIT(wait);

	if (trans->commit_done || (trans->in_commit && !trans->blocked))
		return;

	while (1) {
		prepare_to_wait(&root->fs_info->transaction_wait, &wait,
				TASK_UNINTERRUPTIBLE);
		if (trans->commit_done ||
		    (trans->in_commit && !trans->blocked)) {
			finish_wait(&root->fs_info->transaction_wait,
				    &wait);
			break;
		}
		mutex_unlock(&root->fs_info->trans_mutex);
		schedule();
		mutex_lock(&root->fs_info->trans_mutex);
		finish_wait(&root->fs_info->transaction_wait,
			    &wait);
	}
}

/*
 * 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);
	BUG_ON(!ac);

	INIT_DELAYED_WORK(&ac->work, do_async_commit);
	ac->root = root;
	ac->newtrans = btrfs_join_transaction(root, 0);
1164 1165 1166 1167 1168
	if (IS_ERR(ac->newtrans)) {
		int err = PTR_ERR(ac->newtrans);
		kfree(ac);
		return err;
	}
S
Sage Weil 已提交
1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197

	/* take transaction reference */
	mutex_lock(&root->fs_info->trans_mutex);
	cur_trans = trans->transaction;
	cur_trans->use_count++;
	mutex_unlock(&root->fs_info->trans_mutex);

	btrfs_end_transaction(trans, root);
	schedule_delayed_work(&ac->work, 0);

	/* wait for transaction to start and unblock */
	mutex_lock(&root->fs_info->trans_mutex);
	if (wait_for_unblock)
		wait_current_trans_commit_start_and_unblock(root, cur_trans);
	else
		wait_current_trans_commit_start(root, cur_trans);
	put_transaction(cur_trans);
	mutex_unlock(&root->fs_info->trans_mutex);

	return 0;
}

/*
 * btrfs_transaction state sequence:
 *    in_commit = 0, blocked = 0  (initial)
 *    in_commit = 1, blocked = 1
 *    blocked = 0
 *    commit_done = 1
 */
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int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
			     struct btrfs_root *root)
{
1201
	unsigned long joined = 0;
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	struct btrfs_transaction *cur_trans;
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	struct btrfs_transaction *prev_trans = NULL;
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	DEFINE_WAIT(wait);
1205
	int ret;
1206 1207
	int should_grow = 0;
	unsigned long now = get_seconds();
1208
	int flush_on_commit = btrfs_test_opt(root, FLUSHONCOMMIT);
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1210 1211
	btrfs_run_ordered_operations(root, 0);

1212 1213 1214 1215 1216 1217
	/* 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);

1218 1219
	btrfs_trans_release_metadata(trans, root);

1220
	cur_trans = trans->transaction;
1221 1222 1223 1224
	/*
	 * set the flushing flag so procs in this transaction have to
	 * start sending their work down.
	 */
1225
	cur_trans->delayed_refs.flushing = 1;
1226

1227
	ret = btrfs_run_delayed_refs(trans, root, 0);
1228 1229
	BUG_ON(ret);

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	mutex_lock(&root->fs_info->trans_mutex);
1231 1232
	if (cur_trans->in_commit) {
		cur_trans->use_count++;
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		mutex_unlock(&root->fs_info->trans_mutex);
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		btrfs_end_transaction(trans, root);
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		ret = wait_for_commit(root, cur_trans);
		BUG_ON(ret);
1238 1239

		mutex_lock(&root->fs_info->trans_mutex);
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		put_transaction(cur_trans);
1241 1242
		mutex_unlock(&root->fs_info->trans_mutex);

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		return 0;
	}
1245

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	trans->transaction->in_commit = 1;
1247
	trans->transaction->blocked = 1;
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	wake_up(&root->fs_info->transaction_blocked_wait);

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	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);
1260
			put_transaction(prev_trans);
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		}
	}
1263

1264 1265 1266
	if (now < cur_trans->start_time || now - cur_trans->start_time < 1)
		should_grow = 1;

1267
	do {
1268
		int snap_pending = 0;
1269
		joined = cur_trans->num_joined;
1270 1271 1272
		if (!list_empty(&trans->transaction->pending_snapshots))
			snap_pending = 1;

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		WARN_ON(cur_trans != trans->transaction);
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		mutex_unlock(&root->fs_info->trans_mutex);
1275

1276
		if (flush_on_commit || snap_pending) {
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			btrfs_start_delalloc_inodes(root, 1);
			ret = btrfs_wait_ordered_extents(root, 0, 1);
1279
			BUG_ON(ret);
1280 1281
		}

1282 1283 1284 1285 1286 1287 1288 1289 1290
		/*
		 * 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);

1291 1292 1293
		prepare_to_wait(&cur_trans->writer_wait, &wait,
				TASK_UNINTERRUPTIBLE);

1294
		smp_mb();
1295 1296 1297 1298
		if (cur_trans->num_writers > 1)
			schedule_timeout(MAX_SCHEDULE_TIMEOUT);
		else if (should_grow)
			schedule_timeout(1);
1299

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		mutex_lock(&root->fs_info->trans_mutex);
1301 1302
		finish_wait(&cur_trans->writer_wait, &wait);
	} while (cur_trans->num_writers > 1 ||
1303
		 (should_grow && cur_trans->num_joined != joined));
1304

1305 1306 1307
	ret = create_pending_snapshots(trans, root->fs_info);
	BUG_ON(ret);

1308 1309 1310
	ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
	BUG_ON(ret);

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	WARN_ON(cur_trans != trans->transaction);
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1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327
	/* 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);

1328
	ret = commit_fs_roots(trans, root);
1329 1330
	BUG_ON(ret);

1331
	/* commit_fs_roots gets rid of all the tree log roots, it is now
1332 1333 1334 1335
	 * safe to free the root of tree log roots
	 */
	btrfs_free_log_root_tree(trans, root->fs_info);

1336
	ret = commit_cowonly_roots(trans, root);
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	BUG_ON(ret);
1338

1339 1340
	btrfs_prepare_extent_commit(trans, root);

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	cur_trans = root->fs_info->running_transaction;
1342
	spin_lock(&root->fs_info->new_trans_lock);
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	root->fs_info->running_transaction = NULL;
1344
	spin_unlock(&root->fs_info->new_trans_lock);
1345 1346 1347

	btrfs_set_root_node(&root->fs_info->tree_root->root_item,
			    root->fs_info->tree_root->node);
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	switch_commit_root(root->fs_info->tree_root);
1349 1350 1351

	btrfs_set_root_node(&root->fs_info->chunk_root->root_item,
			    root->fs_info->chunk_root->node);
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	switch_commit_root(root->fs_info->chunk_root);
1353 1354

	update_super_roots(root);
1355 1356 1357 1358 1359 1360

	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);
	}

1361 1362
	memcpy(&root->fs_info->super_for_commit, &root->fs_info->super_copy,
	       sizeof(root->fs_info->super_copy));
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1364
	trans->transaction->blocked = 0;
1365

1366
	wake_up(&root->fs_info->transaction_wait);
1367

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	mutex_unlock(&root->fs_info->trans_mutex);
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	ret = btrfs_write_and_wait_transaction(trans, root);
	BUG_ON(ret);
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	write_ctree_super(trans, root, 0);
1372

1373 1374 1375 1376 1377 1378
	/*
	 * the super is written, we can safely allow the tree-loggers
	 * to go about their business
	 */
	mutex_unlock(&root->fs_info->tree_log_mutex);

1379
	btrfs_finish_extent_commit(trans, root);
1380

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

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	cur_trans->commit_done = 1;
1384

1385
	root->fs_info->last_trans_committed = cur_trans->transid;
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1386

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	wake_up(&cur_trans->commit_wait);
1388

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	put_transaction(cur_trans);
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	put_transaction(cur_trans);
1391

1392 1393
	trace_btrfs_transaction_commit(root);

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	mutex_unlock(&root->fs_info->trans_mutex);
1395

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

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	kmem_cache_free(btrfs_trans_handle_cachep, trans);
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	if (current != root->fs_info->transaction_kthread)
		btrfs_run_delayed_iputs(root);

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	return ret;
}

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/*
 * interface function to delete all the snapshots we have scheduled for deletion
 */
1410 1411
int btrfs_clean_old_snapshots(struct btrfs_root *root)
{
1412 1413 1414 1415 1416 1417
	LIST_HEAD(list);
	struct btrfs_fs_info *fs_info = root->fs_info;

	mutex_lock(&fs_info->trans_mutex);
	list_splice_init(&fs_info->dead_roots, &list);
	mutex_unlock(&fs_info->trans_mutex);
1418

1419 1420
	while (!list_empty(&list)) {
		root = list_entry(list.next, struct btrfs_root, root_list);
1421 1422 1423 1424
		list_del(&root->root_list);

		if (btrfs_header_backref_rev(root->node) <
		    BTRFS_MIXED_BACKREF_REV)
1425
			btrfs_drop_snapshot(root, NULL, 0);
1426
		else
1427
			btrfs_drop_snapshot(root, NULL, 1);
1428 1429 1430
	}
	return 0;
}