path: root/fs/btrfs/delayed-ref.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2009 Oracle.  All rights reserved.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include "ctree.h"
#include "delayed-ref.h"
#include "transaction.h"
#include "qgroup.h"
#include "space-info.h"
#include "tree-mod-log.h"

struct kmem_cache *btrfs_delayed_ref_head_cachep;
struct kmem_cache *btrfs_delayed_tree_ref_cachep;
struct kmem_cache *btrfs_delayed_data_ref_cachep;
struct kmem_cache *btrfs_delayed_extent_op_cachep;
/*
 * delayed back reference update tracking.  For subvolume trees
 * we queue up extent allocations and backref maintenance for
 * delayed processing.   This avoids deep call chains where we
 * add extents in the middle of btrfs_search_slot, and it allows
 * us to buffer up frequently modified backrefs in an rb tree instead
 * of hammering updates on the extent allocation tree.
 */

bool btrfs_check_space_for_delayed_refs(struct btrfs_fs_info *fs_info)
{
	struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
	bool ret = false;
	u64 reserved;

	spin_lock(&global_rsv->lock);
	reserved = global_rsv->reserved;
	spin_unlock(&global_rsv->lock);

	/*
	 * Since the global reserve is just kind of magic we don't really want
	 * to rely on it to save our bacon, so if our size is more than the
	 * delayed_refs_rsv and the global rsv then it's time to think about
	 * bailing.
	 */
	spin_lock(&delayed_refs_rsv->lock);
	reserved += delayed_refs_rsv->reserved;
	if (delayed_refs_rsv->size >= reserved)
		ret = true;
	spin_unlock(&delayed_refs_rsv->lock);
	return ret;
}

int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans)
{
	u64 num_entries =
		atomic_read(&trans->transaction->delayed_refs.num_entries);
	u64 avg_runtime;
	u64 val;

	smp_mb();
	avg_runtime = trans->fs_info->avg_delayed_ref_runtime;
	val = num_entries * avg_runtime;
	if (val >= NSEC_PER_SEC)
		return 1;
	if (val >= NSEC_PER_SEC / 2)
		return 2;

	return btrfs_check_space_for_delayed_refs(trans->fs_info);
}

/**
 * Release a ref head's reservation
 *
 * @fs_info:  the filesystem
 * @nr:       number of items to drop
 *
 * This drops the delayed ref head's count from the delayed refs rsv and frees
 * any excess reservation we had.
 */
void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr)
{
	struct btrfs_block_rsv *block_rsv = &fs_info->delayed_refs_rsv;
	u64 num_bytes = btrfs_calc_insert_metadata_size(fs_info, nr);
	u64 released = 0;

	/*
	 * We have to check the mount option here because we could be enabling
	 * the free space tree for the first time and don't have the compat_ro
	 * option set yet.
	 *
	 * We need extra reservations if we have the free space tree because
	 * we'll have to modify that tree as well.
	 */
	if (btrfs_test_opt(fs_info, FREE_SPACE_TREE))
		num_bytes *= 2;

	released = btrfs_block_rsv_release(fs_info, block_rsv, num_bytes, NULL);
	if (released)
		trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv",
					      0, released, 0);
}

/*
 * btrfs_update_delayed_refs_rsv - adjust the size of the delayed refs rsv
 * @trans - the trans that may have generated delayed refs
 *
 * This is to be called anytime we may have adjusted trans->delayed_ref_updates,
 * it'll calculate the additional size and add it to the delayed_refs_rsv.
 */
void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_refs_rsv;
	u64 num_bytes;

	if (!trans->delayed_ref_updates)
		return;

	num_bytes = btrfs_calc_insert_metadata_size(fs_info,
						    trans->delayed_ref_updates);
	/*
	 * We have to check the mount option here because we could be enabling
	 * the free space tree for the first time and don't have the compat_ro
	 * option set yet.
	 *
	 * We need extra reservations if we have the free space tree because
	 * we'll have to modify that tree as well.
	 */
	if (btrfs_test_opt(fs_info, FREE_SPACE_TREE))
		num_bytes *= 2;

	spin_lock(&delayed_rsv->lock);
	delayed_rsv->size += num_bytes;
	delayed_rsv->full = false;
	spin_unlock(&delayed_rsv->lock);
	trans->delayed_ref_updates = 0;
}

/**
 * Transfer bytes to our delayed refs rsv
 *
 * @fs_info:   the filesystem
 * @num_bytes: number of bytes to transfer
 *
 * This transfers up to the num_bytes amount, previously reserved, to the
 * delayed_refs_rsv.  Any extra bytes are returned to the space info.
 */
void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info,
				       u64 num_bytes)
{
	struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
	u64 to_free = 0;

	spin_lock(&delayed_refs_rsv->lock);
	if (delayed_refs_rsv->size > delayed_refs