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 "messages.h"
#include "ctree.h"
#include "delayed-ref.h"
#include "transaction.h"
#include "qgroup.h"
#include "space-info.h"
#include "tree-mod-log.h"
#include "fs.h"

struct kmem_cache *btrfs_delayed_ref_head_cachep;
struct kmem_cache *btrfs_delayed_ref_node_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;
}

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

	num_bytes = btrfs_calc_delayed_ref_bytes(fs_info, nr_refs);
	num_bytes += btrfs_calc_delayed_ref_csum_bytes(fs_info, nr_csums);

	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);
}

/*
 * Adjust the size of the delayed refs rsv.
 *
 * This is to be called anytime we may have adjusted trans->delayed_ref_updates
 * or trans->delayed_ref_csum_deletions, 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;
	struct btrfs_block_rsv *local_rsv = &trans->delayed_rsv;
	u64 num_bytes;
	u64 reserved_bytes;

	num_bytes = btrfs_calc_delayed_ref_bytes(fs_info, trans->delayed_ref_updates);
	num_bytes += btrfs_calc_delayed_ref_csum_bytes(fs_info,
						       trans->delayed_ref_csum_deletions);

	if (num_bytes == 0)
		return;

	/*
	 * Try to take num_bytes from the transaction's local delayed reserve.
	 * If not possible, try to take as much as it's available. If the local
	 * reserve doesn't have enough reserved space, the delayed refs reserve
	 * will be refilled next time btrfs_delayed_refs_rsv_refill() is called
	 * by someone or if a transaction commit is triggered before that, the
	 * global block reserve will be used. We want to minimize using the
	 * global block reserve for cases we can account for in advance, to
	 * avoid exhausting it and reach -ENOSPC during a transaction commit.
	 */
	spin_lock(&local_rsv->lock);
	reserved_bytes = min(num_bytes, local_rsv->reserved);
	local_rsv->reserved -= reserved_bytes;
	local_rsv->full = (local_rsv->reserved >= local_rsv->size);
	spin_unlock(&local_rsv->lock);

	spin_lock