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_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;
}

/*
 * Release a ref head's reservation.
 *
 * @fs_info:  the filesystem
 * @nr:       number of 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)
{
	struct btrfs_block_rsv *block_rsv = &fs_info->delayed_refs_rsv;
	const u64 num_bytes = btrfs_calc_delayed_ref_bytes(fs_info, nr);
	u64 released = 0;

	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,
 * 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_delayed_ref_bytes(fs_info,
						 trans->delayed_ref_updates);

	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_rsv->reserved) {
		u64 delta = delayed_refs_rsv->size -
			delayed_refs_rsv->reserved;
		if (num_bytes > delta) {
			to_free = num_bytes - delta;
			num_bytes = delta;
		}
	} else {
		to_free = num_bytes;
		num_bytes = 0;
	}

	if (num_bytes)
		delayed_refs_rsv->reserved += num_bytes;
	if (delayed_refs_rsv->reserved >= delayed_refs_rsv->size)
		delayed_refs_rsv->full = true;
	spin_unlock(&delayed_refs_rsv->lock);

	if (num_bytes)
		trace_btrfs_space_reservation(fs_info, "delayed_refs_rsv",
					      0, num_bytes, 1);
	if (to_free)
		btrfs_space_info_free_bytes_may_use(fs_info,
				delayed_refs_rsv->space_info, to_free);
}

/*
 * Refill based on our delayed refs usage.
 *
 * @fs_info: the filesystem
 * @flush:   control how we can flush for this reservation.
 *
 * This will refill the delayed block_rsv up to 1 items size worth of space and
 * will return -ENOSPC if we can't make the reservation.
 */
int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info,
				  enum btrfs_reserve_flush_enum flush)
{
	struct btrfs_block_rsv *block_rsv = &fs_info->