path: root/drivers/md/persistent-data/dm-space-map-metadata.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2011 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#include "dm-space-map.h"
#include "dm-space-map-common.h"
#include "dm-space-map-metadata.h"

#include <linux/list.h>
#include <linux/slab.h>
#include <linux/device-mapper.h>
#include <linux/kernel.h>

#define DM_MSG_PREFIX "space map metadata"

/*----------------------------------------------------------------*/

/*
 * An edge triggered threshold.
 */
struct threshold {
	bool threshold_set;
	bool value_set;
	dm_block_t threshold;
	dm_block_t current_value;
	dm_sm_threshold_fn fn;
	void *context;
};

static void threshold_init(struct threshold *t)
{
	t->threshold_set = false;
	t->value_set = false;
}

static void set_threshold(struct threshold *t, dm_block_t value,
			  dm_sm_threshold_fn fn, void *context)
{
	t->threshold_set = true;
	t->threshold = value;
	t->fn = fn;
	t->context = context;
}

static bool below_threshold(struct threshold *t, dm_block_t value)
{
	return t->threshold_set && value <= t->threshold;
}

static bool threshold_already_triggered(struct threshold *t)
{
	return t->value_set && below_threshold(t, t->current_value);
}

static void check_threshold(struct threshold *t, dm_block_t value)
{
	if (below_threshold(t, value) &&
	    !threshold_already_triggered(t))
		t->fn(t->context);

	t->value_set = true;
	t->current_value = value;
}

/*----------------------------------------------------------------*/

/*
 * Space map interface.
 *
 * The low level disk format is written using the standard btree and
 * transaction manager.  This means that performing disk operations may
 * cause us to recurse into the space map in order to allocate new blocks.
 * For this reason we have a pool of pre-allocated blocks large enough to
 * service any metadata_ll_disk operation.
 */

/*
 * FIXME: we should calculate this based on the size of the device.
 * Only the metadata space map needs this functionality.
 */
#define MAX_RECURSIVE_ALLOCATIONS 1024

enum block_op_type {
	BOP_INC,
	BOP_DEC
};

struct block_op {
	enum block_op_type type;
	dm_block_t b;
	dm_block_t e;
};

struct bop_ring_buffer {
	unsigned int begin;
	unsigned int end;
	struct block_op bops[MAX_RECURSIVE_ALLOCATIONS + 1];
};

static void brb_init(struct bop_ring_buffer *brb)
{
	brb->begin = 0;
	brb->end = 0;
}

static bool brb_empty(struct bop_ring_buffer *brb)
{
	return brb->begin == brb->end;
}

static unsigned int brb_next(struct bop_ring_buffer *brb, unsigned int old)
{
	unsigned int r = old + 1;

	return r >= ARRAY_SIZE(brb->bops) ? 0 : r;
}

static int brb_push(struct bop_ring_buffer *brb,
		    enum block_op_type type, dm_block_t b, dm_block_t e)
{
	struct block_op *bop;
	unsigned int next = brb_next(brb, brb->end);

	/*
	 * We don't allow the last bop to be filled, this way we can
	 * differentiate between full and empty.
	 */
	if (next == brb->begin)
		return -ENOMEM;

	bop = brb->bops + brb->end;
	bop->type = type;
	bop->b = b;
	bop->e = e;

	brb->end = next;

	return 0;
}

static int brb_peek(struct bop_ring_buffer *brb, struct block_op *result)
{
	struct block_op *bop;

	if (brb_empty(brb))
		return -ENODATA;

	bop = brb->bops + brb->begin;
	memcpy(result, bop, sizeof(*result));
	return 0;
}

static int brb_pop(struct bop_ring_buffer *brb)
{
	if (brb_empty(brb))
		return -ENODATA;

	brb->begin = brb_next(brb, brb->begin);

	return 0;
}

/*----------------------------------------------------------------*/

struct sm_metadata {
	struct dm_space_map sm;

	struct ll_disk ll;
	struct ll_disk old_ll;

	dm_block_t begin;

	unsigned int recursion_count;
	unsigned int allocated_this_transaction;
	struct bop_ring_buffer uncommitted;

	struct threshold threshold;
};

static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b, dm_block_t e)
{
	int r = brb_push(&smm->uncommitted, type, b, e);

	if (r) {
		DMERR("too many recursive allocations");
		return -ENOMEM;
	}

	return 0;
}

static int commit_bop(struct sm_metadata *smm, struct block_op *op)
{
	int r = 0;
	int32_t nr_allocations;

	switch (op->type) {
	case BOP_INC:
		r = sm_ll_inc(&smm->ll, op->b, op->e, &