dm-cache-background-tracker.c 5.05 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
/*
 * Copyright (C) 2017 Red Hat. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include "dm-cache-background-tracker.h"

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

#define DM_MSG_PREFIX "dm-background-tracker"

struct bt_work {
	struct list_head list;
	struct rb_node node;
	struct policy_work work;
};

struct background_tracker {
	unsigned max_work;
	atomic_t pending_promotes;
	atomic_t pending_writebacks;
	atomic_t pending_demotes;

	struct list_head issued;
	struct list_head queued;
	struct rb_root pending;

	struct kmem_cache *work_cache;
};

struct background_tracker *btracker_create(unsigned max_work)
{
	struct background_tracker *b = kmalloc(sizeof(*b), GFP_KERNEL);

36 37 38 39 40
	if (!b) {
		DMERR("couldn't create background_tracker");
		return NULL;
	}

41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163
	b->max_work = max_work;
	atomic_set(&b->pending_promotes, 0);
	atomic_set(&b->pending_writebacks, 0);
	atomic_set(&b->pending_demotes, 0);

	INIT_LIST_HEAD(&b->issued);
	INIT_LIST_HEAD(&b->queued);

	b->pending = RB_ROOT;
	b->work_cache = KMEM_CACHE(bt_work, 0);
	if (!b->work_cache) {
		DMERR("couldn't create mempool for background work items");
		kfree(b);
		b = NULL;
	}

	return b;
}
EXPORT_SYMBOL_GPL(btracker_create);

void btracker_destroy(struct background_tracker *b)
{
	kmem_cache_destroy(b->work_cache);
	kfree(b);
}
EXPORT_SYMBOL_GPL(btracker_destroy);

static int cmp_oblock(dm_oblock_t lhs, dm_oblock_t rhs)
{
	if (from_oblock(lhs) < from_oblock(rhs))
		return -1;

	if (from_oblock(rhs) < from_oblock(lhs))
		return 1;

	return 0;
}

static bool __insert_pending(struct background_tracker *b,
			     struct bt_work *nw)
{
	int cmp;
	struct bt_work *w;
	struct rb_node **new = &b->pending.rb_node, *parent = NULL;

	while (*new) {
		w = container_of(*new, struct bt_work, node);

		parent = *new;
		cmp = cmp_oblock(w->work.oblock, nw->work.oblock);
		if (cmp < 0)
			new = &((*new)->rb_left);

		else if (cmp > 0)
			new = &((*new)->rb_right);

		else
			/* already present */
			return false;
	}

	rb_link_node(&nw->node, parent, new);
	rb_insert_color(&nw->node, &b->pending);

	return true;
}

static struct bt_work *__find_pending(struct background_tracker *b,
				      dm_oblock_t oblock)
{
	int cmp;
	struct bt_work *w;
	struct rb_node **new = &b->pending.rb_node;

	while (*new) {
		w = container_of(*new, struct bt_work, node);

		cmp = cmp_oblock(w->work.oblock, oblock);
		if (cmp < 0)
			new = &((*new)->rb_left);

		else if (cmp > 0)
			new = &((*new)->rb_right);

		else
			break;
	}

	return *new ? w : NULL;
}


static void update_stats(struct background_tracker *b, struct policy_work *w, int delta)
{
	switch (w->op) {
	case POLICY_PROMOTE:
		atomic_add(delta, &b->pending_promotes);
		break;

	case POLICY_DEMOTE:
		atomic_add(delta, &b->pending_demotes);
		break;

	case POLICY_WRITEBACK:
		atomic_add(delta, &b->pending_writebacks);
		break;
	}
}

unsigned btracker_nr_writebacks_queued(struct background_tracker *b)
{
	return atomic_read(&b->pending_writebacks);
}
EXPORT_SYMBOL_GPL(btracker_nr_writebacks_queued);

unsigned btracker_nr_demotions_queued(struct background_tracker *b)
{
	return atomic_read(&b->pending_demotes);
}
EXPORT_SYMBOL_GPL(btracker_nr_demotions_queued);

static bool max_work_reached(struct background_tracker *b)
{
164 165 166 167 168
	return atomic_read(&b->pending_promotes) +
		atomic_read(&b->pending_writebacks) +
		atomic_read(&b->pending_demotes) >= b->max_work;
}

169
static struct bt_work *alloc_work(struct background_tracker *b)
170 171 172 173 174
{
	if (max_work_reached(b))
		return NULL;

	return kmem_cache_alloc(b->work_cache, GFP_NOWAIT);
175 176 177 178 179 180 181 182 183 184 185
}

int btracker_queue(struct background_tracker *b,
		   struct policy_work *work,
		   struct policy_work **pwork)
{
	struct bt_work *w;

	if (pwork)
		*pwork = NULL;

186
	w = alloc_work(b);
187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249
	if (!w)
		return -ENOMEM;

	memcpy(&w->work, work, sizeof(*work));

	if (!__insert_pending(b, w)) {
		/*
		 * There was a race, we'll just ignore this second
		 * bit of work for the same oblock.
		 */
		kmem_cache_free(b->work_cache, w);
		return -EINVAL;
	}

	if (pwork) {
		*pwork = &w->work;
		list_add(&w->list, &b->issued);
	} else
		list_add(&w->list, &b->queued);
	update_stats(b, &w->work, 1);

	return 0;
}
EXPORT_SYMBOL_GPL(btracker_queue);

/*
 * Returns -ENODATA if there's no work.
 */
int btracker_issue(struct background_tracker *b, struct policy_work **work)
{
	struct bt_work *w;

	if (list_empty(&b->queued))
		return -ENODATA;

	w = list_first_entry(&b->queued, struct bt_work, list);
	list_move(&w->list, &b->issued);
	*work = &w->work;

	return 0;
}
EXPORT_SYMBOL_GPL(btracker_issue);

void btracker_complete(struct background_tracker *b,
		       struct policy_work *op)
{
	struct bt_work *w = container_of(op, struct bt_work, work);

	update_stats(b, &w->work, -1);
	rb_erase(&w->node, &b->pending);
	list_del(&w->list);
	kmem_cache_free(b->work_cache, w);
}
EXPORT_SYMBOL_GPL(btracker_complete);

bool btracker_promotion_already_present(struct background_tracker *b,
					dm_oblock_t oblock)
{
	return __find_pending(b, oblock) != NULL;
}
EXPORT_SYMBOL_GPL(btracker_promotion_already_present);

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