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/*
* Copyright (C) 2012 Red Hat. All rights reserved.
*
* writeback cache policy supporting flushing out dirty cache blocks.
*
* This file is released under the GPL.
*/
#include "dm-cache-policy.h"
#include "dm.h"
#include <linux/hash.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
/*----------------------------------------------------------------*/
#define DM_MSG_PREFIX "cache cleaner"
/* Cache entry struct. */
struct wb_cache_entry {
struct list_head list;
struct hlist_node hlist;
dm_oblock_t oblock;
dm_cblock_t cblock;
bool dirty:1;
bool pending:1;
};
struct hash {
struct hlist_head *table;
dm_block_t hash_bits;
unsigned nr_buckets;
};
struct policy {
struct dm_cache_policy policy;
spinlock_t lock;
struct list_head free;
struct list_head clean;
struct list_head clean_pending;
struct list_head dirty;
/*
* We know exactly how many cblocks will be needed,
* so we can allocate them up front.
*/
dm_cblock_t cache_size, nr_cblocks_allocated;
struct wb_cache_entry *cblocks;
struct hash chash;
};
/*----------------------------------------------------------------------------*/
/*
* Low-level functions.
*/
static unsigned next_power(unsigned n, unsigned min)
{
return roundup_pow_of_two(max(n, min));
}
static struct policy *to_policy(struct dm_cache_policy *p)
{
return container_of(p, struct policy, policy);
}
static struct list_head *list_pop(struct list_head *q)
{
struct list_head *r = q->next;
list_del(r);
return r;
}
/*----------------------------------------------------------------------------*/
/* Allocate/free various resources. */
static int alloc_hash(struct hash *hash, unsigned elts)
{
hash->nr_buckets = next_power(elts >> 4, 16);
hash->hash_bits = __ffs(hash->nr_buckets);
hash->table = vzalloc(sizeof(*hash->table) * hash->nr_buckets);
return hash->table ? 0 : -ENOMEM;
}
static void free_hash(struct hash *hash)
{
vfree(hash->table);
}
static int alloc_cache_blocks_with_hash(struct policy *p, dm_cblock_t cache_size)
{
int r = -ENOMEM;
p->cblocks = vzalloc(sizeof(*p->cblocks) * from_cblock(cache_size));
if (p->cblocks) {
unsigned u = from_cblock(cache_size);
while (u--)
list_add(&p->cblocks[u].list, &p->free);
p->nr_cblocks_allocated = 0;
/* Cache entries hash. */
r = alloc_hash(&p->chash, from_cblock(cache_size));
if (r)
vfree(p->cblocks);
}
return r;
}
static void free_cache_blocks_and_hash(struct policy *p)
{
free_hash(&p->chash);
vfree(p->cblocks);
}
static struct wb_cache_entry *alloc_cache_entry(struct policy *p)
{
struct wb_cache_entry *e;
BUG_ON(from_cblock(p->nr_cblocks_allocated) >= from_cblock(p->cache_size));
e = list_entry(list_pop(&p->free), struct wb_cache_entry, list);
p->nr_cblocks_allocated = to_cblock(from_cblock(p->nr_cblocks_allocated) + 1);
return e;
}
/*----------------------------------------------------------------------------*/
/* Hash functions (lookup, insert, remove). */
static struct wb_cache_entry *lookup_cache_entry(struct policy *p, dm_oblock_t oblock)
{
struct hash *hash = &p->chash;
unsigned h = hash_64(from_oblock(oblock), hash->hash_bits);
struct wb_cache_entry *cur;
struct hlist_head *bucket = &hash->table[h];
hlist_for_each_entry(cur, bucket, hlist) {
if (cur->oblock == oblock) {
/* Move upfront bucket for faster access. */
hlist_del(&cur->hlist);
hlist_add_head(&cur->hlist, bucket);
return cur;
}
}
return NULL;
}
static void insert_cache_hash_entry(struct policy *p, struct wb_cache_entry *e)
{
unsigned h = hash_64(from_oblock(e->oblock), p->chash.hash_bits);
hlist_add_head(&e->hlist, &p->chash.table[h]);
}
static void remove_cache_hash_entry(struct wb_cache_entry *e)
{
hlist_del(&e->hlist);
}
/* Public interface (see dm-cache-policy.h */
static int wb_map(struct dm_cache_policy *pe, dm_oblock_t oblock,
bool can_block, bool can_migrate, bool discarded_oblock,
struct bio *bio, struct policy_locker *locker,
struct policy_result *result)
{
struct policy *p = to_policy(pe);
struct wb_cache_entry *e;
unsigned long flags;
result->op = POLICY_MISS;
if (can_block)
spin_lock_irqsave(&p->lock, flags);
else if (!spin_trylock_irqsave(&p->lock, flags))
return -EWOULDBLOCK;
e = lookup_cache_entry(p, oblock);
if (e) {
result->op = POLICY_HIT;
result->cblock = e->cblock;
}
spin_unlock_irqrestore(&p->lock, flags);
return 0;
}
static int wb_lookup(struct dm_cache_policy *pe, dm_oblock_t oblock, dm_cblock_t *cblock)
{
int r;
struct policy *p = to_policy(pe);
struct wb_cache_entry *e;
unsigned long flags;
if (!spin_trylock_irqsave(&p->lock, flags))
return -EWOULDBLOCK;
e = lookup_cache_entry(p, oblock);
if (e) {
*cblock = e->cblock;
r = 0;
} else
r = -ENOENT;
spin_unlock_irqrestore(&p->lock, flags);
return r;
}
static void __set_clear_dirty(struct dm_cache_policy *pe, dm_oblock_t oblock, bool set)
{
struct policy *p = to_policy(pe);
struct wb_cache_entry *e;
e = lookup_cache_entry(p, oblock);
BUG_ON(!e);
if (set) {
if (!e->dirty) {
e->dirty = true;
list_move(&e->list, &p->dirty);
}
} else {
if (e->dirty) {
e->pending = false;
e->dirty = false;
list_move(&e->list, &p->clean);
}
}
}
static void wb_set_dirty(struct dm_cache_policy *pe, dm_oblock_t oblock)
{
struct policy *p = to_policy(pe);
unsigned long flags;
spin_lock_irqsave(&p->lock, flags);
__set_clear_dirty(pe, oblock, true);
spin_unlock_irqrestore(&p->lock, flags);
}
static void wb_clear_dirty(struct dm_cache_policy *pe, dm_oblock_t oblock)
{
struct policy *p = to_policy(pe);
unsigned long flags;
spin_lock_irqsave(&p->lock, flags);
__set_clear_dirty(pe, oblock, false);
spin_unlock_irqrestore(&p->lock, flags);
}
static void add_cache_entry(struct policy *p, struct wb_cache_entry *e)
{
insert_cache_hash_entry(p, e);
if (e->dirty)
list_add(&e->list, &p->dirty);
else
list_add(&e->list, &p->clean);
}
static int wb_load_mapping(struct dm_cache_policy *pe,
dm_oblock_t oblock, dm_cblock_t cblock,
uint32_t hint, bool hint_valid)
{
int r;
struct policy *p = to_policy(pe);
struct wb_cache_entry *e = alloc_cache_entry(p);
if (e) {
e->cblock = cblock;
e->oblock = oblock;
e->dirty = false; /* blocks default to clean */
add_cache_entry(p, e);
r = 0;
} else
r = -ENOMEM;
return r;
}
static void wb_destroy(struct dm_cache_policy *pe)
{
struct policy *p = to_policy(pe);
free_cache_blocks_and_hash(p);
kfree(p);
}
static struct wb_cache_entry *__wb_force_remove_mapping(struct policy *p, dm_oblock_t oblock)
{
struct wb_cache_entry *r = lookup_cache_entry(p, oblock);
BUG_ON(!r);
remove_cache_hash_entry(r);
list_del(&r->list);
return r;
}
static void wb_remove_mapping(struct dm_cache_policy *pe, dm_oblock_t oblock)
{
struct policy *p = to_policy(pe);
struct wb_cache_entry *e;
unsigned long flags;
spin_lock_irqsave(&p->lock, flags);
e = __wb_force_remove_mapping(p, oblock);
list_add_tail(&e->list, &p->free);
BUG_ON(!from_cblock(p->nr_cblocks_allocated));
p->nr_cblocks_allocated = to_cblock(from_cblock(p->nr_cblocks_allocated) - 1);
spin_unlock_irqrestore(&p->lock, flags);
}
static void wb_force_mapping(struct dm_cache_policy *pe,
dm_oblock_t current_oblock, dm_oblock_t oblock)
{
struct policy *p = to_policy(pe);
struct wb_cache_entry *e;
unsigned long flags;
spin_lock_irqsave(&p->lock, flags);
e = __wb_force_remove_mapping(p, current_oblock);
e->oblock = oblock;
add_cache_entry(p, e);
spin_unlock_irqrestore(&p->lock, flags);
}
static struct wb_cache_entry *get_next_dirty_entry(struct policy *p)
{
struct list_head *l;
struct wb_cache_entry *r;
if (list_empty(&p->dirty))
return NULL;
l = list_pop(&p->dirty);
r = container_of(l, struct wb_cache_entry, list);
list_add(l, &p->clean_pending);
return r;
}
static int wb_writeback_work(struct dm_cache_policy *pe,
dm_oblock_t *oblock,
dm_cblock_t *cblock,
bool critical_only)
{
int r = -ENOENT;
struct policy *p = to_policy(pe);
struct wb_cache_entry *e;
unsigned long flags;
spin_lock_irqsave(&p->lock, flags);
e = get_next_dirty_entry(p);
if (e) {
*oblock = e->oblock;
*cblock = e->cblock;
r = 0;
}
spin_unlock_irqrestore(&p->lock, flags);
return r;
}
static dm_cblock_t wb_residency(struct dm_cache_policy *pe)
{
return to_policy(pe)->nr_cblocks_allocated;
}
/* Init the policy plugin interface function pointers. */
static void init_policy_functions(struct policy *p)
{
p->policy.destroy = wb_destroy;
p->policy.map = wb_map;
p->policy.lookup = wb_lookup;
p->policy.set_dirty = wb_set_dirty;
p->policy.clear_dirty = wb_clear_dirty;
p->policy.load_mapping = wb_load_mapping;
p->policy.walk_mappings = NULL;
p->policy.remove_mapping = wb_remove_mapping;
p->policy.writeback_work = wb_writeback_work;
p->policy.force_mapping = wb_force_mapping;
p->policy.residency = wb_residency;
p->policy.tick = NULL;
}
static struct dm_cache_policy *wb_create(dm_cblock_t cache_size,
sector_t origin_size,
sector_t cache_block_size)
{
int r;
struct policy *p = kzalloc(sizeof(*p), GFP_KERNEL);
if (!p)
return NULL;
init_policy_functions(p);
INIT_LIST_HEAD(&p->free);
INIT_LIST_HEAD(&p->clean);
INIT_LIST_HEAD(&p->clean_pending);
INIT_LIST_HEAD(&p->dirty);
p->cache_size = cache_size;
spin_lock_init(&p->lock);
/* Allocate cache entry structs and add them to free list. */
r = alloc_cache_blocks_with_hash(p, cache_size);
if (!r)
return &p->policy;
kfree(p);
return NULL;
}
/*----------------------------------------------------------------------------*/
static struct dm_cache_policy_type wb_policy_type = {
.name = "cleaner",
.version = {1, 0, 0},
.hint_size = 4,
.owner = THIS_MODULE,
.create = wb_create
};
static int __init wb_init(void)
{
int r = dm_cache_policy_register(&wb_policy_type);
if (r < 0)
DMERR("register failed %d", r);
else
DMINFO("version %u.%u.%u loaded",
wb_policy_type.version[0],
wb_policy_type.version[1],
wb_policy_type.version[2]);
return r;
}
static void __exit wb_exit(void)
{
dm_cache_policy_unregister(&wb_policy_type);
}
module_init(wb_init);
module_exit(wb_exit);
MODULE_AUTHOR("Heinz Mauelshagen <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("cleaner cache policy");