From: Heinz Mauelshagen A simple cache policy that writes back all data to the origin. This is used to decommission a dm cache by emptying it. Signed-off-by: Heinz Mauelshagen Signed-off-by: Joe Thornber Signed-off-by: Alasdair G Kergon --- Documentation/device-mapper/cache-policies.txt | 5 drivers/md/Kconfig | 8 drivers/md/Makefile | 2 drivers/md/dm-cache-policy-cleaner.c | 464 +++++++++++++++++++++++++ 4 files changed, 479 insertions(+) Index: linux/Documentation/device-mapper/cache-policies.txt =================================================================== --- linux.orig/Documentation/device-mapper/cache-policies.txt +++ linux/Documentation/device-mapper/cache-policies.txt @@ -53,6 +53,11 @@ since spindles tend to have good bandwid contiguous I/Os to try to spot when the io is in one of these sequential modes. +cleaner +------- + +The cleaner writes back all dirty blocks in a cache to decommission it. + Examples ======== Index: linux/drivers/md/Kconfig =================================================================== --- linux.orig/drivers/md/Kconfig +++ linux/drivers/md/Kconfig @@ -291,6 +291,14 @@ config DM_CACHE_MQ This is meant to be a general purpose policy. It prioritises reads over writes. +config DM_CACHE_CLEANER + tristate "Cleaner Cache Policy (EXPERIMENTAL)" + depends on DM_CACHE + default y + ---help--- + A simple cache policy that writes back all data to the + origin. Used when decommissioning a dm-cache. + config DM_MIRROR tristate "Mirror target" depends on BLK_DEV_DM Index: linux/drivers/md/Makefile =================================================================== --- linux.orig/drivers/md/Makefile +++ linux/drivers/md/Makefile @@ -13,6 +13,7 @@ dm-log-userspace-y \ dm-thin-pool-y += dm-thin.o dm-thin-metadata.o dm-cache-y += dm-cache-target.o dm-cache-metadata.o dm-cache-policy.o dm-cache-mq-y += dm-cache-policy-mq.o +dm-cache-cleaner-y += dm-cache-policy-cleaner.o md-mod-y += md.o bitmap.o raid456-y += raid5.o @@ -48,6 +49,7 @@ obj-$(CONFIG_DM_THIN_PROVISIONING) += dm obj-$(CONFIG_DM_VERITY) += dm-verity.o obj-$(CONFIG_DM_CACHE) += dm-cache.o obj-$(CONFIG_DM_CACHE_MQ) += dm-cache-mq.o +obj-$(CONFIG_DM_CACHE_CLEANER) += dm-cache-cleaner.o ifeq ($(CONFIG_DM_UEVENT),y) dm-mod-objs += dm-uevent.o Index: linux/drivers/md/dm-cache-policy-cleaner.c =================================================================== --- /dev/null +++ linux/drivers/md/dm-cache-policy-cleaner.c @@ -0,0 +1,464 @@ +/* + * 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 +#include +#include +#include + +/*----------------------------------------------------------------*/ + +#define DM_MSG_PREFIX "cache cleaner" +#define CLEANER_VERSION "1.0.0" + +/* 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) - 1; + 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_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) +{ + 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", + .hint_size = 0, + .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 " CLEANER_VERSION " loaded"); + + 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 "); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("cleaner cache policy");