4 files changed, 479 insertions, 0 deletions

diff --git a/Documentation/device-mapper/cache-policies.txt b/Documentation/device-mapper/cache-policies.txt
index 731879f97b80..d7c440b444cc 100644
--- a/Documentation/device-mapper/cache-policies.txt
+++ b/Documentation/device-mapper/cache-policies.txt
@@ -53,6 +53,11 @@ since spindles tend to have good bandwidth. The io_tracker counts
 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
 ========
 
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 1a96cbc7afda..e30b490055aa 100644
--- a/drivers/md/Kconfig
+++ b/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
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index adc8710c2408..7ceeaefc0e95 100644
--- a/drivers/md/Makefile
+++ b/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-$(CONFIG_DM_THIN_PROVISIONING)	+= dm-thin-pool.o
 obj-$(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
diff --git a/drivers/md/dm-cache-policy-cleaner.c b/drivers/md/dm-cache-policy-cleaner.c
new file mode 100644
index 000000000000..cc05d70b3cb8
--- /dev/null
+++ b/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 <linux/hash.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+/*----------------------------------------------------------------*/
+
+#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 <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("cleaner cache policy");