dm thin: move bio_prison code to separate module
authorMike Snitzer <snitzer@redhat.com>
Fri, 12 Oct 2012 20:02:13 +0000 (21:02 +0100)
committerAlasdair G Kergon <agk@redhat.com>
Fri, 12 Oct 2012 20:02:13 +0000 (21:02 +0100)
The bio prison code will be useful to other future DM targets so
move it to a separate module.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
drivers/md/Kconfig
drivers/md/Makefile
drivers/md/dm-bio-prison.c [new file with mode: 0644]
drivers/md/dm-bio-prison.h [new file with mode: 0644]
drivers/md/dm-thin.c

index d949b781f6f8b3df59e3952936e3cec7c5d769da..91a02eeeb319aa72283af7358c5cfee0c022ce12 100644 (file)
@@ -216,6 +216,13 @@ config DM_BUFIO
         as a cache, holding recently-read blocks in memory and performing
         delayed writes.
 
+config DM_BIO_PRISON
+       tristate
+       depends on BLK_DEV_DM && EXPERIMENTAL
+       ---help---
+        Some bio locking schemes used by other device-mapper targets
+        including thin provisioning.
+
 source "drivers/md/persistent-data/Kconfig"
 
 config DM_CRYPT
@@ -247,6 +254,7 @@ config DM_THIN_PROVISIONING
        tristate "Thin provisioning target (EXPERIMENTAL)"
        depends on BLK_DEV_DM && EXPERIMENTAL
        select DM_PERSISTENT_DATA
+       select DM_BIO_PRISON
        ---help---
          Provides thin provisioning and snapshots that share a data store.
 
index 8b2e0dffe82e9c7fd4ca571381ea2fdfb0d77986..94dce8b493241b342a23815f9b4bba76e0901597 100644 (file)
@@ -29,6 +29,7 @@ obj-$(CONFIG_MD_FAULTY)               += faulty.o
 obj-$(CONFIG_BLK_DEV_MD)       += md-mod.o
 obj-$(CONFIG_BLK_DEV_DM)       += dm-mod.o
 obj-$(CONFIG_DM_BUFIO)         += dm-bufio.o
+obj-$(CONFIG_DM_BIO_PRISON)    += dm-bio-prison.o
 obj-$(CONFIG_DM_CRYPT)         += dm-crypt.o
 obj-$(CONFIG_DM_DELAY)         += dm-delay.o
 obj-$(CONFIG_DM_FLAKEY)                += dm-flakey.o
diff --git a/drivers/md/dm-bio-prison.c b/drivers/md/dm-bio-prison.c
new file mode 100644 (file)
index 0000000..e4e8415
--- /dev/null
@@ -0,0 +1,415 @@
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include "dm-bio-prison.h"
+
+#include <linux/spinlock.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+/*----------------------------------------------------------------*/
+
+struct dm_bio_prison_cell {
+       struct hlist_node list;
+       struct dm_bio_prison *prison;
+       struct dm_cell_key key;
+       struct bio *holder;
+       struct bio_list bios;
+};
+
+struct dm_bio_prison {
+       spinlock_t lock;
+       mempool_t *cell_pool;
+
+       unsigned nr_buckets;
+       unsigned hash_mask;
+       struct hlist_head *cells;
+};
+
+/*----------------------------------------------------------------*/
+
+static uint32_t calc_nr_buckets(unsigned nr_cells)
+{
+       uint32_t n = 128;
+
+       nr_cells /= 4;
+       nr_cells = min(nr_cells, 8192u);
+
+       while (n < nr_cells)
+               n <<= 1;
+
+       return n;
+}
+
+static struct kmem_cache *_cell_cache;
+
+/*
+ * @nr_cells should be the number of cells you want in use _concurrently_.
+ * Don't confuse it with the number of distinct keys.
+ */
+struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells)
+{
+       unsigned i;
+       uint32_t nr_buckets = calc_nr_buckets(nr_cells);
+       size_t len = sizeof(struct dm_bio_prison) +
+               (sizeof(struct hlist_head) * nr_buckets);
+       struct dm_bio_prison *prison = kmalloc(len, GFP_KERNEL);
+
+       if (!prison)
+               return NULL;
+
+       spin_lock_init(&prison->lock);
+       prison->cell_pool = mempool_create_slab_pool(nr_cells, _cell_cache);
+       if (!prison->cell_pool) {
+               kfree(prison);
+               return NULL;
+       }
+
+       prison->nr_buckets = nr_buckets;
+       prison->hash_mask = nr_buckets - 1;
+       prison->cells = (struct hlist_head *) (prison + 1);
+       for (i = 0; i < nr_buckets; i++)
+               INIT_HLIST_HEAD(prison->cells + i);
+
+       return prison;
+}
+EXPORT_SYMBOL_GPL(dm_bio_prison_create);
+
+void dm_bio_prison_destroy(struct dm_bio_prison *prison)
+{
+       mempool_destroy(prison->cell_pool);
+       kfree(prison);
+}
+EXPORT_SYMBOL_GPL(dm_bio_prison_destroy);
+
+static uint32_t hash_key(struct dm_bio_prison *prison, struct dm_cell_key *key)
+{
+       const unsigned long BIG_PRIME = 4294967291UL;
+       uint64_t hash = key->block * BIG_PRIME;
+
+       return (uint32_t) (hash & prison->hash_mask);
+}
+
+static int keys_equal(struct dm_cell_key *lhs, struct dm_cell_key *rhs)
+{
+              return (lhs->virtual == rhs->virtual) &&
+                      (lhs->dev == rhs->dev) &&
+                      (lhs->block == rhs->block);
+}
+
+static struct dm_bio_prison_cell *__search_bucket(struct hlist_head *bucket,
+                                                 struct dm_cell_key *key)
+{
+       struct dm_bio_prison_cell *cell;
+       struct hlist_node *tmp;
+
+       hlist_for_each_entry(cell, tmp, bucket, list)
+               if (keys_equal(&cell->key, key))
+                       return cell;
+
+       return NULL;
+}
+
+/*
+ * This may block if a new cell needs allocating.  You must ensure that
+ * cells will be unlocked even if the calling thread is blocked.
+ *
+ * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
+ */
+int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
+                 struct bio *inmate, struct dm_bio_prison_cell **ref)
+{
+       int r = 1;
+       unsigned long flags;
+       uint32_t hash = hash_key(prison, key);
+       struct dm_bio_prison_cell *cell, *cell2;
+
+       BUG_ON(hash > prison->nr_buckets);
+
+       spin_lock_irqsave(&prison->lock, flags);
+
+       cell = __search_bucket(prison->cells + hash, key);
+       if (cell) {
+               bio_list_add(&cell->bios, inmate);
+               goto out;
+       }
+
+       /*
+        * Allocate a new cell
+        */
+       spin_unlock_irqrestore(&prison->lock, flags);
+       cell2 = mempool_alloc(prison->cell_pool, GFP_NOIO);
+       spin_lock_irqsave(&prison->lock, flags);
+
+       /*
+        * We've been unlocked, so we have to double check that
+        * nobody else has inserted this cell in the meantime.
+        */
+       cell = __search_bucket(prison->cells + hash, key);
+       if (cell) {
+               mempool_free(cell2, prison->cell_pool);
+               bio_list_add(&cell->bios, inmate);
+               goto out;
+       }
+
+       /*
+        * Use new cell.
+        */
+       cell = cell2;
+
+       cell->prison = prison;
+       memcpy(&cell->key, key, sizeof(cell->key));
+       cell->holder = inmate;
+       bio_list_init(&cell->bios);
+       hlist_add_head(&cell->list, prison->cells + hash);
+
+       r = 0;
+
+out:
+       spin_unlock_irqrestore(&prison->lock, flags);
+
+       *ref = cell;
+
+       return r;
+}
+EXPORT_SYMBOL_GPL(dm_bio_detain);
+
+/*
+ * @inmates must have been initialised prior to this call
+ */
+static void __cell_release(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
+{
+       struct dm_bio_prison *prison = cell->prison;
+
+       hlist_del(&cell->list);
+
+       if (inmates) {
+               bio_list_add(inmates, cell->holder);
+               bio_list_merge(inmates, &cell->bios);
+       }
+
+       mempool_free(cell, prison->cell_pool);
+}
+
+void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios)
+{
+       unsigned long flags;
+       struct dm_bio_prison *prison = cell->prison;
+
+       spin_lock_irqsave(&prison->lock, flags);
+       __cell_release(cell, bios);
+       spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_cell_release);
+
+/*
+ * There are a couple of places where we put a bio into a cell briefly
+ * before taking it out again.  In these situations we know that no other
+ * bio may be in the cell.  This function releases the cell, and also does
+ * a sanity check.
+ */
+static void __cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
+{
+       BUG_ON(cell->holder != bio);
+       BUG_ON(!bio_list_empty(&cell->bios));
+
+       __cell_release(cell, NULL);
+}
+
+void dm_cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
+{
+       unsigned long flags;
+       struct dm_bio_prison *prison = cell->prison;
+
+       spin_lock_irqsave(&prison->lock, flags);
+       __cell_release_singleton(cell, bio);
+       spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_cell_release_singleton);
+
+/*
+ * Sometimes we don't want the holder, just the additional bios.
+ */
+static void __cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
+{
+       struct dm_bio_prison *prison = cell->prison;
+
+       hlist_del(&cell->list);
+       bio_list_merge(inmates, &cell->bios);
+
+       mempool_free(cell, prison->cell_pool);
+}
+
+void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
+{
+       unsigned long flags;
+       struct dm_bio_prison *prison = cell->prison;
+
+       spin_lock_irqsave(&prison->lock, flags);
+       __cell_release_no_holder(cell, inmates);
+       spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_cell_release_no_holder);
+
+void dm_cell_error(struct dm_bio_prison_cell *cell)
+{
+       struct dm_bio_prison *prison = cell->prison;
+       struct bio_list bios;
+       struct bio *bio;
+       unsigned long flags;
+
+       bio_list_init(&bios);
+
+       spin_lock_irqsave(&prison->lock, flags);
+       __cell_release(cell, &bios);
+       spin_unlock_irqrestore(&prison->lock, flags);
+
+       while ((bio = bio_list_pop(&bios)))
+               bio_io_error(bio);
+}
+EXPORT_SYMBOL_GPL(dm_cell_error);
+
+/*----------------------------------------------------------------*/
+
+#define DEFERRED_SET_SIZE 64
+
+struct dm_deferred_entry {
+       struct dm_deferred_set *ds;
+       unsigned count;
+       struct list_head work_items;
+};
+
+struct dm_deferred_set {
+       spinlock_t lock;
+       unsigned current_entry;
+       unsigned sweeper;
+       struct dm_deferred_entry entries[DEFERRED_SET_SIZE];
+};
+
+struct dm_deferred_set *dm_deferred_set_create(void)
+{
+       int i;
+       struct dm_deferred_set *ds;
+
+       ds = kmalloc(sizeof(*ds), GFP_KERNEL);
+       if (!ds)
+               return NULL;
+
+       spin_lock_init(&ds->lock);
+       ds->current_entry = 0;
+       ds->sweeper = 0;
+       for (i = 0; i < DEFERRED_SET_SIZE; i++) {
+               ds->entries[i].ds = ds;
+               ds->entries[i].count = 0;
+               INIT_LIST_HEAD(&ds->entries[i].work_items);
+       }
+
+       return ds;
+}
+EXPORT_SYMBOL_GPL(dm_deferred_set_create);
+
+void dm_deferred_set_destroy(struct dm_deferred_set *ds)
+{
+       kfree(ds);
+}
+EXPORT_SYMBOL_GPL(dm_deferred_set_destroy);
+
+struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds)
+{
+       unsigned long flags;
+       struct dm_deferred_entry *entry;
+
+       spin_lock_irqsave(&ds->lock, flags);
+       entry = ds->entries + ds->current_entry;
+       entry->count++;
+       spin_unlock_irqrestore(&ds->lock, flags);
+
+       return entry;
+}
+EXPORT_SYMBOL_GPL(dm_deferred_entry_inc);
+
+static unsigned ds_next(unsigned index)
+{
+       return (index + 1) % DEFERRED_SET_SIZE;
+}
+
+static void __sweep(struct dm_deferred_set *ds, struct list_head *head)
+{
+       while ((ds->sweeper != ds->current_entry) &&
+              !ds->entries[ds->sweeper].count) {
+               list_splice_init(&ds->entries[ds->sweeper].work_items, head);
+               ds->sweeper = ds_next(ds->sweeper);
+       }
+
+       if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
+               list_splice_init(&ds->entries[ds->sweeper].work_items, head);
+}
+
+void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&entry->ds->lock, flags);
+       BUG_ON(!entry->count);
+       --entry->count;
+       __sweep(entry->ds, head);
+       spin_unlock_irqrestore(&entry->ds->lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_deferred_entry_dec);
+
+/*
+ * Returns 1 if deferred or 0 if no pending items to delay job.
+ */
+int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work)
+{
+       int r = 1;
+       unsigned long flags;
+       unsigned next_entry;
+
+       spin_lock_irqsave(&ds->lock, flags);
+       if ((ds->sweeper == ds->current_entry) &&
+           !ds->entries[ds->current_entry].count)
+               r = 0;
+       else {
+               list_add(work, &ds->entries[ds->current_entry].work_items);
+               next_entry = ds_next(ds->current_entry);
+               if (!ds->entries[next_entry].count)
+                       ds->current_entry = next_entry;
+       }
+       spin_unlock_irqrestore(&ds->lock, flags);
+
+       return r;
+}
+EXPORT_SYMBOL_GPL(dm_deferred_set_add_work);
+
+/*----------------------------------------------------------------*/
+
+static int __init dm_bio_prison_init(void)
+{
+       _cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
+       if (!_cell_cache)
+               return -ENOMEM;
+
+       return 0;
+}
+
+static void __exit dm_bio_prison_exit(void)
+{
+       kmem_cache_destroy(_cell_cache);
+       _cell_cache = NULL;
+}
+
+/*
+ * module hooks
+ */
+module_init(dm_bio_prison_init);
+module_exit(dm_bio_prison_exit);
+
+MODULE_DESCRIPTION(DM_NAME " bio prison");
+MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/md/dm-bio-prison.h b/drivers/md/dm-bio-prison.h
new file mode 100644 (file)
index 0000000..4e0ac37
--- /dev/null
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2011-2012 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BIO_PRISON_H
+#define DM_BIO_PRISON_H
+
+#include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
+#include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
+
+#include <linux/list.h>
+#include <linux/bio.h>
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Sometimes we can't deal with a bio straight away.  We put them in prison
+ * where they can't cause any mischief.  Bios are put in a cell identified
+ * by a key, multiple bios can be in the same cell.  When the cell is
+ * subsequently unlocked the bios become available.
+ */
+struct dm_bio_prison;
+struct dm_bio_prison_cell;
+
+/* FIXME: this needs to be more abstract */
+struct dm_cell_key {
+       int virtual;
+       dm_thin_id dev;
+       dm_block_t block;
+};
+
+struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
+void dm_bio_prison_destroy(struct dm_bio_prison *prison);
+
+/*
+ * This may block if a new cell needs allocating.  You must ensure that
+ * cells will be unlocked even if the calling thread is blocked.
+ *
+ * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
+ */
+int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
+                 struct bio *inmate, struct dm_bio_prison_cell **ref);
+
+void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios);
+void dm_cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio); // FIXME: bio arg not needed
+void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates);
+void dm_cell_error(struct dm_bio_prison_cell *cell);
+
+/*----------------------------------------------------------------*/
+
+/*
+ * We use the deferred set to keep track of pending reads to shared blocks.
+ * We do this to ensure the new mapping caused by a write isn't performed
+ * until these prior reads have completed.  Otherwise the insertion of the
+ * new mapping could free the old block that the read bios are mapped to.
+ */
+
+struct dm_deferred_set;
+struct dm_deferred_entry;
+
+struct dm_deferred_set *dm_deferred_set_create(void);
+void dm_deferred_set_destroy(struct dm_deferred_set *ds);
+
+struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
+void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
+int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
+
+/*----------------------------------------------------------------*/
+
+#endif
index 22a22a701e16c108eb1c69d43fe45088c33de739..058acf3a5ba7aaa43ba58e0eb7dd1acfd1f6399b 100644 (file)
@@ -5,6 +5,7 @@
  */
 
 #include "dm-thin-metadata.h"
+#include "dm-bio-prison.h"
 #include "dm.h"
 
 #include <linux/device-mapper.h>
@@ -21,7 +22,6 @@
  * Tunable constants
  */
 #define ENDIO_HOOK_POOL_SIZE 1024
-#define DEFERRED_SET_SIZE 64
 #define MAPPING_POOL_SIZE 1024
 #define PRISON_CELLS 1024
 #define COMMIT_PERIOD HZ
 
 /*----------------------------------------------------------------*/
 
-/*
- * Sometimes we can't deal with a bio straight away.  We put them in prison
- * where they can't cause any mischief.  Bios are put in a cell identified
- * by a key, multiple bios can be in the same cell.  When the cell is
- * subsequently unlocked the bios become available.
- */
-struct dm_bio_prison;
-
-struct dm_cell_key {
-       int virtual;
-       dm_thin_id dev;
-       dm_block_t block;
-};
-
-struct dm_bio_prison_cell {
-       struct hlist_node list;
-       struct dm_bio_prison *prison;
-       struct dm_cell_key key;
-       struct bio *holder;
-       struct bio_list bios;
-};
-
-struct dm_bio_prison {
-       spinlock_t lock;
-       mempool_t *cell_pool;
-
-       unsigned nr_buckets;
-       unsigned hash_mask;
-       struct hlist_head *cells;
-};
-
-static uint32_t calc_nr_buckets(unsigned nr_cells)
-{
-       uint32_t n = 128;
-
-       nr_cells /= 4;
-       nr_cells = min(nr_cells, 8192u);
-
-       while (n < nr_cells)
-               n <<= 1;
-
-       return n;
-}
-
-static struct kmem_cache *_cell_cache;
-
-/*
- * @nr_cells should be the number of cells you want in use _concurrently_.
- * Don't confuse it with the number of distinct keys.
- */
-static struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells)
-{
-       unsigned i;
-       uint32_t nr_buckets = calc_nr_buckets(nr_cells);
-       size_t len = sizeof(struct dm_bio_prison) +
-               (sizeof(struct hlist_head) * nr_buckets);
-       struct dm_bio_prison *prison = kmalloc(len, GFP_KERNEL);
-
-       if (!prison)
-               return NULL;
-
-       spin_lock_init(&prison->lock);
-       prison->cell_pool = mempool_create_slab_pool(nr_cells, _cell_cache);
-       if (!prison->cell_pool) {
-               kfree(prison);
-               return NULL;
-       }
-
-       prison->nr_buckets = nr_buckets;
-       prison->hash_mask = nr_buckets - 1;
-       prison->cells = (struct hlist_head *) (prison + 1);
-       for (i = 0; i < nr_buckets; i++)
-               INIT_HLIST_HEAD(prison->cells + i);
-
-       return prison;
-}
-
-static void dm_bio_prison_destroy(struct dm_bio_prison *prison)
-{
-       mempool_destroy(prison->cell_pool);
-       kfree(prison);
-}
-
-static uint32_t hash_key(struct dm_bio_prison *prison, struct dm_cell_key *key)
-{
-       const unsigned long BIG_PRIME = 4294967291UL;
-       uint64_t hash = key->block * BIG_PRIME;
-
-       return (uint32_t) (hash & prison->hash_mask);
-}
-
-static int keys_equal(struct dm_cell_key *lhs, struct dm_cell_key *rhs)
-{
-              return (lhs->virtual == rhs->virtual) &&
-                      (lhs->dev == rhs->dev) &&
-                      (lhs->block == rhs->block);
-}
-
-static struct dm_bio_prison_cell *__search_bucket(struct hlist_head *bucket,
-                                                 struct dm_cell_key *key)
-{
-       struct dm_bio_prison_cell *cell;
-       struct hlist_node *tmp;
-
-       hlist_for_each_entry(cell, tmp, bucket, list)
-               if (keys_equal(&cell->key, key))
-                       return cell;
-
-       return NULL;
-}
-
-/*
- * This may block if a new cell needs allocating.  You must ensure that
- * cells will be unlocked even if the calling thread is blocked.
- *
- * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
- */
-static int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
-                        struct bio *inmate, struct dm_bio_prison_cell **ref)
-{
-       int r = 1;
-       unsigned long flags;
-       uint32_t hash = hash_key(prison, key);
-       struct dm_bio_prison_cell *cell, *cell2;
-
-       BUG_ON(hash > prison->nr_buckets);
-
-       spin_lock_irqsave(&prison->lock, flags);
-
-       cell = __search_bucket(prison->cells + hash, key);
-       if (cell) {
-               bio_list_add(&cell->bios, inmate);
-               goto out;
-       }
-
-       /*
-        * Allocate a new cell
-        */
-       spin_unlock_irqrestore(&prison->lock, flags);
-       cell2 = mempool_alloc(prison->cell_pool, GFP_NOIO);
-       spin_lock_irqsave(&prison->lock, flags);
-
-       /*
-        * We've been unlocked, so we have to double check that
-        * nobody else has inserted this cell in the meantime.
-        */
-       cell = __search_bucket(prison->cells + hash, key);
-       if (cell) {
-               mempool_free(cell2, prison->cell_pool);
-               bio_list_add(&cell->bios, inmate);
-               goto out;
-       }
-
-       /*
-        * Use new cell.
-        */
-       cell = cell2;
-
-       cell->prison = prison;
-       memcpy(&cell->key, key, sizeof(cell->key));
-       cell->holder = inmate;
-       bio_list_init(&cell->bios);
-       hlist_add_head(&cell->list, prison->cells + hash);
-
-       r = 0;
-
-out:
-       spin_unlock_irqrestore(&prison->lock, flags);
-
-       *ref = cell;
-
-       return r;
-}
-
-/*
- * @inmates must have been initialised prior to this call
- */
-static void __cell_release(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
-{
-       struct dm_bio_prison *prison = cell->prison;
-
-       hlist_del(&cell->list);
-
-       if (inmates) {
-               bio_list_add(inmates, cell->holder);
-               bio_list_merge(inmates, &cell->bios);
-       }
-
-       mempool_free(cell, prison->cell_pool);
-}
-
-static void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios)
-{
-       unsigned long flags;
-       struct dm_bio_prison *prison = cell->prison;
-
-       spin_lock_irqsave(&prison->lock, flags);
-       __cell_release(cell, bios);
-       spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-/*
- * There are a couple of places where we put a bio into a cell briefly
- * before taking it out again.  In these situations we know that no other
- * bio may be in the cell.  This function releases the cell, and also does
- * a sanity check.
- */
-static void __cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
-{
-       BUG_ON(cell->holder != bio);
-       BUG_ON(!bio_list_empty(&cell->bios));
-
-       __cell_release(cell, NULL);
-}
-
-static void dm_cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
-{
-       unsigned long flags;
-       struct dm_bio_prison *prison = cell->prison;
-
-       spin_lock_irqsave(&prison->lock, flags);
-       __cell_release_singleton(cell, bio);
-       spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-/*
- * Sometimes we don't want the holder, just the additional bios.
- */
-static void __cell_release_no_holder(struct dm_bio_prison_cell *cell,
-                                    struct bio_list *inmates)
-{
-       struct dm_bio_prison *prison = cell->prison;
-
-       hlist_del(&cell->list);
-       bio_list_merge(inmates, &cell->bios);
-
-       mempool_free(cell, prison->cell_pool);
-}
-
-static void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell,
-                                     struct bio_list *inmates)
-{
-       unsigned long flags;
-       struct dm_bio_prison *prison = cell->prison;
-
-       spin_lock_irqsave(&prison->lock, flags);
-       __cell_release_no_holder(cell, inmates);
-       spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-static void dm_cell_error(struct dm_bio_prison_cell *cell)
-{
-       struct dm_bio_prison *prison = cell->prison;
-       struct bio_list bios;
-       struct bio *bio;
-       unsigned long flags;
-
-       bio_list_init(&bios);
-
-       spin_lock_irqsave(&prison->lock, flags);
-       __cell_release(cell, &bios);
-       spin_unlock_irqrestore(&prison->lock, flags);
-
-       while ((bio = bio_list_pop(&bios)))
-               bio_io_error(bio);
-}
-
-/*----------------------------------------------------------------*/
-
-/*
- * We use the deferred set to keep track of pending reads to shared blocks.
- * We do this to ensure the new mapping caused by a write isn't performed
- * until these prior reads have completed.  Otherwise the insertion of the
- * new mapping could free the old block that the read bios are mapped to.
- */
-
-struct dm_deferred_set;
-struct dm_deferred_entry {
-       struct dm_deferred_set *ds;
-       unsigned count;
-       struct list_head work_items;
-};
-
-struct dm_deferred_set {
-       spinlock_t lock;
-       unsigned current_entry;
-       unsigned sweeper;
-       struct dm_deferred_entry entries[DEFERRED_SET_SIZE];
-};
-
-static struct dm_deferred_set *dm_deferred_set_create(void)
-{
-       int i;
-       struct dm_deferred_set *ds;
-
-       ds = kmalloc(sizeof(*ds), GFP_KERNEL);
-       if (!ds)
-               return NULL;
-
-       spin_lock_init(&ds->lock);
-       ds->current_entry = 0;
-       ds->sweeper = 0;
-       for (i = 0; i < DEFERRED_SET_SIZE; i++) {
-               ds->entries[i].ds = ds;
-               ds->entries[i].count = 0;
-               INIT_LIST_HEAD(&ds->entries[i].work_items);
-       }
-
-       return ds;
-}
-
-static void dm_deferred_set_destroy(struct dm_deferred_set *ds)
-{
-       kfree(ds);
-}
-
-static struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds)
-{
-       unsigned long flags;
-       struct dm_deferred_entry *entry;
-
-       spin_lock_irqsave(&ds->lock, flags);
-       entry = ds->entries + ds->current_entry;
-       entry->count++;
-       spin_unlock_irqrestore(&ds->lock, flags);
-
-       return entry;
-}
-
-static unsigned ds_next(unsigned index)
-{
-       return (index + 1) % DEFERRED_SET_SIZE;
-}
-
-static void __sweep(struct dm_deferred_set *ds, struct list_head *head)
-{
-       while ((ds->sweeper != ds->current_entry) &&
-              !ds->entries[ds->sweeper].count) {
-               list_splice_init(&ds->entries[ds->sweeper].work_items, head);
-               ds->sweeper = ds_next(ds->sweeper);
-       }
-
-       if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
-               list_splice_init(&ds->entries[ds->sweeper].work_items, head);
-}
-
-static void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head)
-{
-       unsigned long flags;
-
-       spin_lock_irqsave(&entry->ds->lock, flags);
-       BUG_ON(!entry->count);
-       --entry->count;
-       __sweep(entry->ds, head);
-       spin_unlock_irqrestore(&entry->ds->lock, flags);
-}
-
-/*
- * Returns 1 if deferred or 0 if no pending items to delay job.
- */
-static int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work)
-{
-       int r = 1;
-       unsigned long flags;
-       unsigned next_entry;
-
-       spin_lock_irqsave(&ds->lock, flags);
-       if ((ds->sweeper == ds->current_entry) &&
-           !ds->entries[ds->current_entry].count)
-               r = 0;
-       else {
-               list_add(work, &ds->entries[ds->current_entry].work_items);
-               next_entry = ds_next(ds->current_entry);
-               if (!ds->entries[next_entry].count)
-                       ds->current_entry = next_entry;
-       }
-       spin_unlock_irqrestore(&ds->lock, flags);
-
-       return r;
-}
-
-static int __init dm_bio_prison_init(void)
-{
-       _cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
-       if (!_cell_cache)
-               return -ENOMEM;
-
-       return 0;
-}
-
-static void __exit dm_bio_prison_exit(void)
-{
-       kmem_cache_destroy(_cell_cache);
-       _cell_cache = NULL;
-}
-
-/*----------------------------------------------------------------*/
-
 /*
  * Key building.
  */
@@ -2852,7 +2454,7 @@ static struct target_type pool_target = {
        .name = "thin-pool",
        .features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
                    DM_TARGET_IMMUTABLE,
-       .version = {1, 4, 0},
+       .version = {1, 5, 0},
        .module = THIS_MODULE,
        .ctr = pool_ctr,
        .dtr = pool_dtr,
@@ -3143,7 +2745,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
 
 static struct target_type thin_target = {
        .name = "thin",
-       .version = {1, 4, 0},
+       .version = {1, 5, 0},
        .module = THIS_MODULE,
        .ctr = thin_ctr,
        .dtr = thin_dtr,
@@ -3173,8 +2775,6 @@ static int __init dm_thin_init(void)
 
        r = -ENOMEM;
 
-       dm_bio_prison_init();
-
        _new_mapping_cache = KMEM_CACHE(dm_thin_new_mapping, 0);
        if (!_new_mapping_cache)
                goto bad_new_mapping_cache;
@@ -3200,7 +2800,6 @@ static void dm_thin_exit(void)
        dm_unregister_target(&thin_target);
        dm_unregister_target(&pool_target);
 
-       dm_bio_prison_exit();
        kmem_cache_destroy(_new_mapping_cache);
        kmem_cache_destroy(_endio_hook_cache);
 }