dm thin: move bio_prison code to separate module

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>

1 files changed, 3 insertions, 404 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 22a22a701e1..058acf3a5ba 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -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
@@ -99,404 +99,6 @@
 /*----------------------------------------------------------------*/
 
 /*
- * 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.
  */
 static void build_data_key(struct dm_thin_device *td,
@@ -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);
 }