From 4f81a4176297db57c7ef3b2893092dd837c1e2a8 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Fri, 12 Oct 2012 21:02:13 +0100 Subject: 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 Signed-off-by: Joe Thornber Signed-off-by: Alasdair G Kergon --- drivers/md/dm-bio-prison.c | 415 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 415 insertions(+) create mode 100644 drivers/md/dm-bio-prison.c (limited to 'drivers/md/dm-bio-prison.c') diff --git a/drivers/md/dm-bio-prison.c b/drivers/md/dm-bio-prison.c new file mode 100644 index 00000000000..e4e84156745 --- /dev/null +++ b/drivers/md/dm-bio-prison.c @@ -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 +#include +#include +#include + +/*----------------------------------------------------------------*/ + +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 "); +MODULE_LICENSE("GPL"); -- cgit v1.2.3-70-g09d2