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![Heinz Mauelshagen](/assets/img/avatar_default.png)
Split the single per bio-prison lock by using per bucket locking. Per bucket locking benefits both dm-thin and dm-cache targets by reducing bio-prison lock contention. Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com> Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
408 lines
9.4 KiB
C
408 lines
9.4 KiB
C
/*
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* Copyright (C) 2012 Red Hat, Inc.
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*
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* This file is released under the GPL.
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*/
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#include "dm.h"
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#include "dm-bio-prison.h"
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#include <linux/spinlock.h>
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#include <linux/mempool.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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/*----------------------------------------------------------------*/
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struct bucket {
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spinlock_t lock;
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struct hlist_head cells;
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};
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struct dm_bio_prison {
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mempool_t *cell_pool;
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unsigned nr_buckets;
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unsigned hash_mask;
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struct bucket *buckets;
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};
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/*----------------------------------------------------------------*/
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static uint32_t calc_nr_buckets(unsigned nr_cells)
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{
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uint32_t n = 128;
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nr_cells /= 4;
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nr_cells = min(nr_cells, 8192u);
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while (n < nr_cells)
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n <<= 1;
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return n;
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}
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static struct kmem_cache *_cell_cache;
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static void init_bucket(struct bucket *b)
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{
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spin_lock_init(&b->lock);
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INIT_HLIST_HEAD(&b->cells);
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}
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/*
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* @nr_cells should be the number of cells you want in use _concurrently_.
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* Don't confuse it with the number of distinct keys.
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*/
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struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells)
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{
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unsigned i;
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uint32_t nr_buckets = calc_nr_buckets(nr_cells);
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size_t len = sizeof(struct dm_bio_prison) +
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(sizeof(struct bucket) * nr_buckets);
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struct dm_bio_prison *prison = kmalloc(len, GFP_KERNEL);
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if (!prison)
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return NULL;
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prison->cell_pool = mempool_create_slab_pool(nr_cells, _cell_cache);
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if (!prison->cell_pool) {
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kfree(prison);
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return NULL;
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}
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prison->nr_buckets = nr_buckets;
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prison->hash_mask = nr_buckets - 1;
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prison->buckets = (struct bucket *) (prison + 1);
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for (i = 0; i < nr_buckets; i++)
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init_bucket(prison->buckets + i);
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return prison;
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}
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EXPORT_SYMBOL_GPL(dm_bio_prison_create);
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void dm_bio_prison_destroy(struct dm_bio_prison *prison)
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{
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mempool_destroy(prison->cell_pool);
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kfree(prison);
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}
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EXPORT_SYMBOL_GPL(dm_bio_prison_destroy);
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struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison, gfp_t gfp)
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{
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return mempool_alloc(prison->cell_pool, gfp);
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}
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EXPORT_SYMBOL_GPL(dm_bio_prison_alloc_cell);
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void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
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struct dm_bio_prison_cell *cell)
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{
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mempool_free(cell, prison->cell_pool);
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}
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EXPORT_SYMBOL_GPL(dm_bio_prison_free_cell);
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static uint32_t hash_key(struct dm_bio_prison *prison, struct dm_cell_key *key)
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{
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const unsigned long BIG_PRIME = 4294967291UL;
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uint64_t hash = key->block * BIG_PRIME;
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return (uint32_t) (hash & prison->hash_mask);
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}
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static int keys_equal(struct dm_cell_key *lhs, struct dm_cell_key *rhs)
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{
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return (lhs->virtual == rhs->virtual) &&
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(lhs->dev == rhs->dev) &&
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(lhs->block == rhs->block);
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}
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static struct bucket *get_bucket(struct dm_bio_prison *prison,
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struct dm_cell_key *key)
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{
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return prison->buckets + hash_key(prison, key);
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}
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static struct dm_bio_prison_cell *__search_bucket(struct bucket *b,
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struct dm_cell_key *key)
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{
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struct dm_bio_prison_cell *cell;
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hlist_for_each_entry(cell, &b->cells, list)
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if (keys_equal(&cell->key, key))
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return cell;
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return NULL;
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}
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static void __setup_new_cell(struct bucket *b,
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struct dm_cell_key *key,
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struct bio *holder,
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struct dm_bio_prison_cell *cell)
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{
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memcpy(&cell->key, key, sizeof(cell->key));
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cell->holder = holder;
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bio_list_init(&cell->bios);
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hlist_add_head(&cell->list, &b->cells);
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}
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static int __bio_detain(struct bucket *b,
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struct dm_cell_key *key,
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struct bio *inmate,
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struct dm_bio_prison_cell *cell_prealloc,
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struct dm_bio_prison_cell **cell_result)
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{
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struct dm_bio_prison_cell *cell;
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cell = __search_bucket(b, key);
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if (cell) {
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if (inmate)
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bio_list_add(&cell->bios, inmate);
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*cell_result = cell;
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return 1;
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}
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__setup_new_cell(b, key, inmate, cell_prealloc);
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*cell_result = cell_prealloc;
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return 0;
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}
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static int bio_detain(struct dm_bio_prison *prison,
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struct dm_cell_key *key,
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struct bio *inmate,
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struct dm_bio_prison_cell *cell_prealloc,
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struct dm_bio_prison_cell **cell_result)
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{
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int r;
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unsigned long flags;
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struct bucket *b = get_bucket(prison, key);
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spin_lock_irqsave(&b->lock, flags);
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r = __bio_detain(b, key, inmate, cell_prealloc, cell_result);
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spin_unlock_irqrestore(&b->lock, flags);
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return r;
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}
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int dm_bio_detain(struct dm_bio_prison *prison,
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struct dm_cell_key *key,
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struct bio *inmate,
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struct dm_bio_prison_cell *cell_prealloc,
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struct dm_bio_prison_cell **cell_result)
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{
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return bio_detain(prison, key, inmate, cell_prealloc, cell_result);
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}
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EXPORT_SYMBOL_GPL(dm_bio_detain);
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int dm_get_cell(struct dm_bio_prison *prison,
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struct dm_cell_key *key,
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struct dm_bio_prison_cell *cell_prealloc,
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struct dm_bio_prison_cell **cell_result)
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{
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return bio_detain(prison, key, NULL, cell_prealloc, cell_result);
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}
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EXPORT_SYMBOL_GPL(dm_get_cell);
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/*
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* @inmates must have been initialised prior to this call
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*/
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static void __cell_release(struct dm_bio_prison_cell *cell,
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struct bio_list *inmates)
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{
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hlist_del(&cell->list);
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if (inmates) {
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if (cell->holder)
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bio_list_add(inmates, cell->holder);
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bio_list_merge(inmates, &cell->bios);
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}
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}
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void dm_cell_release(struct dm_bio_prison *prison,
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struct dm_bio_prison_cell *cell,
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struct bio_list *bios)
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{
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unsigned long flags;
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struct bucket *b = get_bucket(prison, &cell->key);
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spin_lock_irqsave(&b->lock, flags);
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__cell_release(cell, bios);
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spin_unlock_irqrestore(&b->lock, flags);
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}
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EXPORT_SYMBOL_GPL(dm_cell_release);
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/*
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* Sometimes we don't want the holder, just the additional bios.
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*/
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static void __cell_release_no_holder(struct dm_bio_prison_cell *cell,
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struct bio_list *inmates)
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{
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hlist_del(&cell->list);
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bio_list_merge(inmates, &cell->bios);
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}
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void dm_cell_release_no_holder(struct dm_bio_prison *prison,
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struct dm_bio_prison_cell *cell,
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struct bio_list *inmates)
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{
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unsigned long flags;
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struct bucket *b = get_bucket(prison, &cell->key);
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spin_lock_irqsave(&b->lock, flags);
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__cell_release_no_holder(cell, inmates);
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spin_unlock_irqrestore(&b->lock, flags);
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}
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EXPORT_SYMBOL_GPL(dm_cell_release_no_holder);
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void dm_cell_error(struct dm_bio_prison *prison,
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struct dm_bio_prison_cell *cell, int error)
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{
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struct bio_list bios;
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struct bio *bio;
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bio_list_init(&bios);
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dm_cell_release(prison, cell, &bios);
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while ((bio = bio_list_pop(&bios)))
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bio_endio(bio, error);
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}
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EXPORT_SYMBOL_GPL(dm_cell_error);
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/*----------------------------------------------------------------*/
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#define DEFERRED_SET_SIZE 64
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struct dm_deferred_entry {
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struct dm_deferred_set *ds;
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unsigned count;
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struct list_head work_items;
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};
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struct dm_deferred_set {
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spinlock_t lock;
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unsigned current_entry;
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unsigned sweeper;
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struct dm_deferred_entry entries[DEFERRED_SET_SIZE];
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};
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struct dm_deferred_set *dm_deferred_set_create(void)
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{
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int i;
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struct dm_deferred_set *ds;
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ds = kmalloc(sizeof(*ds), GFP_KERNEL);
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if (!ds)
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return NULL;
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spin_lock_init(&ds->lock);
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ds->current_entry = 0;
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ds->sweeper = 0;
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for (i = 0; i < DEFERRED_SET_SIZE; i++) {
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ds->entries[i].ds = ds;
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ds->entries[i].count = 0;
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INIT_LIST_HEAD(&ds->entries[i].work_items);
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}
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return ds;
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}
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EXPORT_SYMBOL_GPL(dm_deferred_set_create);
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void dm_deferred_set_destroy(struct dm_deferred_set *ds)
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{
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kfree(ds);
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}
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EXPORT_SYMBOL_GPL(dm_deferred_set_destroy);
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struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds)
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{
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unsigned long flags;
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struct dm_deferred_entry *entry;
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spin_lock_irqsave(&ds->lock, flags);
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entry = ds->entries + ds->current_entry;
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entry->count++;
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spin_unlock_irqrestore(&ds->lock, flags);
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return entry;
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}
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EXPORT_SYMBOL_GPL(dm_deferred_entry_inc);
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static unsigned ds_next(unsigned index)
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{
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return (index + 1) % DEFERRED_SET_SIZE;
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}
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static void __sweep(struct dm_deferred_set *ds, struct list_head *head)
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{
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while ((ds->sweeper != ds->current_entry) &&
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!ds->entries[ds->sweeper].count) {
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list_splice_init(&ds->entries[ds->sweeper].work_items, head);
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ds->sweeper = ds_next(ds->sweeper);
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}
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if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
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list_splice_init(&ds->entries[ds->sweeper].work_items, head);
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}
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void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head)
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{
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unsigned long flags;
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spin_lock_irqsave(&entry->ds->lock, flags);
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BUG_ON(!entry->count);
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--entry->count;
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__sweep(entry->ds, head);
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spin_unlock_irqrestore(&entry->ds->lock, flags);
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}
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EXPORT_SYMBOL_GPL(dm_deferred_entry_dec);
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/*
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* Returns 1 if deferred or 0 if no pending items to delay job.
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*/
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int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work)
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{
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int r = 1;
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unsigned long flags;
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unsigned next_entry;
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spin_lock_irqsave(&ds->lock, flags);
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if ((ds->sweeper == ds->current_entry) &&
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!ds->entries[ds->current_entry].count)
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r = 0;
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else {
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list_add(work, &ds->entries[ds->current_entry].work_items);
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next_entry = ds_next(ds->current_entry);
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if (!ds->entries[next_entry].count)
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ds->current_entry = next_entry;
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}
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spin_unlock_irqrestore(&ds->lock, flags);
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return r;
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}
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EXPORT_SYMBOL_GPL(dm_deferred_set_add_work);
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/*----------------------------------------------------------------*/
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static int __init dm_bio_prison_init(void)
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{
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_cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
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if (!_cell_cache)
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return -ENOMEM;
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return 0;
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}
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static void __exit dm_bio_prison_exit(void)
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{
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kmem_cache_destroy(_cell_cache);
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_cell_cache = NULL;
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}
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/*
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* module hooks
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*/
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module_init(dm_bio_prison_init);
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module_exit(dm_bio_prison_exit);
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MODULE_DESCRIPTION(DM_NAME " bio prison");
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MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
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MODULE_LICENSE("GPL");
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