dm-bio-prison-v2.c
/*
* Copyright (C) 2012-2017 Red Hat, Inc.
*
* This file is released under the GPL.
*/
#include "dm.h"
#include "dm-bio-prison-v2.h"
#include <linux/spinlock.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/rwsem.h>
/*----------------------------------------------------------------*/
#define MIN_CELLS 1024
struct dm_bio_prison_v2 {
struct workqueue_struct *wq;
spinlock_t lock;
struct rb_root cells;
mempool_t cell_pool;
};
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_v2 *dm_bio_prison_create_v2(struct workqueue_struct *wq)
{
struct dm_bio_prison_v2 *prison = kzalloc(sizeof(*prison), GFP_KERNEL);
int ret;
if (!prison)
return NULL;
prison->wq = wq;
spin_lock_init(&prison->lock);
ret = mempool_init_slab_pool(&prison->cell_pool, MIN_CELLS, _cell_cache);
if (ret) {
kfree(prison);
return NULL;
}
prison->cells = RB_ROOT;
return prison;
}
EXPORT_SYMBOL_GPL(dm_bio_prison_create_v2);
void dm_bio_prison_destroy_v2(struct dm_bio_prison_v2 *prison)
{
mempool_exit(&prison->cell_pool);
kfree(prison);
}
EXPORT_SYMBOL_GPL(dm_bio_prison_destroy_v2);
struct dm_bio_prison_cell_v2 *dm_bio_prison_alloc_cell_v2(struct dm_bio_prison_v2 *prison, gfp_t gfp)
{
return mempool_alloc(&prison->cell_pool, gfp);
}
EXPORT_SYMBOL_GPL(dm_bio_prison_alloc_cell_v2);
void dm_bio_prison_free_cell_v2(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell)
{
mempool_free(cell, &prison->cell_pool);
}
EXPORT_SYMBOL_GPL(dm_bio_prison_free_cell_v2);
static void __setup_new_cell(struct dm_cell_key_v2 *key,
struct dm_bio_prison_cell_v2 *cell)
{
memset(cell, 0, sizeof(*cell));
memcpy(&cell->key, key, sizeof(cell->key));
bio_list_init(&cell->bios);
}
static int cmp_keys(struct dm_cell_key_v2 *lhs,
struct dm_cell_key_v2 *rhs)
{
if (lhs->virtual < rhs->virtual)
return -1;
if (lhs->virtual > rhs->virtual)
return 1;
if (lhs->dev < rhs->dev)
return -1;
if (lhs->dev > rhs->dev)
return 1;
if (lhs->block_end <= rhs->block_begin)
return -1;
if (lhs->block_begin >= rhs->block_end)
return 1;
return 0;
}
/*
* Returns true if node found, otherwise it inserts a new one.
*/
static bool __find_or_insert(struct dm_bio_prison_v2 *prison,
struct dm_cell_key_v2 *key,
struct dm_bio_prison_cell_v2 *cell_prealloc,
struct dm_bio_prison_cell_v2 **result)
{
int r;
struct rb_node **new = &prison->cells.rb_node, *parent = NULL;
while (*new) {
struct dm_bio_prison_cell_v2 *cell =
rb_entry(*new, struct dm_bio_prison_cell_v2, node);
r = cmp_keys(key, &cell->key);
parent = *new;
if (r < 0)
new = &((*new)->rb_left);
else if (r > 0)
new = &((*new)->rb_right);
else {
*result = cell;
return true;
}
}
__setup_new_cell(key, cell_prealloc);
*result = cell_prealloc;
rb_link_node(&cell_prealloc->node, parent, new);
rb_insert_color(&cell_prealloc->node, &prison->cells);
return false;
}
static bool __get(struct dm_bio_prison_v2 *prison,
struct dm_cell_key_v2 *key,
unsigned lock_level,
struct bio *inmate,
struct dm_bio_prison_cell_v2 *cell_prealloc,
struct dm_bio_prison_cell_v2 **cell)
{
if (__find_or_insert(prison, key, cell_prealloc, cell)) {
if ((*cell)->exclusive_lock) {
if (lock_level <= (*cell)->exclusive_level) {
bio_list_add(&(*cell)->bios, inmate);
return false;
}
}
(*cell)->shared_count++;
} else
(*cell)->shared_count = 1;
return true;
}
bool dm_cell_get_v2(struct dm_bio_prison_v2 *prison,
struct dm_cell_key_v2 *key,
unsigned lock_level,
struct bio *inmate,
struct dm_bio_prison_cell_v2 *cell_prealloc,
struct dm_bio_prison_cell_v2 **cell_result)
{
int r;
spin_lock_irq(&prison->lock);
r = __get(prison, key, lock_level, inmate, cell_prealloc, cell_result);
spin_unlock_irq(&prison->lock);
return r;
}
EXPORT_SYMBOL_GPL(dm_cell_get_v2);
static bool __put(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell)
{
BUG_ON(!cell->shared_count);
cell->shared_count--;
// FIXME: shared locks granted above the lock level could starve this
if (!cell->shared_count) {
if (cell->exclusive_lock){
if (cell->quiesce_continuation) {
queue_work(prison->wq, cell->quiesce_continuation);
cell->quiesce_continuation = NULL;
}
} else {
rb_erase(&cell->node, &prison->cells);
return true;
}
}
return false;
}
bool dm_cell_put_v2(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell)
{
bool r;
unsigned long flags;
spin_lock_irqsave(&prison->lock, flags);
r = __put(prison, cell);
spin_unlock_irqrestore(&prison->lock, flags);
return r;
}
EXPORT_SYMBOL_GPL(dm_cell_put_v2);
static int __lock(struct dm_bio_prison_v2 *prison,
struct dm_cell_key_v2 *key,
unsigned lock_level,
struct dm_bio_prison_cell_v2 *cell_prealloc,
struct dm_bio_prison_cell_v2 **cell_result)
{
struct dm_bio_prison_cell_v2 *cell;
if (__find_or_insert(prison, key, cell_prealloc, &cell)) {
if (cell->exclusive_lock)
return -EBUSY;
cell->exclusive_lock = true;
cell->exclusive_level = lock_level;
*cell_result = cell;
// FIXME: we don't yet know what level these shared locks
// were taken at, so have to quiesce them all.
return cell->shared_count > 0;
} else {
cell = cell_prealloc;
cell->shared_count = 0;
cell->exclusive_lock = true;
cell->exclusive_level = lock_level;
*cell_result = cell;
}
return 0;
}
int dm_cell_lock_v2(struct dm_bio_prison_v2 *prison,
struct dm_cell_key_v2 *key,
unsigned lock_level,
struct dm_bio_prison_cell_v2 *cell_prealloc,
struct dm_bio_prison_cell_v2 **cell_result)
{
int r;
spin_lock_irq(&prison->lock);
r = __lock(prison, key, lock_level, cell_prealloc, cell_result);
spin_unlock_irq(&prison->lock);
return r;
}
EXPORT_SYMBOL_GPL(dm_cell_lock_v2);
static void __quiesce(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell,
struct work_struct *continuation)
{
if (!cell->shared_count)
queue_work(prison->wq, continuation);
else
cell->quiesce_continuation = continuation;
}
void dm_cell_quiesce_v2(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell,
struct work_struct *continuation)
{
spin_lock_irq(&prison->lock);
__quiesce(prison, cell, continuation);
spin_unlock_irq(&prison->lock);
}
EXPORT_SYMBOL_GPL(dm_cell_quiesce_v2);
static int __promote(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell,
unsigned new_lock_level)
{
if (!cell->exclusive_lock)
return -EINVAL;
cell->exclusive_level = new_lock_level;
return cell->shared_count > 0;
}
int dm_cell_lock_promote_v2(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell,
unsigned new_lock_level)
{
int r;
spin_lock_irq(&prison->lock);
r = __promote(prison, cell, new_lock_level);
spin_unlock_irq(&prison->lock);
return r;
}
EXPORT_SYMBOL_GPL(dm_cell_lock_promote_v2);
static bool __unlock(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell,
struct bio_list *bios)
{
BUG_ON(!cell->exclusive_lock);
bio_list_merge(bios, &cell->bios);
bio_list_init(&cell->bios);
if (cell->shared_count) {
cell->exclusive_lock = false;
return false;
}
rb_erase(&cell->node, &prison->cells);
return true;
}
bool dm_cell_unlock_v2(struct dm_bio_prison_v2 *prison,
struct dm_bio_prison_cell_v2 *cell,
struct bio_list *bios)
{
bool r;
spin_lock_irq(&prison->lock);
r = __unlock(prison, cell, bios);
spin_unlock_irq(&prison->lock);
return r;
}
EXPORT_SYMBOL_GPL(dm_cell_unlock_v2);
/*----------------------------------------------------------------*/
int __init dm_bio_prison_init_v2(void)
{
_cell_cache = KMEM_CACHE(dm_bio_prison_cell_v2, 0);
if (!_cell_cache)
return -ENOMEM;
return 0;
}
void dm_bio_prison_exit_v2(void)
{
kmem_cache_destroy(_cell_cache);
_cell_cache = NULL;
}