dm-bio-prison.h
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/*
* 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;
/* FIXME: this needs to be more abstract */
struct dm_cell_key {
int virtual;
dm_thin_id dev;
dm_block_t block;
};
/*
* Treat this as opaque, only in header so callers can manage allocation
* themselves.
*/
struct dm_bio_prison_cell {
struct hlist_node list;
struct dm_cell_key key;
struct bio *holder;
struct bio_list bios;
};
struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
void dm_bio_prison_destroy(struct dm_bio_prison *prison);
/*
* These two functions just wrap a mempool. This is a transitory step:
* Eventually all bio prison clients should manage their own cell memory.
*
* Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
* in interrupt context or passed GFP_NOWAIT.
*/
struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
gfp_t gfp);
void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell);
/*
* Creates, or retrieves a cell for the given key.
*
* Returns 1 if pre-existing cell returned, zero if new cell created using
* @cell_prealloc.
*/
int dm_get_cell(struct dm_bio_prison *prison,
struct dm_cell_key *key,
struct dm_bio_prison_cell *cell_prealloc,
struct dm_bio_prison_cell **cell_result);
/*
* An atomic op that combines retrieving a cell, and adding a bio to it.
*
* 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 *cell_prealloc,
struct dm_bio_prison_cell **cell_result);
void dm_cell_release(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell,
struct bio_list *bios);
void dm_cell_release_no_holder(struct dm_bio_prison *prison,
struct dm_bio_prison_cell *cell,
struct bio_list *inmates);
void dm_cell_error(struct dm_bio_prison *prison,
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