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dm-bio-prison-v1.h
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dm-bio-prison-v1.h
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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2011-2017 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/bio.h>
#include <linux/rbtree.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;
/*
* Keys define a range of blocks within either a virtual or physical
* device.
*/
struct dm_cell_key {
int virtual;
dm_thin_id dev;
dm_block_t block_begin, block_end;
};
/*
* The range of a key (block_end - block_begin) must not
* exceed BIO_PRISON_MAX_RANGE. Also the range must not
* cross a similarly sized boundary.
*
* Must be a power of 2.
*/
#define BIO_PRISON_MAX_RANGE 1024
#define BIO_PRISON_MAX_RANGE_SHIFT 10
/*
* Treat this as opaque, only in header so callers can manage allocation
* themselves.
*/
struct dm_bio_prison_cell {
struct list_head user_list; /* for client use */
struct rb_node node;
struct dm_cell_key key;
struct bio *holder;
struct bio_list bios;
};
struct dm_bio_prison *dm_bio_prison_create(void);
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 that overlaps 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);
/*
* Returns false if key is beyond BIO_PRISON_MAX_RANGE or spans a boundary.
*/
bool dm_cell_key_has_valid_range(struct dm_cell_key *key);
/*
* An atomic op that combines retrieving or creating 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, blk_status_t error);
/*
* Visits the cell and then releases. Guarantees no new inmates are
* inserted between the visit and release.
*/
void dm_cell_visit_release(struct dm_bio_prison *prison,
void (*visit_fn)(void *, struct dm_bio_prison_cell *),
void *context, struct dm_bio_prison_cell *cell);
/*
* Rather than always releasing the prisoners in a cell, the client may
* want to promote one of them to be the new holder. There is a race here
* though between releasing an empty cell, and other threads adding new
* inmates. So this function makes the decision with its lock held.
*
* This function can have two outcomes:
* i) An inmate is promoted to be the holder of the cell (return value of 0).
* ii) The cell has no inmate for promotion and is released (return value of 1).
*/
int dm_cell_promote_or_release(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