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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (C) 2011-2017 Red Hat, Inc.
4 *
5 * This file is released under the GPL.
6 */
7
8#ifndef DM_BIO_PRISON_H
9#define DM_BIO_PRISON_H
10
11#include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
12#include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
13
14#include <linux/bio.h>
15#include <linux/rbtree.h>
16
17/*----------------------------------------------------------------*/
18
19/*
20 * Sometimes we can't deal with a bio straight away. We put them in prison
21 * where they can't cause any mischief. Bios are put in a cell identified
22 * by a key, multiple bios can be in the same cell. When the cell is
23 * subsequently unlocked the bios become available.
24 */
25struct dm_bio_prison;
26
27/*
28 * Keys define a range of blocks within either a virtual or physical
29 * device.
30 */
31struct dm_cell_key {
32 int virtual;
33 dm_thin_id dev;
34 dm_block_t block_begin, block_end;
35};
36
37/*
38 * The range of a key (block_end - block_begin) must not
39 * exceed BIO_PRISON_MAX_RANGE. Also the range must not
40 * cross a similarly sized boundary.
41 *
42 * Must be a power of 2.
43 */
44#define BIO_PRISON_MAX_RANGE 1024
45#define BIO_PRISON_MAX_RANGE_SHIFT 10
46
47/*
48 * Treat this as opaque, only in header so callers can manage allocation
49 * themselves.
50 */
51struct dm_bio_prison_cell {
52 struct list_head user_list; /* for client use */
53 struct rb_node node;
54
55 struct dm_cell_key key;
56 struct bio *holder;
57 struct bio_list bios;
58};
59
60struct dm_bio_prison *dm_bio_prison_create(void);
61void dm_bio_prison_destroy(struct dm_bio_prison *prison);
62
63/*
64 * These two functions just wrap a mempool. This is a transitory step:
65 * Eventually all bio prison clients should manage their own cell memory.
66 *
67 * Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
68 * in interrupt context or passed GFP_NOWAIT.
69 */
70struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
71 gfp_t gfp);
72void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
73 struct dm_bio_prison_cell *cell);
74
75/*
76 * Returns false if key is beyond BIO_PRISON_MAX_RANGE or spans a boundary.
77 */
78bool dm_cell_key_has_valid_range(struct dm_cell_key *key);
79
80/*
81 * An atomic op that combines retrieving or creating a cell, and adding a
82 * bio to it.
83 *
84 * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
85 */
86int dm_bio_detain(struct dm_bio_prison *prison,
87 struct dm_cell_key *key,
88 struct bio *inmate,
89 struct dm_bio_prison_cell *cell_prealloc,
90 struct dm_bio_prison_cell **cell_result);
91
92void dm_cell_release(struct dm_bio_prison *prison,
93 struct dm_bio_prison_cell *cell,
94 struct bio_list *bios);
95void dm_cell_release_no_holder(struct dm_bio_prison *prison,
96 struct dm_bio_prison_cell *cell,
97 struct bio_list *inmates);
98void dm_cell_error(struct dm_bio_prison *prison,
99 struct dm_bio_prison_cell *cell, blk_status_t error);
100
101/*
102 * Visits the cell and then releases. Guarantees no new inmates are
103 * inserted between the visit and release.
104 */
105void dm_cell_visit_release(struct dm_bio_prison *prison,
106 void (*visit_fn)(void *, struct dm_bio_prison_cell *),
107 void *context, struct dm_bio_prison_cell *cell);
108
109/*----------------------------------------------------------------*/
110
111/*
112 * We use the deferred set to keep track of pending reads to shared blocks.
113 * We do this to ensure the new mapping caused by a write isn't performed
114 * until these prior reads have completed. Otherwise the insertion of the
115 * new mapping could free the old block that the read bios are mapped to.
116 */
117
118struct dm_deferred_set;
119struct dm_deferred_entry;
120
121struct dm_deferred_set *dm_deferred_set_create(void);
122void dm_deferred_set_destroy(struct dm_deferred_set *ds);
123
124struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
125void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
126int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
127
128/*----------------------------------------------------------------*/
129
130#endif