summaryrefslogtreecommitdiffstats
path: root/drivers/md/dm-bio-prison-v1.h
blob: cddd4ac07e2cb2664d3e8b478193f7fe699ee85a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
/*
 * 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;
};

/*
 * 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);

/*
 * 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, int 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