1 /*
2 * Copyright (C) 2011-2017 Red Hat, Inc.
3 *
4 * This file is released under the GPL.
5 */
6
7 #ifndef DM_BIO_PRISON_V2_H
8 #define DM_BIO_PRISON_V2_H
9
10 #include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
11 #include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
12
13 #include <linux/bio.h>
14 #include <linux/rbtree.h>
15 #include <linux/workqueue.h>
16
17 /*----------------------------------------------------------------*/
18
19 int dm_bio_prison_init_v2(void);
20 void dm_bio_prison_exit_v2(void);
21
22 /*
23 * Sometimes we can't deal with a bio straight away. We put them in prison
24 * where they can't cause any mischief. Bios are put in a cell identified
25 * by a key, multiple bios can be in the same cell. When the cell is
26 * subsequently unlocked the bios become available.
27 */
28 struct dm_bio_prison_v2;
29
30 /*
31 * Keys define a range of blocks within either a virtual or physical
32 * device.
33 */
34 struct dm_cell_key_v2 {
35 int virtual;
36 dm_thin_id dev;
37 dm_block_t block_begin, block_end;
38 };
39
40 /*
41 * Treat this as opaque, only in header so callers can manage allocation
42 * themselves.
43 */
44 struct dm_bio_prison_cell_v2 {
45 // FIXME: pack these
46 bool exclusive_lock;
47 unsigned exclusive_level;
48 unsigned shared_count;
49 struct work_struct *quiesce_continuation;
50
51 struct rb_node node;
52 struct dm_cell_key_v2 key;
53 struct bio_list bios;
54 };
55
56 struct dm_bio_prison_v2 *dm_bio_prison_create_v2(struct workqueue_struct *wq);
57 void dm_bio_prison_destroy_v2(struct dm_bio_prison_v2 *prison);
58
59 /*
60 * These two functions just wrap a mempool. This is a transitory step:
61 * Eventually all bio prison clients should manage their own cell memory.
62 *
63 * Like mempool_alloc(), dm_bio_prison_alloc_cell_v2() can only fail if called
64 * in interrupt context or passed GFP_NOWAIT.
65 */
66 struct dm_bio_prison_cell_v2 *dm_bio_prison_alloc_cell_v2(struct dm_bio_prison_v2 *prison,
67 gfp_t gfp);
68 void dm_bio_prison_free_cell_v2(struct dm_bio_prison_v2 *prison,
69 struct dm_bio_prison_cell_v2 *cell);
70
71 /*
72 * Shared locks have a bio associated with them.
73 *
74 * If the lock is granted the caller can continue to use the bio, and must
75 * call dm_cell_put_v2() to drop the reference count when finished using it.
76 *
77 * If the lock cannot be granted then the bio will be tracked within the
78 * cell, and later given to the holder of the exclusive lock.
79 *
80 * See dm_cell_lock_v2() for discussion of the lock_level parameter.
81 *
82 * Compare *cell_result with cell_prealloc to see if the prealloc was used.
83 * If cell_prealloc was used then inmate wasn't added to it.
84 *
85 * Returns true if the lock is granted.
86 */
87 bool dm_cell_get_v2(struct dm_bio_prison_v2 *prison,
88 struct dm_cell_key_v2 *key,
89 unsigned lock_level,
90 struct bio *inmate,
91 struct dm_bio_prison_cell_v2 *cell_prealloc,
92 struct dm_bio_prison_cell_v2 **cell_result);
93
94 /*
95 * Decrement the shared reference count for the lock. Returns true if
96 * returning ownership of the cell (ie. you should free it).
97 */
98 bool dm_cell_put_v2(struct dm_bio_prison_v2 *prison,
99 struct dm_bio_prison_cell_v2 *cell);
100
101 /*
102 * Locks a cell. No associated bio. Exclusive locks get priority. These
103 * locks constrain whether the io locks are granted according to level.
104 *
105 * Shared locks will still be granted if the lock_level is > (not = to) the
106 * exclusive lock level.
107 *
108 * If an _exclusive_ lock is already held then -EBUSY is returned.
109 *
110 * Return values:
111 * < 0 - error
112 * 0 - locked; no quiescing needed
113 * 1 - locked; quiescing needed
114 */
115 int dm_cell_lock_v2(struct dm_bio_prison_v2 *prison,
116 struct dm_cell_key_v2 *key,
117 unsigned lock_level,
118 struct dm_bio_prison_cell_v2 *cell_prealloc,
119 struct dm_bio_prison_cell_v2 **cell_result);
120
121 void dm_cell_quiesce_v2(struct dm_bio_prison_v2 *prison,
122 struct dm_bio_prison_cell_v2 *cell,
123 struct work_struct *continuation);
124
125 /*
126 * Promotes an _exclusive_ lock to a higher lock level.
127 *
128 * Return values:
129 * < 0 - error
130 * 0 - promoted; no quiescing needed
131 * 1 - promoted; quiescing needed
132 */
133 int dm_cell_lock_promote_v2(struct dm_bio_prison_v2 *prison,
134 struct dm_bio_prison_cell_v2 *cell,
135 unsigned new_lock_level);
136
137 /*
138 * Adds any held bios to the bio list.
139 *
140 * There may be shared locks still held at this point even if you quiesced
141 * (ie. different lock levels).
142 *
143 * Returns true if returning ownership of the cell (ie. you should free
144 * it).
145 */
146 bool dm_cell_unlock_v2(struct dm_bio_prison_v2 *prison,
147 struct dm_bio_prison_cell_v2 *cell,
148 struct bio_list *bios);
149
150 /*----------------------------------------------------------------*/
151
152 #endif