1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * Copyright (C) 2011-2017 Red Hat, Inc.
5 * This file is released under the GPL.
8 #ifndef DM_BIO_PRISON_H
9 #define DM_BIO_PRISON_H
11 #include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
12 #include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
14 #include <linux/bio.h>
15 #include <linux/rbtree.h>
17 /*----------------------------------------------------------------*/
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.
28 * Keys define a range of blocks within either a virtual or physical
34 dm_block_t block_begin, block_end;
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.
42 * Must be a power of 2.
44 #define BIO_PRISON_MAX_RANGE 1024
45 #define BIO_PRISON_MAX_RANGE_SHIFT 10
48 * Treat this as opaque, only in header so callers can manage allocation
51 struct dm_bio_prison_cell {
52 struct list_head user_list; /* for client use */
55 struct dm_cell_key key;
60 struct dm_bio_prison *dm_bio_prison_create(void);
61 void dm_bio_prison_destroy(struct dm_bio_prison *prison);
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.
67 * Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
68 * in interrupt context or passed GFP_NOWAIT.
70 struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
72 void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
73 struct dm_bio_prison_cell *cell);
76 * Creates, or retrieves a cell that overlaps the given key.
78 * Returns 1 if pre-existing cell returned, zero if new cell created using
81 int dm_get_cell(struct dm_bio_prison *prison,
82 struct dm_cell_key *key,
83 struct dm_bio_prison_cell *cell_prealloc,
84 struct dm_bio_prison_cell **cell_result);
87 * Returns false if key is beyond BIO_PRISON_MAX_RANGE or spans a boundary.
89 bool dm_cell_key_has_valid_range(struct dm_cell_key *key);
92 * An atomic op that combines retrieving or creating a cell, and adding a
95 * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
97 int dm_bio_detain(struct dm_bio_prison *prison,
98 struct dm_cell_key *key,
100 struct dm_bio_prison_cell *cell_prealloc,
101 struct dm_bio_prison_cell **cell_result);
103 void dm_cell_release(struct dm_bio_prison *prison,
104 struct dm_bio_prison_cell *cell,
105 struct bio_list *bios);
106 void dm_cell_release_no_holder(struct dm_bio_prison *prison,
107 struct dm_bio_prison_cell *cell,
108 struct bio_list *inmates);
109 void dm_cell_error(struct dm_bio_prison *prison,
110 struct dm_bio_prison_cell *cell, blk_status_t error);
113 * Visits the cell and then releases. Guarantees no new inmates are
114 * inserted between the visit and release.
116 void dm_cell_visit_release(struct dm_bio_prison *prison,
117 void (*visit_fn)(void *, struct dm_bio_prison_cell *),
118 void *context, struct dm_bio_prison_cell *cell);
121 * Rather than always releasing the prisoners in a cell, the client may
122 * want to promote one of them to be the new holder. There is a race here
123 * though between releasing an empty cell, and other threads adding new
124 * inmates. So this function makes the decision with its lock held.
126 * This function can have two outcomes:
127 * i) An inmate is promoted to be the holder of the cell (return value of 0).
128 * ii) The cell has no inmate for promotion and is released (return value of 1).
130 int dm_cell_promote_or_release(struct dm_bio_prison *prison,
131 struct dm_bio_prison_cell *cell);
133 /*----------------------------------------------------------------*/
136 * We use the deferred set to keep track of pending reads to shared blocks.
137 * We do this to ensure the new mapping caused by a write isn't performed
138 * until these prior reads have completed. Otherwise the insertion of the
139 * new mapping could free the old block that the read bios are mapped to.
142 struct dm_deferred_set;
143 struct dm_deferred_entry;
145 struct dm_deferred_set *dm_deferred_set_create(void);
146 void dm_deferred_set_destroy(struct dm_deferred_set *ds);
148 struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
149 void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
150 int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
152 /*----------------------------------------------------------------*/