Root/drivers/md/dm-bio-prison.h

1/*
2 * Copyright (C) 2011-2012 Red Hat, Inc.
3 *
4 * This file is released under the GPL.
5 */
6
7#ifndef DM_BIO_PRISON_H
8#define DM_BIO_PRISON_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/list.h>
14#include <linux/bio.h>
15
16/*----------------------------------------------------------------*/
17
18/*
19 * Sometimes we can't deal with a bio straight away. We put them in prison
20 * where they can't cause any mischief. Bios are put in a cell identified
21 * by a key, multiple bios can be in the same cell. When the cell is
22 * subsequently unlocked the bios become available.
23 */
24struct dm_bio_prison;
25
26/* FIXME: this needs to be more abstract */
27struct dm_cell_key {
28    int virtual;
29    dm_thin_id dev;
30    dm_block_t block;
31};
32
33/*
34 * Treat this as opaque, only in header so callers can manage allocation
35 * themselves.
36 */
37struct dm_bio_prison_cell {
38    struct hlist_node list;
39    struct dm_cell_key key;
40    struct bio *holder;
41    struct bio_list bios;
42};
43
44struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
45void dm_bio_prison_destroy(struct dm_bio_prison *prison);
46
47/*
48 * These two functions just wrap a mempool. This is a transitory step:
49 * Eventually all bio prison clients should manage their own cell memory.
50 *
51 * Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
52 * in interrupt context or passed GFP_NOWAIT.
53 */
54struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
55                            gfp_t gfp);
56void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
57                 struct dm_bio_prison_cell *cell);
58
59/*
60 * Creates, or retrieves a cell for the given key.
61 *
62 * Returns 1 if pre-existing cell returned, zero if new cell created using
63 * @cell_prealloc.
64 */
65int dm_get_cell(struct dm_bio_prison *prison,
66        struct dm_cell_key *key,
67        struct dm_bio_prison_cell *cell_prealloc,
68        struct dm_bio_prison_cell **cell_result);
69
70/*
71 * An atomic op that combines retrieving a cell, and adding a bio to it.
72 *
73 * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
74 */
75int dm_bio_detain(struct dm_bio_prison *prison,
76          struct dm_cell_key *key,
77          struct bio *inmate,
78          struct dm_bio_prison_cell *cell_prealloc,
79          struct dm_bio_prison_cell **cell_result);
80
81void dm_cell_release(struct dm_bio_prison *prison,
82             struct dm_bio_prison_cell *cell,
83             struct bio_list *bios);
84void dm_cell_release_no_holder(struct dm_bio_prison *prison,
85                   struct dm_bio_prison_cell *cell,
86                   struct bio_list *inmates);
87void dm_cell_error(struct dm_bio_prison *prison,
88           struct dm_bio_prison_cell *cell);
89
90/*----------------------------------------------------------------*/
91
92/*
93 * We use the deferred set to keep track of pending reads to shared blocks.
94 * We do this to ensure the new mapping caused by a write isn't performed
95 * until these prior reads have completed. Otherwise the insertion of the
96 * new mapping could free the old block that the read bios are mapped to.
97 */
98
99struct dm_deferred_set;
100struct dm_deferred_entry;
101
102struct dm_deferred_set *dm_deferred_set_create(void);
103void dm_deferred_set_destroy(struct dm_deferred_set *ds);
104
105struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
106void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
107int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
108
109/*----------------------------------------------------------------*/
110
111#endif
112

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