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/bio.h>
14#include <linux/rbtree.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/*
27 * Keys define a range of blocks within either a virtual or physical
28 * device.
29 */
30struct dm_cell_key {
31	int virtual;
32	dm_thin_id dev;
33	dm_block_t block_begin, block_end;
34};
35
36/*
37 * Treat this as opaque, only in header so callers can manage allocation
38 * themselves.
39 */
40struct dm_bio_prison_cell {
41	struct list_head user_list;	/* for client use */
42	struct rb_node node;
43
44	struct dm_cell_key key;
45	struct bio *holder;
46	struct bio_list bios;
47};
48
49struct dm_bio_prison *dm_bio_prison_create(void);
50void dm_bio_prison_destroy(struct dm_bio_prison *prison);
51
52/*
53 * These two functions just wrap a mempool.  This is a transitory step:
54 * Eventually all bio prison clients should manage their own cell memory.
55 *
56 * Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
57 * in interrupt context or passed GFP_NOWAIT.
58 */
59struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
60						    gfp_t gfp);
61void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
62			     struct dm_bio_prison_cell *cell);
63
64/*
65 * Creates, or retrieves a cell that overlaps the given key.
66 *
67 * Returns 1 if pre-existing cell returned, zero if new cell created using
68 * @cell_prealloc.
69 */
70int dm_get_cell(struct dm_bio_prison *prison,
71		struct dm_cell_key *key,
72		struct dm_bio_prison_cell *cell_prealloc,
73		struct dm_bio_prison_cell **cell_result);
74
75/*
76 * An atomic op that combines retrieving or creating a cell, and adding a
77 * bio to it.
78 *
79 * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
80 */
81int dm_bio_detain(struct dm_bio_prison *prison,
82		  struct dm_cell_key *key,
83		  struct bio *inmate,
84		  struct dm_bio_prison_cell *cell_prealloc,
85		  struct dm_bio_prison_cell **cell_result);
86
87void dm_cell_release(struct dm_bio_prison *prison,
88		     struct dm_bio_prison_cell *cell,
89		     struct bio_list *bios);
90void dm_cell_release_no_holder(struct dm_bio_prison *prison,
91			       struct dm_bio_prison_cell *cell,
92			       struct bio_list *inmates);
93void dm_cell_error(struct dm_bio_prison *prison,
94		   struct dm_bio_prison_cell *cell, int error);
95
96/*
97 * Visits the cell and then releases.  Guarantees no new inmates are
98 * inserted between the visit and release.
99 */
100void dm_cell_visit_release(struct dm_bio_prison *prison,
101			   void (*visit_fn)(void *, struct dm_bio_prison_cell *),
102			   void *context, struct dm_bio_prison_cell *cell);
103
104/*----------------------------------------------------------------*/
105
106/*
107 * We use the deferred set to keep track of pending reads to shared blocks.
108 * We do this to ensure the new mapping caused by a write isn't performed
109 * until these prior reads have completed.  Otherwise the insertion of the
110 * new mapping could free the old block that the read bios are mapped to.
111 */
112
113struct dm_deferred_set;
114struct dm_deferred_entry;
115
116struct dm_deferred_set *dm_deferred_set_create(void);
117void dm_deferred_set_destroy(struct dm_deferred_set *ds);
118
119struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
120void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
121int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
122
123/*----------------------------------------------------------------*/
124
125#endif
126