xref: /openbmc/linux/drivers/md/dm-bio-prison-v1.h (revision 3f8d3f54)
1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Copyright (C) 2011-2017 Red Hat, Inc.
4  *
5  * This file is released under the GPL.
6  */
7 
8 #ifndef DM_BIO_PRISON_H
9 #define DM_BIO_PRISON_H
10 
11 #include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
12 #include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
13 
14 #include <linux/bio.h>
15 #include <linux/rbtree.h>
16 
17 /*----------------------------------------------------------------*/
18 
19 /*
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.
24  */
25 struct dm_bio_prison;
26 
27 /*
28  * Keys define a range of blocks within either a virtual or physical
29  * device.
30  */
31 struct dm_cell_key {
32 	int virtual;
33 	dm_thin_id dev;
34 	dm_block_t block_begin, block_end;
35 };
36 
37 /*
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.
41  *
42  * Must be a power of 2.
43  */
44 #define BIO_PRISON_MAX_RANGE 1024
45 #define BIO_PRISON_MAX_RANGE_SHIFT 10
46 
47 /*
48  * Treat this as opaque, only in header so callers can manage allocation
49  * themselves.
50  */
51 struct dm_bio_prison_cell {
52 	struct list_head user_list;	/* for client use */
53 	struct rb_node node;
54 
55 	struct dm_cell_key key;
56 	struct bio *holder;
57 	struct bio_list bios;
58 };
59 
60 struct dm_bio_prison *dm_bio_prison_create(void);
61 void dm_bio_prison_destroy(struct dm_bio_prison *prison);
62 
63 /*
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.
66  *
67  * Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
68  * in interrupt context or passed GFP_NOWAIT.
69  */
70 struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
71 						    gfp_t gfp);
72 void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
73 			     struct dm_bio_prison_cell *cell);
74 
75 /*
76  * Creates, or retrieves a cell that overlaps the given key.
77  *
78  * Returns 1 if pre-existing cell returned, zero if new cell created using
79  * @cell_prealloc.
80  */
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);
85 
86 /*
87  * Returns false if key is beyond BIO_PRISON_MAX_RANGE or spans a boundary.
88  */
89 bool dm_cell_key_has_valid_range(struct dm_cell_key *key);
90 
91 /*
92  * An atomic op that combines retrieving or creating a cell, and adding a
93  * bio to it.
94  *
95  * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
96  */
97 int dm_bio_detain(struct dm_bio_prison *prison,
98 		  struct dm_cell_key *key,
99 		  struct bio *inmate,
100 		  struct dm_bio_prison_cell *cell_prealloc,
101 		  struct dm_bio_prison_cell **cell_result);
102 
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);
111 
112 /*
113  * Visits the cell and then releases.  Guarantees no new inmates are
114  * inserted between the visit and release.
115  */
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);
119 
120 /*
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.
125  *
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).
129  */
130 int dm_cell_promote_or_release(struct dm_bio_prison *prison,
131 			       struct dm_bio_prison_cell *cell);
132 
133 /*----------------------------------------------------------------*/
134 
135 /*
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.
140  */
141 
142 struct dm_deferred_set;
143 struct dm_deferred_entry;
144 
145 struct dm_deferred_set *dm_deferred_set_create(void);
146 void dm_deferred_set_destroy(struct dm_deferred_set *ds);
147 
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);
151 
152 /*----------------------------------------------------------------*/
153 
154 #endif
155