LXR linux/drivers/md/dm-bio-prison-v2.h

   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
  19int dm_bio_prison_init_v2(void);
  20void 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 */
  28struct dm_bio_prison_v2;
  29
  30/*
  31 * Keys define a range of blocks within either a virtual or physical
  32 * device.
  33 */
  34struct 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 */
  44struct 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
  56struct dm_bio_prison_v2 *dm_bio_prison_create_v2(struct workqueue_struct *wq);
  57void 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 */
  66struct dm_bio_prison_cell_v2 *dm_bio_prison_alloc_cell_v2(struct dm_bio_prison_v2 *prison,
  67                                                    gfp_t gfp);
  68void 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 */
  87bool 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 */
  98bool 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 */
 115int 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
 121void 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 */
 133int 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 */
 146bool 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
 153