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