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  */
  24 struct dm_bio_prison;
  25
  26 /* FIXME: this needs to be more abstract */
  27 struct 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  */
  37 struct 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
  44 struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
  45 void 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  */
  54 struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
  55                                                     gfp_t gfp);
  56 void 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  */
  65 int 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  */
  75 int 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
  81 void dm_cell_release(struct dm_bio_prison *prison,
  82                      struct dm_bio_prison_cell *cell,
  83                      struct bio_list *bios);
  84 void dm_cell_release_no_holder(struct dm_bio_prison *prison,
  85                                struct dm_bio_prison_cell *cell,
  86                                struct bio_list *inmates);
  87 void 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
  99 struct dm_deferred_set;
 100 struct dm_deferred_entry;
 101
 102 struct dm_deferred_set *dm_deferred_set_create(void);
 103 void dm_deferred_set_destroy(struct dm_deferred_set *ds);
 104
 105 struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
 106 void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
 107 int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
 108
 109 /*----------------------------------------------------------------*/
 110
 111 #endif