linux/drivers/md/dm-bio-prison.h
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   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 */
  24struct dm_bio_prison;
  25
  26/* FIXME: this needs to be more abstract */
  27struct 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 */
  37struct 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
  44struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
  45void 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 */
  54struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
  55                                                    gfp_t gfp);
  56void 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 */
  65int 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 */
  75int 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
  81void dm_cell_release(struct dm_bio_prison *prison,
  82                     struct dm_bio_prison_cell *cell,
  83                     struct bio_list *bios);
  84void dm_cell_release_no_holder(struct dm_bio_prison *prison,
  85                               struct dm_bio_prison_cell *cell,
  86                               struct bio_list *inmates);
  87void 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
  99struct dm_deferred_set;
 100struct dm_deferred_entry;
 101
 102struct dm_deferred_set *dm_deferred_set_create(void);
 103void dm_deferred_set_destroy(struct dm_deferred_set *ds);
 104
 105struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
 106void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
 107int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
 108
 109/*----------------------------------------------------------------*/
 110
 111#endif
 112
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