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/bio.h>
  14 #include <linux/rbtree.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 /*
  27  * Keys define a range of blocks within either a virtual or physical
  28  * device.
  29  */
  30 struct dm_cell_key {
  31         int virtual;
  32         dm_thin_id dev;
  33         dm_block_t block_begin, block_end;
  34 };
  35
  36 /*
  37  * Treat this as opaque, only in header so callers can manage allocation
  38  * themselves.
  39  */
  40 struct dm_bio_prison_cell {
  41         struct list_head user_list;     /* for client use */
  42         struct rb_node node;
  43
  44         struct dm_cell_key key;
  45         struct bio *holder;
  46         struct bio_list bios;
  47 };
  48
  49 struct dm_bio_prison *dm_bio_prison_create(void);
  50 void dm_bio_prison_destroy(struct dm_bio_prison *prison);
  51
  52 /*
  53  * These two functions just wrap a mempool.  This is a transitory step:
  54  * Eventually all bio prison clients should manage their own cell memory.
  55  *
  56  * Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
  57  * in interrupt context or passed GFP_NOWAIT.
  58  */
  59 struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
  60                                                     gfp_t gfp);
  61 void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
  62                              struct dm_bio_prison_cell *cell);
  63
  64 /*
  65  * Creates, or retrieves a cell that overlaps the given key.
  66  *
  67  * Returns 1 if pre-existing cell returned, zero if new cell created using
  68  * @cell_prealloc.
  69  */
  70 int dm_get_cell(struct dm_bio_prison *prison,
  71                 struct dm_cell_key *key,
  72                 struct dm_bio_prison_cell *cell_prealloc,
  73                 struct dm_bio_prison_cell **cell_result);
  74
  75 /*
  76  * An atomic op that combines retrieving or creating a cell, and adding a
  77  * bio to it.
  78  *
  79  * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
  80  */
  81 int dm_bio_detain(struct dm_bio_prison *prison,
  82                   struct dm_cell_key *key,
  83                   struct bio *inmate,
  84                   struct dm_bio_prison_cell *cell_prealloc,
  85                   struct dm_bio_prison_cell **cell_result);
  86
  87 void dm_cell_release(struct dm_bio_prison *prison,
  88                      struct dm_bio_prison_cell *cell,
  89                      struct bio_list *bios);
  90 void dm_cell_release_no_holder(struct dm_bio_prison *prison,
  91                                struct dm_bio_prison_cell *cell,
  92                                struct bio_list *inmates);
  93 void dm_cell_error(struct dm_bio_prison *prison,
  94                    struct dm_bio_prison_cell *cell, int error);
  95
  96 /*
  97  * Visits the cell and then releases.  Guarantees no new inmates are
  98  * inserted between the visit and release.
  99  */
 100 void dm_cell_visit_release(struct dm_bio_prison *prison,
 101                            void (*visit_fn)(void *, struct dm_bio_prison_cell *),
 102                            void *context, struct dm_bio_prison_cell *cell);
 103
 104 /*
 105  * Rather than always releasing the prisoners in a cell, the client may
 106  * want to promote one of them to be the new holder.  There is a race here
 107  * though between releasing an empty cell, and other threads adding new
 108  * inmates.  So this function makes the decision with its lock held.
 109  *
 110  * This function can have two outcomes:
 111  * i) An inmate is promoted to be the holder of the cell (return value of 0).
 112  * ii) The cell has no inmate for promotion and is released (return value of 1).
 113  */
 114 int dm_cell_promote_or_release(struct dm_bio_prison *prison,
 115                                struct dm_bio_prison_cell *cell);
 116
 117 /*----------------------------------------------------------------*/
 118
 119 /*
 120  * We use the deferred set to keep track of pending reads to shared blocks.
 121  * We do this to ensure the new mapping caused by a write isn't performed
 122  * until these prior reads have completed.  Otherwise the insertion of the
 123  * new mapping could free the old block that the read bios are mapped to.
 124  */
 125
 126 struct dm_deferred_set;
 127 struct dm_deferred_entry;
 128
 129 struct dm_deferred_set *dm_deferred_set_create(void);
 130 void dm_deferred_set_destroy(struct dm_deferred_set *ds);
 131
 132 struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
 133 void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
 134 int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
 135
 136 /*----------------------------------------------------------------*/
 137
 138 #endif