fs/btrfs/ulist.h

   1 /*
   2  * Copyright (C) 2011 STRATO AG
   3  * written by Arne Jansen <sensille@gmx.net>
   4  * Distributed under the GNU GPL license version 2.
   5  *
   6  */
   7
   8 #ifndef __ULIST__
   9 #define __ULIST__
  10
  11 #include <linux/list.h>
  12 #include <linux/rbtree.h>
  13
  14 /*
  15  * ulist is a generic data structure to hold a collection of unique u64
  16  * values. The only operations it supports is adding to the list and
  17  * enumerating it.
  18  * It is possible to store an auxiliary value along with the key.
  19  *
  20  * The implementation is preliminary and can probably be sped up
  21  * significantly. A first step would be to store the values in an rbtree
  22  * as soon as ULIST_SIZE is exceeded.
  23  */
  24
  25 /*
  26  * number of elements statically allocated inside struct ulist
  27  */
  28 #define ULIST_SIZE 16
  29
  30 struct ulist_iterator {
  31         int i;
  32 };
  33
  34 /*
  35  * element of the list
  36  */
  37 struct ulist_node {
  38         u64 val;                /* value to store */
  39         u64 aux;                /* auxiliary value saved along with the val */
  40         struct rb_node rb_node; /* used to speed up search */
  41 };
  42
  43 struct ulist {
  44         /*
  45          * number of elements stored in list
  46          */
  47         unsigned long nnodes;
  48
  49         /*
  50          * number of nodes we already have room for
  51          */
  52         unsigned long nodes_alloced;
  53
  54         /*
  55          * pointer to the array storing the elements. The first ULIST_SIZE
  56          * elements are stored inline. In this case the it points to int_nodes.
  57          * After exceeding ULIST_SIZE, dynamic memory is allocated.
  58          */
  59         struct ulist_node *nodes;
  60
  61         struct rb_root root;
  62
  63         /*
  64          * inline storage space for the first ULIST_SIZE entries
  65          */
  66         struct ulist_node int_nodes[ULIST_SIZE];
  67 };
  68
  69 void ulist_init(struct ulist *ulist);
  70 void ulist_fini(struct ulist *ulist);
  71 void ulist_reinit(struct ulist *ulist);
  72 struct ulist *ulist_alloc(gfp_t gfp_mask);
  73 void ulist_free(struct ulist *ulist);
  74 int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask);
  75 int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
  76                     u64 *old_aux, gfp_t gfp_mask);
  77 struct ulist_node *ulist_next(struct ulist *ulist,
  78                               struct ulist_iterator *uiter);
  79
  80 #define ULIST_ITER_INIT(uiter) ((uiter)->i = 0)
  81
  82 #endif