module/zfs/space_reftree.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or https://opensource.org/licenses/CDDL-1.0.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25 /*
  26  * Copyright (c) 2013, 2019 by Delphix. All rights reserved.
  27  */
  28
  29 #include <sys/zfs_context.h>
  30 #include <sys/range_tree.h>
  31 #include <sys/space_reftree.h>
  32
  33 /*
  34  * Space reference trees.
  35  *
  36  * A range tree is a collection of integers.  Every integer is either
  37  * in the tree, or it's not.  A space reference tree generalizes
  38  * the idea: it allows its members to have arbitrary reference counts,
  39  * as opposed to the implicit reference count of 0 or 1 in a range tree.
  40  * This representation comes in handy when computing the union or
  41  * intersection of multiple space maps.  For example, the union of
  42  * N range trees is the subset of the reference tree with refcnt >= 1.
  43  * The intersection of N range trees is the subset with refcnt >= N.
  44  *
  45  * [It's very much like a Fourier transform.  Unions and intersections
  46  * are hard to perform in the 'range tree domain', so we convert the trees
  47  * into the 'reference count domain', where it's trivial, then invert.]
  48  *
  49  * vdev_dtl_reassess() uses computations of this form to determine
  50  * DTL_MISSING and DTL_OUTAGE for interior vdevs -- e.g. a RAID-Z vdev
  51  * has an outage wherever refcnt >= vdev_nparity + 1, and a mirror vdev
  52  * has an outage wherever refcnt >= vdev_children.
  53  */
  54 static int
  55 space_reftree_compare(const void *x1, const void *x2)
  56 {
  57         const space_ref_t *sr1 = (const space_ref_t *)x1;
  58         const space_ref_t *sr2 = (const space_ref_t *)x2;
  59
  60         int cmp = TREE_CMP(sr1->sr_offset, sr2->sr_offset);
  61         if (likely(cmp))
  62                 return (cmp);
  63
  64         return (TREE_PCMP(sr1, sr2));
  65 }
  66
  67 void
  68 space_reftree_create(avl_tree_t *t)
  69 {
  70         avl_create(t, space_reftree_compare,
  71             sizeof (space_ref_t), offsetof(space_ref_t, sr_node));
  72 }
  73
  74 void
  75 space_reftree_destroy(avl_tree_t *t)
  76 {
  77         space_ref_t *sr;
  78         void *cookie = NULL;
  79
  80         while ((sr = avl_destroy_nodes(t, &cookie)) != NULL)
  81                 kmem_free(sr, sizeof (*sr));
  82
  83         avl_destroy(t);
  84 }
  85
  86 static void
  87 space_reftree_add_node(avl_tree_t *t, uint64_t offset, int64_t refcnt)
  88 {
  89         space_ref_t *sr;
  90
  91         sr = kmem_alloc(sizeof (*sr), KM_SLEEP);
  92         sr->sr_offset = offset;
  93         sr->sr_refcnt = refcnt;
  94
  95         avl_add(t, sr);
  96 }
  97
  98 void
  99 space_reftree_add_seg(avl_tree_t *t, uint64_t start, uint64_t end,
 100     int64_t refcnt)
 101 {
 102         space_reftree_add_node(t, start, refcnt);
 103         space_reftree_add_node(t, end, -refcnt);
 104 }
 105
 106 /*
 107  * Convert (or add) a range tree into a reference tree.
 108  */
 109 void
 110 space_reftree_add_map(avl_tree_t *t, range_tree_t *rt, int64_t refcnt)
 111 {
 112         zfs_btree_index_t where;
 113
 114         for (range_seg_t *rs = zfs_btree_first(&rt->rt_root, &where); rs; rs =
 115             zfs_btree_next(&rt->rt_root, &where, &where)) {
 116                 space_reftree_add_seg(t, rs_get_start(rs, rt), rs_get_end(rs,
 117                     rt),  refcnt);
 118         }
 119 }
 120
 121 /*
 122  * Convert a reference tree into a range tree.  The range tree will contain
 123  * all members of the reference tree for which refcnt >= minref.
 124  */
 125 void
 126 space_reftree_generate_map(avl_tree_t *t, range_tree_t *rt, int64_t minref)
 127 {
 128         uint64_t start = -1ULL;
 129         int64_t refcnt = 0;
 130         space_ref_t *sr;
 131
 132         range_tree_vacate(rt, NULL, NULL);
 133
 134         for (sr = avl_first(t); sr != NULL; sr = AVL_NEXT(t, sr)) {
 135                 refcnt += sr->sr_refcnt;
 136                 if (refcnt >= minref) {
 137                         if (start == -1ULL) {
 138                                 start = sr->sr_offset;
 139                         }
 140                 } else {
 141                         if (start != -1ULL) {
 142                                 uint64_t end = sr->sr_offset;
 143                                 ASSERT(start <= end);
 144                                 if (end > start)
 145                                         range_tree_add(rt, start, end - start);
 146                                 start = -1ULL;
 147                         }
 148                 }
 149         }
 150         ASSERT(refcnt == 0);
 151         ASSERT(start == -1ULL);
 152 }