153 lines
4.2 KiB
C
153 lines
4.2 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/*
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* Copyright (c) 2013, 2019 by Delphix. All rights reserved.
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*/
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#include <sys/zfs_context.h>
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#include <sys/range_tree.h>
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#include <sys/space_reftree.h>
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/*
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* Space reference trees.
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*
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* A range tree is a collection of integers. Every integer is either
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* in the tree, or it's not. A space reference tree generalizes
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* the idea: it allows its members to have arbitrary reference counts,
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* as opposed to the implicit reference count of 0 or 1 in a range tree.
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* This representation comes in handy when computing the union or
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* intersection of multiple space maps. For example, the union of
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* N range trees is the subset of the reference tree with refcnt >= 1.
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* The intersection of N range trees is the subset with refcnt >= N.
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*
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* [It's very much like a Fourier transform. Unions and intersections
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* are hard to perform in the 'range tree domain', so we convert the trees
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* into the 'reference count domain', where it's trivial, then invert.]
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*
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* vdev_dtl_reassess() uses computations of this form to determine
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* DTL_MISSING and DTL_OUTAGE for interior vdevs -- e.g. a RAID-Z vdev
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* has an outage wherever refcnt >= vdev_nparity + 1, and a mirror vdev
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* has an outage wherever refcnt >= vdev_children.
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*/
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static int
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space_reftree_compare(const void *x1, const void *x2)
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{
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const space_ref_t *sr1 = (const space_ref_t *)x1;
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const space_ref_t *sr2 = (const space_ref_t *)x2;
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int cmp = TREE_CMP(sr1->sr_offset, sr2->sr_offset);
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if (likely(cmp))
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return (cmp);
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return (TREE_PCMP(sr1, sr2));
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}
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void
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space_reftree_create(avl_tree_t *t)
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{
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avl_create(t, space_reftree_compare,
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sizeof (space_ref_t), offsetof(space_ref_t, sr_node));
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}
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void
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space_reftree_destroy(avl_tree_t *t)
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{
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space_ref_t *sr;
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void *cookie = NULL;
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while ((sr = avl_destroy_nodes(t, &cookie)) != NULL)
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kmem_free(sr, sizeof (*sr));
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avl_destroy(t);
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}
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static void
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space_reftree_add_node(avl_tree_t *t, uint64_t offset, int64_t refcnt)
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{
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space_ref_t *sr;
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sr = kmem_alloc(sizeof (*sr), KM_SLEEP);
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sr->sr_offset = offset;
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sr->sr_refcnt = refcnt;
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avl_add(t, sr);
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}
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void
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space_reftree_add_seg(avl_tree_t *t, uint64_t start, uint64_t end,
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int64_t refcnt)
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{
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space_reftree_add_node(t, start, refcnt);
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space_reftree_add_node(t, end, -refcnt);
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}
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/*
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* Convert (or add) a range tree into a reference tree.
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*/
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void
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space_reftree_add_map(avl_tree_t *t, range_tree_t *rt, int64_t refcnt)
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{
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zfs_btree_index_t where;
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for (range_seg_t *rs = zfs_btree_first(&rt->rt_root, &where); rs; rs =
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zfs_btree_next(&rt->rt_root, &where, &where)) {
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space_reftree_add_seg(t, rs_get_start(rs, rt), rs_get_end(rs,
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rt), refcnt);
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}
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}
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/*
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* Convert a reference tree into a range tree. The range tree will contain
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* all members of the reference tree for which refcnt >= minref.
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*/
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void
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space_reftree_generate_map(avl_tree_t *t, range_tree_t *rt, int64_t minref)
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{
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uint64_t start = -1ULL;
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int64_t refcnt = 0;
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space_ref_t *sr;
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range_tree_vacate(rt, NULL, NULL);
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for (sr = avl_first(t); sr != NULL; sr = AVL_NEXT(t, sr)) {
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refcnt += sr->sr_refcnt;
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if (refcnt >= minref) {
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if (start == -1ULL) {
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start = sr->sr_offset;
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}
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} else {
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if (start != -1ULL) {
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uint64_t end = sr->sr_offset;
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ASSERT(start <= end);
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if (end > start)
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range_tree_add(rt, start, end - start);
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start = -1ULL;
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}
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}
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}
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ASSERT(refcnt == 0);
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ASSERT(start == -1ULL);
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}
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