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15 * If applicable, add the following below this CDDL HEADER, with the
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22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
26 * Copyright (c) 2013, 2015 by Delphix. All rights reserved.
29 #include <sys/zfs_context.h>
30 #include <sys/range_tree.h>
31 #include <sys/space_reftree.h>
34 * Space reference trees.
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.
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.]
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.
55 space_reftree_compare(const void *x1
, const void *x2
)
57 const space_ref_t
*sr1
= (const space_ref_t
*)x1
;
58 const space_ref_t
*sr2
= (const space_ref_t
*)x2
;
60 int cmp
= AVL_CMP(sr1
->sr_offset
, sr2
->sr_offset
);
64 return (AVL_PCMP(sr1
, sr2
));
68 space_reftree_create(avl_tree_t
*t
)
70 avl_create(t
, space_reftree_compare
,
71 sizeof (space_ref_t
), offsetof(space_ref_t
, sr_node
));
75 space_reftree_destroy(avl_tree_t
*t
)
80 while ((sr
= avl_destroy_nodes(t
, &cookie
)) != NULL
)
81 kmem_free(sr
, sizeof (*sr
));
87 space_reftree_add_node(avl_tree_t
*t
, uint64_t offset
, int64_t refcnt
)
91 sr
= kmem_alloc(sizeof (*sr
), KM_SLEEP
);
92 sr
->sr_offset
= offset
;
93 sr
->sr_refcnt
= refcnt
;
99 space_reftree_add_seg(avl_tree_t
*t
, uint64_t start
, uint64_t end
,
102 space_reftree_add_node(t
, start
, refcnt
);
103 space_reftree_add_node(t
, end
, -refcnt
);
107 * Convert (or add) a range tree into a reference tree.
110 space_reftree_add_map(avl_tree_t
*t
, range_tree_t
*rt
, int64_t refcnt
)
114 for (rs
= avl_first(&rt
->rt_root
); rs
; rs
= AVL_NEXT(&rt
->rt_root
, rs
))
115 space_reftree_add_seg(t
, rs
->rs_start
, rs
->rs_end
, refcnt
);
119 * Convert a reference tree into a range tree. The range tree will contain
120 * all members of the reference tree for which refcnt >= minref.
123 space_reftree_generate_map(avl_tree_t
*t
, range_tree_t
*rt
, int64_t minref
)
125 uint64_t start
= -1ULL;
129 range_tree_vacate(rt
, NULL
, NULL
);
131 for (sr
= avl_first(t
); sr
!= NULL
; sr
= AVL_NEXT(t
, sr
)) {
132 refcnt
+= sr
->sr_refcnt
;
133 if (refcnt
>= minref
) {
134 if (start
== -1ULL) {
135 start
= sr
->sr_offset
;
138 if (start
!= -1ULL) {
139 uint64_t end
= sr
->sr_offset
;
140 ASSERT(start
<= end
);
142 range_tree_add(rt
, start
, end
- start
);
148 ASSERT(start
== -1ULL);