zfs-builds-mm/zfs-0.8.1/module/zfs/range_tree.c

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2019-07-06 23:40:11 +02:00
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
* Copyright (c) 2013, 2017 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/dmu.h>
#include <sys/dnode.h>
#include <sys/zio.h>
#include <sys/range_tree.h>
/*
* Range trees are tree-based data structures that can be used to
* track free space or generally any space allocation information.
* A range tree keeps track of individual segments and automatically
* provides facilities such as adjacent extent merging and extent
* splitting in response to range add/remove requests.
*
* A range tree starts out completely empty, with no segments in it.
* Adding an allocation via range_tree_add to the range tree can either:
* 1) create a new extent
* 2) extend an adjacent extent
* 3) merge two adjacent extents
* Conversely, removing an allocation via range_tree_remove can:
* 1) completely remove an extent
* 2) shorten an extent (if the allocation was near one of its ends)
* 3) split an extent into two extents, in effect punching a hole
*
* A range tree is also capable of 'bridging' gaps when adding
* allocations. This is useful for cases when close proximity of
* allocations is an important detail that needs to be represented
* in the range tree. See range_tree_set_gap(). The default behavior
* is not to bridge gaps (i.e. the maximum allowed gap size is 0).
*
* In order to traverse a range tree, use either the range_tree_walk()
* or range_tree_vacate() functions.
*
* To obtain more accurate information on individual segment
* operations that the range tree performs "under the hood", you can
* specify a set of callbacks by passing a range_tree_ops_t structure
* to the range_tree_create function. Any callbacks that are non-NULL
* are then called at the appropriate times.
*
* The range tree code also supports a special variant of range trees
* that can bridge small gaps between segments. This kind of tree is used
* by the dsl scanning code to group I/Os into mostly sequential chunks to
* optimize disk performance. The code here attempts to do this with as
* little memory and computational overhead as possible. One limitation of
* this implementation is that segments of range trees with gaps can only
* support removing complete segments.
*/
kmem_cache_t *range_seg_cache;
/* Generic ops for managing an AVL tree alongside a range tree */
struct range_tree_ops rt_avl_ops = {
.rtop_create = rt_avl_create,
.rtop_destroy = rt_avl_destroy,
.rtop_add = rt_avl_add,
.rtop_remove = rt_avl_remove,
.rtop_vacate = rt_avl_vacate,
};
void
range_tree_init(void)
{
ASSERT(range_seg_cache == NULL);
range_seg_cache = kmem_cache_create("range_seg_cache",
sizeof (range_seg_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
}
void
range_tree_fini(void)
{
kmem_cache_destroy(range_seg_cache);
range_seg_cache = NULL;
}
void
range_tree_stat_verify(range_tree_t *rt)
{
range_seg_t *rs;
uint64_t hist[RANGE_TREE_HISTOGRAM_SIZE] = { 0 };
int i;
for (rs = avl_first(&rt->rt_root); rs != NULL;
rs = AVL_NEXT(&rt->rt_root, rs)) {
uint64_t size = rs->rs_end - rs->rs_start;
int idx = highbit64(size) - 1;
hist[idx]++;
ASSERT3U(hist[idx], !=, 0);
}
for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++) {
if (hist[i] != rt->rt_histogram[i]) {
zfs_dbgmsg("i=%d, hist=%px, hist=%llu, rt_hist=%llu",
i, hist, hist[i], rt->rt_histogram[i]);
}
VERIFY3U(hist[i], ==, rt->rt_histogram[i]);
}
}
static void
range_tree_stat_incr(range_tree_t *rt, range_seg_t *rs)
{
uint64_t size = rs->rs_end - rs->rs_start;
int idx = highbit64(size) - 1;
ASSERT(size != 0);
ASSERT3U(idx, <,
sizeof (rt->rt_histogram) / sizeof (*rt->rt_histogram));
rt->rt_histogram[idx]++;
ASSERT3U(rt->rt_histogram[idx], !=, 0);
}
static void
range_tree_stat_decr(range_tree_t *rt, range_seg_t *rs)
{
uint64_t size = rs->rs_end - rs->rs_start;
int idx = highbit64(size) - 1;
ASSERT(size != 0);
ASSERT3U(idx, <,
sizeof (rt->rt_histogram) / sizeof (*rt->rt_histogram));
ASSERT3U(rt->rt_histogram[idx], !=, 0);
rt->rt_histogram[idx]--;
}
/*
* NOTE: caller is responsible for all locking.
*/
static int
range_tree_seg_compare(const void *x1, const void *x2)
{
const range_seg_t *r1 = (const range_seg_t *)x1;
const range_seg_t *r2 = (const range_seg_t *)x2;
ASSERT3U(r1->rs_start, <=, r1->rs_end);
ASSERT3U(r2->rs_start, <=, r2->rs_end);
return ((r1->rs_start >= r2->rs_end) - (r1->rs_end <= r2->rs_start));
}
range_tree_t *
range_tree_create_impl(range_tree_ops_t *ops, void *arg,
int (*avl_compare) (const void *, const void *), uint64_t gap)
{
range_tree_t *rt = kmem_zalloc(sizeof (range_tree_t), KM_SLEEP);
avl_create(&rt->rt_root, range_tree_seg_compare,
sizeof (range_seg_t), offsetof(range_seg_t, rs_node));
rt->rt_ops = ops;
rt->rt_gap = gap;
rt->rt_arg = arg;
rt->rt_avl_compare = avl_compare;
if (rt->rt_ops != NULL && rt->rt_ops->rtop_create != NULL)
rt->rt_ops->rtop_create(rt, rt->rt_arg);
return (rt);
}
range_tree_t *
range_tree_create(range_tree_ops_t *ops, void *arg)
{
return (range_tree_create_impl(ops, arg, NULL, 0));
}
void
range_tree_destroy(range_tree_t *rt)
{
VERIFY0(rt->rt_space);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_destroy != NULL)
rt->rt_ops->rtop_destroy(rt, rt->rt_arg);
avl_destroy(&rt->rt_root);
kmem_free(rt, sizeof (*rt));
}
void
range_tree_adjust_fill(range_tree_t *rt, range_seg_t *rs, int64_t delta)
{
ASSERT3U(rs->rs_fill + delta, !=, 0);
ASSERT3U(rs->rs_fill + delta, <=, rs->rs_end - rs->rs_start);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_remove != NULL)
rt->rt_ops->rtop_remove(rt, rs, rt->rt_arg);
rs->rs_fill += delta;
if (rt->rt_ops != NULL && rt->rt_ops->rtop_add != NULL)
rt->rt_ops->rtop_add(rt, rs, rt->rt_arg);
}
static void
range_tree_add_impl(void *arg, uint64_t start, uint64_t size, uint64_t fill)
{
range_tree_t *rt = arg;
avl_index_t where;
range_seg_t rsearch, *rs_before, *rs_after, *rs;
uint64_t end = start + size, gap = rt->rt_gap;
uint64_t bridge_size = 0;
boolean_t merge_before, merge_after;
ASSERT3U(size, !=, 0);
ASSERT3U(fill, <=, size);
rsearch.rs_start = start;
rsearch.rs_end = end;
rs = avl_find(&rt->rt_root, &rsearch, &where);
if (gap == 0 && rs != NULL &&
rs->rs_start <= start && rs->rs_end >= end) {
zfs_panic_recover("zfs: allocating allocated segment"
"(offset=%llu size=%llu) of (offset=%llu size=%llu)\n",
(longlong_t)start, (longlong_t)size,
(longlong_t)rs->rs_start,
(longlong_t)rs->rs_end - rs->rs_start);
return;
}
/*
* If this is a gap-supporting range tree, it is possible that we
* are inserting into an existing segment. In this case simply
* bump the fill count and call the remove / add callbacks. If the
* new range will extend an existing segment, we remove the
* existing one, apply the new extent to it and re-insert it using
* the normal code paths.
*/
if (rs != NULL) {
ASSERT3U(gap, !=, 0);
if (rs->rs_start <= start && rs->rs_end >= end) {
range_tree_adjust_fill(rt, rs, fill);
return;
}
avl_remove(&rt->rt_root, rs);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_remove != NULL)
rt->rt_ops->rtop_remove(rt, rs, rt->rt_arg);
range_tree_stat_decr(rt, rs);
rt->rt_space -= rs->rs_end - rs->rs_start;
fill += rs->rs_fill;
start = MIN(start, rs->rs_start);
end = MAX(end, rs->rs_end);
size = end - start;
range_tree_add_impl(rt, start, size, fill);
kmem_cache_free(range_seg_cache, rs);
return;
}
ASSERT3P(rs, ==, NULL);
/*
* Determine whether or not we will have to merge with our neighbors.
* If gap != 0, we might need to merge with our neighbors even if we
* aren't directly touching.
*/
rs_before = avl_nearest(&rt->rt_root, where, AVL_BEFORE);
rs_after = avl_nearest(&rt->rt_root, where, AVL_AFTER);
merge_before = (rs_before != NULL && rs_before->rs_end >= start - gap);
merge_after = (rs_after != NULL && rs_after->rs_start <= end + gap);
if (merge_before && gap != 0)
bridge_size += start - rs_before->rs_end;
if (merge_after && gap != 0)
bridge_size += rs_after->rs_start - end;
if (merge_before && merge_after) {
avl_remove(&rt->rt_root, rs_before);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_remove != NULL) {
rt->rt_ops->rtop_remove(rt, rs_before, rt->rt_arg);
rt->rt_ops->rtop_remove(rt, rs_after, rt->rt_arg);
}
range_tree_stat_decr(rt, rs_before);
range_tree_stat_decr(rt, rs_after);
rs_after->rs_fill += rs_before->rs_fill + fill;
rs_after->rs_start = rs_before->rs_start;
kmem_cache_free(range_seg_cache, rs_before);
rs = rs_after;
} else if (merge_before) {
if (rt->rt_ops != NULL && rt->rt_ops->rtop_remove != NULL)
rt->rt_ops->rtop_remove(rt, rs_before, rt->rt_arg);
range_tree_stat_decr(rt, rs_before);
rs_before->rs_fill += fill;
rs_before->rs_end = end;
rs = rs_before;
} else if (merge_after) {
if (rt->rt_ops != NULL && rt->rt_ops->rtop_remove != NULL)
rt->rt_ops->rtop_remove(rt, rs_after, rt->rt_arg);
range_tree_stat_decr(rt, rs_after);
rs_after->rs_fill += fill;
rs_after->rs_start = start;
rs = rs_after;
} else {
rs = kmem_cache_alloc(range_seg_cache, KM_SLEEP);
rs->rs_fill = fill;
rs->rs_start = start;
rs->rs_end = end;
avl_insert(&rt->rt_root, rs, where);
}
if (gap != 0)
ASSERT3U(rs->rs_fill, <=, rs->rs_end - rs->rs_start);
else
ASSERT3U(rs->rs_fill, ==, rs->rs_end - rs->rs_start);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_add != NULL)
rt->rt_ops->rtop_add(rt, rs, rt->rt_arg);
range_tree_stat_incr(rt, rs);
rt->rt_space += size + bridge_size;
}
void
range_tree_add(void *arg, uint64_t start, uint64_t size)
{
range_tree_add_impl(arg, start, size, size);
}
static void
range_tree_remove_impl(range_tree_t *rt, uint64_t start, uint64_t size,
boolean_t do_fill)
{
avl_index_t where;
range_seg_t rsearch, *rs, *newseg;
uint64_t end = start + size;
boolean_t left_over, right_over;
VERIFY3U(size, !=, 0);
VERIFY3U(size, <=, rt->rt_space);
rsearch.rs_start = start;
rsearch.rs_end = end;
rs = avl_find(&rt->rt_root, &rsearch, &where);
/* Make sure we completely overlap with someone */
if (rs == NULL) {
zfs_panic_recover("zfs: freeing free segment "
"(offset=%llu size=%llu)",
(longlong_t)start, (longlong_t)size);
return;
}
/*
* Range trees with gap support must only remove complete segments
* from the tree. This allows us to maintain accurate fill accounting
* and to ensure that bridged sections are not leaked. If we need to
* remove less than the full segment, we can only adjust the fill count.
*/
if (rt->rt_gap != 0) {
if (do_fill) {
if (rs->rs_fill == size) {
start = rs->rs_start;
end = rs->rs_end;
size = end - start;
} else {
range_tree_adjust_fill(rt, rs, -size);
return;
}
} else if (rs->rs_start != start || rs->rs_end != end) {
zfs_panic_recover("zfs: freeing partial segment of "
"gap tree (offset=%llu size=%llu) of "
"(offset=%llu size=%llu)",
(longlong_t)start, (longlong_t)size,
(longlong_t)rs->rs_start,
(longlong_t)rs->rs_end - rs->rs_start);
return;
}
}
VERIFY3U(rs->rs_start, <=, start);
VERIFY3U(rs->rs_end, >=, end);
left_over = (rs->rs_start != start);
right_over = (rs->rs_end != end);
range_tree_stat_decr(rt, rs);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_remove != NULL)
rt->rt_ops->rtop_remove(rt, rs, rt->rt_arg);
if (left_over && right_over) {
newseg = kmem_cache_alloc(range_seg_cache, KM_SLEEP);
newseg->rs_start = end;
newseg->rs_end = rs->rs_end;
newseg->rs_fill = newseg->rs_end - newseg->rs_start;
range_tree_stat_incr(rt, newseg);
rs->rs_end = start;
avl_insert_here(&rt->rt_root, newseg, rs, AVL_AFTER);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_add != NULL)
rt->rt_ops->rtop_add(rt, newseg, rt->rt_arg);
} else if (left_over) {
rs->rs_end = start;
} else if (right_over) {
rs->rs_start = end;
} else {
avl_remove(&rt->rt_root, rs);
kmem_cache_free(range_seg_cache, rs);
rs = NULL;
}
if (rs != NULL) {
/*
* The fill of the leftover segment will always be equal to
* the size, since we do not support removing partial segments
* of range trees with gaps.
*/
rs->rs_fill = rs->rs_end - rs->rs_start;
range_tree_stat_incr(rt, rs);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_add != NULL)
rt->rt_ops->rtop_add(rt, rs, rt->rt_arg);
}
rt->rt_space -= size;
}
void
range_tree_remove(void *arg, uint64_t start, uint64_t size)
{
range_tree_remove_impl(arg, start, size, B_FALSE);
}
void
range_tree_remove_fill(range_tree_t *rt, uint64_t start, uint64_t size)
{
range_tree_remove_impl(rt, start, size, B_TRUE);
}
void
range_tree_resize_segment(range_tree_t *rt, range_seg_t *rs,
uint64_t newstart, uint64_t newsize)
{
int64_t delta = newsize - (rs->rs_end - rs->rs_start);
range_tree_stat_decr(rt, rs);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_remove != NULL)
rt->rt_ops->rtop_remove(rt, rs, rt->rt_arg);
rs->rs_start = newstart;
rs->rs_end = newstart + newsize;
range_tree_stat_incr(rt, rs);
if (rt->rt_ops != NULL && rt->rt_ops->rtop_add != NULL)
rt->rt_ops->rtop_add(rt, rs, rt->rt_arg);
rt->rt_space += delta;
}
static range_seg_t *
range_tree_find_impl(range_tree_t *rt, uint64_t start, uint64_t size)
{
range_seg_t rsearch;
uint64_t end = start + size;
VERIFY(size != 0);
rsearch.rs_start = start;
rsearch.rs_end = end;
return (avl_find(&rt->rt_root, &rsearch, NULL));
}
range_seg_t *
range_tree_find(range_tree_t *rt, uint64_t start, uint64_t size)
{
range_seg_t *rs = range_tree_find_impl(rt, start, size);
if (rs != NULL && rs->rs_start <= start && rs->rs_end >= start + size)
return (rs);
return (NULL);
}
void
range_tree_verify_not_present(range_tree_t *rt, uint64_t off, uint64_t size)
{
range_seg_t *rs = range_tree_find(rt, off, size);
if (rs != NULL)
panic("segment already in tree; rs=%p", (void *)rs);
}
boolean_t
range_tree_contains(range_tree_t *rt, uint64_t start, uint64_t size)
{
return (range_tree_find(rt, start, size) != NULL);
}
/*
* Ensure that this range is not in the tree, regardless of whether
* it is currently in the tree.
*/
void
range_tree_clear(range_tree_t *rt, uint64_t start, uint64_t size)
{
range_seg_t *rs;
if (size == 0)
return;
while ((rs = range_tree_find_impl(rt, start, size)) != NULL) {
uint64_t free_start = MAX(rs->rs_start, start);
uint64_t free_end = MIN(rs->rs_end, start + size);
range_tree_remove(rt, free_start, free_end - free_start);
}
}
void
range_tree_swap(range_tree_t **rtsrc, range_tree_t **rtdst)
{
range_tree_t *rt;
ASSERT0(range_tree_space(*rtdst));
ASSERT0(avl_numnodes(&(*rtdst)->rt_root));
rt = *rtsrc;
*rtsrc = *rtdst;
*rtdst = rt;
}
void
range_tree_vacate(range_tree_t *rt, range_tree_func_t *func, void *arg)
{
range_seg_t *rs;
void *cookie = NULL;
if (rt->rt_ops != NULL && rt->rt_ops->rtop_vacate != NULL)
rt->rt_ops->rtop_vacate(rt, rt->rt_arg);
while ((rs = avl_destroy_nodes(&rt->rt_root, &cookie)) != NULL) {
if (func != NULL)
func(arg, rs->rs_start, rs->rs_end - rs->rs_start);
kmem_cache_free(range_seg_cache, rs);
}
bzero(rt->rt_histogram, sizeof (rt->rt_histogram));
rt->rt_space = 0;
}
void
range_tree_walk(range_tree_t *rt, range_tree_func_t *func, void *arg)
{
range_seg_t *rs;
for (rs = avl_first(&rt->rt_root); rs; rs = AVL_NEXT(&rt->rt_root, rs))
func(arg, rs->rs_start, rs->rs_end - rs->rs_start);
}
range_seg_t *
range_tree_first(range_tree_t *rt)
{
return (avl_first(&rt->rt_root));
}
uint64_t
range_tree_space(range_tree_t *rt)
{
return (rt->rt_space);
}
boolean_t
range_tree_is_empty(range_tree_t *rt)
{
ASSERT(rt != NULL);
return (range_tree_space(rt) == 0);
}
/* Generic range tree functions for maintaining segments in an AVL tree. */
void
rt_avl_create(range_tree_t *rt, void *arg)
{
avl_tree_t *tree = arg;
avl_create(tree, rt->rt_avl_compare, sizeof (range_seg_t),
offsetof(range_seg_t, rs_pp_node));
}
void
rt_avl_destroy(range_tree_t *rt, void *arg)
{
avl_tree_t *tree = arg;
ASSERT0(avl_numnodes(tree));
avl_destroy(tree);
}
void
rt_avl_add(range_tree_t *rt, range_seg_t *rs, void *arg)
{
avl_tree_t *tree = arg;
avl_add(tree, rs);
}
void
rt_avl_remove(range_tree_t *rt, range_seg_t *rs, void *arg)
{
avl_tree_t *tree = arg;
avl_remove(tree, rs);
}
void
rt_avl_vacate(range_tree_t *rt, void *arg)
{
/*
* Normally one would walk the tree freeing nodes along the way.
* Since the nodes are shared with the range trees we can avoid
* walking all nodes and just reinitialize the avl tree. The nodes
* will be freed by the range tree, so we don't want to free them here.
*/
rt_avl_create(rt, arg);
}
uint64_t
range_tree_min(range_tree_t *rt)
{
range_seg_t *rs = avl_first(&rt->rt_root);
return (rs != NULL ? rs->rs_start : 0);
}
uint64_t
range_tree_max(range_tree_t *rt)
{
range_seg_t *rs = avl_last(&rt->rt_root);
return (rs != NULL ? rs->rs_end : 0);
}
uint64_t
range_tree_span(range_tree_t *rt)
{
return (range_tree_max(rt) - range_tree_min(rt));
}