zfs-builds-mm/zfs-0.8.5/module/zfs/space_map.c

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2020-10-22 13:48:46 +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) 2012, 2018 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/dmu.h>
#include <sys/dmu_tx.h>
#include <sys/dnode.h>
#include <sys/dsl_pool.h>
#include <sys/zio.h>
#include <sys/space_map.h>
#include <sys/refcount.h>
#include <sys/zfeature.h>
/*
* Note on space map block size:
*
* The data for a given space map can be kept on blocks of any size.
* Larger blocks entail fewer I/O operations, but they also cause the
* DMU to keep more data in-core, and also to waste more I/O bandwidth
* when only a few blocks have changed since the last transaction group.
*/
/*
* Enabled whenever we want to stress test the use of double-word
* space map entries.
*/
boolean_t zfs_force_some_double_word_sm_entries = B_FALSE;
/*
* Override the default indirect block size of 128K, instead use 16K for
* spacemaps (2^14 bytes). This dramatically reduces write inflation since
* appending to a spacemap typically has to write one data block (4KB) and one
* or two indirect blocks (16K-32K, rather than 128K).
*/
int space_map_ibs = 14;
boolean_t
sm_entry_is_debug(uint64_t e)
{
return (SM_PREFIX_DECODE(e) == SM_DEBUG_PREFIX);
}
boolean_t
sm_entry_is_single_word(uint64_t e)
{
uint8_t prefix = SM_PREFIX_DECODE(e);
return (prefix != SM_DEBUG_PREFIX && prefix != SM2_PREFIX);
}
boolean_t
sm_entry_is_double_word(uint64_t e)
{
return (SM_PREFIX_DECODE(e) == SM2_PREFIX);
}
/*
* Iterate through the space map, invoking the callback on each (non-debug)
* space map entry. Stop after reading 'end' bytes of the space map.
*/
int
space_map_iterate(space_map_t *sm, uint64_t end, sm_cb_t callback, void *arg)
{
uint64_t blksz = sm->sm_blksz;
ASSERT3U(blksz, !=, 0);
ASSERT3U(end, <=, space_map_length(sm));
ASSERT0(P2PHASE(end, sizeof (uint64_t)));
dmu_prefetch(sm->sm_os, space_map_object(sm), 0, 0, end,
ZIO_PRIORITY_SYNC_READ);
int error = 0;
for (uint64_t block_base = 0; block_base < end && error == 0;
block_base += blksz) {
dmu_buf_t *db;
error = dmu_buf_hold(sm->sm_os, space_map_object(sm),
block_base, FTAG, &db, DMU_READ_PREFETCH);
if (error != 0)
return (error);
uint64_t *block_start = db->db_data;
uint64_t block_length = MIN(end - block_base, blksz);
uint64_t *block_end = block_start +
(block_length / sizeof (uint64_t));
VERIFY0(P2PHASE(block_length, sizeof (uint64_t)));
VERIFY3U(block_length, !=, 0);
ASSERT3U(blksz, ==, db->db_size);
for (uint64_t *block_cursor = block_start;
block_cursor < block_end && error == 0; block_cursor++) {
uint64_t e = *block_cursor;
if (sm_entry_is_debug(e)) /* Skip debug entries */
continue;
uint64_t raw_offset, raw_run, vdev_id;
maptype_t type;
if (sm_entry_is_single_word(e)) {
type = SM_TYPE_DECODE(e);
vdev_id = SM_NO_VDEVID;
raw_offset = SM_OFFSET_DECODE(e);
raw_run = SM_RUN_DECODE(e);
} else {
/* it is a two-word entry */
ASSERT(sm_entry_is_double_word(e));
raw_run = SM2_RUN_DECODE(e);
vdev_id = SM2_VDEV_DECODE(e);
/* move on to the second word */
block_cursor++;
e = *block_cursor;
VERIFY3P(block_cursor, <=, block_end);
type = SM2_TYPE_DECODE(e);
raw_offset = SM2_OFFSET_DECODE(e);
}
uint64_t entry_offset = (raw_offset << sm->sm_shift) +
sm->sm_start;
uint64_t entry_run = raw_run << sm->sm_shift;
VERIFY0(P2PHASE(entry_offset, 1ULL << sm->sm_shift));
VERIFY0(P2PHASE(entry_run, 1ULL << sm->sm_shift));
ASSERT3U(entry_offset, >=, sm->sm_start);
ASSERT3U(entry_offset, <, sm->sm_start + sm->sm_size);
ASSERT3U(entry_run, <=, sm->sm_size);
ASSERT3U(entry_offset + entry_run, <=,
sm->sm_start + sm->sm_size);
space_map_entry_t sme = {
.sme_type = type,
.sme_vdev = vdev_id,
.sme_offset = entry_offset,
.sme_run = entry_run
};
error = callback(&sme, arg);
}
dmu_buf_rele(db, FTAG);
}
return (error);
}
/*
* Reads the entries from the last block of the space map into
* buf in reverse order. Populates nwords with number of words
* in the last block.
*
* Refer to block comment within space_map_incremental_destroy()
* to understand why this function is needed.
*/
static int
space_map_reversed_last_block_entries(space_map_t *sm, uint64_t *buf,
uint64_t bufsz, uint64_t *nwords)
{
int error = 0;
dmu_buf_t *db;
/*
* Find the offset of the last word in the space map and use
* that to read the last block of the space map with
* dmu_buf_hold().
*/
uint64_t last_word_offset =
sm->sm_phys->smp_length - sizeof (uint64_t);
error = dmu_buf_hold(sm->sm_os, space_map_object(sm), last_word_offset,
FTAG, &db, DMU_READ_NO_PREFETCH);
if (error != 0)
return (error);
ASSERT3U(sm->sm_object, ==, db->db_object);
ASSERT3U(sm->sm_blksz, ==, db->db_size);
ASSERT3U(bufsz, >=, db->db_size);
ASSERT(nwords != NULL);
uint64_t *words = db->db_data;
*nwords =
(sm->sm_phys->smp_length - db->db_offset) / sizeof (uint64_t);
ASSERT3U(*nwords, <=, bufsz / sizeof (uint64_t));
uint64_t n = *nwords;
uint64_t j = n - 1;
for (uint64_t i = 0; i < n; i++) {
uint64_t entry = words[i];
if (sm_entry_is_double_word(entry)) {
/*
* Since we are populating the buffer backwards
* we have to be extra careful and add the two
* words of the double-word entry in the right
* order.
*/
ASSERT3U(j, >, 0);
buf[j - 1] = entry;
i++;
ASSERT3U(i, <, n);
entry = words[i];
buf[j] = entry;
j -= 2;
} else {
ASSERT(sm_entry_is_debug(entry) ||
sm_entry_is_single_word(entry));
buf[j] = entry;
j--;
}
}
/*
* Assert that we wrote backwards all the
* way to the beginning of the buffer.
*/
ASSERT3S(j, ==, -1);
dmu_buf_rele(db, FTAG);
return (error);
}
/*
* Note: This function performs destructive actions - specifically
* it deletes entries from the end of the space map. Thus, callers
* should ensure that they are holding the appropriate locks for
* the space map that they provide.
*/
int
space_map_incremental_destroy(space_map_t *sm, sm_cb_t callback, void *arg,
dmu_tx_t *tx)
{
uint64_t bufsz = MAX(sm->sm_blksz, SPA_MINBLOCKSIZE);
uint64_t *buf = zio_buf_alloc(bufsz);
dmu_buf_will_dirty(sm->sm_dbuf, tx);
/*
* Ideally we would want to iterate from the beginning of the
* space map to the end in incremental steps. The issue with this
* approach is that we don't have any field on-disk that points
* us where to start between each step. We could try zeroing out
* entries that we've destroyed, but this doesn't work either as
* an entry that is 0 is a valid one (ALLOC for range [0x0:0x200]).
*
* As a result, we destroy its entries incrementally starting from
* the end after applying the callback to each of them.
*
* The problem with this approach is that we cannot literally
* iterate through the words in the space map backwards as we
* can't distinguish two-word space map entries from their second
* word. Thus we do the following:
*
* 1] We get all the entries from the last block of the space map
* and put them into a buffer in reverse order. This way the
* last entry comes first in the buffer, the second to last is
* second, etc.
* 2] We iterate through the entries in the buffer and we apply
* the callback to each one. As we move from entry to entry we
* we decrease the size of the space map, deleting effectively
* each entry.
* 3] If there are no more entries in the space map or the callback
* returns a value other than 0, we stop iterating over the
* space map. If there are entries remaining and the callback
* returned 0, we go back to step [1].
*/
int error = 0;
while (space_map_length(sm) > 0 && error == 0) {
uint64_t nwords = 0;
error = space_map_reversed_last_block_entries(sm, buf, bufsz,
&nwords);
if (error != 0)
break;
ASSERT3U(nwords, <=, bufsz / sizeof (uint64_t));
for (uint64_t i = 0; i < nwords; i++) {
uint64_t e = buf[i];
if (sm_entry_is_debug(e)) {
sm->sm_phys->smp_length -= sizeof (uint64_t);
continue;
}
int words = 1;
uint64_t raw_offset, raw_run, vdev_id;
maptype_t type;
if (sm_entry_is_single_word(e)) {
type = SM_TYPE_DECODE(e);
vdev_id = SM_NO_VDEVID;
raw_offset = SM_OFFSET_DECODE(e);
raw_run = SM_RUN_DECODE(e);
} else {
ASSERT(sm_entry_is_double_word(e));
words = 2;
raw_run = SM2_RUN_DECODE(e);
vdev_id = SM2_VDEV_DECODE(e);
/* move to the second word */
i++;
e = buf[i];
ASSERT3P(i, <=, nwords);
type = SM2_TYPE_DECODE(e);
raw_offset = SM2_OFFSET_DECODE(e);
}
uint64_t entry_offset =
(raw_offset << sm->sm_shift) + sm->sm_start;
uint64_t entry_run = raw_run << sm->sm_shift;
VERIFY0(P2PHASE(entry_offset, 1ULL << sm->sm_shift));
VERIFY0(P2PHASE(entry_run, 1ULL << sm->sm_shift));
VERIFY3U(entry_offset, >=, sm->sm_start);
VERIFY3U(entry_offset, <, sm->sm_start + sm->sm_size);
VERIFY3U(entry_run, <=, sm->sm_size);
VERIFY3U(entry_offset + entry_run, <=,
sm->sm_start + sm->sm_size);
space_map_entry_t sme = {
.sme_type = type,
.sme_vdev = vdev_id,
.sme_offset = entry_offset,
.sme_run = entry_run
};
error = callback(&sme, arg);
if (error != 0)
break;
if (type == SM_ALLOC)
sm->sm_phys->smp_alloc -= entry_run;
else
sm->sm_phys->smp_alloc += entry_run;
sm->sm_phys->smp_length -= words * sizeof (uint64_t);
}
}
if (space_map_length(sm) == 0) {
ASSERT0(error);
ASSERT0(space_map_allocated(sm));
}
zio_buf_free(buf, bufsz);
return (error);
}
typedef struct space_map_load_arg {
space_map_t *smla_sm;
range_tree_t *smla_rt;
maptype_t smla_type;
} space_map_load_arg_t;
static int
space_map_load_callback(space_map_entry_t *sme, void *arg)
{
space_map_load_arg_t *smla = arg;
if (sme->sme_type == smla->smla_type) {
VERIFY3U(range_tree_space(smla->smla_rt) + sme->sme_run, <=,
smla->smla_sm->sm_size);
range_tree_add(smla->smla_rt, sme->sme_offset, sme->sme_run);
} else {
range_tree_remove(smla->smla_rt, sme->sme_offset, sme->sme_run);
}
return (0);
}
/*
* Load the spacemap into the rangetree, like space_map_load. But only
* read the first 'length' bytes of the spacemap.
*/
int
space_map_load_length(space_map_t *sm, range_tree_t *rt, maptype_t maptype,
uint64_t length)
{
space_map_load_arg_t smla;
VERIFY0(range_tree_space(rt));
if (maptype == SM_FREE)
range_tree_add(rt, sm->sm_start, sm->sm_size);
smla.smla_rt = rt;
smla.smla_sm = sm;
smla.smla_type = maptype;
int err = space_map_iterate(sm, length,
space_map_load_callback, &smla);
if (err != 0)
range_tree_vacate(rt, NULL, NULL);
return (err);
}
/*
* Load the space map disk into the specified range tree. Segments of maptype
* are added to the range tree, other segment types are removed.
*/
int
space_map_load(space_map_t *sm, range_tree_t *rt, maptype_t maptype)
{
return (space_map_load_length(sm, rt, maptype, space_map_length(sm)));
}
void
space_map_histogram_clear(space_map_t *sm)
{
if (sm->sm_dbuf->db_size != sizeof (space_map_phys_t))
return;
bzero(sm->sm_phys->smp_histogram, sizeof (sm->sm_phys->smp_histogram));
}
boolean_t
space_map_histogram_verify(space_map_t *sm, range_tree_t *rt)
{
/*
* Verify that the in-core range tree does not have any
* ranges smaller than our sm_shift size.
*/
for (int i = 0; i < sm->sm_shift; i++) {
if (rt->rt_histogram[i] != 0)
return (B_FALSE);
}
return (B_TRUE);
}
void
space_map_histogram_add(space_map_t *sm, range_tree_t *rt, dmu_tx_t *tx)
{
int idx = 0;
ASSERT(dmu_tx_is_syncing(tx));
VERIFY3U(space_map_object(sm), !=, 0);
if (sm->sm_dbuf->db_size != sizeof (space_map_phys_t))
return;
dmu_buf_will_dirty(sm->sm_dbuf, tx);
ASSERT(space_map_histogram_verify(sm, rt));
/*
* Transfer the content of the range tree histogram to the space
* map histogram. The space map histogram contains 32 buckets ranging
* between 2^sm_shift to 2^(32+sm_shift-1). The range tree,
* however, can represent ranges from 2^0 to 2^63. Since the space
* map only cares about allocatable blocks (minimum of sm_shift) we
* can safely ignore all ranges in the range tree smaller than sm_shift.
*/
for (int i = sm->sm_shift; i < RANGE_TREE_HISTOGRAM_SIZE; i++) {
/*
* Since the largest histogram bucket in the space map is
* 2^(32+sm_shift-1), we need to normalize the values in
* the range tree for any bucket larger than that size. For
* example given an sm_shift of 9, ranges larger than 2^40
* would get normalized as if they were 1TB ranges. Assume
* the range tree had a count of 5 in the 2^44 (16TB) bucket,
* the calculation below would normalize this to 5 * 2^4 (16).
*/
ASSERT3U(i, >=, idx + sm->sm_shift);
sm->sm_phys->smp_histogram[idx] +=
rt->rt_histogram[i] << (i - idx - sm->sm_shift);
/*
* Increment the space map's index as long as we haven't
* reached the maximum bucket size. Accumulate all ranges
* larger than the max bucket size into the last bucket.
*/
if (idx < SPACE_MAP_HISTOGRAM_SIZE - 1) {
ASSERT3U(idx + sm->sm_shift, ==, i);
idx++;
ASSERT3U(idx, <, SPACE_MAP_HISTOGRAM_SIZE);
}
}
}
static void
space_map_write_intro_debug(space_map_t *sm, maptype_t maptype, dmu_tx_t *tx)
{
dmu_buf_will_dirty(sm->sm_dbuf, tx);
uint64_t dentry = SM_PREFIX_ENCODE(SM_DEBUG_PREFIX) |
SM_DEBUG_ACTION_ENCODE(maptype) |
SM_DEBUG_SYNCPASS_ENCODE(spa_sync_pass(tx->tx_pool->dp_spa)) |
SM_DEBUG_TXG_ENCODE(dmu_tx_get_txg(tx));
dmu_write(sm->sm_os, space_map_object(sm), sm->sm_phys->smp_length,
sizeof (dentry), &dentry, tx);
sm->sm_phys->smp_length += sizeof (dentry);
}
/*
* Writes one or more entries given a segment.
*
* Note: The function may release the dbuf from the pointer initially
* passed to it, and return a different dbuf. Also, the space map's
* dbuf must be dirty for the changes in sm_phys to take effect.
*/
static void
space_map_write_seg(space_map_t *sm, range_seg_t *rs, maptype_t maptype,
uint64_t vdev_id, uint8_t words, dmu_buf_t **dbp, void *tag, dmu_tx_t *tx)
{
ASSERT3U(words, !=, 0);
ASSERT3U(words, <=, 2);
/* ensure the vdev_id can be represented by the space map */
ASSERT3U(vdev_id, <=, SM_NO_VDEVID);
/*
* if this is a single word entry, ensure that no vdev was
* specified.
*/
IMPLY(words == 1, vdev_id == SM_NO_VDEVID);
dmu_buf_t *db = *dbp;
ASSERT3U(db->db_size, ==, sm->sm_blksz);
uint64_t *block_base = db->db_data;
uint64_t *block_end = block_base + (sm->sm_blksz / sizeof (uint64_t));
uint64_t *block_cursor = block_base +
(sm->sm_phys->smp_length - db->db_offset) / sizeof (uint64_t);
ASSERT3P(block_cursor, <=, block_end);
uint64_t size = (rs->rs_end - rs->rs_start) >> sm->sm_shift;
uint64_t start = (rs->rs_start - sm->sm_start) >> sm->sm_shift;
uint64_t run_max = (words == 2) ? SM2_RUN_MAX : SM_RUN_MAX;
ASSERT3U(rs->rs_start, >=, sm->sm_start);
ASSERT3U(rs->rs_start, <, sm->sm_start + sm->sm_size);
ASSERT3U(rs->rs_end - rs->rs_start, <=, sm->sm_size);
ASSERT3U(rs->rs_end, <=, sm->sm_start + sm->sm_size);
while (size != 0) {
ASSERT3P(block_cursor, <=, block_end);
/*
* If we are at the end of this block, flush it and start
* writing again from the beginning.
*/
if (block_cursor == block_end) {
dmu_buf_rele(db, tag);
uint64_t next_word_offset = sm->sm_phys->smp_length;
VERIFY0(dmu_buf_hold(sm->sm_os,
space_map_object(sm), next_word_offset,
tag, &db, DMU_READ_PREFETCH));
dmu_buf_will_dirty(db, tx);
/* update caller's dbuf */
*dbp = db;
ASSERT3U(db->db_size, ==, sm->sm_blksz);
block_base = db->db_data;
block_cursor = block_base;
block_end = block_base +
(db->db_size / sizeof (uint64_t));
}
/*
* If we are writing a two-word entry and we only have one
* word left on this block, just pad it with an empty debug
* entry and write the two-word entry in the next block.
*/
uint64_t *next_entry = block_cursor + 1;
if (next_entry == block_end && words > 1) {
ASSERT3U(words, ==, 2);
*block_cursor = SM_PREFIX_ENCODE(SM_DEBUG_PREFIX) |
SM_DEBUG_ACTION_ENCODE(0) |
SM_DEBUG_SYNCPASS_ENCODE(0) |
SM_DEBUG_TXG_ENCODE(0);
block_cursor++;
sm->sm_phys->smp_length += sizeof (uint64_t);
ASSERT3P(block_cursor, ==, block_end);
continue;
}
uint64_t run_len = MIN(size, run_max);
switch (words) {
case 1:
*block_cursor = SM_OFFSET_ENCODE(start) |
SM_TYPE_ENCODE(maptype) |
SM_RUN_ENCODE(run_len);
block_cursor++;
break;
case 2:
/* write the first word of the entry */
*block_cursor = SM_PREFIX_ENCODE(SM2_PREFIX) |
SM2_RUN_ENCODE(run_len) |
SM2_VDEV_ENCODE(vdev_id);
block_cursor++;
/* move on to the second word of the entry */
ASSERT3P(block_cursor, <, block_end);
*block_cursor = SM2_TYPE_ENCODE(maptype) |
SM2_OFFSET_ENCODE(start);
block_cursor++;
break;
default:
panic("%d-word space map entries are not supported",
words);
break;
}
sm->sm_phys->smp_length += words * sizeof (uint64_t);
start += run_len;
size -= run_len;
}
ASSERT0(size);
}
/*
* Note: The space map's dbuf must be dirty for the changes in sm_phys to
* take effect.
*/
static void
space_map_write_impl(space_map_t *sm, range_tree_t *rt, maptype_t maptype,
uint64_t vdev_id, dmu_tx_t *tx)
{
spa_t *spa = tx->tx_pool->dp_spa;
dmu_buf_t *db;
space_map_write_intro_debug(sm, maptype, tx);
#ifdef DEBUG
/*
* We do this right after we write the intro debug entry
* because the estimate does not take it into account.
*/
uint64_t initial_objsize = sm->sm_phys->smp_length;
uint64_t estimated_growth =
space_map_estimate_optimal_size(sm, rt, SM_NO_VDEVID);
uint64_t estimated_final_objsize = initial_objsize + estimated_growth;
#endif
/*
* Find the offset right after the last word in the space map
* and use that to get a hold of the last block, so we can
* start appending to it.
*/
uint64_t next_word_offset = sm->sm_phys->smp_length;
VERIFY0(dmu_buf_hold(sm->sm_os, space_map_object(sm),
next_word_offset, FTAG, &db, DMU_READ_PREFETCH));
ASSERT3U(db->db_size, ==, sm->sm_blksz);
dmu_buf_will_dirty(db, tx);
avl_tree_t *t = &rt->rt_root;
for (range_seg_t *rs = avl_first(t); rs != NULL; rs = AVL_NEXT(t, rs)) {
uint64_t offset = (rs->rs_start - sm->sm_start) >> sm->sm_shift;
uint64_t length = (rs->rs_end - rs->rs_start) >> sm->sm_shift;
uint8_t words = 1;
/*
* We only write two-word entries when both of the following
* are true:
*
* [1] The feature is enabled.
* [2] The offset or run is too big for a single-word entry,
* or the vdev_id is set (meaning not equal to
* SM_NO_VDEVID).
*
* Note that for purposes of testing we've added the case that
* we write two-word entries occasionally when the feature is
* enabled and zfs_force_some_double_word_sm_entries has been
* set.
*/
if (spa_feature_is_active(spa, SPA_FEATURE_SPACEMAP_V2) &&
(offset >= (1ULL << SM_OFFSET_BITS) ||
length > SM_RUN_MAX ||
vdev_id != SM_NO_VDEVID ||
(zfs_force_some_double_word_sm_entries &&
spa_get_random(100) == 0)))
words = 2;
space_map_write_seg(sm, rs, maptype, vdev_id, words,
&db, FTAG, tx);
}
dmu_buf_rele(db, FTAG);
#ifdef DEBUG
/*
* We expect our estimation to be based on the worst case
* scenario [see comment in space_map_estimate_optimal_size()].
* Therefore we expect the actual objsize to be equal or less
* than whatever we estimated it to be.
*/
ASSERT3U(estimated_final_objsize, >=, sm->sm_phys->smp_length);
#endif
}
/*
* Note: This function manipulates the state of the given space map but
* does not hold any locks implicitly. Thus the caller is responsible
* for synchronizing writes to the space map.
*/
void
space_map_write(space_map_t *sm, range_tree_t *rt, maptype_t maptype,
uint64_t vdev_id, dmu_tx_t *tx)
{
ASSERT(dsl_pool_sync_context(dmu_objset_pool(sm->sm_os)));
VERIFY3U(space_map_object(sm), !=, 0);
dmu_buf_will_dirty(sm->sm_dbuf, tx);
/*
* This field is no longer necessary since the in-core space map
* now contains the object number but is maintained for backwards
* compatibility.
*/
sm->sm_phys->smp_object = sm->sm_object;
if (range_tree_is_empty(rt)) {
VERIFY3U(sm->sm_object, ==, sm->sm_phys->smp_object);
return;
}
if (maptype == SM_ALLOC)
sm->sm_phys->smp_alloc += range_tree_space(rt);
else
sm->sm_phys->smp_alloc -= range_tree_space(rt);
uint64_t nodes = avl_numnodes(&rt->rt_root);
uint64_t rt_space = range_tree_space(rt);
space_map_write_impl(sm, rt, maptype, vdev_id, tx);
/*
* Ensure that the space_map's accounting wasn't changed
* while we were in the middle of writing it out.
*/
VERIFY3U(nodes, ==, avl_numnodes(&rt->rt_root));
VERIFY3U(range_tree_space(rt), ==, rt_space);
}
static int
space_map_open_impl(space_map_t *sm)
{
int error;
u_longlong_t blocks;
error = dmu_bonus_hold(sm->sm_os, sm->sm_object, sm, &sm->sm_dbuf);
if (error)
return (error);
dmu_object_size_from_db(sm->sm_dbuf, &sm->sm_blksz, &blocks);
sm->sm_phys = sm->sm_dbuf->db_data;
return (0);
}
int
space_map_open(space_map_t **smp, objset_t *os, uint64_t object,
uint64_t start, uint64_t size, uint8_t shift)
{
space_map_t *sm;
int error;
ASSERT(*smp == NULL);
ASSERT(os != NULL);
ASSERT(object != 0);
sm = kmem_alloc(sizeof (space_map_t), KM_SLEEP);
sm->sm_start = start;
sm->sm_size = size;
sm->sm_shift = shift;
sm->sm_os = os;
sm->sm_object = object;
sm->sm_blksz = 0;
sm->sm_dbuf = NULL;
sm->sm_phys = NULL;
error = space_map_open_impl(sm);
if (error != 0) {
space_map_close(sm);
return (error);
}
*smp = sm;
return (0);
}
void
space_map_close(space_map_t *sm)
{
if (sm == NULL)
return;
if (sm->sm_dbuf != NULL)
dmu_buf_rele(sm->sm_dbuf, sm);
sm->sm_dbuf = NULL;
sm->sm_phys = NULL;
kmem_free(sm, sizeof (*sm));
}
void
space_map_truncate(space_map_t *sm, int blocksize, dmu_tx_t *tx)
{
objset_t *os = sm->sm_os;
spa_t *spa = dmu_objset_spa(os);
dmu_object_info_t doi;
ASSERT(dsl_pool_sync_context(dmu_objset_pool(os)));
ASSERT(dmu_tx_is_syncing(tx));
VERIFY3U(dmu_tx_get_txg(tx), <=, spa_final_dirty_txg(spa));
dmu_object_info_from_db(sm->sm_dbuf, &doi);
/*
* If the space map has the wrong bonus size (because
* SPA_FEATURE_SPACEMAP_HISTOGRAM has recently been enabled), or
* the wrong block size (because space_map_blksz has changed),
* free and re-allocate its object with the updated sizes.
*
* Otherwise, just truncate the current object.
*/
if ((spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM) &&
doi.doi_bonus_size != sizeof (space_map_phys_t)) ||
doi.doi_data_block_size != blocksize ||
doi.doi_metadata_block_size != 1 << space_map_ibs) {
zfs_dbgmsg("txg %llu, spa %s, sm %px, reallocating "
"object[%llu]: old bonus %u, old blocksz %u",
dmu_tx_get_txg(tx), spa_name(spa), sm, sm->sm_object,
doi.doi_bonus_size, doi.doi_data_block_size);
space_map_free(sm, tx);
dmu_buf_rele(sm->sm_dbuf, sm);
sm->sm_object = space_map_alloc(sm->sm_os, blocksize, tx);
VERIFY0(space_map_open_impl(sm));
} else {
VERIFY0(dmu_free_range(os, space_map_object(sm), 0, -1ULL, tx));
/*
* If the spacemap is reallocated, its histogram
* will be reset. Do the same in the common case so that
* bugs related to the uncommon case do not go unnoticed.
*/
bzero(sm->sm_phys->smp_histogram,
sizeof (sm->sm_phys->smp_histogram));
}
dmu_buf_will_dirty(sm->sm_dbuf, tx);
sm->sm_phys->smp_length = 0;
sm->sm_phys->smp_alloc = 0;
}
uint64_t
space_map_alloc(objset_t *os, int blocksize, dmu_tx_t *tx)
{
spa_t *spa = dmu_objset_spa(os);
uint64_t object;
int bonuslen;
if (spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM)) {
spa_feature_incr(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM, tx);
bonuslen = sizeof (space_map_phys_t);
ASSERT3U(bonuslen, <=, dmu_bonus_max());
} else {
bonuslen = SPACE_MAP_SIZE_V0;
}
object = dmu_object_alloc_ibs(os, DMU_OT_SPACE_MAP, blocksize,
space_map_ibs, DMU_OT_SPACE_MAP_HEADER, bonuslen, tx);
return (object);
}
void
space_map_free_obj(objset_t *os, uint64_t smobj, dmu_tx_t *tx)
{
spa_t *spa = dmu_objset_spa(os);
if (spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM)) {
dmu_object_info_t doi;
VERIFY0(dmu_object_info(os, smobj, &doi));
if (doi.doi_bonus_size != SPACE_MAP_SIZE_V0) {
spa_feature_decr(spa,
SPA_FEATURE_SPACEMAP_HISTOGRAM, tx);
}
}
VERIFY0(dmu_object_free(os, smobj, tx));
}
void
space_map_free(space_map_t *sm, dmu_tx_t *tx)
{
if (sm == NULL)
return;
space_map_free_obj(sm->sm_os, space_map_object(sm), tx);
sm->sm_object = 0;
}
/*
* Given a range tree, it makes a worst-case estimate of how much
* space would the tree's segments take if they were written to
* the given space map.
*/
uint64_t
space_map_estimate_optimal_size(space_map_t *sm, range_tree_t *rt,
uint64_t vdev_id)
{
spa_t *spa = dmu_objset_spa(sm->sm_os);
uint64_t shift = sm->sm_shift;
uint64_t *histogram = rt->rt_histogram;
uint64_t entries_for_seg = 0;
/*
* In order to get a quick estimate of the optimal size that this
* range tree would have on-disk as a space map, we iterate through
* its histogram buckets instead of iterating through its nodes.
*
* Note that this is a highest-bound/worst-case estimate for the
* following reasons:
*
* 1] We assume that we always add a debug padding for each block
* we write and we also assume that we start at the last word
* of a block attempting to write a two-word entry.
* 2] Rounding up errors due to the way segments are distributed
* in the buckets of the range tree's histogram.
* 3] The activation of zfs_force_some_double_word_sm_entries
* (tunable) when testing.
*
* = Math and Rounding Errors =
*
* rt_histogram[i] bucket of a range tree represents the number
* of entries in [2^i, (2^(i+1))-1] of that range_tree. Given
* that, we want to divide the buckets into groups: Buckets that
* can be represented using a single-word entry, ones that can
* be represented with a double-word entry, and ones that can
* only be represented with multiple two-word entries.
*
* [Note that if the new encoding feature is not enabled there
* are only two groups: single-word entry buckets and multiple
* single-word entry buckets. The information below assumes
* two-word entries enabled, but it can easily applied when
* the feature is not enabled]
*
* To find the highest bucket that can be represented with a
* single-word entry we look at the maximum run that such entry
* can have, which is 2^(SM_RUN_BITS + sm_shift) [remember that
* the run of a space map entry is shifted by sm_shift, thus we
* add it to the exponent]. This way, excluding the value of the
* maximum run that can be represented by a single-word entry,
* all runs that are smaller exist in buckets 0 to
* SM_RUN_BITS + shift - 1.
*
* To find the highest bucket that can be represented with a
* double-word entry, we follow the same approach. Finally, any
* bucket higher than that are represented with multiple two-word
* entries. To be more specific, if the highest bucket whose
* segments can be represented with a single two-word entry is X,
* then bucket X+1 will need 2 two-word entries for each of its
* segments, X+2 will need 4, X+3 will need 8, ...etc.
*
* With all of the above we make our estimation based on bucket
* groups. There is a rounding error though. As we mentioned in
* the example with the one-word entry, the maximum run that can
* be represented in a one-word entry 2^(SM_RUN_BITS + shift) is
* not part of bucket SM_RUN_BITS + shift - 1. Thus, segments of
* that length fall into the next bucket (and bucket group) where
* we start counting two-word entries and this is one more reason
* why the estimated size may end up being bigger than the actual
* size written.
*/
uint64_t size = 0;
uint64_t idx = 0;
if (!spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_V2) ||
(vdev_id == SM_NO_VDEVID && sm->sm_size < SM_OFFSET_MAX)) {
/*
* If we are trying to force some double word entries just
* assume the worst-case of every single word entry being
* written as a double word entry.
*/
uint64_t entry_size =
(spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_V2) &&
zfs_force_some_double_word_sm_entries) ?
(2 * sizeof (uint64_t)) : sizeof (uint64_t);
uint64_t single_entry_max_bucket = SM_RUN_BITS + shift - 1;
for (; idx <= single_entry_max_bucket; idx++)
size += histogram[idx] * entry_size;
if (!spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_V2)) {
for (; idx < RANGE_TREE_HISTOGRAM_SIZE; idx++) {
ASSERT3U(idx, >=, single_entry_max_bucket);
entries_for_seg =
1ULL << (idx - single_entry_max_bucket);
size += histogram[idx] *
entries_for_seg * entry_size;
}
return (size);
}
}
ASSERT(spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_V2));
uint64_t double_entry_max_bucket = SM2_RUN_BITS + shift - 1;
for (; idx <= double_entry_max_bucket; idx++)
size += histogram[idx] * 2 * sizeof (uint64_t);
for (; idx < RANGE_TREE_HISTOGRAM_SIZE; idx++) {
ASSERT3U(idx, >=, double_entry_max_bucket);
entries_for_seg = 1ULL << (idx - double_entry_max_bucket);
size += histogram[idx] *
entries_for_seg * 2 * sizeof (uint64_t);
}
/*
* Assume the worst case where we start with the padding at the end
* of the current block and we add an extra padding entry at the end
* of all subsequent blocks.
*/
size += ((size / sm->sm_blksz) + 1) * sizeof (uint64_t);
return (size);
}
uint64_t
space_map_object(space_map_t *sm)
{
return (sm != NULL ? sm->sm_object : 0);
}
int64_t
space_map_allocated(space_map_t *sm)
{
return (sm != NULL ? sm->sm_phys->smp_alloc : 0);
}
uint64_t
space_map_length(space_map_t *sm)
{
return (sm != NULL ? sm->sm_phys->smp_length : 0);
}