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zfs/module/zfs/vdev_indirect.c

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/*
* CDDL HEADER START
*
* This file and its contents are supplied under the terms of the
* Common Development and Distribution License ("CDDL"), version 1.0.
* You may only use this file in accordance with the terms of version
* 1.0 of the CDDL.
*
* A full copy of the text of the CDDL should have accompanied this
* source. A copy of the CDDL is also available via the Internet at
* http://www.illumos.org/license/CDDL.
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2014, 2017 by Delphix. All rights reserved.
* Copyright (c) 2019, loli10K <ezomori.nozomu@gmail.com>. All rights reserved.
* Copyright (c) 2014, 2020 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/vdev_impl.h>
#include <sys/fs/zfs.h>
#include <sys/zio.h>
#include <sys/zio_checksum.h>
#include <sys/metaslab.h>
#include <sys/dmu.h>
#include <sys/vdev_indirect_mapping.h>
#include <sys/dmu_tx.h>
#include <sys/dsl_synctask.h>
#include <sys/zap.h>
#include <sys/abd.h>
#include <sys/zthr.h>
/*
* An indirect vdev corresponds to a vdev that has been removed. Since
* we cannot rewrite block pointers of snapshots, etc., we keep a
* mapping from old location on the removed device to the new location
* on another device in the pool and use this mapping whenever we need
* to access the DVA. Unfortunately, this mapping did not respect
* logical block boundaries when it was first created, and so a DVA on
* this indirect vdev may be "split" into multiple sections that each
* map to a different location. As a consequence, not all DVAs can be
* translated to an equivalent new DVA. Instead we must provide a
* "vdev_remap" operation that executes a callback on each contiguous
* segment of the new location. This function is used in multiple ways:
*
* - i/os to this vdev use the callback to determine where the
* data is now located, and issue child i/os for each segment's new
* location.
*
* - frees and claims to this vdev use the callback to free or claim
* each mapped segment. (Note that we don't actually need to claim
* log blocks on indirect vdevs, because we don't allocate to
* removing vdevs. However, zdb uses zio_claim() for its leak
* detection.)
*/
/*
* "Big theory statement" for how we mark blocks obsolete.
*
* When a block on an indirect vdev is freed or remapped, a section of
* that vdev's mapping may no longer be referenced (aka "obsolete"). We
* keep track of how much of each mapping entry is obsolete. When
* an entry becomes completely obsolete, we can remove it, thus reducing
* the memory used by the mapping. The complete picture of obsolescence
* is given by the following data structures, described below:
* - the entry-specific obsolete count
* - the vdev-specific obsolete spacemap
* - the pool-specific obsolete bpobj
*
* == On disk data structures used ==
*
* We track the obsolete space for the pool using several objects. Each
* of these objects is created on demand and freed when no longer
* needed, and is assumed to be empty if it does not exist.
* SPA_FEATURE_OBSOLETE_COUNTS includes the count of these objects.
*
* - Each vic_mapping_object (associated with an indirect vdev) can
* have a vimp_counts_object. This is an array of uint32_t's
* with the same number of entries as the vic_mapping_object. When
* the mapping is condensed, entries from the vic_obsolete_sm_object
* (see below) are folded into the counts. Therefore, each
* obsolete_counts entry tells us the number of bytes in the
* corresponding mapping entry that were not referenced when the
* mapping was last condensed.
*
* - Each indirect or removing vdev can have a vic_obsolete_sm_object.
* This is a space map containing an alloc entry for every DVA that
* has been obsoleted since the last time this indirect vdev was
* condensed. We use this object in order to improve performance
* when marking a DVA as obsolete. Instead of modifying an arbitrary
* offset of the vimp_counts_object, we only need to append an entry
* to the end of this object. When a DVA becomes obsolete, it is
* added to the obsolete space map. This happens when the DVA is
* freed, remapped and not referenced by a snapshot, or the last
* snapshot referencing it is destroyed.
*
* - Each dataset can have a ds_remap_deadlist object. This is a
* deadlist object containing all blocks that were remapped in this
* dataset but referenced in a previous snapshot. Blocks can *only*
* appear on this list if they were remapped (dsl_dataset_block_remapped);
* blocks that were killed in a head dataset are put on the normal
* ds_deadlist and marked obsolete when they are freed.
*
* - The pool can have a dp_obsolete_bpobj. This is a list of blocks
* in the pool that need to be marked obsolete. When a snapshot is
* destroyed, we move some of the ds_remap_deadlist to the obsolete
* bpobj (see dsl_destroy_snapshot_handle_remaps()). We then
* asynchronously process the obsolete bpobj, moving its entries to
* the specific vdevs' obsolete space maps.
*
* == Summary of how we mark blocks as obsolete ==
*
* - When freeing a block: if any DVA is on an indirect vdev, append to
* vic_obsolete_sm_object.
* - When remapping a block, add dva to ds_remap_deadlist (if prev snap
* references; otherwise append to vic_obsolete_sm_object).
* - When freeing a snapshot: move parts of ds_remap_deadlist to
* dp_obsolete_bpobj (same algorithm as ds_deadlist).
* - When syncing the spa: process dp_obsolete_bpobj, moving ranges to
* individual vdev's vic_obsolete_sm_object.
*/
/*
* "Big theory statement" for how we condense indirect vdevs.
*
* Condensing an indirect vdev's mapping is the process of determining
* the precise counts of obsolete space for each mapping entry (by
* integrating the obsolete spacemap into the obsolete counts) and
* writing out a new mapping that contains only referenced entries.
*
* We condense a vdev when we expect the mapping to shrink (see
* vdev_indirect_should_condense()), but only perform one condense at a
* time to limit the memory usage. In addition, we use a separate
* open-context thread (spa_condense_indirect_thread) to incrementally
* create the new mapping object in a way that minimizes the impact on
* the rest of the system.
*
* == Generating a new mapping ==
*
* To generate a new mapping, we follow these steps:
*
* 1. Save the old obsolete space map and create a new mapping object
* (see spa_condense_indirect_start_sync()). This initializes the
* spa_condensing_indirect_phys with the "previous obsolete space map",
* which is now read only. Newly obsolete DVAs will be added to a
* new (initially empty) obsolete space map, and will not be
* considered as part of this condense operation.
*
* 2. Construct in memory the precise counts of obsolete space for each
* mapping entry, by incorporating the obsolete space map into the
* counts. (See vdev_indirect_mapping_load_obsolete_{counts,spacemap}().)
*
* 3. Iterate through each mapping entry, writing to the new mapping any
* entries that are not completely obsolete (i.e. which don't have
* obsolete count == mapping length). (See
* spa_condense_indirect_generate_new_mapping().)
*
* 4. Destroy the old mapping object and switch over to the new one
* (spa_condense_indirect_complete_sync).
*
* == Restarting from failure ==
*
* To restart the condense when we import/open the pool, we must start
* at the 2nd step above: reconstruct the precise counts in memory,
* based on the space map + counts. Then in the 3rd step, we start
* iterating where we left off: at vimp_max_offset of the new mapping
* object.
*/
int zfs_condense_indirect_vdevs_enable = B_TRUE;
/*
* Condense if at least this percent of the bytes in the mapping is
* obsolete. With the default of 25%, the amount of space mapped
* will be reduced to 1% of its original size after at most 16
* condenses. Higher values will condense less often (causing less
* i/o); lower values will reduce the mapping size more quickly.
*/
int zfs_condense_indirect_obsolete_pct = 25;
/*
* Condense if the obsolete space map takes up more than this amount of
* space on disk (logically). This limits the amount of disk space
* consumed by the obsolete space map; the default of 1GB is small enough
* that we typically don't mind "wasting" it.
*/
unsigned long zfs_condense_max_obsolete_bytes = 1024 * 1024 * 1024;
/*
* Don't bother condensing if the mapping uses less than this amount of
* memory. The default of 128KB is considered a "trivial" amount of
* memory and not worth reducing.
*/
unsigned long zfs_condense_min_mapping_bytes = 128 * 1024;
/*
* This is used by the test suite so that it can ensure that certain
* actions happen while in the middle of a condense (which might otherwise
* complete too quickly). If used to reduce the performance impact of
* condensing in production, a maximum value of 1 should be sufficient.
*/
int zfs_condense_indirect_commit_entry_delay_ms = 0;
/*
* If an indirect split block contains more than this many possible unique
* combinations when being reconstructed, consider it too computationally
* expensive to check them all. Instead, try at most 100 randomly-selected
* combinations each time the block is accessed. This allows all segment
* copies to participate fairly in the reconstruction when all combinations
* cannot be checked and prevents repeated use of one bad copy.
*/
int zfs_reconstruct_indirect_combinations_max = 4096;
/*
* Enable to simulate damaged segments and validate reconstruction. This
* is intentionally not exposed as a module parameter.
*/
unsigned long zfs_reconstruct_indirect_damage_fraction = 0;
/*
* The indirect_child_t represents the vdev that we will read from, when we
* need to read all copies of the data (e.g. for scrub or reconstruction).
* For plain (non-mirror) top-level vdevs (i.e. is_vdev is not a mirror),
* ic_vdev is the same as is_vdev. However, for mirror top-level vdevs,
* ic_vdev is a child of the mirror.
*/
typedef struct indirect_child {
abd_t *ic_data;
vdev_t *ic_vdev;
/*
* ic_duplicate is NULL when the ic_data contents are unique, when it
* is determined to be a duplicate it references the primary child.
*/
struct indirect_child *ic_duplicate;
list_node_t ic_node; /* node on is_unique_child */
int ic_error; /* set when a child does not contain the data */
} indirect_child_t;
/*
* The indirect_split_t represents one mapped segment of an i/o to the
* indirect vdev. For non-split (contiguously-mapped) blocks, there will be
* only one indirect_split_t, with is_split_offset==0 and is_size==io_size.
* For split blocks, there will be several of these.
*/
typedef struct indirect_split {
list_node_t is_node; /* link on iv_splits */
/*
* is_split_offset is the offset into the i/o.
* This is the sum of the previous splits' is_size's.
*/
uint64_t is_split_offset;
vdev_t *is_vdev; /* top-level vdev */
uint64_t is_target_offset; /* offset on is_vdev */
uint64_t is_size;
int is_children; /* number of entries in is_child[] */
int is_unique_children; /* number of entries in is_unique_child */
list_t is_unique_child;
/*
* is_good_child is the child that we are currently using to
* attempt reconstruction.
*/
indirect_child_t *is_good_child;
indirect_child_t is_child[1]; /* variable-length */
} indirect_split_t;
/*
* The indirect_vsd_t is associated with each i/o to the indirect vdev.
* It is the "Vdev-Specific Data" in the zio_t's io_vsd.
*/
typedef struct indirect_vsd {
boolean_t iv_split_block;
boolean_t iv_reconstruct;
uint64_t iv_unique_combinations;
uint64_t iv_attempts;
uint64_t iv_attempts_max;
list_t iv_splits; /* list of indirect_split_t's */
} indirect_vsd_t;
static void
vdev_indirect_map_free(zio_t *zio)
{
indirect_vsd_t *iv = zio->io_vsd;
indirect_split_t *is;
while ((is = list_head(&iv->iv_splits)) != NULL) {
for (int c = 0; c < is->is_children; c++) {
indirect_child_t *ic = &is->is_child[c];
if (ic->ic_data != NULL)
abd_free(ic->ic_data);
}
list_remove(&iv->iv_splits, is);
indirect_child_t *ic;
while ((ic = list_head(&is->is_unique_child)) != NULL)
list_remove(&is->is_unique_child, ic);
list_destroy(&is->is_unique_child);
kmem_free(is,
offsetof(indirect_split_t, is_child[is->is_children]));
}
kmem_free(iv, sizeof (*iv));
}
static const zio_vsd_ops_t vdev_indirect_vsd_ops = {
.vsd_free = vdev_indirect_map_free,
};
/*
* Mark the given offset and size as being obsolete.
*/
void
vdev_indirect_mark_obsolete(vdev_t *vd, uint64_t offset, uint64_t size)
{
spa_t *spa = vd->vdev_spa;
ASSERT3U(vd->vdev_indirect_config.vic_mapping_object, !=, 0);
ASSERT(vd->vdev_removing || vd->vdev_ops == &vdev_indirect_ops);
ASSERT(size > 0);
VERIFY(vdev_indirect_mapping_entry_for_offset(
vd->vdev_indirect_mapping, offset) != NULL);
if (spa_feature_is_enabled(spa, SPA_FEATURE_OBSOLETE_COUNTS)) {
mutex_enter(&vd->vdev_obsolete_lock);
range_tree_add(vd->vdev_obsolete_segments, offset, size);
mutex_exit(&vd->vdev_obsolete_lock);
vdev_dirty(vd, 0, NULL, spa_syncing_txg(spa));
}
}
/*
* Mark the DVA vdev_id:offset:size as being obsolete in the given tx. This
* wrapper is provided because the DMU does not know about vdev_t's and
* cannot directly call vdev_indirect_mark_obsolete.
*/
void
spa_vdev_indirect_mark_obsolete(spa_t *spa, uint64_t vdev_id, uint64_t offset,
uint64_t size, dmu_tx_t *tx)
{
vdev_t *vd = vdev_lookup_top(spa, vdev_id);
ASSERT(dmu_tx_is_syncing(tx));
/* The DMU can only remap indirect vdevs. */
ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops);
vdev_indirect_mark_obsolete(vd, offset, size);
}
static spa_condensing_indirect_t *
spa_condensing_indirect_create(spa_t *spa)
{
spa_condensing_indirect_phys_t *scip =
&spa->spa_condensing_indirect_phys;
spa_condensing_indirect_t *sci = kmem_zalloc(sizeof (*sci), KM_SLEEP);
objset_t *mos = spa->spa_meta_objset;
for (int i = 0; i < TXG_SIZE; i++) {
list_create(&sci->sci_new_mapping_entries[i],
sizeof (vdev_indirect_mapping_entry_t),
offsetof(vdev_indirect_mapping_entry_t, vime_node));
}
sci->sci_new_mapping =
vdev_indirect_mapping_open(mos, scip->scip_next_mapping_object);
return (sci);
}
static void
spa_condensing_indirect_destroy(spa_condensing_indirect_t *sci)
{
for (int i = 0; i < TXG_SIZE; i++)
list_destroy(&sci->sci_new_mapping_entries[i]);
if (sci->sci_new_mapping != NULL)
vdev_indirect_mapping_close(sci->sci_new_mapping);
kmem_free(sci, sizeof (*sci));
}
boolean_t
vdev_indirect_should_condense(vdev_t *vd)
{
vdev_indirect_mapping_t *vim = vd->vdev_indirect_mapping;
spa_t *spa = vd->vdev_spa;
ASSERT(dsl_pool_sync_context(spa->spa_dsl_pool));
if (!zfs_condense_indirect_vdevs_enable)
return (B_FALSE);
/*
* We can only condense one indirect vdev at a time.
*/
if (spa->spa_condensing_indirect != NULL)
return (B_FALSE);
if (spa_shutting_down(spa))
return (B_FALSE);
/*
* The mapping object size must not change while we are
* condensing, so we can only condense indirect vdevs
* (not vdevs that are still in the middle of being removed).
*/
if (vd->vdev_ops != &vdev_indirect_ops)
return (B_FALSE);
/*
* If nothing new has been marked obsolete, there is no
* point in condensing.
*/
uint64_t obsolete_sm_obj __maybe_unused;
ASSERT0(vdev_obsolete_sm_object(vd, &obsolete_sm_obj));
if (vd->vdev_obsolete_sm == NULL) {
ASSERT0(obsolete_sm_obj);
return (B_FALSE);
}
ASSERT(vd->vdev_obsolete_sm != NULL);
ASSERT3U(obsolete_sm_obj, ==, space_map_object(vd->vdev_obsolete_sm));
uint64_t bytes_mapped = vdev_indirect_mapping_bytes_mapped(vim);
uint64_t bytes_obsolete = space_map_allocated(vd->vdev_obsolete_sm);
uint64_t mapping_size = vdev_indirect_mapping_size(vim);
uint64_t obsolete_sm_size = space_map_length(vd->vdev_obsolete_sm);
ASSERT3U(bytes_obsolete, <=, bytes_mapped);
/*
* If a high percentage of the bytes that are mapped have become
* obsolete, condense (unless the mapping is already small enough).
* This has a good chance of reducing the amount of memory used
* by the mapping.
*/
if (bytes_obsolete * 100 / bytes_mapped >=
zfs_condense_indirect_obsolete_pct &&
mapping_size > zfs_condense_min_mapping_bytes) {
zfs_dbgmsg("should condense vdev %llu because obsolete "
"spacemap covers %d%% of %lluMB mapping",
(u_longlong_t)vd->vdev_id,
(int)(bytes_obsolete * 100 / bytes_mapped),
(u_longlong_t)bytes_mapped / 1024 / 1024);
return (B_TRUE);
}
/*
* If the obsolete space map takes up too much space on disk,
* condense in order to free up this disk space.
*/
if (obsolete_sm_size >= zfs_condense_max_obsolete_bytes) {
zfs_dbgmsg("should condense vdev %llu because obsolete sm "
"length %lluMB >= max size %lluMB",
(u_longlong_t)vd->vdev_id,
(u_longlong_t)obsolete_sm_size / 1024 / 1024,
(u_longlong_t)zfs_condense_max_obsolete_bytes /
1024 / 1024);
return (B_TRUE);
}
return (B_FALSE);
}
/*
* This sync task completes (finishes) a condense, deleting the old
* mapping and replacing it with the new one.
*/
static void
spa_condense_indirect_complete_sync(void *arg, dmu_tx_t *tx)
{
spa_condensing_indirect_t *sci = arg;
spa_t *spa = dmu_tx_pool(tx)->dp_spa;
spa_condensing_indirect_phys_t *scip =
&spa->spa_condensing_indirect_phys;
vdev_t *vd = vdev_lookup_top(spa, scip->scip_vdev);
vdev_indirect_config_t *vic = &vd->vdev_indirect_config;
objset_t *mos = spa->spa_meta_objset;
vdev_indirect_mapping_t *old_mapping = vd->vdev_indirect_mapping;
uint64_t old_count = vdev_indirect_mapping_num_entries(old_mapping);
uint64_t new_count =
vdev_indirect_mapping_num_entries(sci->sci_new_mapping);
ASSERT(dmu_tx_is_syncing(tx));
ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops);
ASSERT3P(sci, ==, spa->spa_condensing_indirect);
for (int i = 0; i < TXG_SIZE; i++) {
ASSERT(list_is_empty(&sci->sci_new_mapping_entries[i]));
}
ASSERT(vic->vic_mapping_object != 0);
ASSERT3U(vd->vdev_id, ==, scip->scip_vdev);
ASSERT(scip->scip_next_mapping_object != 0);
ASSERT(scip->scip_prev_obsolete_sm_object != 0);
/*
* Reset vdev_indirect_mapping to refer to the new object.
*/
rw_enter(&vd->vdev_indirect_rwlock, RW_WRITER);
vdev_indirect_mapping_close(vd->vdev_indirect_mapping);
vd->vdev_indirect_mapping = sci->sci_new_mapping;
rw_exit(&vd->vdev_indirect_rwlock);
sci->sci_new_mapping = NULL;
vdev_indirect_mapping_free(mos, vic->vic_mapping_object, tx);
vic->vic_mapping_object = scip->scip_next_mapping_object;
scip->scip_next_mapping_object = 0;
space_map_free_obj(mos, scip->scip_prev_obsolete_sm_object, tx);
spa_feature_decr(spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
scip->scip_prev_obsolete_sm_object = 0;
scip->scip_vdev = 0;
VERIFY0(zap_remove(mos, DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_CONDENSING_INDIRECT, tx));
spa_condensing_indirect_destroy(spa->spa_condensing_indirect);
spa->spa_condensing_indirect = NULL;
zfs_dbgmsg("finished condense of vdev %llu in txg %llu: "
"new mapping object %llu has %llu entries "
"(was %llu entries)",
(u_longlong_t)vd->vdev_id, (u_longlong_t)dmu_tx_get_txg(tx),
(u_longlong_t)vic->vic_mapping_object,
(u_longlong_t)new_count, (u_longlong_t)old_count);
vdev_config_dirty(spa->spa_root_vdev);
}
/*
* This sync task appends entries to the new mapping object.
*/
static void
spa_condense_indirect_commit_sync(void *arg, dmu_tx_t *tx)
{
spa_condensing_indirect_t *sci = arg;
uint64_t txg = dmu_tx_get_txg(tx);
spa_t *spa __maybe_unused = dmu_tx_pool(tx)->dp_spa;
ASSERT(dmu_tx_is_syncing(tx));
ASSERT3P(sci, ==, spa->spa_condensing_indirect);
vdev_indirect_mapping_add_entries(sci->sci_new_mapping,
&sci->sci_new_mapping_entries[txg & TXG_MASK], tx);
ASSERT(list_is_empty(&sci->sci_new_mapping_entries[txg & TXG_MASK]));
}
/*
* Open-context function to add one entry to the new mapping. The new
* entry will be remembered and written from syncing context.
*/
static void
spa_condense_indirect_commit_entry(spa_t *spa,
vdev_indirect_mapping_entry_phys_t *vimep, uint32_t count)
{
spa_condensing_indirect_t *sci = spa->spa_condensing_indirect;
ASSERT3U(count, <, DVA_GET_ASIZE(&vimep->vimep_dst));
dmu_tx_t *tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir);
dmu_tx_hold_space(tx, sizeof (*vimep) + sizeof (count));
VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
int txgoff = dmu_tx_get_txg(tx) & TXG_MASK;
/*
* If we are the first entry committed this txg, kick off the sync
* task to write to the MOS on our behalf.
*/
if (list_is_empty(&sci->sci_new_mapping_entries[txgoff])) {
dsl_sync_task_nowait(dmu_tx_pool(tx),
spa_condense_indirect_commit_sync, sci, tx);
}
vdev_indirect_mapping_entry_t *vime =
kmem_alloc(sizeof (*vime), KM_SLEEP);
vime->vime_mapping = *vimep;
vime->vime_obsolete_count = count;
list_insert_tail(&sci->sci_new_mapping_entries[txgoff], vime);
dmu_tx_commit(tx);
}
static void
spa_condense_indirect_generate_new_mapping(vdev_t *vd,
uint32_t *obsolete_counts, uint64_t start_index, zthr_t *zthr)
{
spa_t *spa = vd->vdev_spa;
uint64_t mapi = start_index;
vdev_indirect_mapping_t *old_mapping = vd->vdev_indirect_mapping;
uint64_t old_num_entries =
vdev_indirect_mapping_num_entries(old_mapping);
ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops);
ASSERT3U(vd->vdev_id, ==, spa->spa_condensing_indirect_phys.scip_vdev);
zfs_dbgmsg("starting condense of vdev %llu from index %llu",
(u_longlong_t)vd->vdev_id,
(u_longlong_t)mapi);
while (mapi < old_num_entries) {
if (zthr_iscancelled(zthr)) {
zfs_dbgmsg("pausing condense of vdev %llu "
"at index %llu", (u_longlong_t)vd->vdev_id,
(u_longlong_t)mapi);
break;
}
vdev_indirect_mapping_entry_phys_t *entry =
&old_mapping->vim_entries[mapi];
uint64_t entry_size = DVA_GET_ASIZE(&entry->vimep_dst);
ASSERT3U(obsolete_counts[mapi], <=, entry_size);
if (obsolete_counts[mapi] < entry_size) {
spa_condense_indirect_commit_entry(spa, entry,
obsolete_counts[mapi]);
/*
* This delay may be requested for testing, debugging,
* or performance reasons.
*/
hrtime_t now = gethrtime();
hrtime_t sleep_until = now + MSEC2NSEC(
zfs_condense_indirect_commit_entry_delay_ms);
zfs_sleep_until(sleep_until);
}
mapi++;
}
}
static boolean_t
spa_condense_indirect_thread_check(void *arg, zthr_t *zthr)
{
(void) zthr;
spa_t *spa = arg;
return (spa->spa_condensing_indirect != NULL);
}
static void
spa_condense_indirect_thread(void *arg, zthr_t *zthr)
{
spa_t *spa = arg;
vdev_t *vd;
ASSERT3P(spa->spa_condensing_indirect, !=, NULL);
spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
vd = vdev_lookup_top(spa, spa->spa_condensing_indirect_phys.scip_vdev);
ASSERT3P(vd, !=, NULL);
spa_config_exit(spa, SCL_VDEV, FTAG);
spa_condensing_indirect_t *sci = spa->spa_condensing_indirect;
spa_condensing_indirect_phys_t *scip =
&spa->spa_condensing_indirect_phys;
uint32_t *counts;
uint64_t start_index;
vdev_indirect_mapping_t *old_mapping = vd->vdev_indirect_mapping;
space_map_t *prev_obsolete_sm = NULL;
ASSERT3U(vd->vdev_id, ==, scip->scip_vdev);
ASSERT(scip->scip_next_mapping_object != 0);
ASSERT(scip->scip_prev_obsolete_sm_object != 0);
ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops);
for (int i = 0; i < TXG_SIZE; i++) {
/*
* The list must start out empty in order for the
* _commit_sync() sync task to be properly registered
* on the first call to _commit_entry(); so it's wise
* to double check and ensure we actually are starting
* with empty lists.
*/
ASSERT(list_is_empty(&sci->sci_new_mapping_entries[i]));
}
VERIFY0(space_map_open(&prev_obsolete_sm, spa->spa_meta_objset,
scip->scip_prev_obsolete_sm_object, 0, vd->vdev_asize, 0));
counts = vdev_indirect_mapping_load_obsolete_counts(old_mapping);
if (prev_obsolete_sm != NULL) {
vdev_indirect_mapping_load_obsolete_spacemap(old_mapping,
counts, prev_obsolete_sm);
}
space_map_close(prev_obsolete_sm);
/*
* Generate new mapping. Determine what index to continue from
* based on the max offset that we've already written in the
* new mapping.
*/
uint64_t max_offset =
vdev_indirect_mapping_max_offset(sci->sci_new_mapping);
if (max_offset == 0) {
/* We haven't written anything to the new mapping yet. */
start_index = 0;
} else {
/*
* Pick up from where we left off. _entry_for_offset()
* returns a pointer into the vim_entries array. If
* max_offset is greater than any of the mappings
* contained in the table NULL will be returned and
* that indicates we've exhausted our iteration of the
* old_mapping.
*/
vdev_indirect_mapping_entry_phys_t *entry =
vdev_indirect_mapping_entry_for_offset_or_next(old_mapping,
max_offset);
if (entry == NULL) {
/*
* We've already written the whole new mapping.
* This special value will cause us to skip the
* generate_new_mapping step and just do the sync
* task to complete the condense.
*/
start_index = UINT64_MAX;
} else {
start_index = entry - old_mapping->vim_entries;
ASSERT3U(start_index, <,
vdev_indirect_mapping_num_entries(old_mapping));
}
}
spa_condense_indirect_generate_new_mapping(vd, counts,
start_index, zthr);
vdev_indirect_mapping_free_obsolete_counts(old_mapping, counts);
/*
* If the zthr has received a cancellation signal while running
* in generate_new_mapping() or at any point after that, then bail
* early. We don't want to complete the condense if the spa is
* shutting down.
*/
if (zthr_iscancelled(zthr))
return;
VERIFY0(dsl_sync_task(spa_name(spa), NULL,
spa_condense_indirect_complete_sync, sci, 0,
ZFS_SPACE_CHECK_EXTRA_RESERVED));
}
/*
* Sync task to begin the condensing process.
*/
void
spa_condense_indirect_start_sync(vdev_t *vd, dmu_tx_t *tx)
{
spa_t *spa = vd->vdev_spa;
spa_condensing_indirect_phys_t *scip =
&spa->spa_condensing_indirect_phys;
ASSERT0(scip->scip_next_mapping_object);
ASSERT0(scip->scip_prev_obsolete_sm_object);
ASSERT0(scip->scip_vdev);
ASSERT(dmu_tx_is_syncing(tx));
ASSERT3P(vd->vdev_ops, ==, &vdev_indirect_ops);
ASSERT(spa_feature_is_active(spa, SPA_FEATURE_OBSOLETE_COUNTS));
ASSERT(vdev_indirect_mapping_num_entries(vd->vdev_indirect_mapping));
uint64_t obsolete_sm_obj;
VERIFY0(vdev_obsolete_sm_object(vd, &obsolete_sm_obj));
ASSERT3U(obsolete_sm_obj, !=, 0);
scip->scip_vdev = vd->vdev_id;
scip->scip_next_mapping_object =
vdev_indirect_mapping_alloc(spa->spa_meta_objset, tx);
scip->scip_prev_obsolete_sm_object = obsolete_sm_obj;
/*
* We don't need to allocate a new space map object, since
* vdev_indirect_sync_obsolete will allocate one when needed.
*/
space_map_close(vd->vdev_obsolete_sm);
vd->vdev_obsolete_sm = NULL;
VERIFY0(zap_remove(spa->spa_meta_objset, vd->vdev_top_zap,
VDEV_TOP_ZAP_INDIRECT_OBSOLETE_SM, tx));
VERIFY0(zap_add(spa->spa_dsl_pool->dp_meta_objset,
DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_CONDENSING_INDIRECT, sizeof (uint64_t),
sizeof (*scip) / sizeof (uint64_t), scip, tx));
ASSERT3P(spa->spa_condensing_indirect, ==, NULL);
spa->spa_condensing_indirect = spa_condensing_indirect_create(spa);
zfs_dbgmsg("starting condense of vdev %llu in txg %llu: "
"posm=%llu nm=%llu",
(u_longlong_t)vd->vdev_id, (u_longlong_t)dmu_tx_get_txg(tx),
(u_longlong_t)scip->scip_prev_obsolete_sm_object,
(u_longlong_t)scip->scip_next_mapping_object);
zthr_wakeup(spa->spa_condense_zthr);
}
/*
* Sync to the given vdev's obsolete space map any segments that are no longer
* referenced as of the given txg.
*
* If the obsolete space map doesn't exist yet, create and open it.
*/
void
vdev_indirect_sync_obsolete(vdev_t *vd, dmu_tx_t *tx)
{
spa_t *spa = vd->vdev_spa;
vdev_indirect_config_t *vic __maybe_unused = &vd->vdev_indirect_config;
ASSERT3U(vic->vic_mapping_object, !=, 0);
ASSERT(range_tree_space(vd->vdev_obsolete_segments) > 0);
ASSERT(vd->vdev_removing || vd->vdev_ops == &vdev_indirect_ops);
ASSERT(spa_feature_is_enabled(spa, SPA_FEATURE_OBSOLETE_COUNTS));
uint64_t obsolete_sm_object;
VERIFY0(vdev_obsolete_sm_object(vd, &obsolete_sm_object));
if (obsolete_sm_object == 0) {
obsolete_sm_object = space_map_alloc(spa->spa_meta_objset,
zfs_vdev_standard_sm_blksz, tx);
ASSERT(vd->vdev_top_zap != 0);
VERIFY0(zap_add(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap,
VDEV_TOP_ZAP_INDIRECT_OBSOLETE_SM,
sizeof (obsolete_sm_object), 1, &obsolete_sm_object, tx));
ASSERT0(vdev_obsolete_sm_object(vd, &obsolete_sm_object));
ASSERT3U(obsolete_sm_object, !=, 0);
spa_feature_incr(spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
VERIFY0(space_map_open(&vd->vdev_obsolete_sm,
spa->spa_meta_objset, obsolete_sm_object,
0, vd->vdev_asize, 0));
}
ASSERT(vd->vdev_obsolete_sm != NULL);
ASSERT3U(obsolete_sm_object, ==,
space_map_object(vd->vdev_obsolete_sm));
space_map_write(vd->vdev_obsolete_sm,
vd->vdev_obsolete_segments, SM_ALLOC, SM_NO_VDEVID, tx);
range_tree_vacate(vd->vdev_obsolete_segments, NULL, NULL);
}
int
spa_condense_init(spa_t *spa)
{
int error = zap_lookup(spa->spa_meta_objset,
DMU_POOL_DIRECTORY_OBJECT,
DMU_POOL_CONDENSING_INDIRECT, sizeof (uint64_t),
sizeof (spa->spa_condensing_indirect_phys) / sizeof (uint64_t),
&spa->spa_condensing_indirect_phys);
if (error == 0) {
if (spa_writeable(spa)) {
spa->spa_condensing_indirect =
spa_condensing_indirect_create(spa);
}
return (0);
} else if (error == ENOENT) {
return (0);
} else {
return (error);
}
}
void
spa_condense_fini(spa_t *spa)
{
if (spa->spa_condensing_indirect != NULL) {
spa_condensing_indirect_destroy(spa->spa_condensing_indirect);
spa->spa_condensing_indirect = NULL;
}
}
void
spa_start_indirect_condensing_thread(spa_t *spa)
{
ASSERT3P(spa->spa_condense_zthr, ==, NULL);
spa->spa_condense_zthr = zthr_create("z_indirect_condense",
spa_condense_indirect_thread_check,
spa_condense_indirect_thread, spa, minclsyspri);
}
/*
* Gets the obsolete spacemap object from the vdev's ZAP. On success sm_obj
* will contain either the obsolete spacemap object or zero if none exists.
* All other errors are returned to the caller.
*/
int
vdev_obsolete_sm_object(vdev_t *vd, uint64_t *sm_obj)
{
ASSERT0(spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER));
if (vd->vdev_top_zap == 0) {
*sm_obj = 0;
return (0);
}
int error = zap_lookup(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap,
VDEV_TOP_ZAP_INDIRECT_OBSOLETE_SM, sizeof (uint64_t), 1, sm_obj);
if (error == ENOENT) {
*sm_obj = 0;
error = 0;
}
return (error);
}
/*
* Gets the obsolete count are precise spacemap object from the vdev's ZAP.
* On success are_precise will be set to reflect if the counts are precise.
* All other errors are returned to the caller.
*/
int
vdev_obsolete_counts_are_precise(vdev_t *vd, boolean_t *are_precise)
{
ASSERT0(spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER));
if (vd->vdev_top_zap == 0) {
*are_precise = B_FALSE;
return (0);
}
uint64_t val = 0;
int error = zap_lookup(vd->vdev_spa->spa_meta_objset, vd->vdev_top_zap,
VDEV_TOP_ZAP_OBSOLETE_COUNTS_ARE_PRECISE, sizeof (val), 1, &val);
if (error == 0) {
*are_precise = (val != 0);
} else if (error == ENOENT) {
*are_precise = B_FALSE;
error = 0;
}
return (error);
}
static void
vdev_indirect_close(vdev_t *vd)
{
(void) vd;
}
static int
vdev_indirect_open(vdev_t *vd, uint64_t *psize, uint64_t *max_psize,
uint64_t *logical_ashift, uint64_t *physical_ashift)
{
*psize = *max_psize = vd->vdev_asize +
VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE;
*logical_ashift = vd->vdev_ashift;
*physical_ashift = vd->vdev_physical_ashift;
return (0);
}
typedef struct remap_segment {
vdev_t *rs_vd;
uint64_t rs_offset;
uint64_t rs_asize;
uint64_t rs_split_offset;
list_node_t rs_node;
} remap_segment_t;
static remap_segment_t *
rs_alloc(vdev_t *vd, uint64_t offset, uint64_t asize, uint64_t split_offset)
{
remap_segment_t *rs = kmem_alloc(sizeof (remap_segment_t), KM_SLEEP);
rs->rs_vd = vd;
rs->rs_offset = offset;
rs->rs_asize = asize;
rs->rs_split_offset = split_offset;
return (rs);
}
/*
* Given an indirect vdev and an extent on that vdev, it duplicates the
* physical entries of the indirect mapping that correspond to the extent
* to a new array and returns a pointer to it. In addition, copied_entries
* is populated with the number of mapping entries that were duplicated.
*
* Note that the function assumes that the caller holds vdev_indirect_rwlock.
* This ensures that the mapping won't change due to condensing as we
* copy over its contents.
*
* Finally, since we are doing an allocation, it is up to the caller to
* free the array allocated in this function.
*/
static vdev_indirect_mapping_entry_phys_t *
vdev_indirect_mapping_duplicate_adjacent_entries(vdev_t *vd, uint64_t offset,
uint64_t asize, uint64_t *copied_entries)
{
vdev_indirect_mapping_entry_phys_t *duplicate_mappings = NULL;
vdev_indirect_mapping_t *vim = vd->vdev_indirect_mapping;
uint64_t entries = 0;
ASSERT(RW_READ_HELD(&vd->vdev_indirect_rwlock));
vdev_indirect_mapping_entry_phys_t *first_mapping =
vdev_indirect_mapping_entry_for_offset(vim, offset);
ASSERT3P(first_mapping, !=, NULL);
vdev_indirect_mapping_entry_phys_t *m = first_mapping;
while (asize > 0) {
uint64_t size = DVA_GET_ASIZE(&m->vimep_dst);
ASSERT3U(offset, >=, DVA_MAPPING_GET_SRC_OFFSET(m));
ASSERT3U(offset, <, DVA_MAPPING_GET_SRC_OFFSET(m) + size);
uint64_t inner_offset = offset - DVA_MAPPING_GET_SRC_OFFSET(m);
uint64_t inner_size = MIN(asize, size - inner_offset);
offset += inner_size;
asize -= inner_size;
entries++;
m++;
}
size_t copy_length = entries * sizeof (*first_mapping);
duplicate_mappings = kmem_alloc(copy_length, KM_SLEEP);
bcopy(first_mapping, duplicate_mappings, copy_length);
*copied_entries = entries;
return (duplicate_mappings);
}
/*
* Goes through the relevant indirect mappings until it hits a concrete vdev
* and issues the callback. On the way to the concrete vdev, if any other
* indirect vdevs are encountered, then the callback will also be called on
* each of those indirect vdevs. For example, if the segment is mapped to
* segment A on indirect vdev 1, and then segment A on indirect vdev 1 is
* mapped to segment B on concrete vdev 2, then the callback will be called on
* both vdev 1 and vdev 2.
*
* While the callback passed to vdev_indirect_remap() is called on every vdev
* the function encounters, certain callbacks only care about concrete vdevs.
* These types of callbacks should return immediately and explicitly when they
* are called on an indirect vdev.
*
* Because there is a possibility that a DVA section in the indirect device
* has been split into multiple sections in our mapping, we keep track
* of the relevant contiguous segments of the new location (remap_segment_t)
* in a stack. This way we can call the callback for each of the new sections
* created by a single section of the indirect device. Note though, that in
* this scenario the callbacks in each split block won't occur in-order in
* terms of offset, so callers should not make any assumptions about that.
*
* For callbacks that don't handle split blocks and immediately return when
* they encounter them (as is the case for remap_blkptr_cb), the caller can
* assume that its callback will be applied from the first indirect vdev
* encountered to the last one and then the concrete vdev, in that order.
*/
static void
vdev_indirect_remap(vdev_t *vd, uint64_t offset, uint64_t asize,
void (*func)(uint64_t, vdev_t *, uint64_t, uint64_t, void *), void *arg)
{
list_t stack;
spa_t *spa = vd->vdev_spa;
list_create(&stack, sizeof (remap_segment_t),
offsetof(remap_segment_t, rs_node));
for (remap_segment_t *rs = rs_alloc(vd, offset, asize, 0);
rs != NULL; rs = list_remove_head(&stack)) {
vdev_t *v = rs->rs_vd;
uint64_t num_entries = 0;
ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);
ASSERT(rs->rs_asize > 0);
/*
* Note: As this function can be called from open context
* (e.g. zio_read()), we need the following rwlock to
* prevent the mapping from being changed by condensing.
*
* So we grab the lock and we make a copy of the entries
* that are relevant to the extent that we are working on.
* Once that is done, we drop the lock and iterate over
* our copy of the mapping. Once we are done with the with
* the remap segment and we free it, we also free our copy
* of the indirect mapping entries that are relevant to it.
*
* This way we don't need to wait until the function is
* finished with a segment, to condense it. In addition, we
* don't need a recursive rwlock for the case that a call to
* vdev_indirect_remap() needs to call itself (through the
* codepath of its callback) for the same vdev in the middle
* of its execution.
*/
rw_enter(&v->vdev_indirect_rwlock, RW_READER);
ASSERT3P(v->vdev_indirect_mapping, !=, NULL);
vdev_indirect_mapping_entry_phys_t *mapping =
vdev_indirect_mapping_duplicate_adjacent_entries(v,
rs->rs_offset, rs->rs_asize, &num_entries);
ASSERT3P(mapping, !=, NULL);
ASSERT3U(num_entries, >, 0);
rw_exit(&v->vdev_indirect_rwlock);
for (uint64_t i = 0; i < num_entries; i++) {
/*
* Note: the vdev_indirect_mapping can not change
* while we are running. It only changes while the
* removal is in progress, and then only from syncing
* context. While a removal is in progress, this
* function is only called for frees, which also only
* happen from syncing context.
*/
vdev_indirect_mapping_entry_phys_t *m = &mapping[i];
ASSERT3P(m, !=, NULL);
ASSERT3U(rs->rs_asize, >, 0);
uint64_t size = DVA_GET_ASIZE(&m->vimep_dst);
uint64_t dst_offset = DVA_GET_OFFSET(&m->vimep_dst);
uint64_t dst_vdev = DVA_GET_VDEV(&m->vimep_dst);
ASSERT3U(rs->rs_offset, >=,
DVA_MAPPING_GET_SRC_OFFSET(m));
ASSERT3U(rs->rs_offset, <,
DVA_MAPPING_GET_SRC_OFFSET(m) + size);
ASSERT3U(dst_vdev, !=, v->vdev_id);
uint64_t inner_offset = rs->rs_offset -
DVA_MAPPING_GET_SRC_OFFSET(m);
uint64_t inner_size =
MIN(rs->rs_asize, size - inner_offset);
vdev_t *dst_v = vdev_lookup_top(spa, dst_vdev);
ASSERT3P(dst_v, !=, NULL);
if (dst_v->vdev_ops == &vdev_indirect_ops) {
list_insert_head(&stack,
rs_alloc(dst_v, dst_offset + inner_offset,
inner_size, rs->rs_split_offset));
}
if ((zfs_flags & ZFS_DEBUG_INDIRECT_REMAP) &&
IS_P2ALIGNED(inner_size, 2 * SPA_MINBLOCKSIZE)) {
/*
* Note: This clause exists only solely for
* testing purposes. We use it to ensure that
* split blocks work and that the callbacks
* using them yield the same result if issued
* in reverse order.
*/
uint64_t inner_half = inner_size / 2;
func(rs->rs_split_offset + inner_half, dst_v,
dst_offset + inner_offset + inner_half,
inner_half, arg);
func(rs->rs_split_offset, dst_v,
dst_offset + inner_offset,
inner_half, arg);
} else {
func(rs->rs_split_offset, dst_v,
dst_offset + inner_offset,
inner_size, arg);
}
rs->rs_offset += inner_size;
rs->rs_asize -= inner_size;
rs->rs_split_offset += inner_size;
}
VERIFY0(rs->rs_asize);
kmem_free(mapping, num_entries * sizeof (*mapping));
kmem_free(rs, sizeof (remap_segment_t));
}
list_destroy(&stack);
}
static void
vdev_indirect_child_io_done(zio_t *zio)
{
zio_t *pio = zio->io_private;
mutex_enter(&pio->io_lock);
pio->io_error = zio_worst_error(pio->io_error, zio->io_error);
mutex_exit(&pio->io_lock);
abd_free(zio->io_abd);
}
/*
* This is a callback for vdev_indirect_remap() which allocates an
* indirect_split_t for each split segment and adds it to iv_splits.
*/
static void
vdev_indirect_gather_splits(uint64_t split_offset, vdev_t *vd, uint64_t offset,
uint64_t size, void *arg)
{
zio_t *zio = arg;
indirect_vsd_t *iv = zio->io_vsd;
ASSERT3P(vd, !=, NULL);
if (vd->vdev_ops == &vdev_indirect_ops)
return;
int n = 1;
if (vd->vdev_ops == &vdev_mirror_ops)
n = vd->vdev_children;
indirect_split_t *is =
kmem_zalloc(offsetof(indirect_split_t, is_child[n]), KM_SLEEP);
is->is_children = n;
is->is_size = size;
is->is_split_offset = split_offset;
is->is_target_offset = offset;
is->is_vdev = vd;
list_create(&is->is_unique_child, sizeof (indirect_child_t),
offsetof(indirect_child_t, ic_node));
/*
* Note that we only consider multiple copies of the data for
* *mirror* vdevs. We don't for "replacing" or "spare" vdevs, even
* though they use the same ops as mirror, because there's only one
* "good" copy under the replacing/spare.
*/
if (vd->vdev_ops == &vdev_mirror_ops) {
for (int i = 0; i < n; i++) {
is->is_child[i].ic_vdev = vd->vdev_child[i];
list_link_init(&is->is_child[i].ic_node);
}
} else {
is->is_child[0].ic_vdev = vd;
}
list_insert_tail(&iv->iv_splits, is);
}
static void
vdev_indirect_read_split_done(zio_t *zio)
{
indirect_child_t *ic = zio->io_private;
if (zio->io_error != 0) {
/*
* Clear ic_data to indicate that we do not have data for this
* child.
*/
abd_free(ic->ic_data);
ic->ic_data = NULL;
}
}
/*
* Issue reads for all copies (mirror children) of all splits.
*/
static void
vdev_indirect_read_all(zio_t *zio)
{
indirect_vsd_t *iv = zio->io_vsd;
ASSERT3U(zio->io_type, ==, ZIO_TYPE_READ);
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
for (int i = 0; i < is->is_children; i++) {
indirect_child_t *ic = &is->is_child[i];
if (!vdev_readable(ic->ic_vdev))
continue;
/*
* If a child is missing the data, set ic_error. Used
* in vdev_indirect_repair(). We perform the read
* nevertheless which provides the opportunity to
* reconstruct the split block if at all possible.
*/
if (vdev_dtl_contains(ic->ic_vdev, DTL_MISSING,
zio->io_txg, 1))
ic->ic_error = SET_ERROR(ESTALE);
ic->ic_data = abd_alloc_sametype(zio->io_abd,
is->is_size);
ic->ic_duplicate = NULL;
zio_nowait(zio_vdev_child_io(zio, NULL,
ic->ic_vdev, is->is_target_offset, ic->ic_data,
is->is_size, zio->io_type, zio->io_priority, 0,
vdev_indirect_read_split_done, ic));
}
}
iv->iv_reconstruct = B_TRUE;
}
static void
vdev_indirect_io_start(zio_t *zio)
{
spa_t *spa __maybe_unused = zio->io_spa;
indirect_vsd_t *iv = kmem_zalloc(sizeof (*iv), KM_SLEEP);
list_create(&iv->iv_splits,
sizeof (indirect_split_t), offsetof(indirect_split_t, is_node));
zio->io_vsd = iv;
zio->io_vsd_ops = &vdev_indirect_vsd_ops;
ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);
if (zio->io_type != ZIO_TYPE_READ) {
ASSERT3U(zio->io_type, ==, ZIO_TYPE_WRITE);
/*
* Note: this code can handle other kinds of writes,
* but we don't expect them.
*/
ASSERT((zio->io_flags & (ZIO_FLAG_SELF_HEAL |
ZIO_FLAG_RESILVER | ZIO_FLAG_INDUCE_DAMAGE)) != 0);
}
vdev_indirect_remap(zio->io_vd, zio->io_offset, zio->io_size,
vdev_indirect_gather_splits, zio);
indirect_split_t *first = list_head(&iv->iv_splits);
if (first->is_size == zio->io_size) {
/*
* This is not a split block; we are pointing to the entire
* data, which will checksum the same as the original data.
* Pass the BP down so that the child i/o can verify the
* checksum, and try a different location if available
* (e.g. on a mirror).
*
* While this special case could be handled the same as the
* general (split block) case, doing it this way ensures
* that the vast majority of blocks on indirect vdevs
* (which are not split) are handled identically to blocks
* on non-indirect vdevs. This allows us to be less strict
* about performance in the general (but rare) case.
*/
ASSERT0(first->is_split_offset);
ASSERT3P(list_next(&iv->iv_splits, first), ==, NULL);
zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
first->is_vdev, first->is_target_offset,
abd_get_offset(zio->io_abd, 0),
zio->io_size, zio->io_type, zio->io_priority, 0,
vdev_indirect_child_io_done, zio));
} else {
iv->iv_split_block = B_TRUE;
if (zio->io_type == ZIO_TYPE_READ &&
zio->io_flags & (ZIO_FLAG_SCRUB | ZIO_FLAG_RESILVER)) {
/*
* Read all copies. Note that for simplicity,
* we don't bother consulting the DTL in the
* resilver case.
*/
vdev_indirect_read_all(zio);
} else {
/*
* If this is a read zio, we read one copy of each
* split segment, from the top-level vdev. Since
* we don't know the checksum of each split
* individually, the child zio can't ensure that
* we get the right data. E.g. if it's a mirror,
* it will just read from a random (healthy) leaf
* vdev. We have to verify the checksum in
* vdev_indirect_io_done().
*
* For write zios, the vdev code will ensure we write
* to all children.
*/
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
zio_nowait(zio_vdev_child_io(zio, NULL,
is->is_vdev, is->is_target_offset,
abd_get_offset(zio->io_abd,
is->is_split_offset), is->is_size,
zio->io_type, zio->io_priority, 0,
vdev_indirect_child_io_done, zio));
}
}
}
zio_execute(zio);
}
/*
* Report a checksum error for a child.
*/
static void
vdev_indirect_checksum_error(zio_t *zio,
indirect_split_t *is, indirect_child_t *ic)
{
vdev_t *vd = ic->ic_vdev;
if (zio->io_flags & ZIO_FLAG_SPECULATIVE)
return;
mutex_enter(&vd->vdev_stat_lock);
vd->vdev_stat.vs_checksum_errors++;
mutex_exit(&vd->vdev_stat_lock);
zio_bad_cksum_t zbc = {{{ 0 }}};
abd_t *bad_abd = ic->ic_data;
abd_t *good_abd = is->is_good_child->ic_data;
(void) zfs_ereport_post_checksum(zio->io_spa, vd, NULL, zio,
is->is_target_offset, is->is_size, good_abd, bad_abd, &zbc);
}
/*
* Issue repair i/os for any incorrect copies. We do this by comparing
* each split segment's correct data (is_good_child's ic_data) with each
* other copy of the data. If they differ, then we overwrite the bad data
* with the good copy. The DTL is checked in vdev_indirect_read_all() and
* if a vdev is missing a copy of the data we set ic_error and the read is
* performed. This provides the opportunity to reconstruct the split block
* if at all possible. ic_error is checked here and if set it suppresses
* incrementing the checksum counter. Aside from this DTLs are not checked,
* which simplifies this code and also issues the optimal number of writes
* (based on which copies actually read bad data, as opposed to which we
* think might be wrong). For the same reason, we always use
* ZIO_FLAG_SELF_HEAL, to bypass the DTL check in zio_vdev_io_start().
*/
static void
vdev_indirect_repair(zio_t *zio)
{
indirect_vsd_t *iv = zio->io_vsd;
if (!spa_writeable(zio->io_spa))
return;
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
for (int c = 0; c < is->is_children; c++) {
indirect_child_t *ic = &is->is_child[c];
if (ic == is->is_good_child)
continue;
if (ic->ic_data == NULL)
continue;
if (ic->ic_duplicate == is->is_good_child)
continue;
zio_nowait(zio_vdev_child_io(zio, NULL,
ic->ic_vdev, is->is_target_offset,
is->is_good_child->ic_data, is->is_size,
ZIO_TYPE_WRITE, ZIO_PRIORITY_ASYNC_WRITE,
ZIO_FLAG_IO_REPAIR | ZIO_FLAG_SELF_HEAL,
NULL, NULL));
/*
* If ic_error is set the current child does not have
* a copy of the data, so suppress incrementing the
* checksum counter.
*/
if (ic->ic_error == ESTALE)
continue;
vdev_indirect_checksum_error(zio, is, ic);
}
}
}
/*
* Report checksum errors on all children that we read from.
*/
static void
vdev_indirect_all_checksum_errors(zio_t *zio)
{
indirect_vsd_t *iv = zio->io_vsd;
if (zio->io_flags & ZIO_FLAG_SPECULATIVE)
return;
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
for (int c = 0; c < is->is_children; c++) {
indirect_child_t *ic = &is->is_child[c];
if (ic->ic_data == NULL)
continue;
vdev_t *vd = ic->ic_vdev;
(void) zfs_ereport_post_checksum(zio->io_spa, vd,
NULL, zio, is->is_target_offset, is->is_size,
NULL, NULL, NULL);
mutex_enter(&vd->vdev_stat_lock);
vd->vdev_stat.vs_checksum_errors++;
mutex_exit(&vd->vdev_stat_lock);
}
}
}
/*
* Copy data from all the splits to a main zio then validate the checksum.
* If then checksum is successfully validated return success.
*/
static int
vdev_indirect_splits_checksum_validate(indirect_vsd_t *iv, zio_t *zio)
{
zio_bad_cksum_t zbc;
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
ASSERT3P(is->is_good_child->ic_data, !=, NULL);
ASSERT3P(is->is_good_child->ic_duplicate, ==, NULL);
abd_copy_off(zio->io_abd, is->is_good_child->ic_data,
is->is_split_offset, 0, is->is_size);
}
return (zio_checksum_error(zio, &zbc));
}
/*
* There are relatively few possible combinations making it feasible to
* deterministically check them all. We do this by setting the good_child
* to the next unique split version. If we reach the end of the list then
* "carry over" to the next unique split version (like counting in base
* is_unique_children, but each digit can have a different base).
*/
static int
vdev_indirect_splits_enumerate_all(indirect_vsd_t *iv, zio_t *zio)
{
boolean_t more = B_TRUE;
iv->iv_attempts = 0;
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is))
is->is_good_child = list_head(&is->is_unique_child);
while (more == B_TRUE) {
iv->iv_attempts++;
more = B_FALSE;
if (vdev_indirect_splits_checksum_validate(iv, zio) == 0)
return (0);
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
is->is_good_child = list_next(&is->is_unique_child,
is->is_good_child);
if (is->is_good_child != NULL) {
more = B_TRUE;
break;
}
is->is_good_child = list_head(&is->is_unique_child);
}
}
ASSERT3S(iv->iv_attempts, <=, iv->iv_unique_combinations);
return (SET_ERROR(ECKSUM));
}
/*
* There are too many combinations to try all of them in a reasonable amount
* of time. So try a fixed number of random combinations from the unique
* split versions, after which we'll consider the block unrecoverable.
*/
static int
vdev_indirect_splits_enumerate_randomly(indirect_vsd_t *iv, zio_t *zio)
{
iv->iv_attempts = 0;
while (iv->iv_attempts < iv->iv_attempts_max) {
iv->iv_attempts++;
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
indirect_child_t *ic = list_head(&is->is_unique_child);
int children = is->is_unique_children;
for (int i = random_in_range(children); i > 0; i--)
ic = list_next(&is->is_unique_child, ic);
ASSERT3P(ic, !=, NULL);
is->is_good_child = ic;
}
if (vdev_indirect_splits_checksum_validate(iv, zio) == 0)
return (0);
}
return (SET_ERROR(ECKSUM));
}
/*
* This is a validation function for reconstruction. It randomly selects
* a good combination, if one can be found, and then it intentionally
* damages all other segment copes by zeroing them. This forces the
* reconstruction algorithm to locate the one remaining known good copy.
*/
static int
vdev_indirect_splits_damage(indirect_vsd_t *iv, zio_t *zio)
{
int error;
/* Presume all the copies are unique for initial selection. */
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
is->is_unique_children = 0;
for (int i = 0; i < is->is_children; i++) {
indirect_child_t *ic = &is->is_child[i];
if (ic->ic_data != NULL) {
is->is_unique_children++;
list_insert_tail(&is->is_unique_child, ic);
}
}
if (list_is_empty(&is->is_unique_child)) {
error = SET_ERROR(EIO);
goto out;
}
}
/*
* Set each is_good_child to a randomly-selected child which
* is known to contain validated data.
*/
error = vdev_indirect_splits_enumerate_randomly(iv, zio);
if (error)
goto out;
/*
* Damage all but the known good copy by zeroing it. This will
* result in two or less unique copies per indirect_child_t.
* Both may need to be checked in order to reconstruct the block.
* Set iv->iv_attempts_max such that all unique combinations will
* enumerated, but limit the damage to at most 12 indirect splits.
*/
iv->iv_attempts_max = 1;
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
for (int c = 0; c < is->is_children; c++) {
indirect_child_t *ic = &is->is_child[c];
if (ic == is->is_good_child)
continue;
if (ic->ic_data == NULL)
continue;
abd_zero(ic->ic_data, abd_get_size(ic->ic_data));
}
iv->iv_attempts_max *= 2;
if (iv->iv_attempts_max >= (1ULL << 12)) {
iv->iv_attempts_max = UINT64_MAX;
break;
}
}
out:
/* Empty the unique children lists so they can be reconstructed. */
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
indirect_child_t *ic;
while ((ic = list_head(&is->is_unique_child)) != NULL)
list_remove(&is->is_unique_child, ic);
is->is_unique_children = 0;
}
return (error);
}
/*
* This function is called when we have read all copies of the data and need
* to try to find a combination of copies that gives us the right checksum.
*
* If we pointed to any mirror vdevs, this effectively does the job of the
* mirror. The mirror vdev code can't do its own job because we don't know
* the checksum of each split segment individually.
*
* We have to try every unique combination of copies of split segments, until
* we find one that checksums correctly. Duplicate segment copies are first
* identified and latter skipped during reconstruction. This optimization
* reduces the search space and ensures that of the remaining combinations
* at most one is correct.
*
* When the total number of combinations is small they can all be checked.
* For example, if we have 3 segments in the split, and each points to a
* 2-way mirror with unique copies, we will have the following pieces of data:
*
* | mirror child
* split | [0] [1]
* ======|=====================
* A | data_A_0 data_A_1
* B | data_B_0 data_B_1
* C | data_C_0 data_C_1
*
* We will try the following (mirror children)^(number of splits) (2^3=8)
* combinations, which is similar to bitwise-little-endian counting in
* binary. In general each "digit" corresponds to a split segment, and the
* base of each digit is is_children, which can be different for each
* digit.
*
* "low bit" "high bit"
* v v
* data_A_0 data_B_0 data_C_0
* data_A_1 data_B_0 data_C_0
* data_A_0 data_B_1 data_C_0
* data_A_1 data_B_1 data_C_0
* data_A_0 data_B_0 data_C_1
* data_A_1 data_B_0 data_C_1
* data_A_0 data_B_1 data_C_1
* data_A_1 data_B_1 data_C_1
*
* Note that the split segments may be on the same or different top-level
* vdevs. In either case, we may need to try lots of combinations (see
* zfs_reconstruct_indirect_combinations_max). This ensures that if a mirror
* has small silent errors on all of its children, we can still reconstruct
* the correct data, as long as those errors are at sufficiently-separated
* offsets (specifically, separated by the largest block size - default of
* 128KB, but up to 16MB).
*/
static void
vdev_indirect_reconstruct_io_done(zio_t *zio)
{
indirect_vsd_t *iv = zio->io_vsd;
boolean_t known_good = B_FALSE;
int error;
iv->iv_unique_combinations = 1;
iv->iv_attempts_max = UINT64_MAX;
if (zfs_reconstruct_indirect_combinations_max > 0)
iv->iv_attempts_max = zfs_reconstruct_indirect_combinations_max;
/*
* If nonzero, every 1/x blocks will be damaged, in order to validate
* reconstruction when there are split segments with damaged copies.
* Known_good will be TRUE when reconstruction is known to be possible.
*/
if (zfs_reconstruct_indirect_damage_fraction != 0 &&
random_in_range(zfs_reconstruct_indirect_damage_fraction) == 0)
known_good = (vdev_indirect_splits_damage(iv, zio) == 0);
/*
* Determine the unique children for a split segment and add them
* to the is_unique_child list. By restricting reconstruction
* to these children, only unique combinations will be considered.
* This can vastly reduce the search space when there are a large
* number of indirect splits.
*/
for (indirect_split_t *is = list_head(&iv->iv_splits);
is != NULL; is = list_next(&iv->iv_splits, is)) {
is->is_unique_children = 0;
for (int i = 0; i < is->is_children; i++) {
indirect_child_t *ic_i = &is->is_child[i];
if (ic_i->ic_data == NULL ||
ic_i->ic_duplicate != NULL)
continue;
for (int j = i + 1; j < is->is_children; j++) {
indirect_child_t *ic_j = &is->is_child[j];
if (ic_j->ic_data == NULL ||
ic_j->ic_duplicate != NULL)
continue;
if (abd_cmp(ic_i->ic_data, ic_j->ic_data) == 0)
ic_j->ic_duplicate = ic_i;
}
is->is_unique_children++;
list_insert_tail(&is->is_unique_child, ic_i);
}
/* Reconstruction is impossible, no valid children */
EQUIV(list_is_empty(&is->is_unique_child),
is->is_unique_children == 0);
if (list_is_empty(&is->is_unique_child)) {
zio->io_error = EIO;
vdev_indirect_all_checksum_errors(zio);
zio_checksum_verified(zio);
return;
}
iv->iv_unique_combinations *= is->is_unique_children;
}
if (iv->iv_unique_combinations <= iv->iv_attempts_max)
error = vdev_indirect_splits_enumerate_all(iv, zio);
else
error = vdev_indirect_splits_enumerate_randomly(iv, zio);
if (error != 0) {
/* All attempted combinations failed. */
ASSERT3B(known_good, ==, B_FALSE);
zio->io_error = error;
vdev_indirect_all_checksum_errors(zio);
} else {
/*
* The checksum has been successfully validated. Issue
* repair I/Os to any copies of splits which don't match
* the validated version.
*/
ASSERT0(vdev_indirect_splits_checksum_validate(iv, zio));
vdev_indirect_repair(zio);
zio_checksum_verified(zio);
}
}
static void
vdev_indirect_io_done(zio_t *zio)
{
indirect_vsd_t *iv = zio->io_vsd;
if (iv->iv_reconstruct) {
/*
* We have read all copies of the data (e.g. from mirrors),
* either because this was a scrub/resilver, or because the
* one-copy read didn't checksum correctly.
*/
vdev_indirect_reconstruct_io_done(zio);
return;
}
if (!iv->iv_split_block) {
/*
* This was not a split block, so we passed the BP down,
* and the checksum was handled by the (one) child zio.
*/
return;
}
zio_bad_cksum_t zbc;
int ret = zio_checksum_error(zio, &zbc);
if (ret == 0) {
zio_checksum_verified(zio);
return;
}
/*
* The checksum didn't match. Read all copies of all splits, and
* then we will try to reconstruct. The next time
* vdev_indirect_io_done() is called, iv_reconstruct will be set.
*/
vdev_indirect_read_all(zio);
zio_vdev_io_redone(zio);
}
vdev_ops_t vdev_indirect_ops = {
.vdev_op_init = NULL,
.vdev_op_fini = NULL,
.vdev_op_open = vdev_indirect_open,
.vdev_op_close = vdev_indirect_close,
.vdev_op_asize = vdev_default_asize,
.vdev_op_min_asize = vdev_default_min_asize,
.vdev_op_min_alloc = NULL,
.vdev_op_io_start = vdev_indirect_io_start,
.vdev_op_io_done = vdev_indirect_io_done,
.vdev_op_state_change = NULL,
.vdev_op_need_resilver = NULL,
.vdev_op_hold = NULL,
.vdev_op_rele = NULL,
.vdev_op_remap = vdev_indirect_remap,
.vdev_op_xlate = NULL,
.vdev_op_rebuild_asize = NULL,
.vdev_op_metaslab_init = NULL,
.vdev_op_config_generate = NULL,
.vdev_op_nparity = NULL,
.vdev_op_ndisks = NULL,
.vdev_op_type = VDEV_TYPE_INDIRECT, /* name of this vdev type */
.vdev_op_leaf = B_FALSE /* leaf vdev */
};
EXPORT_SYMBOL(spa_condense_fini);
EXPORT_SYMBOL(spa_start_indirect_condensing_thread);
EXPORT_SYMBOL(spa_condense_indirect_start_sync);
EXPORT_SYMBOL(spa_condense_init);
EXPORT_SYMBOL(spa_vdev_indirect_mark_obsolete);
EXPORT_SYMBOL(vdev_indirect_mark_obsolete);
EXPORT_SYMBOL(vdev_indirect_should_condense);
EXPORT_SYMBOL(vdev_indirect_sync_obsolete);
EXPORT_SYMBOL(vdev_obsolete_counts_are_precise);
EXPORT_SYMBOL(vdev_obsolete_sm_object);
/* BEGIN CSTYLED */
ZFS_MODULE_PARAM(zfs_condense, zfs_condense_, indirect_vdevs_enable, INT, ZMOD_RW,
"Whether to attempt condensing indirect vdev mappings");
ZFS_MODULE_PARAM(zfs_condense, zfs_condense_, indirect_obsolete_pct, INT, ZMOD_RW,
"Minimum obsolete percent of bytes in the mapping to attempt condensing");
ZFS_MODULE_PARAM(zfs_condense, zfs_condense_, min_mapping_bytes, ULONG, ZMOD_RW,
"Don't bother condensing if the mapping uses less than this amount of "
"memory");
ZFS_MODULE_PARAM(zfs_condense, zfs_condense_, max_obsolete_bytes, ULONG, ZMOD_RW,
"Minimum size obsolete spacemap to attempt condensing");
ZFS_MODULE_PARAM(zfs_condense, zfs_condense_, indirect_commit_entry_delay_ms, INT, ZMOD_RW,
"Used by tests to ensure certain actions happen in the middle of a "
"condense. A maximum value of 1 should be sufficient.");
ZFS_MODULE_PARAM(zfs_reconstruct, zfs_reconstruct_, indirect_combinations_max, INT, ZMOD_RW,
"Maximum number of combinations when reconstructing split segments");
/* END CSTYLED */
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