Reduce dirty records memory usage

[zfs.git] / module / zfs / vdev_indirect_mapping.c

/*
 * 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) 2015, 2017 by Delphix. All rights reserved.
 */

#include <sys/dmu_tx.h>
#include <sys/dsl_pool.h>
#include <sys/spa.h>
#include <sys/vdev_impl.h>
#include <sys/vdev_indirect_mapping.h>
#include <sys/zfeature.h>
#include <sys/dmu_objset.h>

#ifdef ZFS_DEBUG
static boolean_t
vdev_indirect_mapping_verify(vdev_indirect_mapping_t *vim)
{
        ASSERT(vim != NULL);

        ASSERT(vim->vim_object != 0);
        ASSERT(vim->vim_objset != NULL);
        ASSERT(vim->vim_phys != NULL);
        ASSERT(vim->vim_dbuf != NULL);

        EQUIV(vim->vim_phys->vimp_num_entries > 0,
            vim->vim_entries != NULL);
        if (vim->vim_phys->vimp_num_entries > 0) {
                vdev_indirect_mapping_entry_phys_t *last_entry __maybe_unused =
                    &vim->vim_entries[vim->vim_phys->vimp_num_entries - 1];
                uint64_t offset __maybe_unused =
                    DVA_MAPPING_GET_SRC_OFFSET(last_entry);
                uint64_t size __maybe_unused =
                    DVA_GET_ASIZE(&last_entry->vimep_dst);

                ASSERT3U(vim->vim_phys->vimp_max_offset, >=, offset + size);
        }
        if (vim->vim_havecounts) {
                ASSERT(vim->vim_phys->vimp_counts_object != 0);
        }

        return (B_TRUE);
}
#else
#define vdev_indirect_mapping_verify(vim) ((void) sizeof (vim), B_TRUE)
#endif

uint64_t
vdev_indirect_mapping_num_entries(vdev_indirect_mapping_t *vim)
{
        ASSERT(vdev_indirect_mapping_verify(vim));

        return (vim->vim_phys->vimp_num_entries);
}

uint64_t
vdev_indirect_mapping_max_offset(vdev_indirect_mapping_t *vim)
{
        ASSERT(vdev_indirect_mapping_verify(vim));

        return (vim->vim_phys->vimp_max_offset);
}

uint64_t
vdev_indirect_mapping_object(vdev_indirect_mapping_t *vim)
{
        ASSERT(vdev_indirect_mapping_verify(vim));

        return (vim->vim_object);
}

uint64_t
vdev_indirect_mapping_bytes_mapped(vdev_indirect_mapping_t *vim)
{
        ASSERT(vdev_indirect_mapping_verify(vim));

        return (vim->vim_phys->vimp_bytes_mapped);
}

/*
 * The length (in bytes) of the mapping object array in memory and
 * (logically) on disk.
 *
 * Note that unlike most of our accessor functions,
 * we don't assert that the struct is consistent; therefore it can be
 * called while there may be concurrent changes, if we don't care about
 * the value being immediately stale (e.g. from spa_removal_get_stats()).
 */
uint64_t
vdev_indirect_mapping_size(vdev_indirect_mapping_t *vim)
{
        return (vim->vim_phys->vimp_num_entries * sizeof (*vim->vim_entries));
}

/*
 * Compare an offset with an indirect mapping entry; there are three
 * possible scenarios:
 *
 *     1. The offset is "less than" the mapping entry; meaning the
 *        offset is less than the source offset of the mapping entry. In
 *        this case, there is no overlap between the offset and the
 *        mapping entry and -1 will be returned.
 *
 *     2. The offset is "greater than" the mapping entry; meaning the
 *        offset is greater than the mapping entry's source offset plus
 *        the entry's size. In this case, there is no overlap between
 *        the offset and the mapping entry and 1 will be returned.
 *
 *        NOTE: If the offset is actually equal to the entry's offset
 *        plus size, this is considered to be "greater" than the entry,
 *        and this case applies (i.e. 1 will be returned). Thus, the
 *        entry's "range" can be considered to be inclusive at its
 *        start, but exclusive at its end: e.g. [src, src + size).
 *
 *     3. The last case to consider is if the offset actually falls
 *        within the mapping entry's range. If this is the case, the
 *        offset is considered to be "equal to" the mapping entry and
 *        0 will be returned.
 *
 *        NOTE: If the offset is equal to the entry's source offset,
 *        this case applies and 0 will be returned. If the offset is
 *        equal to the entry's source plus its size, this case does
 *        *not* apply (see "NOTE" above for scenario 2), and 1 will be
 *        returned.
 */
static int
dva_mapping_overlap_compare(const void *v_key, const void *v_array_elem)
{
        const uint64_t * const key = v_key;
        const vdev_indirect_mapping_entry_phys_t * const array_elem =
            v_array_elem;
        uint64_t src_offset = DVA_MAPPING_GET_SRC_OFFSET(array_elem);

        if (*key < src_offset) {
                return (-1);
        } else if (*key < src_offset + DVA_GET_ASIZE(&array_elem->vimep_dst)) {
                return (0);
        } else {
                return (1);
        }
}

/*
 * Returns the mapping entry for the given offset.
 *
 * It's possible that the given offset will not be in the mapping table
 * (i.e. no mapping entries contain this offset), in which case, the
 * return value value depends on the "next_if_missing" parameter.
 *
 * If the offset is not found in the table and "next_if_missing" is
 * B_FALSE, then NULL will always be returned. The behavior is intended
 * to allow consumers to get the entry corresponding to the offset
 * parameter, iff the offset overlaps with an entry in the table.
 *
 * If the offset is not found in the table and "next_if_missing" is
 * B_TRUE, then the entry nearest to the given offset will be returned,
 * such that the entry's source offset is greater than the offset
 * passed in (i.e. the "next" mapping entry in the table is returned, if
 * the offset is missing from the table). If there are no entries whose
 * source offset is greater than the passed in offset, NULL is returned.
 */
static vdev_indirect_mapping_entry_phys_t *
vdev_indirect_mapping_entry_for_offset_impl(vdev_indirect_mapping_t *vim,
    uint64_t offset, boolean_t next_if_missing)
{
        ASSERT(vdev_indirect_mapping_verify(vim));
        ASSERT(vim->vim_phys->vimp_num_entries > 0);

        vdev_indirect_mapping_entry_phys_t *entry = NULL;

        uint64_t last = vim->vim_phys->vimp_num_entries - 1;
        uint64_t base = 0;

        /*
         * We don't define these inside of the while loop because we use
         * their value in the case that offset isn't in the mapping.
         */
        uint64_t mid;
        int result;

        while (last >= base) {
                mid = base + ((last - base) >> 1);

                result = dva_mapping_overlap_compare(&offset,
                    &vim->vim_entries[mid]);

                if (result == 0) {
                        entry = &vim->vim_entries[mid];
                        break;
                } else if (result < 0) {
                        last = mid - 1;
                } else {
                        base = mid + 1;
                }
        }

        if (entry == NULL && next_if_missing) {
                ASSERT3U(base, ==, last + 1);
                ASSERT(mid == base || mid == last);
                ASSERT3S(result, !=, 0);

                /*
                 * The offset we're looking for isn't actually contained
                 * in the mapping table, thus we need to return the
                 * closest mapping entry that is greater than the
                 * offset. We reuse the result of the last comparison,
                 * comparing the mapping entry at index "mid" and the
                 * offset. The offset is guaranteed to lie between
                 * indices one less than "mid", and one greater than
                 * "mid"; we just need to determine if offset is greater
                 * than, or less than the mapping entry contained at
                 * index "mid".
                 */

                uint64_t index;
                if (result < 0)
                        index = mid;
                else
                        index = mid + 1;

                ASSERT3U(index, <=, vim->vim_phys->vimp_num_entries);

                if (index == vim->vim_phys->vimp_num_entries) {
                        /*
                         * If "index" is past the end of the entries
                         * array, then not only is the offset not in the
                         * mapping table, but it's actually greater than
                         * all entries in the table. In this case, we
                         * can't return a mapping entry greater than the
                         * offset (since none exist), so we return NULL.
                         */

                        ASSERT3S(dva_mapping_overlap_compare(&offset,
                            &vim->vim_entries[index - 1]), >, 0);

                        return (NULL);
                } else {
                        /*
                         * Just to be safe, we verify the offset falls
                         * in between the mapping entries at index and
                         * one less than index. Since we know the offset
                         * doesn't overlap an entry, and we're supposed
                         * to return the entry just greater than the
                         * offset, both of the following tests must be
                         * true.
                         */
                        ASSERT3S(dva_mapping_overlap_compare(&offset,
                            &vim->vim_entries[index]), <, 0);
                        IMPLY(index >= 1, dva_mapping_overlap_compare(&offset,
                            &vim->vim_entries[index - 1]) > 0);

                        return (&vim->vim_entries[index]);
                }
        } else {
                return (entry);
        }
}

vdev_indirect_mapping_entry_phys_t *
vdev_indirect_mapping_entry_for_offset(vdev_indirect_mapping_t *vim,
    uint64_t offset)
{
        return (vdev_indirect_mapping_entry_for_offset_impl(vim, offset,
            B_FALSE));
}

vdev_indirect_mapping_entry_phys_t *
vdev_indirect_mapping_entry_for_offset_or_next(vdev_indirect_mapping_t *vim,
    uint64_t offset)
{
        return (vdev_indirect_mapping_entry_for_offset_impl(vim, offset,
            B_TRUE));
}

void
vdev_indirect_mapping_close(vdev_indirect_mapping_t *vim)
{
        ASSERT(vdev_indirect_mapping_verify(vim));

        if (vim->vim_phys->vimp_num_entries > 0) {
                uint64_t map_size = vdev_indirect_mapping_size(vim);
                vmem_free(vim->vim_entries, map_size);
                vim->vim_entries = NULL;
        }

        dmu_buf_rele(vim->vim_dbuf, vim);

        vim->vim_objset = NULL;
        vim->vim_object = 0;
        vim->vim_dbuf = NULL;
        vim->vim_phys = NULL;

        kmem_free(vim, sizeof (*vim));
}

uint64_t
vdev_indirect_mapping_alloc(objset_t *os, dmu_tx_t *tx)
{
        uint64_t object;
        ASSERT(dmu_tx_is_syncing(tx));
        uint64_t bonus_size = VDEV_INDIRECT_MAPPING_SIZE_V0;

        if (spa_feature_is_enabled(os->os_spa, SPA_FEATURE_OBSOLETE_COUNTS)) {
                bonus_size = sizeof (vdev_indirect_mapping_phys_t);
        }

        object = dmu_object_alloc(os,
            DMU_OTN_UINT64_METADATA, SPA_OLD_MAXBLOCKSIZE,
            DMU_OTN_UINT64_METADATA, bonus_size,
            tx);

        if (spa_feature_is_enabled(os->os_spa, SPA_FEATURE_OBSOLETE_COUNTS)) {
                dmu_buf_t *dbuf;
                vdev_indirect_mapping_phys_t *vimp;

                VERIFY0(dmu_bonus_hold(os, object, FTAG, &dbuf));
                dmu_buf_will_dirty(dbuf, tx);
                vimp = dbuf->db_data;
                vimp->vimp_counts_object = dmu_object_alloc(os,
                    DMU_OTN_UINT32_METADATA, SPA_OLD_MAXBLOCKSIZE,
                    DMU_OT_NONE, 0, tx);
                spa_feature_incr(os->os_spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
                dmu_buf_rele(dbuf, FTAG);
        }

        return (object);
}


vdev_indirect_mapping_t *
vdev_indirect_mapping_open(objset_t *os, uint64_t mapping_object)
{
        vdev_indirect_mapping_t *vim = kmem_zalloc(sizeof (*vim), KM_SLEEP);
        dmu_object_info_t doi;
        VERIFY0(dmu_object_info(os, mapping_object, &doi));

        vim->vim_objset = os;
        vim->vim_object = mapping_object;

        VERIFY0(dmu_bonus_hold(os, vim->vim_object, vim,
            &vim->vim_dbuf));
        vim->vim_phys = vim->vim_dbuf->db_data;

        vim->vim_havecounts =
            (doi.doi_bonus_size > VDEV_INDIRECT_MAPPING_SIZE_V0);

        if (vim->vim_phys->vimp_num_entries > 0) {
                uint64_t map_size = vdev_indirect_mapping_size(vim);
                vim->vim_entries = vmem_alloc(map_size, KM_SLEEP);
                VERIFY0(dmu_read(os, vim->vim_object, 0, map_size,
                    vim->vim_entries, DMU_READ_PREFETCH));
        }

        ASSERT(vdev_indirect_mapping_verify(vim));

        return (vim);
}

void
vdev_indirect_mapping_free(objset_t *os, uint64_t object, dmu_tx_t *tx)
{
        vdev_indirect_mapping_t *vim = vdev_indirect_mapping_open(os, object);
        if (vim->vim_havecounts) {
                VERIFY0(dmu_object_free(os, vim->vim_phys->vimp_counts_object,
                    tx));
                spa_feature_decr(os->os_spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
        }
        vdev_indirect_mapping_close(vim);

        VERIFY0(dmu_object_free(os, object, tx));
}

/*
 * Append the list of vdev_indirect_mapping_entry_t's to the on-disk
 * mapping object.  Also remove the entries from the list and free them.
 * This also implicitly extends the max_offset of the mapping (to the end
 * of the last entry).
 */
void
vdev_indirect_mapping_add_entries(vdev_indirect_mapping_t *vim,
    list_t *list, dmu_tx_t *tx)
{
        vdev_indirect_mapping_entry_phys_t *mapbuf;
        uint64_t old_size;
        uint32_t *countbuf = NULL;
        vdev_indirect_mapping_entry_phys_t *old_entries;
        uint64_t old_count;
        uint64_t entries_written = 0;

        ASSERT(vdev_indirect_mapping_verify(vim));
        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(dsl_pool_sync_context(dmu_tx_pool(tx)));
        ASSERT(!list_is_empty(list));

        old_size = vdev_indirect_mapping_size(vim);
        old_entries = vim->vim_entries;
        old_count = vim->vim_phys->vimp_num_entries;

        dmu_buf_will_dirty(vim->vim_dbuf, tx);

        mapbuf = vmem_alloc(SPA_OLD_MAXBLOCKSIZE, KM_SLEEP);
        if (vim->vim_havecounts) {
                countbuf = vmem_alloc(SPA_OLD_MAXBLOCKSIZE, KM_SLEEP);
                ASSERT(spa_feature_is_active(vim->vim_objset->os_spa,
                    SPA_FEATURE_OBSOLETE_COUNTS));
        }
        while (!list_is_empty(list)) {
                uint64_t i;
                /*
                 * Write entries from the list to the
                 * vdev_im_object in batches of size SPA_OLD_MAXBLOCKSIZE.
                 */
                for (i = 0; i < SPA_OLD_MAXBLOCKSIZE / sizeof (*mapbuf); i++) {
                        vdev_indirect_mapping_entry_t *entry =
                            list_remove_head(list);
                        if (entry == NULL)
                                break;

                        uint64_t size =
                            DVA_GET_ASIZE(&entry->vime_mapping.vimep_dst);
                        uint64_t src_offset =
                            DVA_MAPPING_GET_SRC_OFFSET(&entry->vime_mapping);

                        /*
                         * We shouldn't be adding an entry which is fully
                         * obsolete.
                         */
                        ASSERT3U(entry->vime_obsolete_count, <, size);
                        IMPLY(entry->vime_obsolete_count != 0,
                            vim->vim_havecounts);

                        mapbuf[i] = entry->vime_mapping;
                        if (vim->vim_havecounts)
                                countbuf[i] = entry->vime_obsolete_count;

                        vim->vim_phys->vimp_bytes_mapped += size;
                        ASSERT3U(src_offset, >=,
                            vim->vim_phys->vimp_max_offset);
                        vim->vim_phys->vimp_max_offset = src_offset + size;

                        entries_written++;

                        vmem_free(entry, sizeof (*entry));
                }
                dmu_write(vim->vim_objset, vim->vim_object,
                    vim->vim_phys->vimp_num_entries * sizeof (*mapbuf),
                    i * sizeof (*mapbuf),
                    mapbuf, tx);
                if (vim->vim_havecounts) {
                        dmu_write(vim->vim_objset,
                            vim->vim_phys->vimp_counts_object,
                            vim->vim_phys->vimp_num_entries *
                            sizeof (*countbuf),
                            i * sizeof (*countbuf), countbuf, tx);
                }
                vim->vim_phys->vimp_num_entries += i;
        }
        vmem_free(mapbuf, SPA_OLD_MAXBLOCKSIZE);
        if (vim->vim_havecounts)
                vmem_free(countbuf, SPA_OLD_MAXBLOCKSIZE);

        /*
         * Update the entry array to reflect the new entries. First, copy
         * over any old entries then read back the new entries we just wrote.
         */
        uint64_t new_size = vdev_indirect_mapping_size(vim);
        ASSERT3U(new_size, >, old_size);
        ASSERT3U(new_size - old_size, ==,
            entries_written * sizeof (vdev_indirect_mapping_entry_phys_t));
        vim->vim_entries = vmem_alloc(new_size, KM_SLEEP);
        if (old_size > 0) {
                memcpy(vim->vim_entries, old_entries, old_size);
                vmem_free(old_entries, old_size);
        }
        VERIFY0(dmu_read(vim->vim_objset, vim->vim_object, old_size,
            new_size - old_size, &vim->vim_entries[old_count],
            DMU_READ_PREFETCH));

        zfs_dbgmsg("txg %llu: wrote %llu entries to "
            "indirect mapping obj %llu; max offset=0x%llx",
            (u_longlong_t)dmu_tx_get_txg(tx),
            (u_longlong_t)entries_written,
            (u_longlong_t)vim->vim_object,
            (u_longlong_t)vim->vim_phys->vimp_max_offset);
}

/*
 * Increment the relevant counts for the specified offset and length.
 * The counts array must be obtained from
 * vdev_indirect_mapping_load_obsolete_counts().
 */
void
vdev_indirect_mapping_increment_obsolete_count(vdev_indirect_mapping_t *vim,
    uint64_t offset, uint64_t length, uint32_t *counts)
{
        vdev_indirect_mapping_entry_phys_t *mapping;
        uint64_t index;

        mapping = vdev_indirect_mapping_entry_for_offset(vim,  offset);

        ASSERT(length > 0);
        ASSERT3P(mapping, !=, NULL);

        index = mapping - vim->vim_entries;

        while (length > 0) {
                ASSERT3U(index, <, vdev_indirect_mapping_num_entries(vim));

                uint64_t size = DVA_GET_ASIZE(&mapping->vimep_dst);
                uint64_t inner_offset = offset -
                    DVA_MAPPING_GET_SRC_OFFSET(mapping);
                VERIFY3U(inner_offset, <, size);
                uint64_t inner_size = MIN(length, size - inner_offset);

                VERIFY3U(counts[index] + inner_size, <=, size);
                counts[index] += inner_size;

                offset += inner_size;
                length -= inner_size;
                mapping++;
                index++;
        }
}

typedef struct load_obsolete_space_map_arg {
        vdev_indirect_mapping_t *losma_vim;
        uint32_t                *losma_counts;
} load_obsolete_space_map_arg_t;

static int
load_obsolete_sm_callback(space_map_entry_t *sme, void *arg)
{
        load_obsolete_space_map_arg_t *losma = arg;
        ASSERT3S(sme->sme_type, ==, SM_ALLOC);

        vdev_indirect_mapping_increment_obsolete_count(losma->losma_vim,
            sme->sme_offset, sme->sme_run, losma->losma_counts);

        return (0);
}

/*
 * Modify the counts (increment them) based on the spacemap.
 */
void
vdev_indirect_mapping_load_obsolete_spacemap(vdev_indirect_mapping_t *vim,
    uint32_t *counts, space_map_t *obsolete_space_sm)
{
        load_obsolete_space_map_arg_t losma;
        losma.losma_counts = counts;
        losma.losma_vim = vim;
        VERIFY0(space_map_iterate(obsolete_space_sm,
            space_map_length(obsolete_space_sm),
            load_obsolete_sm_callback, &losma));
}

/*
 * Read the obsolete counts from disk, returning them in an array.
 */
uint32_t *
vdev_indirect_mapping_load_obsolete_counts(vdev_indirect_mapping_t *vim)
{
        ASSERT(vdev_indirect_mapping_verify(vim));

        uint64_t counts_size =
            vim->vim_phys->vimp_num_entries * sizeof (uint32_t);
        uint32_t *counts = vmem_alloc(counts_size, KM_SLEEP);
        if (vim->vim_havecounts) {
                VERIFY0(dmu_read(vim->vim_objset,
                    vim->vim_phys->vimp_counts_object,
                    0, counts_size,
                    counts, DMU_READ_PREFETCH));
        } else {
                memset(counts, 0, counts_size);
        }
        return (counts);
}

extern void
vdev_indirect_mapping_free_obsolete_counts(vdev_indirect_mapping_t *vim,
    uint32_t *counts)
{
        ASSERT(vdev_indirect_mapping_verify(vim));

        vmem_free(counts, vim->vim_phys->vimp_num_entries * sizeof (uint32_t));
}

#if defined(_KERNEL)
EXPORT_SYMBOL(vdev_indirect_mapping_add_entries);
EXPORT_SYMBOL(vdev_indirect_mapping_alloc);
EXPORT_SYMBOL(vdev_indirect_mapping_bytes_mapped);
EXPORT_SYMBOL(vdev_indirect_mapping_close);
EXPORT_SYMBOL(vdev_indirect_mapping_entry_for_offset);
EXPORT_SYMBOL(vdev_indirect_mapping_entry_for_offset_or_next);
EXPORT_SYMBOL(vdev_indirect_mapping_free);
EXPORT_SYMBOL(vdev_indirect_mapping_free_obsolete_counts);
EXPORT_SYMBOL(vdev_indirect_mapping_increment_obsolete_count);
EXPORT_SYMBOL(vdev_indirect_mapping_load_obsolete_counts);
EXPORT_SYMBOL(vdev_indirect_mapping_load_obsolete_spacemap);
EXPORT_SYMBOL(vdev_indirect_mapping_max_offset);
EXPORT_SYMBOL(vdev_indirect_mapping_num_entries);
EXPORT_SYMBOL(vdev_indirect_mapping_object);
EXPORT_SYMBOL(vdev_indirect_mapping_open);
EXPORT_SYMBOL(vdev_indirect_mapping_size);
#endif