Function space_map_truncate

freebsd/contrib/openzfs/module/zfs/space_map.c:854–904

}

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)