Function zil_destroy

freebsd/contrib/openzfs/module/zfs/zil.c:743–792

* In one tx, free all log blocks and clear the log header. If keep_first * is set, then we're replaying a log with no content. We want to keep the * first block, however, so that the first synchronous transaction doesn't * require a txg_wait_synced() in zil_create(). We don't need to * txg_wait_synced() here either when keep_first is set, because both * zil_create() and zil_destroy() will wai

 * to complete.
 */
void
zil_destroy(zilog_t *zilog, boolean_t keep_first)
{
	const zil_header_t *zh = zilog->zl_header;
	lwb_t *lwb;
	dmu_tx_t *tx;
	uint64_t txg;

	/*
	 * Wait for any previous destroy to complete.
	 */
	txg_wait_synced(zilog->zl_dmu_pool, zilog->zl_destroy_txg);

	zilog->zl_old_header = *zh;		/* debugging aid */

	if (BP_IS_HOLE(&zh->zh_log))
		return;

	tx = dmu_tx_create(zilog->zl_os);
	VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
	dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
	txg = dmu_tx_get_txg(tx);

	mutex_enter(&zilog->zl_lock);

	ASSERT3U(zilog->zl_destroy_txg, <, txg);
	zilog->zl_destroy_txg = txg;
	zilog->zl_keep_first = keep_first;

	if (!list_is_empty(&zilog->zl_lwb_list)) {
		ASSERT(zh->zh_claim_txg == 0);
		VERIFY(!keep_first);
		while ((lwb = list_head(&zilog->zl_lwb_list)) != NULL) {
			if (lwb->lwb_fastwrite)
				metaslab_fastwrite_unmark(zilog->zl_spa,
				    &lwb->lwb_blk);

			list_remove(&zilog->zl_lwb_list, lwb);
			if (lwb->lwb_buf != NULL)
				zio_buf_free(lwb->lwb_buf, lwb->lwb_sz);
			zio_free(zilog->zl_spa, txg, &lwb->lwb_blk);
			zil_free_lwb(zilog, lwb);
		}
	} else if (!keep_first) {
		zil_destroy_sync(zilog, tx);
	}
	mutex_exit(&zilog->zl_lock);

	dmu_tx_commit(tx);
}

void
zil_destroy_sync(zilog_t *zilog, dmu_tx_t *tx)