Function zil_prune_commit_list

freebsd/contrib/openzfs/module/zfs/zil.c:2164–2200

* This function will prune commit itxs that are at the head of the * commit list (it won't prune past the first non-commit itx), and * either: a) attach them to the last lwb that's still pending * completion, or b) skip them altogether. * * This is used as a performance optimization to prevent commit itxs * from generating new lwbs when it's unnecessary to do so. */

 * from generating new lwbs when it's unnecessary to do so.
 */
static void
zil_prune_commit_list(zilog_t *zilog)
{
	itx_t *itx;

	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));

	while ((itx = list_head(&zilog->zl_itx_commit_list)) != NULL) {
		lr_t *lrc = &itx->itx_lr;
		if (lrc->lrc_txtype != TX_COMMIT)
			break;

		mutex_enter(&zilog->zl_lock);

		lwb_t *last_lwb = zilog->zl_last_lwb_opened;
		if (last_lwb == NULL ||
		    last_lwb->lwb_state == LWB_STATE_FLUSH_DONE) {
			/*
			 * All of the itxs this waiter was waiting on
			 * must have already completed (or there were
			 * never any itx's for it to wait on), so it's
			 * safe to skip this waiter and mark it done.
			 */
			zil_commit_waiter_skip(itx->itx_private);
		} else {
			zil_commit_waiter_link_lwb(itx->itx_private, last_lwb);
			itx->itx_private = NULL;
		}

		mutex_exit(&zilog->zl_lock);

		list_remove(&zilog->zl_itx_commit_list, itx);
		zil_itx_destroy(itx);
	}

	IMPLY(itx != NULL, itx->itx_lr.lrc_txtype != TX_COMMIT);
}

static void
zil_commit_writer_stall(zilog_t *zilog)