8027 tighten up dsl_pool_dirty_delta

Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

usr/src/uts/common/fs/zfs/dsl_pool.c

@@ -459,7 +459,7 @@ dsl_pool_dirty_delta(dsl_pool_t *dp, int64_t delta)
 	 * Note: we signal even when increasing dp_dirty_total.
 	 * This ensures forward progress -- each thread wakes the next waiter.
 	 */
-	if (dp->dp_dirty_total <= zfs_dirty_data_max)
+	if (dp->dp_dirty_total < zfs_dirty_data_max)
 		cv_signal(&dp->dp_spaceavail_cv);
 }