MFC r268859: MFV r268851:

When a sync task is waiting for a txg to complete, we should hurry it along
by increasing the number of outstanding async writes (i.e. make
vdev_queue_max_async_writes() return a larger number).

Illumos issue:
    4753 increase number of outstanding async writes when sync task is waiting

1 files changed, 10 insertions, 0 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa_misc.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa_misc.c
index d09fb5b..21904490 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa_misc.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa_misc.c
@@ -1938,6 +1938,16 @@ spa_writeable(spa_t *spa)
 	return (!!(spa->spa_mode & FWRITE));
 }
 
+/*
+ * Returns true if there is a pending sync task in any of the current
+ * syncing txg, the current quiescing txg, or the current open txg.
+ */
+boolean_t
+spa_has_pending_synctask(spa_t *spa)
+{
+	return (!txg_all_lists_empty(&spa->spa_dsl_pool->dp_sync_tasks));
+}
+
 int
 spa_mode(spa_t *spa)
 {