btrfs: remove hipri_workers workqueue

Now that btrfs_wq_submit_bio is never called for synchronous I/O,
the hipri_workers workqueue is not used anymore and can be removed.

Reviewed-by: Chris Mason <clm@fb.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index dabc79c..f4adda2 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1991,7 +1991,6 @@ static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
 {
 	btrfs_destroy_workqueue(fs_info->fixup_workers);
 	btrfs_destroy_workqueue(fs_info->delalloc_workers);
-	btrfs_destroy_workqueue(fs_info->hipri_workers);
 	btrfs_destroy_workqueue(fs_info->workers);
 	if (fs_info->endio_workers)
 		destroy_workqueue(fs_info->endio_workers);
@@ -2186,9 +2185,6 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info)
 
 	fs_info->workers =
 		btrfs_alloc_workqueue(fs_info, "worker", flags, max_active, 16);
-	fs_info->hipri_workers =
-		btrfs_alloc_workqueue(fs_info, "worker-high",
-				      flags | WQ_HIGHPRI, max_active, 16);
 
 	fs_info->delalloc_workers =
 		btrfs_alloc_workqueue(fs_info, "delalloc",
@@ -2225,7 +2221,7 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info)
 	fs_info->discard_ctl.discard_workers =
 		alloc_workqueue("btrfs_discard", WQ_UNBOUND | WQ_FREEZABLE, 1);
 
-	if (!(fs_info->workers && fs_info->hipri_workers &&
+	if (!(fs_info->workers &&
 	      fs_info->delalloc_workers && fs_info->flush_workers &&
 	      fs_info->endio_workers && fs_info->endio_meta_workers &&
 	      fs_info->compressed_write_workers &&