btrfs: Replace fs_info->delalloc_workers with btrfs_workqueue

Much like the fs_info->workers, replace the fs_info->delalloc_workers
use the same btrfs_workqueue.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Tested-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index faafa51..7eeb45f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1997,7 +1997,7 @@
 {
 	btrfs_stop_workers(&fs_info->generic_worker);
 	btrfs_stop_workers(&fs_info->fixup_workers);
-	btrfs_stop_workers(&fs_info->delalloc_workers);
+	btrfs_destroy_workqueue(fs_info->delalloc_workers);
 	btrfs_destroy_workqueue(fs_info->workers);
 	btrfs_stop_workers(&fs_info->endio_workers);
 	btrfs_stop_workers(&fs_info->endio_meta_workers);
@@ -2480,8 +2480,8 @@
 		btrfs_alloc_workqueue("worker", flags | WQ_HIGHPRI,
 				      max_active, 16);
 
-	btrfs_init_workers(&fs_info->delalloc_workers, "delalloc",
-			   fs_info->thread_pool_size, NULL);
+	fs_info->delalloc_workers =
+		btrfs_alloc_workqueue("delalloc", flags, max_active, 2);
 
 	btrfs_init_workers(&fs_info->flush_workers, "flush_delalloc",
 			   fs_info->thread_pool_size, NULL);
@@ -2499,9 +2499,6 @@
 	 */
 	fs_info->submit_workers.idle_thresh = 64;
 
-	fs_info->delalloc_workers.idle_thresh = 2;
-	fs_info->delalloc_workers.ordered = 1;
-
 	btrfs_init_workers(&fs_info->fixup_workers, "fixup", 1,
 			   &fs_info->generic_worker);
 	btrfs_init_workers(&fs_info->endio_workers, "endio",
@@ -2552,7 +2549,6 @@
 	 */
 	ret = btrfs_start_workers(&fs_info->generic_worker);
 	ret |= btrfs_start_workers(&fs_info->submit_workers);
-	ret |= btrfs_start_workers(&fs_info->delalloc_workers);
 	ret |= btrfs_start_workers(&fs_info->fixup_workers);
 	ret |= btrfs_start_workers(&fs_info->endio_workers);
 	ret |= btrfs_start_workers(&fs_info->endio_meta_workers);
@@ -2570,7 +2566,7 @@
 		err = -ENOMEM;
 		goto fail_sb_buffer;
 	}
-	if (!(fs_info->workers)) {
+	if (!(fs_info->workers && fs_info->delalloc_workers)) {
 		err = -ENOMEM;
 		goto fail_sb_buffer;
 	}