From: David Sterba <dsterba@suse.com>
Date: Sat, 12 Oct 2019 18:42:10 +0200
Subject: btrfs: don't needlessly create extent-refs kernel thread
Git-commit: 80ed4548d0711d15ca51be5dee0ff813051cfc90
Patch-mainline: 5.4-rc5
References: bnc#1151927 5.3.8

The patch 32b593bfcb58 ("Btrfs: remove no longer used function to run
delayed refs asynchronously") removed the async delayed refs but the
thread has been created, without any use. Remove it to avoid resource
consumption.

Fixes: 32b593bfcb58 ("Btrfs: remove no longer used function to run delayed refs asynchronously")
CC: stable@vger.kernel.org # 5.2+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/btrfs/ctree.h   |    2 --
 fs/btrfs/disk-io.c |    6 ------
 2 files changed, 8 deletions(-)

--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -908,8 +908,6 @@ struct btrfs_fs_info {
 	struct btrfs_workqueue *fixup_workers;
 	struct btrfs_workqueue *delayed_workers;
 
-	/* the extent workers do delayed refs on the extent allocation tree */
-	struct btrfs_workqueue *extent_workers;
 	struct task_struct *transaction_kthread;
 	struct task_struct *cleaner_kthread;
 	u32 thread_pool_size;
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2036,7 +2036,6 @@ static void btrfs_stop_all_workers(struc
 	btrfs_destroy_workqueue(fs_info->readahead_workers);
 	btrfs_destroy_workqueue(fs_info->flush_workers);
 	btrfs_destroy_workqueue(fs_info->qgroup_rescan_workers);
-	btrfs_destroy_workqueue(fs_info->extent_workers);
 	/*
 	 * Now that all other work queues are destroyed, we can safely destroy
 	 * the queues used for metadata I/O, since tasks from those other work
@@ -2242,10 +2241,6 @@ static int btrfs_init_workqueues(struct
 				      max_active, 2);
 	fs_info->qgroup_rescan_workers =
 		btrfs_alloc_workqueue(fs_info, "qgroup-rescan", flags, 1, 0);
-	fs_info->extent_workers =
-		btrfs_alloc_workqueue(fs_info, "extent-refs", flags,
-				      min_t(u64, fs_devices->num_devices,
-					    max_active), 8);
 
 	if (!(fs_info->workers && fs_info->delalloc_workers &&
 	      fs_info->submit_workers && fs_info->flush_workers &&
@@ -2256,7 +2251,6 @@ static int btrfs_init_workqueues(struct
 	      fs_info->endio_freespace_worker && fs_info->rmw_workers &&
 	      fs_info->caching_workers && fs_info->readahead_workers &&
 	      fs_info->fixup_workers && fs_info->delayed_workers &&
-	      fs_info->extent_workers &&
 	      fs_info->qgroup_rescan_workers)) {
 		return -ENOMEM;
 	}