Re: [PATCH 1/3] btrfs: qgroups, fix rescan worker running races

[David Sterba <dsterba@suse.cz>]

On Thu, Apr 26, 2018 at 03:23:49PM -0400, jeffm@suse.com wrote:
> From: Jeff Mahoney <jeffm@suse.com>
> +static void queue_rescan_worker(struct btrfs_fs_info *fs_info)
> +{
> +	mutex_lock(&fs_info->qgroup_rescan_lock);
> +	if (btrfs_fs_closing(fs_info)) {
> +		mutex_unlock(&fs_info->qgroup_rescan_lock);
> +		return;
> +	}
> +	if (WARN_ON(fs_info->qgroup_rescan_running)) {

The warning is quite noisy, I see it after tests btrfs/ 017, 022, 124,
139, 153. Is it necessary for non-debugging builds?

The tested branch was full for-next so it could be your patchset
interacting with other fixes, but the warning noise level question still
stands.

> +		btrfs_warn(fs_info, "rescan worker already queued");
> +		mutex_unlock(&fs_info->qgroup_rescan_lock);
> +		return;
> +	}
> +
> +	/*
> +	 * Being queued is enough for btrfs_qgroup_wait_for_completion
> +	 * to need to wait.
> +	 */
> +	fs_info->qgroup_rescan_running = true;
> +	mutex_unlock(&fs_info->qgroup_rescan_lock);
> +
> +	btrfs_queue_work(fs_info->qgroup_rescan_workers,
> +			 &fs_info->qgroup_rescan_work);
> +}