Re: [PATCH] btrfs: scrub: add assertions for worker pointers

[Anand Jain <anand.jain@oracle.com>]

On 2/13/19 1:15 AM, David Sterba wrote:
> The scrub worker pointers are not NULL iff the scrub is running, so
> reset them back once the last reference is dropped. Add assertions to
> the initial phase of scrub to verify that.

makes sense.

> Signed-off-by: David Sterba <dsterba@suse.com>


Reviewed-by: Anand Jain <anand.jain@oracle.com>



> ---
>   fs/btrfs/ctree.h | 4 ++++
>   fs/btrfs/scrub.c | 7 +++++++
>   2 files changed, 11 insertions(+)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 7efa1edb30cd..f92f97304e69 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1075,6 +1075,10 @@ struct btrfs_fs_info {
>   	atomic_t scrubs_paused;
>   	atomic_t scrub_cancel_req;
>   	wait_queue_head_t scrub_pause_wait;
> +	/*
> +	 * The worker pointers are NULL iff the refcount is 0, ie. scrub is not
> +	 * running.
> +	 */
>   	refcount_t scrub_workers_refcnt;
>   	struct btrfs_workqueue *scrub_workers;
>   	struct btrfs_workqueue *scrub_wr_completion_workers;
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index d20150d68a90..669bedfec4a9 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -3744,17 +3744,20 @@ static noinline_for_stack int scrub_workers_get(struct btrfs_fs_info *fs_info,
>   	lockdep_assert_held(&fs_info->scrub_lock);
>   
>   	if (refcount_read(&fs_info->scrub_workers_refcnt) == 0) {
> +		ASSERT(fs_info->scrub_workers == NULL);
>   		fs_info->scrub_workers = btrfs_alloc_workqueue(fs_info, "scrub",
>   				flags, is_dev_replace ? 1 : max_active, 4);
>   		if (!fs_info->scrub_workers)
>   			goto fail_scrub_workers;
>   
> +		ASSERT(fs_info->scrub_wr_completion_workers == NULL);
>   		fs_info->scrub_wr_completion_workers =
>   			btrfs_alloc_workqueue(fs_info, "scrubwrc", flags,
>   					      max_active, 2);
>   		if (!fs_info->scrub_wr_completion_workers)
>   			goto fail_scrub_wr_completion_workers;
>   
> +		ASSERT(fs_info->scrub_parity_workers == NULL);
>   		fs_info->scrub_parity_workers =
>   			btrfs_alloc_workqueue(fs_info, "scrubparity", flags,
>   					      max_active, 2);
> @@ -3934,6 +3937,10 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
>   		scrub_workers = fs_info->scrub_workers;
>   		scrub_wr_comp = fs_info->scrub_wr_completion_workers;
>   		scrub_parity = fs_info->scrub_parity_workers;
> +
> +		fs_info->scrub_workers = NULL;
> +		fs_info->scrub_wr_completion_workers = NULL;
> +		fs_info->scrub_parity_workers = NULL;
>   	}
>   	mutex_unlock(&fs_info->scrub_lock);
>   
>