Re: [PATCH] btrfs: remove warnings superseded by refcount_t usage

[Nikolay Borisov <nborisov@suse.com>]

On 25.06.2018 19:38, David Sterba wrote:
> There are several WARN_ON calls that catch incrorrect reference counter
> updates, but this is what the refcount_t does already:
> 
> * refcount_inc from 0 will warn
> * refcount_dec_and_test from 0 will warn
> 

But these warnings are only going to be triggered in the case of
CONFIG_REFCOUNT_FULL otherwise refcount falls back to plain atomic
operations.

> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/delayed-ref.h | 1 -
>  fs/btrfs/extent_map.c  | 2 +-
>  fs/btrfs/transaction.c | 1 -
>  fs/btrfs/volumes.c     | 1 -
>  4 files changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h
> index ea1aecb6a50d..16ee92c541bf 100644
> --- a/fs/btrfs/delayed-ref.h
> +++ b/fs/btrfs/delayed-ref.h
> @@ -210,7 +210,6 @@ btrfs_free_delayed_extent_op(struct btrfs_delayed_extent_op *op)
>  
>  static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
>  {
> -	WARN_ON(refcount_read(&ref->refs) == 0);
>  	if (refcount_dec_and_test(&ref->refs)) {
>  		WARN_ON(ref->in_tree);
>  		switch (ref->type) {
> diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
> index 6648d55e5339..6808ad4ed3c9 100644
> --- a/fs/btrfs/extent_map.c
> +++ b/fs/btrfs/extent_map.c
> @@ -72,7 +72,7 @@ void free_extent_map(struct extent_map *em)
>  {
>  	if (!em)
>  		return;
> -	WARN_ON(refcount_read(&em->refs) == 0);
> +
>  	if (refcount_dec_and_test(&em->refs)) {
>  		WARN_ON(extent_map_in_tree(em));
>  		WARN_ON(!list_empty(&em->list));
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index 4485eae41e88..f6b68099b767 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -41,7 +41,6 @@ static const unsigned int btrfs_blocked_trans_types[TRANS_STATE_MAX] = {
>  
>  void btrfs_put_transaction(struct btrfs_transaction *transaction)
>  {
> -	WARN_ON(refcount_read(&transaction->use_count) == 0);
>  	if (refcount_dec_and_test(&transaction->use_count)) {
>  		BUG_ON(!list_empty(&transaction->list));
>  		WARN_ON(!RB_EMPTY_ROOT(&transaction->delayed_refs.href_root));
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index e034ad9e23b4..f64d26b4f278 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -5330,7 +5330,6 @@ static struct btrfs_bio *alloc_btrfs_bio(int total_stripes, int real_stripes)
>  
>  void btrfs_get_bbio(struct btrfs_bio *bbio)
>  {
> -	WARN_ON(!refcount_read(&bbio->refs));
>  	refcount_inc(&bbio->refs);
>  }
>  
>