Re: [PATCH v2 2/4] blk-crypto: make blk_crypto_evict_key() more robust

[Christoph Hellwig <hch@infradead.org>]

On Wed, Mar 08, 2023 at 11:36:43AM -0800, Eric Biggers wrote:
>  			   const struct blk_crypto_key *key)
> @@ -389,22 +377,22 @@ int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
>  
>  	blk_crypto_hw_enter(profile);
>  	slot = blk_crypto_find_keyslot(profile, key);
> +	if (slot) {

Isn't !slot also an error condition that we should warn on?

> +		if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
> +			/* BUG: key is still in use by I/O */
> +			err = -EBUSY;

Either way two gotos to jump forward for the error case would improve
the readability of the code a fair bit I think.

> +		} else {
> +			err = profile->ll_ops.keyslot_evict(
> +					profile, key,
> +					blk_crypto_keyslot_index(slot));
> +		}
> +		/*
> +		 * Callers may free the key even on error, so unlink the key
> +		 * from the hash table and clear slot->key even on error.
> +		 */
> +		hlist_del(&slot->hash_node);
> +		slot->key = NULL;
>  	}
>  	blk_crypto_hw_exit(profile);
>  	return err;

Also given your above accurate description of the calling context,
what is the point of even returning an error here vs just logging
an error message?