blk-crypto: drop the NULL check from blk_crypto_put_keyslot()

Now that all callers of blk_crypto_put_keyslot() check for NULL before
calling it, there is no need for blk_crypto_put_keyslot() to do the NULL
check itself.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20230315183907.53675-2-ebiggers@kernel.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-crypto-profile.c

@@ -227,14 +227,13 @@ EXPORT_SYMBOL_GPL(blk_crypto_keyslot_index);
  * @profile: the crypto profile of the device the key will be used on
  * @key: the key that will be used
  * @slot_ptr: If a keyslot is allocated, an opaque pointer to the keyslot struct
- *	      will be stored here; otherwise NULL will be stored here.
+ *	      will be stored here.  blk_crypto_put_keyslot() must be called
+ *	      later to release it.  Otherwise, NULL will be stored here.
  *
  * If the device has keyslots, this gets a keyslot that's been programmed with
  * the specified key.  If the key is already in a slot, this reuses it;
  * otherwise this waits for a slot to become idle and programs the key into it.
  *
- * This must be paired with a call to blk_crypto_put_keyslot().
- *
  * Context: Process context. Takes and releases profile->lock.
  * Return: BLK_STS_OK on success, meaning that either a keyslot was allocated or
  *	   one wasn't needed; or a blk_status_t error on failure.
@@ -312,20 +311,15 @@ blk_status_t blk_crypto_get_keyslot(struct blk_crypto_profile *profile,
 
 /**
  * blk_crypto_put_keyslot() - Release a reference to a keyslot
- * @slot: The keyslot to release the reference of (may be NULL).
+ * @slot: The keyslot to release the reference of
  *
  * Context: Any context.
  */
 void blk_crypto_put_keyslot(struct blk_crypto_keyslot *slot)
 {
-	struct blk_crypto_profile *profile;
+	struct blk_crypto_profile *profile = slot->profile;
 	unsigned long flags;
 
-	if (!slot)
-		return;
-
-	profile = slot->profile;
-
 	if (atomic_dec_and_lock_irqsave(&slot->slot_refs,
 					&profile->idle_slots_lock, flags)) {
 		list_add_tail(&slot->idle_slot_node, &profile->idle_slots);