block: change wait on bd_claiming to use a var_waitqueue

bd_prepare_to_claim() waits for a var to change, not for a bit to be
cleared. Change from bit_waitqueue() to __var_waitqueue() and
correspondingly use wake_up_var(). This will allow a future patch which
change the "bit" function to expect an "unsigned long *" instead of
"void *".
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20240826063659.15327-2-neilb@suse.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/bdev.c

@@ -548,7 +548,7 @@ int bd_prepare_to_claim(struct block_device *bdev, void *holder,
 
 	/* if claiming is already in progress, wait for it to finish */
 	if (whole->bd_claiming) {
-		wait_queue_head_t *wq = bit_waitqueue(&whole->bd_claiming, 0);
+		wait_queue_head_t *wq = __var_waitqueue(&whole->bd_claiming);
 		DEFINE_WAIT(wait);
 
 		prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
@@ -571,7 +571,7 @@ static void bd_clear_claiming(struct block_device *whole, void *holder)
 	/* tell others that we're done */
 	BUG_ON(whole->bd_claiming != holder);
 	whole->bd_claiming = NULL;
-	wake_up_bit(&whole->bd_claiming, 0);
+	wake_up_var(&whole->bd_claiming);
 }
 
 /**