ublk: fix canceling flag handling in batch I/O recovery

Two issues with ubq->canceling flag handling:

1) In ublk_queue_reset_io_flags(), ubq->canceling is set outside
   cancel_lock, violating the locking requirement. Move it inside
   the spinlock-protected section.

2) In ublk_batch_unprep_io(), when rolling back after a batch prep
   failure, if the queue became ready during prep (which cleared
   canceling), the flag is not restored when the queue becomes
   not-ready again. This allows new requests to be queued to
   uninitialized IO slots.

Fix by restoring ubq->canceling = true under cancel_lock when the
queue transitions from ready to not-ready during rollback.

Reported-by: Jens Axboe <[email protected]>
Fixes: 3f38507 ("ublk: fix batch I/O recovery -ENODEV error")
Signed-off-by: Ming Lei <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: Ming Lei

drivers/block/ublk_drv.c

@@ -2806,9 +2806,9 @@ static void ublk_queue_reset_io_flags(struct ublk_queue *ubq)
 	spin_lock(&ubq->cancel_lock);
 	for (j = 0; j < ubq->q_depth; j++)
 		ubq->ios[j].flags &= ~UBLK_IO_FLAG_CANCELED;
+	ubq->canceling = false;
 	spin_unlock(&ubq->cancel_lock);
 	ubq->fail_io = false;
-	ubq->canceling = false;
 }
 
 /* device can only be started after all IOs are ready */
@@ -3435,10 +3435,15 @@ static int ublk_batch_unprep_io(struct ublk_queue *ubq,
 
 	/*
 	 * If queue was ready before this decrement, it won't be anymore,
-	 * so we need to decrement the queue ready count too.
+	 * so we need to decrement the queue ready count and restore the
+	 * canceling flag to prevent new requests from being queued.
 	 */
-	if (ublk_queue_ready(ubq))
+	if (ublk_queue_ready(ubq)) {
 		data->ub->nr_queue_ready--;
+		spin_lock(&ubq->cancel_lock);
+		ubq->canceling = true;
+		spin_unlock(&ubq->cancel_lock);
+	}
 	ubq->nr_io_ready--;
 
 	ublk_io_lock(io);