ublk: clean up user copy references on ublk server exit

If a ublk server process releases a ublk char device file, any requests
dispatched to the ublk server but not yet completed will retain a ref
value of UBLK_REFCOUNT_INIT. Before commit e63d222 ("ublk: simplify
aborting ublk request"), __ublk_fail_req() would decrement the reference
count before completing the failed request. However, that commit
optimized __ublk_fail_req() to call __ublk_complete_rq() directly
without decrementing the request reference count.
The leaked reference count incorrectly allows user copy and zero copy
operations on the completed ublk request. It also triggers the
WARN_ON_ONCE(refcount_read(&io->ref)) warnings in ublk_queue_reinit()
and ublk_deinit_queue().
Commit c5c5eb2 ("ublk: avoid ublk_io_release() called after ublk
char dev is closed") already fixed the issue for ublk devices using
UBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference
count leak also affects UBLK_F_USER_COPY, the other reference-counted
data copy mode. Fix the condition in ublk_check_and_reset_active_ref()
to include all reference-counted data copy modes. This ensures that any
ublk requests still owned by the ublk server when it exits have their
reference counts reset to 0.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Fixes: e63d222 ("ublk: simplify aborting ublk request")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: calebsander

drivers/block/ublk_drv.c

@@ -1607,8 +1607,7 @@ static bool ublk_check_and_reset_active_ref(struct ublk_device *ub)
 {
 	int i, j;
 
-	if (!(ub->dev_info.flags & (UBLK_F_SUPPORT_ZERO_COPY |
-					UBLK_F_AUTO_BUF_REG)))
+	if (!ublk_dev_need_req_ref(ub))
 		return false;
 
 	for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {