ublk_drv: define macros for recovery feature and check them

Define some macros for recovery feature.

UBLK_S_DEV_QUIESCED implies that ublk_device is quiesced
and is ready for recovery. This state can be observed by userspace.

UBLK_F_USER_RECOVERY implies that:
(1) ublk_drv enables recovery feature. It won't let monitor_work to
    automatically abort rqs and release the device.
(2) With a dying ubq_daemon, ublk_drv ends(aborts) rqs issued to
    userspace(ublksrv) before crash.
(3) With a dying ubq_daemon, in task work and ublk_queue_rq(),
    ublk_drv requeues rqs.

Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220923153919.44078-3-ZiyangZhang@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/ublk_drv.c

@@ -49,7 +49,8 @@
 /* All UBLK_F_* have to be included into UBLK_F_ALL */
 #define UBLK_F_ALL (UBLK_F_SUPPORT_ZERO_COPY \
 		| UBLK_F_URING_CMD_COMP_IN_TASK \
-		| UBLK_F_NEED_GET_DATA)
+		| UBLK_F_NEED_GET_DATA \
+		| UBLK_F_USER_RECOVERY)
 
 /* All UBLK_PARAM_TYPE_* should be included here */
 #define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD)
@@ -323,6 +324,21 @@ static inline int ublk_queue_cmd_buf_size(struct ublk_device *ub, int q_id)
 			PAGE_SIZE);
 }
 
+static inline bool ublk_queue_can_use_recovery(
+		struct ublk_queue *ubq)
+{
+	if (ubq->flags & UBLK_F_USER_RECOVERY)
+		return true;
+	return false;
+}
+
+static inline bool ublk_can_use_recovery(struct ublk_device *ub)
+{
+	if (ub->dev_info.flags & UBLK_F_USER_RECOVERY)
+		return true;
+	return false;
+}
+
 static void ublk_free_disk(struct gendisk *disk)
 {
 	struct ublk_device *ub = disk->private_data;

include/uapi/linux/ublk_cmd.h

@@ -74,9 +74,12 @@
  */
 #define UBLK_F_NEED_GET_DATA (1UL << 2)
 
+#define UBLK_F_USER_RECOVERY	(1UL << 3)
+
 /* device state */
 #define UBLK_S_DEV_DEAD	0
 #define UBLK_S_DEV_LIVE	1
+#define UBLK_S_DEV_QUIESCED	2
 
 /* shipped via sqe->cmd of io_uring command */
 struct ublksrv_ctrl_cmd {