1 files changed, 30 insertions, 17 deletions

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index c2c11f2a01e7..4ca6ec738c93 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -19,6 +19,7 @@
 #include <linux/errno.h>
 #include <linux/major.h>
 #include <linux/wait.h>
+#include <linux/wait_bit.h>
 #include <linux/blkdev.h>
 #include <linux/init.h>
 #include <linux/swap.h>
@@ -26,7 +27,6 @@
 #include <linux/compat.h>
 #include <linux/mutex.h>
 #include <linux/writeback.h>
-#include <linux/completion.h>
 #include <linux/highmem.h>
 #include <linux/sysfs.h>
 #include <linux/miscdevice.h>
@@ -327,7 +327,6 @@ struct ublk_device {
 
 	struct ublk_params	params;
 
-	struct completion	completion;
 	u32			nr_queue_ready;
 	bool 			unprivileged_daemons;
 	struct mutex cancel_mutex;
@@ -3054,12 +3053,12 @@ static void ublk_mark_io_ready(struct ublk_device *ub, u16 q_id,
 	if (ublk_dev_ready(ub)) {
 		/*
 		 * All queues ready - clear device-level canceling flag
-		 * and complete the recovery/initialization.
+		 * and wake ublk_dev_ready() waiters.
 		 */
 		mutex_lock(&ub->cancel_mutex);
 		ub->canceling = false;
 		mutex_unlock(&ub->cancel_mutex);
-		complete_all(&ub->completion);
+		wake_up_var(&ub->nr_queue_ready);
 	}
 }
 
@@ -4273,7 +4272,6 @@ static int ublk_init_queues(struct ublk_device *ub)
 			goto fail;
 	}
 
-	init_completion(&ub->completion);
 	return 0;
 
  fail:
@@ -4417,6 +4415,26 @@ static bool ublk_validate_user_pid(struct ublk_device *ub, pid_t ublksrv_pid)
 	return ub->ublksrv_tgid == ublksrv_pid;
 }
 
+/*
+ * Wait until all queues have fetched their I/O commands, and return with
+ * ub->mutex held and readiness guaranteed: then every queue's ->canceling
+ * is cleared. Ready may regress between wakeup and mutex_lock() (F_BATCH
+ * UNPREP, daemon death), so re-check it under the mutex and wait again.
+ */
+static int ublk_wait_dev_ready_and_lock(struct ublk_device *ub)
+{
+	while (true) {
+		if (wait_var_event_interruptible(&ub->nr_queue_ready,
+						 ublk_dev_ready(ub)))
+			return -EINTR;
+
+		mutex_lock(&ub->mutex);
+		if (ublk_dev_ready(ub))
+			return 0;
+		mutex_unlock(&ub->mutex);
+	}
+}
+
 static int ublk_ctrl_start_dev(struct ublk_device *ub,
 		const struct ublksrv_ctrl_cmd *header)
 {
@@ -4499,15 +4517,10 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub,
 		};
 	}
 
-	if (wait_for_completion_interruptible(&ub->completion) != 0)
+	if (ublk_wait_dev_ready_and_lock(ub))
 		return -EINTR;
 
-	if (!ublk_validate_user_pid(ub, ublksrv_pid))
-		return -EINVAL;
-
-	mutex_lock(&ub->mutex);
-	/* device may become not ready in case of F_BATCH */
-	if (!ublk_dev_ready(ub)) {
+	if (!ublk_validate_user_pid(ub, ublksrv_pid)) {
 		ret = -EINVAL;
 		goto out_unlock;
 	}
@@ -5071,7 +5084,6 @@ static int ublk_ctrl_start_recovery(struct ublk_device *ub)
 		goto out_unlock;
 	}
 	pr_devel("%s: start recovery for dev id %d\n", __func__, ub->ub_number);
-	init_completion(&ub->completion);
 	ret = 0;
  out_unlock:
 	mutex_unlock(&ub->mutex);
@@ -5087,16 +5099,17 @@ static int ublk_ctrl_end_recovery(struct ublk_device *ub,
 	pr_devel("%s: Waiting for all FETCH_REQs, dev id %d...\n", __func__,
 		 header->dev_id);
 
-	if (wait_for_completion_interruptible(&ub->completion))
+	if (ublk_wait_dev_ready_and_lock(ub))
 		return -EINTR;
 
 	pr_devel("%s: All FETCH_REQs received, dev id %d\n", __func__,
 		 header->dev_id);
 
-	if (!ublk_validate_user_pid(ub, ublksrv_pid))
-		return -EINVAL;
+	if (!ublk_validate_user_pid(ub, ublksrv_pid)) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
 
-	mutex_lock(&ub->mutex);
 	if (ublk_nosrv_should_stop_dev(ub))
 		goto out_unlock;