1 files changed, 356 insertions, 222 deletions

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 9fd284fa76dc..6561d2a561fa 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -48,6 +48,8 @@
 
 #define UBLK_MINORS		(1U << MINORBITS)
 
+#define UBLK_INVALID_BUF_IDX 	((u16)-1)
+
 /* private ioctl command mirror */
 #define UBLK_CMD_DEL_DEV_ASYNC	_IOC_NR(UBLK_U_CMD_DEL_DEV_ASYNC)
 #define UBLK_CMD_UPDATE_SIZE	_IOC_NR(UBLK_U_CMD_UPDATE_SIZE)
@@ -70,7 +72,8 @@
 		| UBLK_F_UPDATE_SIZE \
 		| UBLK_F_AUTO_BUF_REG \
 		| UBLK_F_QUIESCE \
-		| UBLK_F_PER_IO_DAEMON)
+		| UBLK_F_PER_IO_DAEMON \
+		| UBLK_F_BUF_REG_OFF_DAEMON)
 
 #define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \
 		| UBLK_F_USER_RECOVERY_REISSUE \
@@ -82,14 +85,6 @@
 	 UBLK_PARAM_TYPE_DEVT | UBLK_PARAM_TYPE_ZONED |    \
 	 UBLK_PARAM_TYPE_DMA_ALIGN | UBLK_PARAM_TYPE_SEGMENT)
 
-struct ublk_rq_data {
-	refcount_t ref;
-
-	/* for auto-unregister buffer in case of UBLK_F_AUTO_BUF_REG */
-	u16 buf_index;
-	void *buf_ctx_handle;
-};
-
 struct ublk_uring_cmd_pdu {
 	/*
 	 * Store requests in same batch temporarily for queuing them to
@@ -110,8 +105,6 @@ struct ublk_uring_cmd_pdu {
 	 */
 	struct ublk_queue *ubq;
 
-	struct ublk_auto_buf_reg buf;
-
 	u16 tag;
 };
 
@@ -155,9 +148,19 @@ struct ublk_uring_cmd_pdu {
 /* atomic RW with ubq->cancel_lock */
 #define UBLK_IO_FLAG_CANCELED	0x80000000
 
+/*
+ * Initialize refcount to a large number to include any registered buffers.
+ * UBLK_IO_COMMIT_AND_FETCH_REQ will release these references minus those for
+ * any buffers registered on the io daemon task.
+ */
+#define UBLK_REFCOUNT_INIT (REFCOUNT_MAX / 2)
+
 struct ublk_io {
 	/* userspace buffer address from io cmd */
-	__u64	addr;
+	union {
+		__u64	addr;
+		struct ublk_auto_buf_reg buf;
+	};
 	unsigned int flags;
 	int res;
 
@@ -169,7 +172,24 @@ struct ublk_io {
 	};
 
 	struct task_struct *task;
-};
+
+	/*
+	 * The number of uses of this I/O by the ublk server
+	 * if user copy or zero copy are enabled:
+	 * - UBLK_REFCOUNT_INIT from dispatch to the server
+	 *   until UBLK_IO_COMMIT_AND_FETCH_REQ
+	 * - 1 for each inflight ublk_ch_{read,write}_iter() call
+	 * - 1 for each io_uring registered buffer not registered on task
+	 * The I/O can only be completed once all references are dropped.
+	 * User copy and buffer registration operations are only permitted
+	 * if the reference count is nonzero.
+	 */
+	refcount_t ref;
+	/* Count of buffers registered on task and not yet unregistered */
+	unsigned task_registered_buffers;
+
+	void *buf_ctx_handle;
+} ____cacheline_aligned_in_smp;
 
 struct ublk_queue {
 	int q_id;
@@ -216,6 +236,9 @@ struct ublk_device {
 	struct completion	completion;
 	unsigned int		nr_queues_ready;
 	unsigned int		nr_privileged_daemon;
+	struct mutex cancel_mutex;
+	bool canceling;
+	pid_t 	ublksrv_tgid;
 };
 
 /* header of ublk_params */
@@ -228,7 +251,8 @@ static void ublk_io_release(void *priv);
 static void ublk_stop_dev_unlocked(struct ublk_device *ub);
 static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq);
 static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
-		const struct ublk_queue *ubq, int tag, size_t offset);
+		const struct ublk_queue *ubq, struct ublk_io *io,
+		size_t offset);
 static inline unsigned int ublk_req_build_flags(struct request *req);
 
 static inline struct ublksrv_io_desc *
@@ -673,38 +697,29 @@ static inline bool ublk_need_req_ref(const struct ublk_queue *ubq)
 }
 
 static inline void ublk_init_req_ref(const struct ublk_queue *ubq,
-		struct request *req)
+		struct ublk_io *io)
 {
-	if (ublk_need_req_ref(ubq)) {
-		struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
-
-		refcount_set(&data->ref, 1);
-	}
+	if (ublk_need_req_ref(ubq))
+		refcount_set(&io->ref, UBLK_REFCOUNT_INIT);
 }
 
-static inline bool ublk_get_req_ref(const struct ublk_queue *ubq,
-		struct request *req)
+static inline bool ublk_get_req_ref(struct ublk_io *io)
 {
-	if (ublk_need_req_ref(ubq)) {
-		struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
-
-		return refcount_inc_not_zero(&data->ref);
-	}
+	return refcount_inc_not_zero(&io->ref);
+}
 
-	return true;
+static inline void ublk_put_req_ref(struct ublk_io *io, struct request *req)
+{
+	if (refcount_dec_and_test(&io->ref))
+		__ublk_complete_rq(req);
 }
 
-static inline void ublk_put_req_ref(const struct ublk_queue *ubq,
-		struct request *req)
+static inline bool ublk_sub_req_ref(struct ublk_io *io)
 {
-	if (ublk_need_req_ref(ubq)) {
-		struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
+	unsigned sub_refs = UBLK_REFCOUNT_INIT - io->task_registered_buffers;
 
-		if (refcount_dec_and_test(&data->ref))
-			__ublk_complete_rq(req);
-	} else {
-		__ublk_complete_rq(req);
-	}
+	io->task_registered_buffers = 0;
+	return refcount_sub_and_test(sub_refs, &io->ref);
 }
 
 static inline bool ublk_need_get_data(const struct ublk_queue *ubq)
@@ -981,7 +996,7 @@ static inline bool ublk_need_unmap_req(const struct request *req)
 }
 
 static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req,
-		struct ublk_io *io)
+		       const struct ublk_io *io)
 {
 	const unsigned int rq_bytes = blk_rq_bytes(req);
 
@@ -1005,7 +1020,7 @@ static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req,
 
 static int ublk_unmap_io(const struct ublk_queue *ubq,
 		const struct request *req,
-		struct ublk_io *io)
+		const struct ublk_io *io)
 {
 	const unsigned int rq_bytes = blk_rq_bytes(req);
 
@@ -1140,7 +1155,7 @@ static inline void __ublk_complete_rq(struct request *req)
 
 	if (blk_update_request(req, BLK_STS_OK, io->res))
 		blk_mq_requeue_request(req, true);
-	else
+	else if (likely(!blk_should_fake_timeout(req->q)))
 		__blk_mq_end_request(req, BLK_STS_OK);
 
 	return;
@@ -1188,39 +1203,33 @@ static inline void __ublk_abort_rq(struct ublk_queue *ubq,
 		blk_mq_end_request(rq, BLK_STS_IOERR);
 }
 
-static void ublk_auto_buf_reg_fallback(struct request *req)
+static void
+ublk_auto_buf_reg_fallback(const struct ublk_queue *ubq, struct ublk_io *io)
 {
-	const struct ublk_queue *ubq = req->mq_hctx->driver_data;
-	struct ublksrv_io_desc *iod = ublk_get_iod(ubq, req->tag);
-	struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
+	unsigned tag = io - ubq->ios;
+	struct ublksrv_io_desc *iod = ublk_get_iod(ubq, tag);
 
 	iod->op_flags |= UBLK_IO_F_NEED_REG_BUF;
-	refcount_set(&data->ref, 1);
 }
 
-static bool ublk_auto_buf_reg(struct request *req, struct ublk_io *io,
-			      unsigned int issue_flags)
+static bool ublk_auto_buf_reg(const struct ublk_queue *ubq, struct request *req,
+			      struct ublk_io *io, unsigned int issue_flags)
 {
-	struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(io->cmd);
-	struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
 	int ret;
 
 	ret = io_buffer_register_bvec(io->cmd, req, ublk_io_release,
-				      pdu->buf.index, issue_flags);
+				      io->buf.index, issue_flags);
 	if (ret) {
-		if (pdu->buf.flags & UBLK_AUTO_BUF_REG_FALLBACK) {
-			ublk_auto_buf_reg_fallback(req);
+		if (io->buf.flags & UBLK_AUTO_BUF_REG_FALLBACK) {
+			ublk_auto_buf_reg_fallback(ubq, io);
 			return true;
 		}
 		blk_mq_end_request(req, BLK_STS_IOERR);
 		return false;
 	}
-	/* one extra reference is dropped by ublk_io_release */
-	refcount_set(&data->ref, 2);
 
-	data->buf_ctx_handle = io_uring_cmd_ctx_handle(io->cmd);
-	/* store buffer index in request payload */
-	data->buf_index = pdu->buf.index;
+	io->task_registered_buffers = 1;
+	io->buf_ctx_handle = io_uring_cmd_ctx_handle(io->cmd);
 	io->flags |= UBLK_IO_FLAG_AUTO_BUF_REG;
 	return true;
 }
@@ -1229,10 +1238,10 @@ static bool ublk_prep_auto_buf_reg(struct ublk_queue *ubq,
 				   struct request *req, struct ublk_io *io,
 				   unsigned int issue_flags)
 {
+	ublk_init_req_ref(ubq, io);
 	if (ublk_support_auto_buf_reg(ubq) && ublk_rq_has_data(req))
-		return ublk_auto_buf_reg(req, io, issue_flags);
+		return ublk_auto_buf_reg(ubq, req, io, issue_flags);
 
-	ublk_init_req_ref(ubq, req);
 	return true;
 }
 
@@ -1356,14 +1365,23 @@ static void ublk_queue_cmd_list(struct ublk_io *io, struct rq_list *l)
 static enum blk_eh_timer_return ublk_timeout(struct request *rq)
 {
 	struct ublk_queue *ubq = rq->mq_hctx->driver_data;
-	struct ublk_io *io = &ubq->ios[rq->tag];
+	pid_t tgid = ubq->dev->ublksrv_tgid;
+	struct task_struct *p;
+	struct pid *pid;
 
-	if (ubq->flags & UBLK_F_UNPRIVILEGED_DEV) {
-		send_sig(SIGKILL, io->task, 0);
-		return BLK_EH_DONE;
-	}
+	if (!(ubq->flags & UBLK_F_UNPRIVILEGED_DEV))
+		return BLK_EH_RESET_TIMER;
 
-	return BLK_EH_RESET_TIMER;
+	if (unlikely(!tgid))
+		return BLK_EH_RESET_TIMER;
+
+	rcu_read_lock();
+	pid = find_vpid(tgid);
+	p = pid_task(pid, PIDTYPE_PID);
+	if (p)
+		send_sig(SIGKILL, p, 0);
+	rcu_read_unlock();
+	return BLK_EH_DONE;
 }
 
 static blk_status_t ublk_prep_req(struct ublk_queue *ubq, struct request *rq,
@@ -1504,6 +1522,9 @@ static void ublk_queue_reinit(struct ublk_device *ub, struct ublk_queue *ubq)
 			put_task_struct(io->task);
 			io->task = NULL;
 		}
+
+		WARN_ON_ONCE(refcount_read(&io->ref));
+		WARN_ON_ONCE(io->task_registered_buffers);
 	}
 }
 
@@ -1515,6 +1536,7 @@ static int ublk_ch_open(struct inode *inode, struct file *filp)
 	if (test_and_set_bit(UB_STATE_OPEN, &ub->state))
 		return -EBUSY;
 	filp->private_data = ub;
+	ub->ublksrv_tgid = current->tgid;
 	return 0;
 }
 
@@ -1529,6 +1551,7 @@ static void ublk_reset_ch_dev(struct ublk_device *ub)
 	ub->mm = NULL;
 	ub->nr_queues_ready = 0;
 	ub->nr_privileged_daemon = 0;
+	ub->ublksrv_tgid = -1;
 }
 
 static struct gendisk *ublk_get_disk(struct ublk_device *ub)
@@ -1550,6 +1573,27 @@ static void ublk_put_disk(struct gendisk *disk)
 		put_device(disk_to_dev(disk));
 }
 
+/*
+ * Use this function to ensure that ->canceling is consistently set for
+ * the device and all queues. Do not set these flags directly.
+ *
+ * Caller must ensure that:
+ * - cancel_mutex is held. This ensures that there is no concurrent
+ *   access to ub->canceling and no concurrent writes to ubq->canceling.
+ * - there are no concurrent reads of ubq->canceling from the queue_rq
+ *   path. This can be done by quiescing the queue, or through other
+ *   means.
+ */
+static void ublk_set_canceling(struct ublk_device *ub, bool canceling)
+	__must_hold(&ub->cancel_mutex)
+{
+	int i;
+
+	ub->canceling = canceling;
+	for (i = 0; i < ub->dev_info.nr_hw_queues; i++)
+		ublk_get_queue(ub, i)->canceling = canceling;
+}
+
 static int ublk_ch_release(struct inode *inode, struct file *filp)
 {
 	struct ublk_device *ub = filp->private_data;
@@ -1578,12 +1622,11 @@ static int ublk_ch_release(struct inode *inode, struct file *filp)
 	 * All requests may be inflight, so ->canceling may not be set, set
 	 * it now.
 	 */
-	for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
-		struct ublk_queue *ubq = ublk_get_queue(ub, i);
-
-		ubq->canceling = true;
-		ublk_abort_queue(ub, ubq);
-	}
+	mutex_lock(&ub->cancel_mutex);
+	ublk_set_canceling(ub, true);
+	for (i = 0; i < ub->dev_info.nr_hw_queues; i++)
+		ublk_abort_queue(ub, ublk_get_queue(ub, i));
+	mutex_unlock(&ub->cancel_mutex);
 	blk_mq_kick_requeue_list(disk->queue);
 
 	/*
@@ -1706,23 +1749,17 @@ static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq)
 	}
 }
 
-/* Must be called when queue is frozen */
-static void ublk_mark_queue_canceling(struct ublk_queue *ubq)
+static void ublk_start_cancel(struct ublk_device *ub)
 {
-	spin_lock(&ubq->cancel_lock);
-	if (!ubq->canceling)
-		ubq->canceling = true;
-	spin_unlock(&ubq->cancel_lock);
-}
-
-static void ublk_start_cancel(struct ublk_queue *ubq)
-{
-	struct ublk_device *ub = ubq->dev;
 	struct gendisk *disk = ublk_get_disk(ub);
 
 	/* Our disk has been dead */
 	if (!disk)
 		return;
+
+	mutex_lock(&ub->cancel_mutex);
+	if (ub->canceling)
+		goto out;
 	/*
 	 * Now we are serialized with ublk_queue_rq()
 	 *
@@ -1731,8 +1768,10 @@ static void ublk_start_cancel(struct ublk_queue *ubq)
 	 * touch completed uring_cmd
 	 */
 	blk_mq_quiesce_queue(disk->queue);
-	ublk_mark_queue_canceling(ubq);
+	ublk_set_canceling(ub, true);
 	blk_mq_unquiesce_queue(disk->queue);
+out:
+	mutex_unlock(&ub->cancel_mutex);
 	ublk_put_disk(disk);
 }
 
@@ -1805,8 +1844,7 @@ static void ublk_uring_cmd_cancel_fn(struct io_uring_cmd *cmd,
 	if (WARN_ON_ONCE(task && task != io->task))
 		return;
 
-	if (!ubq->canceling)
-		ublk_start_cancel(ubq);
+	ublk_start_cancel(ubq->dev);
 
 	WARN_ON_ONCE(io->cmd != cmd);
 	ublk_cancel_cmd(ubq, pdu->tag, issue_flags);
@@ -1930,9 +1968,11 @@ static void ublk_reset_io_flags(struct ublk_device *ub)
 		for (j = 0; j < ubq->q_depth; j++)
 			ubq->ios[j].flags &= ~UBLK_IO_FLAG_CANCELED;
 		spin_unlock(&ubq->cancel_lock);
-		ubq->canceling = false;
 		ubq->fail_io = false;
 	}
+	mutex_lock(&ub->cancel_mutex);
+	ublk_set_canceling(ub, false);
+	mutex_unlock(&ub->cancel_mutex);
 }
 
 /* device can only be started after all IOs are ready */
@@ -1967,12 +2007,66 @@ static inline int ublk_check_cmd_op(u32 cmd_op)
 	return 0;
 }
 
-static inline void ublk_fill_io_cmd(struct ublk_io *io,
-		struct io_uring_cmd *cmd, unsigned long buf_addr)
+static inline int ublk_set_auto_buf_reg(struct ublk_io *io, struct io_uring_cmd *cmd)
+{
+	io->buf = ublk_sqe_addr_to_auto_buf_reg(READ_ONCE(cmd->sqe->addr));
+
+	if (io->buf.reserved0 || io->buf.reserved1)
+		return -EINVAL;
+
+	if (io->buf.flags & ~UBLK_AUTO_BUF_REG_F_MASK)
+		return -EINVAL;
+	return 0;
+}
+
+static int ublk_handle_auto_buf_reg(struct ublk_io *io,
+				    struct io_uring_cmd *cmd,
+				    u16 *buf_idx)
 {
+	if (io->flags & UBLK_IO_FLAG_AUTO_BUF_REG) {
+		io->flags &= ~UBLK_IO_FLAG_AUTO_BUF_REG;
+
+		/*
+		 * `UBLK_F_AUTO_BUF_REG` only works iff `UBLK_IO_FETCH_REQ`
+		 * and `UBLK_IO_COMMIT_AND_FETCH_REQ` are issued from same
+		 * `io_ring_ctx`.
+		 *
+		 * If this uring_cmd's io_ring_ctx isn't same with the
+		 * one for registering the buffer, it is ublk server's
+		 * responsibility for unregistering the buffer, otherwise
+		 * this ublk request gets stuck.
+		 */
+		if (io->buf_ctx_handle == io_uring_cmd_ctx_handle(cmd))
+			*buf_idx = io->buf.index;
+	}
+
+	return ublk_set_auto_buf_reg(io, cmd);
+}
+
+/* Once we return, `io->req` can't be used any more */
+static inline struct request *
+ublk_fill_io_cmd(struct ublk_io *io, struct io_uring_cmd *cmd)
+{
+	struct request *req = io->req;
+
 	io->cmd = cmd;
 	io->flags |= UBLK_IO_FLAG_ACTIVE;
+	/* now this cmd slot is owned by ublk driver */
+	io->flags &= ~UBLK_IO_FLAG_OWNED_BY_SRV;
+
+	return req;
+}
+
+static inline int
+ublk_config_io_buf(const struct ublk_queue *ubq, struct ublk_io *io,
+		   struct io_uring_cmd *cmd, unsigned long buf_addr,
+		   u16 *buf_idx)
+{
+	if (ublk_support_auto_buf_reg(ubq))
+		return ublk_handle_auto_buf_reg(io, cmd, buf_idx);
+
 	io->addr = buf_addr;
+	return 0;
 }
 
 static inline void ublk_prep_cancel(struct io_uring_cmd *cmd,
@@ -1990,30 +2084,25 @@ static inline void ublk_prep_cancel(struct io_uring_cmd *cmd,
 	io_uring_cmd_mark_cancelable(cmd, issue_flags);
 }
 
-static inline int ublk_set_auto_buf_reg(struct io_uring_cmd *cmd)
-{
-	struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
-
-	pdu->buf = ublk_sqe_addr_to_auto_buf_reg(READ_ONCE(cmd->sqe->addr));
-
-	if (pdu->buf.reserved0 || pdu->buf.reserved1)
-		return -EINVAL;
-
-	if (pdu->buf.flags & ~UBLK_AUTO_BUF_REG_F_MASK)
-		return -EINVAL;
-	return 0;
-}
-
 static void ublk_io_release(void *priv)
 {
 	struct request *rq = priv;
 	struct ublk_queue *ubq = rq->mq_hctx->driver_data;
+	struct ublk_io *io = &ubq->ios[rq->tag];
 
-	ublk_put_req_ref(ubq, rq);
+	/*
+	 * task_registered_buffers may be 0 if buffers were registered off task
+	 * but unregistered on task. Or after UBLK_IO_COMMIT_AND_FETCH_REQ.
+	 */
+	if (current == io->task && io->task_registered_buffers)
+		io->task_registered_buffers--;
+	else
+		ublk_put_req_ref(io, rq);
 }
 
 static int ublk_register_io_buf(struct io_uring_cmd *cmd,
-				const struct ublk_queue *ubq, unsigned int tag,
+				const struct ublk_queue *ubq,
+				struct ublk_io *io,
 				unsigned int index, unsigned int issue_flags)
 {
 	struct ublk_device *ub = cmd->file->private_data;
@@ -2023,30 +2112,75 @@ static int ublk_register_io_buf(struct io_uring_cmd *cmd,
 	if (!ublk_support_zero_copy(ubq))
 		return -EINVAL;
 
-	req = __ublk_check_and_get_req(ub, ubq, tag, 0);
+	req = __ublk_check_and_get_req(ub, ubq, io, 0);
 	if (!req)
 		return -EINVAL;
 
 	ret = io_buffer_register_bvec(cmd, req, ublk_io_release, index,
 				      issue_flags);
 	if (ret) {
-		ublk_put_req_ref(ubq, req);
+		ublk_put_req_ref(io, req);
 		return ret;
 	}
 
 	return 0;
 }
 
+static int
+ublk_daemon_register_io_buf(struct io_uring_cmd *cmd,
+			    const struct ublk_queue *ubq, struct ublk_io *io,
+			    unsigned index, unsigned issue_flags)
+{
+	unsigned new_registered_buffers;
+	struct request *req = io->req;
+	int ret;
+
+	/*
+	 * Ensure there are still references for ublk_sub_req_ref() to release.
+	 * If not, fall back on the thread-safe buffer registration.
+	 */
+	new_registered_buffers = io->task_registered_buffers + 1;
+	if (unlikely(new_registered_buffers >= UBLK_REFCOUNT_INIT))
+		return ublk_register_io_buf(cmd, ubq, io, index, issue_flags);
+
+	if (!ublk_support_zero_copy(ubq) || !ublk_rq_has_data(req))
+		return -EINVAL;
+
+	ret = io_buffer_register_bvec(cmd, req, ublk_io_release, index,
+				      issue_flags);
+	if (ret)
+		return ret;
+
+	io->task_registered_buffers = new_registered_buffers;
+	return 0;
+}
+
 static int ublk_unregister_io_buf(struct io_uring_cmd *cmd,
-				  const struct ublk_queue *ubq,
+				  const struct ublk_device *ub,
 				  unsigned int index, unsigned int issue_flags)
 {
-	if (!ublk_support_zero_copy(ubq))
+	if (!(ub->dev_info.flags & UBLK_F_SUPPORT_ZERO_COPY))
 		return -EINVAL;
 
 	return io_buffer_unregister_bvec(cmd, index, issue_flags);
 }
 
+static int ublk_check_fetch_buf(const struct ublk_queue *ubq, __u64 buf_addr)
+{
+	if (ublk_need_map_io(ubq)) {
+		/*
+		 * FETCH_RQ has to provide IO buffer if NEED GET
+		 * DATA is not enabled
+		 */
+		if (!buf_addr && !ublk_need_get_data(ubq))
+			return -EINVAL;
+	} else if (buf_addr) {
+		/* User copy requires addr to be unset */
+		return -EINVAL;
+	}
+	return 0;
+}
+
 static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
 		      struct ublk_io *io, __u64 buf_addr)
 {
@@ -2073,26 +2207,11 @@ static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
 
 	WARN_ON_ONCE(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV);
 
-	if (ublk_need_map_io(ubq)) {
-		/*
-		 * FETCH_RQ has to provide IO buffer if NEED GET
-		 * DATA is not enabled
-		 */
-		if (!buf_addr && !ublk_need_get_data(ubq))
-			goto out;
-	} else if (buf_addr) {
-		/* User copy requires addr to be unset */
-		ret = -EINVAL;
+	ublk_fill_io_cmd(io, cmd);
+	ret = ublk_config_io_buf(ubq, io, cmd, buf_addr, NULL);
+	if (ret)
 		goto out;
-	}
 
-	if (ublk_support_auto_buf_reg(ubq)) {
-		ret = ublk_set_auto_buf_reg(cmd);
-		if (ret)
-			goto out;
-	}
-
-	ublk_fill_io_cmd(io, cmd, buf_addr);
 	WRITE_ONCE(io->task, get_task_struct(current));
 	ublk_mark_io_ready(ub, ubq);
 out:
@@ -2100,10 +2219,8 @@ out:
 	return ret;
 }
 
-static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
-				 struct ublk_io *io, struct io_uring_cmd *cmd,
-				 const struct ublksrv_io_cmd *ub_cmd,
-				 unsigned int issue_flags)
+static int ublk_check_commit_and_fetch(const struct ublk_queue *ubq,
+				       struct ublk_io *io, __u64 buf_addr)
 {
 	struct request *req = io->req;
 
@@ -2112,10 +2229,10 @@ static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
 		 * COMMIT_AND_FETCH_REQ has to provide IO buffer if
 		 * NEED GET DATA is not enabled or it is Read IO.
 		 */
-		if (!ub_cmd->addr && (!ublk_need_get_data(ubq) ||
+		if (!buf_addr && (!ublk_need_get_data(ubq) ||
 					req_op(req) == REQ_OP_READ))
 			return -EINVAL;
-	} else if (req_op(req) != REQ_OP_ZONE_APPEND && ub_cmd->addr) {
+	} else if (req_op(req) != REQ_OP_ZONE_APPEND && buf_addr) {
 		/*
 		 * User copy requires addr to be unset when command is
 		 * not zone append
@@ -2123,48 +2240,17 @@ static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
 		return -EINVAL;
 	}
 
-	if (ublk_support_auto_buf_reg(ubq)) {
-		int ret;
-
-		/*
-		 * `UBLK_F_AUTO_BUF_REG` only works iff `UBLK_IO_FETCH_REQ`
-		 * and `UBLK_IO_COMMIT_AND_FETCH_REQ` are issued from same
-		 * `io_ring_ctx`.
-		 *
-		 * If this uring_cmd's io_ring_ctx isn't same with the
-		 * one for registering the buffer, it is ublk server's
-		 * responsibility for unregistering the buffer, otherwise
-		 * this ublk request gets stuck.
-		 */
-		if (io->flags & UBLK_IO_FLAG_AUTO_BUF_REG) {
-			struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
-
-			if (data->buf_ctx_handle == io_uring_cmd_ctx_handle(cmd))
-				io_buffer_unregister_bvec(cmd, data->buf_index,
-						issue_flags);
-			io->flags &= ~UBLK_IO_FLAG_AUTO_BUF_REG;
-		}
-
-		ret = ublk_set_auto_buf_reg(cmd);
-		if (ret)
-			return ret;
-	}
-
-	ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
-
-	/* now this cmd slot is owned by ublk driver */
-	io->flags &= ~UBLK_IO_FLAG_OWNED_BY_SRV;
-	io->res = ub_cmd->result;
-
-	if (req_op(req) == REQ_OP_ZONE_APPEND)
-		req->__sector = ub_cmd->zone_append_lba;
-
-	if (likely(!blk_should_fake_timeout(req->q)))
-		ublk_put_req_ref(ubq, req);
-
 	return 0;
 }
 
+static bool ublk_need_complete_req(const struct ublk_queue *ubq,
+				   struct ublk_io *io)
+{
+	if (ublk_need_req_ref(ubq))
+		return ublk_sub_req_ref(io);
+	return true;
+}
+
 static bool ublk_get_data(const struct ublk_queue *ubq, struct ublk_io *io,
 			  struct request *req)
 {
@@ -2187,19 +2273,33 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 			       unsigned int issue_flags,
 			       const struct ublksrv_io_cmd *ub_cmd)
 {
+	u16 buf_idx = UBLK_INVALID_BUF_IDX;
 	struct ublk_device *ub = cmd->file->private_data;
-	struct task_struct *task;
 	struct ublk_queue *ubq;
 	struct ublk_io *io;
 	u32 cmd_op = cmd->cmd_op;
 	unsigned tag = ub_cmd->tag;
-	int ret = -EINVAL;
 	struct request *req;
+	int ret;
+	bool compl;
 
 	pr_devel("%s: received: cmd op %d queue %d tag %d result %d\n",
 			__func__, cmd->cmd_op, ub_cmd->q_id, tag,
 			ub_cmd->result);
 
+	ret = ublk_check_cmd_op(cmd_op);
+	if (ret)
+		goto out;
+
+	/*
+	 * io_buffer_unregister_bvec() doesn't access the ubq or io,
+	 * so no need to validate the q_id, tag, or task
+	 */
+	if (_IOC_NR(cmd_op) == UBLK_IO_UNREGISTER_IO_BUF)
+		return ublk_unregister_io_buf(cmd, ub, ub_cmd->addr,
+					      issue_flags);
+
+	ret = -EINVAL;
 	if (ub_cmd->q_id >= ub->dev_info.nr_hw_queues)
 		goto out;
 
@@ -2209,21 +2309,37 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 		goto out;
 
 	io = &ubq->ios[tag];
-	task = READ_ONCE(io->task);
-	if (task && task != current)
+	/* UBLK_IO_FETCH_REQ can be handled on any task, which sets io->task */
+	if (unlikely(_IOC_NR(cmd_op) == UBLK_IO_FETCH_REQ)) {
+		ret = ublk_check_fetch_buf(ubq, ub_cmd->addr);
+		if (ret)
+			goto out;
+		ret = ublk_fetch(cmd, ubq, io, ub_cmd->addr);
+		if (ret)
+			goto out;
+
+		ublk_prep_cancel(cmd, issue_flags, ubq, tag);
+		return -EIOCBQUEUED;
+	}
+
+	if (READ_ONCE(io->task) != current) {
+		/*
+		 * ublk_register_io_buf() accesses only the io's refcount,
+		 * so can be handled on any task
+		 */
+		if (_IOC_NR(cmd_op) == UBLK_IO_REGISTER_IO_BUF)
+			return ublk_register_io_buf(cmd, ubq, io, ub_cmd->addr,
+						    issue_flags);
+
 		goto out;
+	}
 
 	/* there is pending io cmd, something must be wrong */
-	if (io->flags & UBLK_IO_FLAG_ACTIVE) {
+	if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)) {
 		ret = -EBUSY;
 		goto out;
 	}
 
-	/* only UBLK_IO_FETCH_REQ is allowed if io is not OWNED_BY_SRV */
-	if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV) &&
-	    _IOC_NR(cmd_op) != UBLK_IO_FETCH_REQ)
-		goto out;
-
 	/*
 	 * ensure that the user issues UBLK_IO_NEED_GET_DATA
 	 * iff the driver have set the UBLK_IO_FLAG_NEED_GET_DATA.
@@ -2232,23 +2348,27 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 			^ (_IOC_NR(cmd_op) == UBLK_IO_NEED_GET_DATA))
 		goto out;
 
-	ret = ublk_check_cmd_op(cmd_op);
-	if (ret)
-		goto out;
-
-	ret = -EINVAL;
 	switch (_IOC_NR(cmd_op)) {
 	case UBLK_IO_REGISTER_IO_BUF:
-		return ublk_register_io_buf(cmd, ubq, tag, ub_cmd->addr, issue_flags);
-	case UBLK_IO_UNREGISTER_IO_BUF:
-		return ublk_unregister_io_buf(cmd, ubq, ub_cmd->addr, issue_flags);
-	case UBLK_IO_FETCH_REQ:
-		ret = ublk_fetch(cmd, ubq, io, ub_cmd->addr);
+		return ublk_daemon_register_io_buf(cmd, ubq, io, ub_cmd->addr,
+						   issue_flags);
+	case UBLK_IO_COMMIT_AND_FETCH_REQ:
+		ret = ublk_check_commit_and_fetch(ubq, io, ub_cmd->addr);
 		if (ret)
 			goto out;
-		break;
-	case UBLK_IO_COMMIT_AND_FETCH_REQ:
-		ret = ublk_commit_and_fetch(ubq, io, cmd, ub_cmd, issue_flags);
+		io->res = ub_cmd->result;
+		req = ublk_fill_io_cmd(io, cmd);
+		ret = ublk_config_io_buf(ubq, io, cmd, ub_cmd->addr, &buf_idx);
+		compl = ublk_need_complete_req(ubq, io);
+
+		/* can't touch 'ublk_io' any more */
+		if (buf_idx != UBLK_INVALID_BUF_IDX)
+			io_buffer_unregister_bvec(cmd, buf_idx, issue_flags);
+		if (req_op(req) == REQ_OP_ZONE_APPEND)
+			req->__sector = ub_cmd->zone_append_lba;
+		if (compl)
+			__ublk_complete_rq(req);
+
 		if (ret)
 			goto out;
 		break;
@@ -2258,9 +2378,9 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 		 * uring_cmd active first and prepare for handling new requeued
 		 * request
 		 */
-		req = io->req;
-		ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
-		io->flags &= ~UBLK_IO_FLAG_OWNED_BY_SRV;
+		req = ublk_fill_io_cmd(io, cmd);
+		ret = ublk_config_io_buf(ubq, io, cmd, ub_cmd->addr, NULL);
+		WARN_ON_ONCE(ret);
 		if (likely(ublk_get_data(ubq, io, req))) {
 			__ublk_prep_compl_io_cmd(io, req);
 			return UBLK_IO_RES_OK;
@@ -2279,15 +2399,20 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 }
 
 static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
-		const struct ublk_queue *ubq, int tag, size_t offset)
+		const struct ublk_queue *ubq, struct ublk_io *io, size_t offset)
 {
+	unsigned tag = io - ubq->ios;
 	struct request *req;
 
+	/*
+	 * can't use io->req in case of concurrent UBLK_IO_COMMIT_AND_FETCH_REQ,
+	 * which would overwrite it with io->cmd
+	 */
 	req = blk_mq_tag_to_rq(ub->tag_set.tags[ubq->q_id], tag);
 	if (!req)
 		return NULL;
 
-	if (!ublk_get_req_ref(ubq, req))
+	if (!ublk_get_req_ref(io))
 		return NULL;
 
 	if (unlikely(!blk_mq_request_started(req) || req->tag != tag))
@@ -2301,7 +2426,7 @@ static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
 
 	return req;
 fail_put:
-	ublk_put_req_ref(ubq, req);
+	ublk_put_req_ref(io, req);
 	return NULL;
 }
 
@@ -2368,7 +2493,8 @@ static inline bool ublk_check_ubuf_dir(const struct request *req,
 }
 
 static struct request *ublk_check_and_get_req(struct kiocb *iocb,
-		struct iov_iter *iter, size_t *off, int dir)
+		struct iov_iter *iter, size_t *off, int dir,
+		struct ublk_io **io)
 {
 	struct ublk_device *ub = iocb->ki_filp->private_data;
 	struct ublk_queue *ubq;
@@ -2402,7 +2528,8 @@ static struct request *ublk_check_and_get_req(struct kiocb *iocb,
 	if (tag >= ubq->q_depth)
 		return ERR_PTR(-EINVAL);
 
-	req = __ublk_check_and_get_req(ub, ubq, tag, buf_off);
+	*io = &ubq->ios[tag];
+	req = __ublk_check_and_get_req(ub, ubq, *io, buf_off);
 	if (!req)
 		return ERR_PTR(-EINVAL);
 
@@ -2415,42 +2542,40 @@ static struct request *ublk_check_and_get_req(struct kiocb *iocb,
 	*off = buf_off;
 	return req;
 fail:
-	ublk_put_req_ref(ubq, req);
+	ublk_put_req_ref(*io, req);
 	return ERR_PTR(-EACCES);
 }
 
 static ssize_t ublk_ch_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
-	struct ublk_queue *ubq;
 	struct request *req;
+	struct ublk_io *io;
 	size_t buf_off;
 	size_t ret;
 
-	req = ublk_check_and_get_req(iocb, to, &buf_off, ITER_DEST);
+	req = ublk_check_and_get_req(iocb, to, &buf_off, ITER_DEST, &io);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
 	ret = ublk_copy_user_pages(req, buf_off, to, ITER_DEST);
-	ubq = req->mq_hctx->driver_data;
-	ublk_put_req_ref(ubq, req);
+	ublk_put_req_ref(io, req);
 
 	return ret;
 }
 
 static ssize_t ublk_ch_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
-	struct ublk_queue *ubq;
 	struct request *req;
+	struct ublk_io *io;
 	size_t buf_off;
 	size_t ret;
 
-	req = ublk_check_and_get_req(iocb, from, &buf_off, ITER_SOURCE);
+	req = ublk_check_and_get_req(iocb, from, &buf_off, ITER_SOURCE, &io);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
 	ret = ublk_copy_user_pages(req, buf_off, from, ITER_SOURCE);
-	ubq = req->mq_hctx->driver_data;
-	ublk_put_req_ref(ubq, req);
+	ublk_put_req_ref(io, req);
 
 	return ret;
 }
@@ -2475,6 +2600,8 @@ static void ublk_deinit_queue(struct ublk_device *ub, int q_id)
 		struct ublk_io *io = &ubq->ios[i];
 		if (io->task)
 			put_task_struct(io->task);
+		WARN_ON_ONCE(refcount_read(&io->ref));
+		WARN_ON_ONCE(io->task_registered_buffers);
 	}
 
 	if (ubq->io_cmd_buf)
@@ -2513,7 +2640,7 @@ static void ublk_deinit_queues(struct ublk_device *ub)
 
 	for (i = 0; i < nr_queues; i++)
 		ublk_deinit_queue(ub, i);
-	kfree(ub->__queues);
+	kvfree(ub->__queues);
 }
 
 static int ublk_init_queues(struct ublk_device *ub)
@@ -2524,7 +2651,7 @@ static int ublk_init_queues(struct ublk_device *ub)
 	int i, ret = -ENOMEM;
 
 	ub->queue_size = ubq_size;
-	ub->__queues = kcalloc(nr_queues, ubq_size, GFP_KERNEL);
+	ub->__queues = kvcalloc(nr_queues, ubq_size, GFP_KERNEL);
 	if (!ub->__queues)
 		return ret;
 
@@ -2580,6 +2707,7 @@ static void ublk_cdev_rel(struct device *dev)
 	ublk_deinit_queues(ub);
 	ublk_free_dev_number(ub);
 	mutex_destroy(&ub->mutex);
+	mutex_destroy(&ub->cancel_mutex);
 	kfree(ub);
 }
 
@@ -2627,7 +2755,6 @@ static int ublk_add_tag_set(struct ublk_device *ub)
 	ub->tag_set.nr_hw_queues = ub->dev_info.nr_hw_queues;
 	ub->tag_set.queue_depth = ub->dev_info.queue_depth;
 	ub->tag_set.numa_node = NUMA_NO_NODE;
-	ub->tag_set.cmd_size = sizeof(struct ublk_rq_data);
 	ub->tag_set.driver_data = ub;
 	return blk_mq_alloc_tag_set(&ub->tag_set);
 }
@@ -2729,6 +2856,9 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub,
 	if (wait_for_completion_interruptible(&ub->completion) != 0)
 		return -EINTR;
 
+	if (ub->ublksrv_tgid != ublksrv_pid)
+		return -EINVAL;
+
 	mutex_lock(&ub->mutex);
 	if (ub->dev_info.state == UBLK_S_DEV_LIVE ||
 	    test_bit(UB_STATE_USED, &ub->state)) {
@@ -2933,6 +3063,7 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
 		goto out_unlock;
 	mutex_init(&ub->mutex);
 	spin_lock_init(&ub->lock);
+	mutex_init(&ub->cancel_mutex);
 
 	ret = ublk_alloc_dev_number(ub, header->dev_id);
 	if (ret < 0)
@@ -2953,7 +3084,8 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
 
 	ub->dev_info.flags |= UBLK_F_CMD_IOCTL_ENCODE |
 		UBLK_F_URING_CMD_COMP_IN_TASK |
-		UBLK_F_PER_IO_DAEMON;
+		UBLK_F_PER_IO_DAEMON |
+		UBLK_F_BUF_REG_OFF_DAEMON;
 
 	/* GET_DATA isn't needed any more with USER_COPY or ZERO COPY */
 	if (ub->dev_info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY |
@@ -3003,6 +3135,7 @@ out_free_dev_number:
 	ublk_free_dev_number(ub);
 out_free_ub:
 	mutex_destroy(&ub->mutex);
+	mutex_destroy(&ub->cancel_mutex);
 	kfree(ub);
 out_unlock:
 	mutex_unlock(&ublk_ctl_mutex);
@@ -3227,6 +3360,9 @@ static int ublk_ctrl_end_recovery(struct ublk_device *ub,
 	pr_devel("%s: All FETCH_REQs received, dev id %d\n", __func__,
 		 header->dev_id);
 
+	if (ub->ublksrv_tgid != ublksrv_pid)
+		return -EINVAL;
+
 	mutex_lock(&ub->mutex);
 	if (ublk_nosrv_should_stop_dev(ub))
 		goto out_unlock;
@@ -3340,7 +3476,7 @@ static int ublk_ctrl_quiesce_dev(struct ublk_device *ub,
 	/* zero means wait forever */
 	u64 timeout_ms = header->data[0];
 	struct gendisk *disk;
-	int i, ret = -ENODEV;
+	int ret = -ENODEV;
 
 	if (!(ub->dev_info.flags & UBLK_F_QUIESCE))
 		return -EOPNOTSUPP;
@@ -3357,14 +3493,12 @@ static int ublk_ctrl_quiesce_dev(struct ublk_device *ub,
 	if (ub->dev_info.state != UBLK_S_DEV_LIVE)
 		goto put_disk;
 
-	/* Mark all queues as canceling */
+	/* Mark the device as canceling */
+	mutex_lock(&ub->cancel_mutex);
 	blk_mq_quiesce_queue(disk->queue);
-	for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
-		struct ublk_queue *ubq = ublk_get_queue(ub, i);
-
-		ubq->canceling = true;
-	}
+	ublk_set_canceling(ub, true);
 	blk_mq_unquiesce_queue(disk->queue);
+	mutex_unlock(&ub->cancel_mutex);
 
 	if (!timeout_ms)
 		timeout_ms = UINT_MAX;