Commit 57c27f02 authored by Jim Harris's avatar Jim Harris Committed by Tomasz Zawadzki
Browse files

ublk: remove extra pthreads from ctrl uring processing 



We make a few changes here to enable this:

1) Set IORING_SETUP_SQPOLL on the control ring.
   Otherwise when UBLK_START_DEV is submitted it
   will be processed in the context of the system
   call itself, resulting the kernel block layer
   submitting reads to the new device which blocks
   the thread - meaning the system call may never
   return.
2) Save the cmd_op in each sqe, along with the
   spdk_ublk_dev pointer.
3) Add a poller to poll the ctrl ring.  The poller
   can get the ublk and cmd_op from the cqe to
   know which ctrl operation completed and take
   next steps as necessary.

Signed-off-by: default avatarJim Harris <james.r.harris@intel.com>
Change-Id: Ia0e51a4ff74781c85967c54969fbfc67a0d3f115
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/16404


Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarKonrad Sztyber <konrad.sztyber@intel.com>
Reviewed-by: default avatarXiaodong Liu <xiaodong.liu@intel.com>
Reviewed-by: default avatarMichal Berger <michal.berger@intel.com>
Reviewed-by: default avatarBen Walker <benjamin.walker@intel.com>
parent a5a75f34

lib/ublk/ublk.c

+86 −87
Original line number Diff line number Diff line
@@ -43,7 +43,9 @@ struct ublk_thread_ctx; 
static void ublk_submit_bdev_io(struct ublk_queue *q, uint16_t tag);

static void ublk_dev_queue_fini(struct ublk_queue *q);

static int ublk_poll(void *arg);

static int finish_start(struct spdk_ublk_dev *ublk);

static void ublk_set_params(struct spdk_ublk_dev *ublk);

static void ublk_finish_start(struct spdk_ublk_dev *ublk);

static void ublk_delete_dev(struct spdk_ublk_dev *ublk);



struct ublk_io {

	void			*payload;
@@ -91,14 +93,14 @@ struct spdk_ublk_dev { 
	struct spdk_mempool	*io_buf_pool;

	struct ublk_queue	queues[UBLK_DEV_MAX_QUEUES];



	/* Synchronize ublk_start_kernel pthread and ublk_stop */

	volatile int8_t		pending_ublk_pthread;

	struct spdk_poller	*retry_poller;

	int			retry_count;

	uint32_t		q_deinit_num;

	volatile bool		is_closing;

	ublk_del_cb		del_cb;

	void			*cb_arg;

	uint32_t		last_cmd_op;

	uint32_t		ctrl_ops_in_progress;



	TAILQ_ENTRY(spdk_ublk_dev) tailq;

};
@@ -116,6 +118,8 @@ struct ublk_tgt { 
	spdk_ublk_fini_cb	cb_fn;

	void			*cb_arg;

	struct io_uring		ctrl_ring;

	struct spdk_poller	*ctrl_poller;

	uint32_t		ctrl_ops_in_progress;

	struct ublk_thread_ctx	thread_ctx[UBLK_THREAD_MAX];

};
@@ -186,13 +190,54 @@ spdk_ublk_init(void) 
	}

}



static int

ublk_ctrl_poller(void *arg)

{

	struct io_uring *ring = &g_ublk_tgt.ctrl_ring;

	struct spdk_ublk_dev *ublk;

	struct io_uring_cqe *cqe;

	const int max = 8;

	int i, count = 0, rc;



	for (i = 0; i < max; i++) {

		rc = io_uring_peek_cqe(ring, &cqe);

		if (rc == -EAGAIN) {

			break;

		}



		assert(cqe != NULL);

		g_ublk_tgt.ctrl_ops_in_progress--;

		if (g_ublk_tgt.ctrl_ops_in_progress == 0) {

			spdk_poller_unregister(&g_ublk_tgt.ctrl_poller);

		}

		ublk = (struct spdk_ublk_dev *)cqe->user_data;

		ublk->ctrl_ops_in_progress--;

		switch (ublk->last_cmd_op) {

		case UBLK_CMD_ADD_DEV:

			ublk_set_params(ublk);

			break;

		case UBLK_CMD_SET_PARAMS:

			ublk_finish_start(ublk);

			break;

		case UBLK_CMD_DEL_DEV:

			ublk_delete_dev(ublk);

			break;

		default:

			break;

		}

		io_uring_cqe_seen(ring, cqe);

		count++;

	}



	return count > 0 ? SPDK_POLLER_BUSY : SPDK_POLLER_IDLE;

}



static int

ublk_ctrl_cmd(struct spdk_ublk_dev *ublk, uint32_t cmd_op, void *args)

{

	uint32_t dev_id = ublk->ublk_id;

	int rc = -EINVAL;

	struct io_uring_sqe *sqe;

	struct io_uring_cqe *cqe;

	struct ublksrv_ctrl_cmd *cmd;

	int *ublk_pid;

	struct ublksrv_ctrl_dev_info *dev_info;
@@ -209,6 +254,7 @@ ublk_ctrl_cmd(struct spdk_ublk_dev *ublk, uint32_t cmd_op, void *args) 
	sqe->ioprio = 0;

	cmd->dev_id = dev_id;

	cmd->queue_id = -1;

	ublk->last_cmd_op = cmd_op;



	switch (cmd_op) {

	case UBLK_CMD_START_DEV:
@@ -234,22 +280,21 @@ ublk_ctrl_cmd(struct spdk_ublk_dev *ublk, uint32_t cmd_op, void *args) 
		return -EINVAL;

	}

	ublk_set_sqe_cmd_op(sqe, cmd_op);

	io_uring_sqe_set_data(sqe, cmd);

	io_uring_sqe_set_data(sqe, ublk);



	rc = io_uring_submit(&g_ublk_tgt.ctrl_ring);

	if (rc < 0) {

		SPDK_ERRLOG("uring submit rc %d\n", rc);

		return rc;

	if (g_ublk_tgt.ctrl_ops_in_progress == 0) {

		g_ublk_tgt.ctrl_poller = SPDK_POLLER_REGISTER(ublk_ctrl_poller, NULL, 10);

	}



	rc = io_uring_wait_cqe(&g_ublk_tgt.ctrl_ring, &cqe);

	rc = io_uring_submit(&g_ublk_tgt.ctrl_ring);

	if (rc < 0) {

		SPDK_ERRLOG("wait cqe: %s\n", strerror(-rc));

		SPDK_ERRLOG("uring submit rc %d\n", rc);

		return rc;

	}

	io_uring_cqe_seen(&g_ublk_tgt.ctrl_ring, cqe);

	g_ublk_tgt.ctrl_ops_in_progress++;

	ublk->ctrl_ops_in_progress++;



	return cqe->res;

	return 0;

}



static int
@@ -274,7 +319,8 @@ ublk_open(void) 
		return -rc;

	}



	rc = ublk_setup_ring(UBLK_CTRL_RING_DEPTH, &g_ublk_tgt.ctrl_ring, IORING_SETUP_SQE128);

	rc = ublk_setup_ring(UBLK_CTRL_RING_DEPTH, &g_ublk_tgt.ctrl_ring,

			     IORING_SETUP_SQE128 | IORING_SETUP_SQPOLL);

	if (rc < 0) {

		SPDK_ERRLOG("UBLK ctrl queue_init: %s\n", spdk_strerror(-rc));

		close(g_ublk_tgt.ctrl_fd);
@@ -403,84 +449,33 @@ ublk_thread_exit(void *args) 
	}

}



static void *

_ublk_start_kernel(void *arg)

static int

ublk_start_kernel(void *arg)

{

	struct spdk_ublk_dev *ublk = arg;

	int rc;



	SPDK_DEBUGLOG(ublk, "Enter start pthread for ublk %d\n", ublk->ublk_id);

	assert(ublk->dev_info.ublksrv_pid == getpid());

	rc = ublk_ctrl_cmd(ublk, UBLK_CMD_START_DEV, &ublk->dev_info.ublksrv_pid);

	if (rc < 0) {

		SPDK_ERRLOG("start dev %d failed, rc %s\n", ublk->ublk_id,

			    spdk_strerror(-rc));

	}

	__atomic_fetch_sub(&ublk->pending_ublk_pthread, 1, __ATOMIC_RELAXED);

	SPDK_DEBUGLOG(ublk, "Exit start pthread for ublk %d\n", ublk->ublk_id);



	pthread_exit(NULL);

	return rc;

}



static int

ublk_start_kernel(struct spdk_ublk_dev *ublk)

{

	pthread_t tid;

	int rc;



	__atomic_fetch_add(&ublk->pending_ublk_pthread, 1, __ATOMIC_RELAXED);

	/*

	 * Commands UBLK_CMD_START_DEV will block the reactor while some io are

	 * transfered to SPDK for processing, which leads hanging. To avoid that,

	 * a pthread needs to be created. It's also the same scenario for UBLK_CMD_STOP_DEV.

	 */

	rc = pthread_create(&tid, NULL, _ublk_start_kernel, ublk);

	if (rc != 0) {

		__atomic_fetch_sub(&ublk->pending_ublk_pthread, 1, __ATOMIC_RELAXED);

		SPDK_ERRLOG("could not create thread: %s\n", spdk_strerror(rc));

		return -rc;

	}

	rc = pthread_detach(tid);

	assert(rc == 0);



	return 0;

}



static void *

_ublk_stop_kernel(void *arg)

ublk_stop_kernel(struct spdk_ublk_dev *ublk)

{

	struct spdk_ublk_dev *ublk = arg;

	int rc;



	SPDK_DEBUGLOG(ublk, "Enter stop pthread for ublk %d\n", ublk->ublk_id);



	rc = ublk_ctrl_cmd(ublk, UBLK_CMD_STOP_DEV, NULL);

	if (rc < 0) {

		SPDK_ERRLOG("stop dev %d failed\n", ublk->ublk_id);

	}

	__atomic_fetch_sub(&ublk->pending_ublk_pthread, 1, __ATOMIC_RELAXED);

	SPDK_DEBUGLOG(ublk, "Exit stop pthread for ublk %d\n", ublk->ublk_id);



	pthread_exit(NULL);

}



static int

ublk_stop_kernel(struct spdk_ublk_dev *ublk)

{

	pthread_t tid;

	int rc;



	__atomic_fetch_add(&ublk->pending_ublk_pthread, 1, __ATOMIC_RELAXED);

	rc = pthread_create(&tid, NULL, _ublk_stop_kernel, ublk);

	if (rc != 0) {

		__atomic_fetch_sub(&ublk->pending_ublk_pthread, 1, __ATOMIC_RELAXED);

		SPDK_ERRLOG("could not create thread: %s\n", spdk_strerror(rc));

		return -rc;

	}

	rc = pthread_detach(tid);

	assert(rc == 0);



	return 0;

	return rc;

}



static int
@@ -506,6 +501,7 @@ _ublk_fini(void *args) 


	/* Check if all ublks closed */

	if (TAILQ_EMPTY(&g_ublk_bdevs)) {

		spdk_poller_unregister(&g_ublk_tgt.ctrl_poller);

		close(g_ublk_tgt.ctrl_ring.ring_fd);

		close(g_ublk_tgt.ctrl_fd);

		g_ublk_tgt.ctrl_ring.ring_fd = 0;
@@ -701,7 +697,11 @@ ublk_close_dev_done(void *arg) 
	if (rc < 0) {

		SPDK_ERRLOG("delete dev %d failed\n", ublk->ublk_id);

	}

}



static void

ublk_delete_dev(struct spdk_ublk_dev *ublk)

{

	if (ublk->bdev_desc) {

		spdk_bdev_close(ublk->bdev_desc);

		ublk->bdev_desc = NULL;
@@ -722,8 +722,7 @@ _ublk_try_close_dev(void *arg) 
	struct spdk_ublk_dev *ublk = arg;



	assert(spdk_get_thread() == ublk->app_thread);

	/* Continue the stop procedure after the exit of ublk_start_kernel pthread */

	if (__atomic_load_n(&ublk->pending_ublk_pthread, __ATOMIC_RELAXED) > 0) {

	if (ublk->ctrl_ops_in_progress > 0) {

		if (ublk->retry_poller == NULL) {

			ublk->retry_count = UBLK_STOP_BUSY_WAITING_MS * 1000ULL / UBLK_BUSY_POLLING_INTERVAL_US;

			ublk->retry_poller = SPDK_POLLER_REGISTER(_ublk_try_close_dev, ublk,
@@ -733,7 +732,7 @@ _ublk_try_close_dev(void *arg) 
		if (ublk->retry_count-- > 0) {

			return SPDK_POLLER_BUSY;

		}

		SPDK_ERRLOG("Failed to wait for returning of ublk pthread.\n");

		SPDK_ERRLOG("Timeout on ctrl op completion.\n");

	}

	spdk_poller_unregister(&ublk->retry_poller);

	/* Update queue deinit number */
@@ -1184,20 +1183,22 @@ _ublk_start_disk(struct spdk_ublk_dev *ublk) 
	rc = ublk_ctrl_cmd(ublk, UBLK_CMD_ADD_DEV, &ublk->dev_info);

	if (rc < 0) {

		SPDK_ERRLOG("UBLK can't add dev %d, rc %s\n", ublk->ublk_id, spdk_strerror(-rc));

		goto err;

	}



	return rc;

}



static void

ublk_set_params(struct spdk_ublk_dev *ublk)

{

	int rc;



	ublk->dev_params.len = sizeof(struct ublk_params);

	rc = ublk_ctrl_cmd(ublk, UBLK_CMD_SET_PARAMS, &ublk->dev_params);

	if (rc < 0) {

		SPDK_ERRLOG("UBLK can't set params for dev %d, rc %s\n", ublk->ublk_id, spdk_strerror(-rc));

		goto err;

		_ublk_try_close_dev(ublk);

	}



	return 0;



err:

	return rc;

}



/* Set ublk device parameters based on bdev */
@@ -1386,15 +1387,15 @@ ublk_start_disk(const char *bdev_name, uint32_t ublk_id, 
		goto err;

	}



	return finish_start(ublk);

	return 0;



err:

	_ublk_try_close_dev(ublk);

	return rc;

}



static int

finish_start(struct spdk_ublk_dev *ublk)

static void

ublk_finish_start(struct spdk_ublk_dev *ublk)

{

	int			rc;

	uint32_t		q_id, i;
@@ -1419,8 +1420,7 @@ finish_start(struct spdk_ublk_dev *ublk) 
		}

	}



	rc = ublk_start_kernel(ublk);

	if (rc != 0) {

	if (ublk_start_kernel(ublk) != 0) {

		goto err;

	}
@@ -1435,11 +1435,10 @@ finish_start(struct spdk_ublk_dev *ublk) 
		}

	}



	return 0;

	return;



err:

	_ublk_try_close_dev(ublk);

	return rc;

}



SPDK_LOG_REGISTER_COMPONENT(ublk)