Commit a16f8896 authored by Meir Elisha's avatar Meir Elisha Committed by Keith Busch
Browse files

nvmet-tcp: Fix a possible sporadic response drops in weakly ordered arch 



The order in which queue->cmd and rcv_state are updated is crucial.
If these assignments are reordered by the compiler, the worker might not
get queued in nvmet_tcp_queue_response(), hanging the IO. to enforce the
the correct reordering, set rcv_state using smp_store_release().

Fixes: bdaf1327 ("nvmet-tcp: fix a segmentation fault during io parsing error")

Signed-off-by: default avatarMeir Elisha <meir.elisha@volumez.com>
Reviewed-by: default avatarSagi Grimberg <sagi@grimberg.me>
Signed-off-by: default avatarKeith Busch <kbusch@kernel.org>
parent ad95bab0

drivers/nvme/target/tcp.c

+11 −4
Original line number Diff line number Diff line
@@ -571,10 +571,16 @@ static void nvmet_tcp_queue_response(struct nvmet_req *req) 
	struct nvmet_tcp_cmd *cmd =

		container_of(req, struct nvmet_tcp_cmd, req);

	struct nvmet_tcp_queue	*queue = cmd->queue;

	enum nvmet_tcp_recv_state queue_state;

	struct nvmet_tcp_cmd *queue_cmd;

	struct nvme_sgl_desc *sgl;

	u32 len;



	if (unlikely(cmd == queue->cmd)) {

	/* Pairs with store_release in nvmet_prepare_receive_pdu() */

	queue_state = smp_load_acquire(&queue->rcv_state);

	queue_cmd = READ_ONCE(queue->cmd);



	if (unlikely(cmd == queue_cmd)) {

		sgl = &cmd->req.cmd->common.dptr.sgl;

		len = le32_to_cpu(sgl->length);
@@ -583,7 +589,7 @@ static void nvmet_tcp_queue_response(struct nvmet_req *req) 
		 * Avoid using helpers, this might happen before

		 * nvmet_req_init is completed.

		 */

		if (queue->rcv_state == NVMET_TCP_RECV_PDU &&

		if (queue_state == NVMET_TCP_RECV_PDU &&

		    len && len <= cmd->req.port->inline_data_size &&

		    nvme_is_write(cmd->req.cmd))

			return;
@@ -847,8 +853,9 @@ static void nvmet_prepare_receive_pdu(struct nvmet_tcp_queue *queue) 
{

	queue->offset = 0;

	queue->left = sizeof(struct nvme_tcp_hdr);

	queue->cmd = NULL;

	queue->rcv_state = NVMET_TCP_RECV_PDU;

	WRITE_ONCE(queue->cmd, NULL);

	/* Ensure rcv_state is visible only after queue->cmd is set */

	smp_store_release(&queue->rcv_state, NVMET_TCP_RECV_PDU);

}



static void nvmet_tcp_free_crypto(struct nvmet_tcp_queue *queue)