Commit 068ca77a authored Mar 09, 2022 by Shuhei Matsumoto Committed by Tomasz Zawadzki Mar 15, 2022

bdev/nvme: Disconnect and then free I/O qpair when deleting ctrlr_channel



For RDMA transport, current synchronous qpair disconnect occupied CPU for
a second when qpair disconnect gets timeout.

To remove this limitation, we will do the following:
- make spdk_nvme_ctrlr_disconnect_io_qpair() asynchronous,
- spdk_nvme_qpair_process_completions() returns -ENXIO only if the
  qpair is actually disconnected.

Even at this patch, spdk_nvme_poll_group_process_completions() invokes
disconnected_qpair_cb only if a qpair is actually disconnected. This
behavior will be maintained.

To use the upcoming asynchronous qpair disconnect easily, when
deleting a ctrlr_channel, disconnect the qpair, and then free the qpair
and release a reference to the poll group when the qpair is actually
disconnected.

We need to delete a nvme_qpair asynchronously after the corresponding
nvme_ctrlr_channel is deleted and defer the deletion of the corresponding
nvme_ctrlr until the nvme_qpair is deleted. To satisfy this requirement,
utilize the reference count of the nvme_ctrlr.

disconnected_qpair_cb() may call spdk_nvme_ctrlr_free_io_qpair() and
spdk_io_device_unregister() successively. The spdk_io_device_unregister()
will execute spdk_nvme_detach_async() from its callback.
spdk_nvme_ctrlr_free_io_qpair() has to complete earlier than
spdk_nvme_detach_async() starts. spdk_nvme_ctrlr_free_io_qpair() is
executed after unwinding stack. spdk_nvme_detach_async() is executed
after sending a message. Sending message is later than unwinding stack.
Hence the requirement is satisfied naturally.

spdk_io_device_unregister() for the nvme_ctrlr is required to be called
on the nvme_ctrlr->thread. To satisfy this requirement, redirect
nvme_ctrlr_unregister() to the nvme_ctrlr->thread. This change is too
small to stand as an independent patch. So include the change in this
patch.

Change-Id: Id8c01966c40b1dae9c4ef17f1b0b3f60a0bd17d5
Signed-off-by: Shuhei Matsumoto <smatsumoto@nvidia.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/10765


Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

parent 12854819

module/bdev/nvme/bdev_nvme.c

+27 −7

Original line number	Diff line number	Diff line
		@@ -515,8 +515,10 @@ nvme_ctrlr_unregister_cb(void *io_device)
		}

		static void
		nvme_ctrlr_unregister(struct nvme_ctrlr *nvme_ctrlr)
		nvme_ctrlr_unregister(void *ctx)
		{
		struct nvme_ctrlr *nvme_ctrlr = ctx;

		spdk_io_device_unregister(nvme_ctrlr, nvme_ctrlr_unregister_cb);
		}

		@@ -558,7 +560,7 @@ nvme_ctrlr_release(struct nvme_ctrlr *nvme_ctrlr)

		pthread_mutex_unlock(&nvme_ctrlr->mutex);

		nvme_ctrlr_unregister(nvme_ctrlr);
		spdk_thread_exec_msg(nvme_ctrlr->thread, nvme_ctrlr_unregister, nvme_ctrlr);
		}

		static struct nvme_io_path *
		@@ -1095,6 +1097,8 @@ nvme_poll_group_get_qpair(struct nvme_poll_group *group, struct spdk_nvme_qpair
		return nvme_qpair;
		}

		static void nvme_qpair_delete(struct nvme_qpair *nvme_qpair);

		static void
		bdev_nvme_disconnected_qpair_cb(struct spdk_nvme_qpair qpair, void poll_group_ctx)
		{
		@@ -1115,7 +1119,12 @@ bdev_nvme_disconnected_qpair_cb(struct spdk_nvme_qpair qpair, void poll_group_

		_bdev_nvme_clear_io_path_cache(nvme_qpair);

		if (nvme_qpair->ctrlr_ch != NULL) {
		bdev_nvme_reset(nvme_qpair->ctrlr);
		} else {
		/* In this case, ctrlr_channel is already deleted. */
		nvme_qpair_delete(nvme_qpair);
		}
		}
		}

		@@ -2105,6 +2114,10 @@ nvme_qpair_create(struct nvme_ctrlr nvme_ctrlr, struct nvme_ctrlr_channel ctrl

		ctrlr_ch->qpair = nvme_qpair;

		pthread_mutex_lock(&nvme_qpair->ctrlr->mutex);
		nvme_qpair->ctrlr->ref++;
		pthread_mutex_unlock(&nvme_qpair->ctrlr->mutex);

		return 0;
		}

		@@ -2128,6 +2141,8 @@ nvme_qpair_delete(struct nvme_qpair *nvme_qpair)

		spdk_put_io_channel(spdk_io_channel_from_ctx(nvme_qpair->group));

		nvme_ctrlr_release(nvme_qpair->ctrlr);

		free(nvme_qpair);
		}

		@@ -2143,12 +2158,17 @@ bdev_nvme_destroy_ctrlr_channel_cb(void io_device, void ctx_buf)
		_bdev_nvme_clear_io_path_cache(nvme_qpair);

		if (nvme_qpair->qpair != NULL) {
		spdk_nvme_ctrlr_free_io_qpair(nvme_qpair->qpair);
		nvme_qpair->qpair = NULL;
		}
		spdk_nvme_ctrlr_disconnect_io_qpair(nvme_qpair->qpair);

		/* We cannot release a reference to the poll group now.
		* The qpair may be disconnected asynchronously later.
		* We need to poll it until it is actually disconnected.
		*/
		nvme_qpair->ctrlr_ch = NULL;
		} else {
		nvme_qpair_delete(nvme_qpair);
		}
		}

		static void
		bdev_nvme_submit_accel_crc32c(void ctx, uint32_t dst, struct iovec *iov,