[SPDK] [RFC PATCH 3/4] Add ScanTarget to optimize spdk app start time

[Ming Lin <minggr at gmail.com>]

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From: Ming Lin <ming.lin(a)alibaba-inc.com>

For example,

 [VirtioUser0]
  Path /var/run/vhost.nvme0
  Queues 3
  Name nvme0
  ScanTarget 0

"ScanTarget 0" tells virtio scsi only scans vhost target 0.
If not specified, will do a full scan.

Signed-off-by: Ming Lin <ming.lin(a)alibaba-inc.com>
---
 lib/bdev/virtio/bdev_virtio_scsi.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/lib/bdev/virtio/bdev_virtio_scsi.c b/lib/bdev/virtio/bdev_virtio_scsi.c
index 0602597..e677a50 100644
--- a/lib/bdev/virtio/bdev_virtio_scsi.c
+++ b/lib/bdev/virtio/bdev_virtio_scsi.c
@@ -97,6 +97,8 @@ struct virtio_scsi_dev {
 
 	/** protect reconnect process */
 	pthread_mutex_t reconn_mutex;
+
+	int scan_target;
 };
 
 struct virtio_scsi_io_ctx {
@@ -351,6 +353,8 @@ virtio_user_scsi_dev_create(const char *name, const char *path,
 		return NULL;
 	}
 
+	svdev->scan_target = -1;
+
 	vdev = &svdev->vdev;
 	rc = virtio_user_dev_init(vdev, name, path, queue_size);
 	if (rc != 0) {
@@ -869,8 +873,13 @@ bdev_virtio_poll(void *arg)
 
 			if (scan_ctx->restart) {
 				scan_ctx->restart = false;
-				scan_ctx->full_scan = true;
-				_virtio_scsi_dev_scan_tgt(scan_ctx, 0);
+				if (svdev->scan_target == -1) {
+					scan_ctx->full_scan = true;
+					_virtio_scsi_dev_scan_tgt(scan_ctx, 0);
+				} else {
+					scan_ctx->full_scan = false;
+					_virtio_scsi_dev_scan_tgt(scan_ctx, svdev->scan_target);
+				}
 				continue;
 			}
 
@@ -1588,6 +1597,7 @@ bdev_virtio_process_config(void)
 	char *path, *name;
 	unsigned vdev_num;
 	int num_queues;
+	int scan_target;
 	bool enable_pci;
 	int rc = 0;
 
@@ -1629,6 +1639,9 @@ bdev_virtio_process_config(void)
 			rc = -1;
 			goto out;
 		}
+
+		scan_target = spdk_conf_section_get_intval(sp, "ScanTarget");
+		svdev->scan_target = scan_target;
 	}
 
 	sp = spdk_conf_find_section(NULL, "VirtioPci");
@@ -1734,9 +1747,13 @@ virtio_scsi_dev_scan(struct virtio_scsi_dev *svdev, bdev_virtio_create_cb cb_fn,
 	base = svdev->scan_ctx;
 	base->cb_fn = cb_fn;
 	base->cb_arg = cb_arg;
-	base->full_scan = true;
-
-	_virtio_scsi_dev_scan_tgt(base, 0);
+	if (svdev->scan_target == -1) {
+		base->full_scan = true;
+		_virtio_scsi_dev_scan_tgt(base, 0);
+	} else {
+		base->full_scan = false;
+		_virtio_scsi_dev_scan_tgt(base, svdev->scan_target);
+	}
 	return 0;
 }
 
@@ -1766,7 +1783,7 @@ virtio_scsi_dev_scan_tgt(struct virtio_scsi_dev *svdev, uint8_t target)
 	}
 
 	base = svdev->scan_ctx;
-	base->full_scan = true;
+	base->full_scan = (svdev->scan_target == -1) ? true : false;
 	_virtio_scsi_dev_scan_tgt(base, target);
 	return 0;
 }
-- 
1.9.1