[PATCH] Add a parameter to set sd driver's probe mode.

["longguang.yue" <bigclouds@163.com>]

Asynchronous probe leads to the change of disk name, so it is hard
to trace disk by its name for monitoring system.

Signed-off-by: longguang.yue <bigclouds@163.com>
---
 drivers/scsi/sd.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 4bb87043e6db..ea0ac8823599 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -99,6 +99,11 @@ MODULE_ALIAS_SCSI_DEVICE(TYPE_ZBC);
 
 #define SD_MINORS	16
 
+static unsigned int async = PROBE_PREFER_ASYNCHRONOUS;
+module_param(async, uint, 0644);
+MODULE_PARM_DESC(async,
+		 "probe scsi disk asynchronously or not. Default is 1 asynchronous.");
+
 static void sd_config_discard(struct scsi_disk *, unsigned int);
 static void sd_config_write_same(struct scsi_disk *);
 static int  sd_revalidate_disk(struct gendisk *);
@@ -3839,6 +3844,9 @@ static int __init init_sd(void)
 
 	SCSI_LOG_HLQUEUE(3, printk("init_sd: sd driver entry point\n"));
 
+	if (async != PROBE_PREFER_ASYNCHRONOUS)
+		sd_template.gendrv.probe_type = PROBE_FORCE_SYNCHRONOUS;
+
 	for (i = 0; i < SD_MAJORS; i++) {
 		if (__register_blkdev(sd_major(i), "sd", sd_default_probe))
 			continue;
-- 
2.34.1