When a device is unplugged from a SCSI controller, if the scsi_device is
still in use by application layer, it won't get released until users
close it.

In this case, scsi_device_remove just set the scsi_device's state to be
SDEV_DEL. But if you plug the disk just before the old scsi_device is
released, then there will be two scsi_device structures in
scsi_host->__devices. When the next unplug event happens, some low-level
drivers will check whether the scsi_device has been added to host (for
example the MegaRAID SAS series controller) by calling
scsi_device_lookup(call __scsi_device_lookup) in function
megasas_aen_polling. __scsi_device_lookup will return the first
scsi_device. Because its state is SDEV_DEL, the scsi_device_lookup will
return NULL, making the low-level driver assume that the scsi_device has
been removed, and won't call scsi_device_remove which will lead to hot
swap failure.
Signed-off-by: Zhou Zhengping <johnzzpcrystal@gmail.com>
Tested-by: Zeng Rujia <ZengRujia@sangfor.com.cn>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=195607Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>