On 4/19/23 07:02, James Bottomley wrote:
device_shutdown() goes in reverse devices_kset->list order, so it looks like it would do the PCI device then the SCSI device then the ULD then block, so we can use the queues in SCSI for emergency actions (like flush or stop) before block goes down. Although this isn't guaranteed; there are things, like device_link_add, which reorder this kset, so we'd need to make sure the above assumption is correct.
Hi James,My understanding is that both the block device associated with /dev/sd<x> and the struct scsi_disk associated with the same SCSI device have the sdev_gendev member of struct scsi_device as parent. In other words, without creating device links, there are no guarantees about the order in which the .shutdown() methods of struct block_device.bd_device and struct scsi_disk.disk_dev are called. Adding device links seems like an unnecessary complexity to me. Hence my preference to make sd_shutdown() responsible for quiescing future SCSI command activity.
See also the attached diagram (not sure I got that diagram right). Bart.
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