On Tue, Oct 03, 2017 at 01:47:55PM -0700, Matthew Wilcox wrote:

On Tue, Oct 03, 2017 at 10:05:11PM +0200, Luis R. Rodriguez wrote:

quoted

On Wed, Oct 04, 2017 at 03:33:01AM +0800, Ming Lei wrote:

quoted

Even though this patch can make kthread to not do I/O during
suspend/resume, the SCSI quiesce still can cause similar issue
in other case, like when sending SCSI domain validation
to transport_spi, which happens in revalidate path, nothing
to do with suspend/resume.

Are you saying that the SCSI layer can generate IO even without the filesystem
triggering it?

The SCSI layer can send SCSI commands; they aren't I/Os in the sense that
they do reads and writes to media,

Then there should be no issue waiting for the device to respond?

but they are block requests.  Maybe those should be allowed even to frozen
devices?

I'm afraid *maybe* won't suffice here, we need a clear explanation as
to what happens with frozen devices on the block layer *if* the device
driver is already suspended. Does the block layer just queue these?
If the goal is to just get queued but not processed, then why even
send these quiesce commands? Wouldn't they only be processed *after*
resume?

  Luis