On Wed, 2017-10-04 at 19:30 +0800, Ming Lei wrote: > Last time, I asked which issue is fixed by this patch, but > never get answered, so again, what is issue fixed by > this patch? That's not correct. I did answer your question. See e.g. https://marc.info/?l=linux-block&m=150695879309606. > Given the following patches for making SCSI quiesce safe > is required in either PM suspend/resume or other path > of transport_spi revalidate. So once theses patches are > in, I don't see any I/O hang in suspend/resume given > the SCSI quiesce issue is very specific one, and not > see this issue on other kind of device. There are many more storage drivers and filesystems than the md driver that can submit I/O after user space processes have been frozen, e.g. the BTRFS RAID and scrub functionalities. It will take time to fix all these drivers and also to add filesystem freeze/thaw functionality to the suspend and resume sequences. As long as not all drivers have been fixed we will need SCSI device quiescing and resuming as a workaround to avoid that any I/O occurs while a hibernation image is being created. Bart.
