Brian King wrote:
One thing that having a per-port SCSI host buys us is that it isolates EH to the port rather than the entire SCSI host. The way that the new libata EH is designed, it can end up spending a fair amount of time in EH and may even sleep for seconds at a time, waiting for the device to come ready. Quiescing all devices on a SAS host due to a single SATA device gets *very* painful. The new libata EH does much more than just EH. It wakes up for every ATAPI check condition... Before we can move to a single SCSI host model, we will have to make some changes regarding how EH is done in libata...
Good points. There definitely needs to be a discussion about how to integrate libata EH with libsas model and ipr model (which are distinct, if similar).
libata EH was coded to largely be "in the driver's seat", which isn't true in a world where it is a peer to SAS devices. Also libata EH duplicates some of the link EH stuff that SAS deals with, and must subsume (since libsas knows about both SAS and SATA phys, and an ideal world doesn't have the two as separate as they are now).
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