On Wed, 2010-07-28 at 16:23 +0200, Tejun Heo wrote: > Hello, > > On 07/28/2010 03:55 PM, Vladislav Bolkhovitin wrote: > >> The only benefit of doing it in the block layer, and probably the > >> reason why it was done this way at all, is making use of advanced > >> ordering features of some devices - ordered tag and linked commands. > >> The latter is deprecated and the former is fundamentally broken in > >> error handling anyway. > > > > Why? SCSI provides ACA and UA_INTLCK which provide all needed > > facilities for errors handling in deep ordered queues. > > I don't remember all the details now but IIRC what was necessary was > earlier write failure failing all commands scheduled as ordered. Does > ACA / UA_INTLCK or whatever allow that? No. That requires support for QErr ... which is in the same mode page. The real reason we have difficulty is that BUSY/QUEUE_FULL can cause reordering in the issue queue, which is a driver problem and not in the SCSI standards. James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
