Hello, James. James Bottomley wrote: > > The fact that tasks can proceed in parallel, only the command components > individual linked tasks must be serialised. so it supports the TCQ > paradigm. > > Really, also, linked tasks is exactly what a JFS wants because most of > the updates that would be linked are something like update log entry; > modify metadata (or data); remove log entry. > I see your point, so it's not really a barrier anymore, but a sequence of ordered writes with an intervening flush independent of other unrelated writes. Some random thoughts... * All writes in the ordered sequence will have to be done sequentially, but unrelated writes are not affected. This can be overall gain. * Can be implemented in block layer proper without using SCSI linked task (probably with separate ->ordered_requests queue). What would be the advantage of SCSI linked task? * As it's finer grained than wholesale barrier, FS layer will need to pay more attention. Thanks for the explanation. :-) -- tejun - : 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
