On Mon, 2016-08-01 at 10:20 -0400, Tejun Heo wrote: > Hello, > > If any real IO depends on those devices then this is not sufficient and > > they need some form of guarantee for progress (aka mempool). > > Oliver, Alan, what do you think? If USB itself can't operate without > allocating memory during transactions, whatever USB storage drivers It cannot. The IO must be described to the hardware with a data structure in memory. > are doing isn't all that meaningful. Can we proceed with the > workqueue patches? Also, it could be that the only thing GFP_NOIO and > GFP_ATOMIC are doing is increasing the chance of IO failures under > memory pressure. Maybe it'd be a good idea to reconsider the > approach? We had actual deadlocks with GFP_KERNEL. It seems to me that the SCSI layer can deal with IO that cannot be completed due to a lack of memory at least somewhat, but a deadlock within a driver would obviously be deadly. So I don't think that mempools would remove the need for GFP_NOIO as there are places in usbcore we cannot enter the page laundering path from. They are an additional need. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
