On Thu, 2015-07-02 at 13:35 +0200, Hans de Goede wrote: > Hi, > > On 02-07-15 10:45, Oliver Neukum wrote: > > On Wed, 2015-07-01 at 10:06 +0100, Daniel P. Berrange wrote: > > > >> I don't really think it is sensible to be defining & implementing new > >> network services which can't support strong encryption and authentication. > >> Rather than passing the file descriptor to the kernel and having it do > >> the I/O directly, I think it would be better to dissassociate the kernel > >> from the network transport, and thus leave all sockets layer data I/O > >> to userspace daemons so they can layer in TLS or SASL or whatever else > >> is appropriate for the security need. > > > > Hi, > > > > this hits a fundamental limit. Block IO must be done entirely in kernel > > space or the system will deadlock. The USB stack is part of the block > > layer and the SCSI error handling. Thus if you involve user space you > > cannot honor memory allocation with GFP_NOFS and you break all APIs > > where we pass GFP_NOIO in the USB stack. > > > > Supposed you need to reset a storage device for error handling. > > Your user space programm does a syscall, which allocates memory > > and needs to launder pages. It proceeds to write to the storage device > > you wish to reset. > > > > It is the same problem FUSE has with writable mmap. You cannot do > > block devices in user space sanely. > > So how is this dealt with for usbip ? As far as I can tell, it isn't. Running a storage device over usbip is a bit dangerous. 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
