On Sat, 27 Dec 2014, Christoph Hellwig wrote: > On Tue, Dec 23, 2014 at 11:48:40PM -0800, Kenneth R. Crudup wrote: > > > Looks like we need to quirk it. Can you try to echo different limits > > > to the /sys/block/sdc/queue/max_hw_sectors_kb file for the device to > > > find the limit for it? > > > > Looks like it's 32767; making it an even 32K sectors starts the EIOs again. > > > > To recap for the various lists: > > > > Vendor: Samsung Model: D3 Station Rev: 0202 > > Type: Direct-Access ANSI SCSI revision: 06 > > > > It's the 4TB model: > > > > /sys/block/sdc/size:7814037160 > > /sys/block/sdc/queue/max_hw_sectors_kb:61440 > > > > Works OK if I echo 32767 > /sys/block/sdc/queue/max_sectors_kb > > Interesting. Basically this is the limit for modern ATA disks: > > drivers/ata/libata-core.c: dev->max_sectors = ATA_MAX_SECTORS_LBA48; > drivers/ata/libata-core.c: dev->max_sectors = ATA_MAX_SECTORS_LBA48; > include/linux/ata.h: ATA_MAX_SECTORS_LBA48 = 65535,/* TODO: 65536? */ > > Seems like the USB bridge isn't properly communicating this limit to the SCSI > layer. Maybe it's a good idea to generally limit USB storage to this size? (Is this a USB device? Presumably you wouldn't have CC'ed the linux-usb and usb-storage mailing lists if it wasn't...) The only limits usb-storage imposes on max_sectors are those needed to work around bugs in the devices' USB bridges. (Okay, there's also something for tape drive devices, but it probably doesn't belong in usb-storage -- it should be handled by the SCSI tape driver.) If the ATA layer needs to set a limit on max_sectors, why doesn't it simply go ahead and do so? Alan Stern -- 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
