On Tue, Dec 23, 2014 at 11:48:40PM -0800, Kenneth R. Crudup wrote:

quoted

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?

Has anyone seen a disk out there that's got a (properly-supported)
"max_hw_sectors_kb" >= 32K? If not, maybe we should clamp that value to
prevent other misreporting(?) disks?

Yes, lots of SCSI disks and arrays properly support this.