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? > 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. -- 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
