Created attachment 899626 [details]
strace blockdev --report /dev/dasdc1

Log from strace is attached.

Reproduced with kernel-3.11.10-301.fc20.s390x and kernel-3.14.3-200.fc20.s390x

The disk type is DASD:

[root@rtt7 ~]# lsdasd -l 0.0.3627
0.0.3627/dasdc/94:8
  status:       active
  type:         ECKD
  blksz:        4096
  size:         2347MB
  blocks:       601020
  use_diag:     0
  readonly:     0
  eer_enabled:  0
  erplog:       0
  uid:          IBM.750000000L2591.0017.27.0000000000000d0a0000000000000000

[root@rtt7 ~]# dmesg | grep dasd
[    0.000000] Kernel command line: rd.lvm.lv=fedora_rtt7/root rd.lvm.lv=fedora_rtt7/swap rd.dasd=0.0.3527 cio_ignore=all,!0.0.0009 rd.dasd=0.0.3727 rd.lvm.lv=fedora_rtt7/boot rd.dasd=0.0.3627 vconsole.font=latarcyrheb-sun16 root=/dev/mapper/fedora_rtt7-root LANG=en_US.UTF-8 BOOT_IMAGE=0
[    0.564846] dasd-eckd 0.0.3727: New DASD 3390/0A (CU 3990/01) with 3339 cylinders, 15 heads, 224 sectors
[    0.565435] dasd-eckd 0.0.3627: New DASD 3390/0A (CU 3990/01) with 3339 cylinders, 15 heads, 224 sectors
[    0.567945] dasd-eckd 0.0.3627: DASD with 4 KB/block, 2404080 KB total size, 48 KB/track, compatible disk layout
[    0.568812] dasd-eckd 0.0.3727: DASD with 4 KB/block, 2404080 KB total size, 48 KB/track, compatible disk layout
[    0.568935] dasd-eckd 0.0.3527: New DASD 3390/0A (CU 3990/01) with 3339 cylinders, 15 heads, 224 sectors
[    0.569530] dasd-eckd 0.0.3527: DASD with 4 KB/block, 2404080 KB total size, 48 KB/track, compatible disk layout
[    0.569666]  dasdc:VOL1/  0X3627: dasdc1
[    0.570342]  dasdb:VOL1/  0X3727: dasdb1
[    0.571338]  dasda:VOL1/  0X3527: dasda1
[root@rtt7 ~]#

Please, let me know what additional information would be helpful.

A note - the output of blockdev is used by the bootloader installer to calculate the position of the boot data on disk.

"blockdev --report <device>" reads the information from
/sys/dev/block/<maj:min>/start now, because the original solution based on
HDIO_GETGEO ioctl was fragile. This bug report is just another proof :-)

Linux reports all offsets in /sys in 512-byte sectors independently on the
block device topology (it means it's in 512 for 4K disks too).

The same it's with HDIO_GETGEO ioctl hd_geometry.start. It's also reported in
512-bytes sectors -- except for dasd disks! 

(dasd HDIO_GETGEO: 24 * 4096 = 98304; sysfs: 192 * 512 = 98304)

See kernel code:

block/ioctl.c: HDIO_GETGEO:

          geo.start = get_start_sect(bdev);
          ret = disk->fops->getgeo(bdev, &geo);

this is generic part of the ioctl, unfortunately dasd driver modifies the start
offset:

drivers/s390/block/dasd.c: dasd_getgeo():
        
         geo->start = get_start_sect(bdev) >> base->block->s2b_shift;

so it reports native sectors. It seems kernel (dasd driver) is pretty
inconsistent here. Unfortunately, your bootloader installer depends on this
inconsistency.

IMHO this is kernel issue.

My recommendation is to read /sys/dev/block/<maj:min>/start directly from the 
installer to avoid dependence on blockdev versions and dependence on strange
HDIO_GETGEO behavior.

Note that I really don't want to add exception to blockdev for dasd to 
emulate the strange behaviour.

I have asked on linux-s390 list for more details. 

http://marc.info/?l=linux-s390&m=140127913331109&w=2

According to feedback from kernel upstream dasd HDIO_GETGEO is there for backward compatibility with kernel 2.4 :-)

switching to s390utils so we have this tracked

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