On Tue, Nov 15, 2011 at 08:34:18AM +0100, Milan Broz wrote:
> On 11/14/2011 03:26 AM, Josh Triplett wrote:
> > OK, I suppose I don't actually care what rotational shows for a
> > device-mapper device backed by rotating media. The case I care about:
> > when the underlying media has rotational=0, the dm device definitely
> > shouldn't have rotational=1.
>
> Rotational flag is inherited in DM core, nothing dm-crypt specific.
> And it works (for several kernel releases already):
>
>
> create test scsi disk (also with discards)
> # modprobe scsi_debug dev_size_mb=16 sector_size=512 num_tgts=1 lbpu=1
> # grep scsi_debug /sys/block/*/device/model
> /sys/block/sdj/device/model:scsi_debug
>
> Map some crypt device over it
> # echo "password" | cryptsetup create sdj_crypt /dev/sdj
>
> And now see inherited ROTA flag (it is /sys rotational)
>
> # lsblk -t /dev/sdj
> NAME ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED RQ-SIZE
> sdj 0 512 32768 512 512 0 cfq 128
> `-sdj_crypt (dm-0) 0 512 32768 512 512 0 128
>
>
> Please paste lsblk -t output tree if you think there is a bug, do not blindly
> check all dm-X devices queues.
I didn't know about that command; very nice, thanks! lsblk confirms
that on my system, the physical disk has rotational=0 but the dm-crypt
and LVM devices have rotational=1:
NAME ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED
sda 0 512 0 512 512 0 cfq
├─sda1 0 512 0 512 512 0 cfq
└─sda2 0 512 0 512 512 0 cfq
└─sda2_crypt (dm-0) 0 512 0 512 512 1
├─leaf-swap (dm-1) 0 512 0 512 512 1
└─leaf-root (dm-2) 0 512 0 512 512 1
Does that help?
- Josh Triplett
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