Bug 90761

Summary:	USB stick show as rotational disk
Product:	Drivers	Reporter:	chepioq (chepioq)
Component:	Flash/Memory Technology Devices	Assignee:	David Woodhouse (dwmw2)
Status:	NEW ---
Severity:	normal	CC:	chepioq, madko77, marcos.souza.org
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	3.17.7-300.fc21.x86_64	Subsystem:
Regression:	No	Bisected commit-id:

Description chepioq 2015-01-04 09:08:28 UTC

I have a ssd on my laptop, and it show that not rotational:

[dominique@host-192-168-1-2 ~]$ cat /sys/block/sda/queue/rotational
0

and it's normal.
But with usb stick I have :
[dominique@host-192-168-1-2 ~]$ cat /sys/block/sdb/queue/rotational
1

that mean usb's stick is shown as rotational disk, and it's not normal.

This problem is present on fedora and ubuntu, and I think it's a kernel problem.

Fedora subject : http://forums.fedora-fr.org/viewtopic.php?id=63254

Ubuntu subject : https://bugs.launchpad.net/linux/+bug/499237

Say me if you want another precision.

Comment 1 chepioq 2015-01-11 07:56:15 UTC

Anybody here ?

Comment 2 Marcos Souza 2019-05-27 03:18:34 UTC

I can reproduce the behavior in a recent kernel:

cat /sys/block/sdc/queue/rotational
1
cat /sys/block/sdc/device/model 
Cruzer Blade    

Looking at the kernel code related SCSI (created by usb-storage module), it first unsets the NONROT flag (leaving it as rotational)[1], letting to be checked by vpd[2]. In my test, my usb storage devices does not have bdc (Block Device Characteristics):

sudo /usr/bin/sg_vpd --page 0x0 /dev/sdc
[sudo] password for root: 
Supported VPD pages VPD page:
  Supported VPD pages [sv]
  Unit serial number [sn]
  Device identification [di]

For example, take a look of the info reported when checking a SSD device which have VPD BDC support:
sudo /usr/bin/sg_vpd --page 0x0 /dev/sda
Supported VPD pages VPD page:
  Supported VPD pages [sv]
  Unit serial number [sn]
  Device identification [di]
  ATA information (SAT) [ai]
  Block limits (SBC) [bl]
  Block device characteristics (SBC) [bdc] <---- bdc support
  Logical block provisioning (SBC) [lbpv]

sudo /usr/bin/sg_vpd --page 0xb1 /dev/sda
Block device characteristics VPD page (SBC):
  Non-rotating medium (e.g. solid state) <---- Non rotating...
  Product type: Not specified
  WABEREQ=0
  WACEREQ=0
  Nominal form factor not reported
  ZONED=0
  RBWZ=0
  BOCS=0
  FUAB=0
  VBULS=0
  DEPOPULATION_TIME=0 (seconds)


I will check SCSI specialists if this can be clarified at code level.

[1]: https://github.com/torvalds/linux/blob/master/drivers/scsi/sd.c#L3123
[2]: https://github.com/torvalds/linux/blob/master/drivers/scsi/sd.c#L2931

Comment 3 Marcos Souza 2019-05-28 11:08:06 UTC

Currently, there is no way to distinguish if an USB that don't have VPD is a flash disk, because VPD BDC is used. USB sticks that have VPD BDC should be set as not rotational as expected. So it's a known issue, but so far there is no way to fix it.