[Bug 106861] New: DPOFUA should not be related to WCE / Caching mode page

[Bug 106861] New: DPOFUA should not be related to WCE / Caching mode page

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=106861

            Bug ID: 106861
           Summary: DPOFUA should not be related to WCE / Caching mode
                    page
           Product: IO/Storage
           Version: 2.5
    Kernel Version: 4.2.4
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: SCSI
          Assignee: linux-scsi@vger.kernel.org
          Reporter: tom.ty89@gmail.com
        Regression: No

The sd driver checks whether the device supports DPO/FUA and reports it to the
FUA readonly attribute. However, they are somehow "depended" on the Caching
mode page and WCE (sd.c).

The fact is, the DPOFUA bit just isn't part of the Caching mode page. Instead
it is reported in DEVICE-SPECIFIC PARAMETER of mode parameter header.

Moreover, I don't see what impact does WCE have on DPO/FUA as per SBC or SAT.
As long as it is implemented correctly, DPO/FUA should be completely fine on
drives without write cache as well.

So IMHO how the kernel handles the checking and reporting simply has logical
mistake.

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[Bug 106861] DPOFUA should not be related to WCE / Caching mode page

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=106861

--- Comment #1 from Tom Yan <tom.ty89@gmail.com> ---
Example drive:

[tom@localhost ~]$ sudo sdparm --long /dev/sdc
    /dev/sdc: WD        My Passport 083A  1065
    Direct access device specific parameters: WP=0  DPOFUA=1
Control [co] mode page:
  SWP         0  [cha: n, def:  0, sav:  0]  Software write protect
[tom@localhost ~]$ sudo sdparm -a --long /dev/sdc
    /dev/sdc: WD        My Passport 083A  1065
    Direct access device specific parameters: WP=0  DPOFUA=1
Control [co] mode page:
  TST         0  [cha: n, def:  0, sav:  0]  Task set type
  TMF_ONLY    0  [cha: n, def:  0, sav:  0]  Task management functions only
  DPICZ       0  [cha: n, def:  0, sav:  0]  Disable protection information
check if protect field zero
  D_SENSE     0  [cha: n, def:  0, sav:  0]  Descriptor format sense data
  GLTSD       0  [cha: n, def:  0, sav:  0]  Global logging target save disable
  RLEC        0  [cha: n, def:  0, sav:  0]  Report log exception condition
  QAM         1  [cha: n, def:  1, sav:  1]  Queue algorithm modifier
  NUAR        0  [cha: n, def:  0, sav:  0]  No unit attention on release
  QERR        0  [cha: n, def:  0, sav:  0]  Queue error management
  RAC         0  [cha: n, def:  0, sav:  0]  Report a check
  UA_INTLCK   0  [cha: n, def:  0, sav:  0]  Unit attention interlocks control
  SWP         0  [cha: n, def:  0, sav:  0]  Software write protect
  ATO         0  [cha: n, def:  0, sav:  0]  Application tag owner
  TAS         0  [cha: n, def:  0, sav:  0]  Task aborted status
  ATMPE       0  [cha: n, def:  0, sav:  0]  Application tag mode page enabled
  RWWP        0  [cha: n, def:  0, sav:  0]  Reject write without protection
  AUTOLOAD    0  [cha: n, def:  0, sav:  0]  Autoload mode
  BTP         0  [cha: n, def:  0, sav:  0]  Busy timeout period (100us)
  ESTCT       0  [cha: n, def:  0, sav:  0]  Extended self test completion time
(sec)
Power condition [po] mode page:
  PM_BG       0  [cha: n, def:  0, sav:  0]  Power management, background
functions, precedence
  STANDBY_Y   0  [cha: n, def:  0, sav:  0]  Standby_y timer enable
  IDLE_C      0  [cha: n, def:  0, sav:  0]  Idle_c timer enable
  IDLE_B      0  [cha: n, def:  0, sav:  0]  Idle_b timer enable
  IDLE        0  [cha: n, def:  0, sav:  0]  Idle_a timer enable
  STANDBY     1  [cha: y, def:  1, sav:  1]  Standby_z timer enable
  ICT         0  [cha: n, def:  0, sav:  0]  Idle_a condition timer (100 ms)
  SCT       18000  [cha: y, def:18000, sav:18000]  Standby_z condition timer
(100 ms)
  IBCT        0  [cha: n, def:  0, sav:  0]  Idle_b condition timer (100 ms)
  ICCT        0  [cha: n, def:  0, sav:  0]  Idle_c condition timer (100 ms)
  SYCT        0  [cha: n, def:  0, sav:  0]  Standby_y condition timer (100 ms)
  CCF_IDLE    0  [cha: n, def:  0, sav:  0]  check condition on transition from
idle
  CCF_STAND   0  [cha: n, def:  0, sav:  0]  check condition on transition from
standby
  CCF_STOPP   0  [cha: n, def:  0, sav:  0]  check condition on transition from
stopped

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