The patch did not work, although it did get pass the earlier condition
which I mentioned- but still Write Cache is not taken into account –
seems mode sensing in sd_read_cache_type() does not send proper
request to the device – or does not read in proper bytes for this(as
per hdparm command analysis):
Logs After Connecting:
scsi 0:0:0:0: Direct-Access Seagate Portable 0130 PQ: 0 ANSI: 4
sd 0:0:0:0: [sda] 488397168 512-byte logical blocks: (250 GB/232 GiB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] No Caching mode page present
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] No Caching mode page present
sd 0:0:0:0: [sda] Assuming drive cache: write through
sda: sda1 sda2 sda3 sda4
sd 0:0:0:0: [sda] No Caching mode page present
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] Attached SCSI disk
Second Hard-Disk
usb 4-1.4: new high speed USB device using ehci-sdp and address 3
usb 4-1.4: New USB device found, idVendor=152d, idProduct=2339
usb 4-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=5
usb 4-1.4: Product: USB to ATA/ATAPI Bridge
usb 4-1.4: Manufacturer: JMicron
usb 4-1.4: SerialNumber: 3446184AA01C
scsi0 : usb-storage 4-1.4:1.0
usb 3-1.1.1: new full speed USB device using ehci-sdp and address 4
usb 3-1.1.1: New USB device found, idVendor=0a5c, idProduct=4502
usb 3-1.1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 3-1.1.2: new full speed USB device using ehci-sdp and address 5
usb 3-1.1.2: New USB device found, idVendor=0a5c, idProduct=4503
usb 3-1.1.2: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 3-1.1.3: new full speed USB device using ehci-sdp and address 6
usb 3-1.1.3: New USB device found, idVendor=0a5c, idProduct=2046
usb 3-1.1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-1.1.3: Product: BCM2046B1
usb 3-1.1.3: Manufacturer: Broadcom Corp
usb 3-1.1.3: SerialNumber: E4E0C53861A2
scsi 0:0:0:0: Direct-Access SAMSUNG HM501IX PQ: 0 ANSI: 2 CCS
sd 0:0:0:0: [sda] 976773168 512-byte logical blocks: (500 GB/465 GiB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't
support DPO or FUA
sda:
sda1 sda2
sd 0:0:0:0: [sda] Attached SCSI disk
Device Identification Retrieved using “hdparm –I” shows this:
#> hdparm --verbose -I /dev/sda3
/dev/sda3:
outgoing cdb: 85 08 0e 00 00 00 01 00 00 00 00 00 00 40 ec 00
SG_IO: ATA_16 status=0x0, host_status=0x0, driver_status=0x0
SG_IO: sb[]: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00
incoming_data: 5a 0c ff 3f 37 c8 10 00 00 00 00 00 3f 00 00 00 00 00
00 00 20 20 20 20 20 20 20 20 20 20 20 20 56 36 51 43 4e 33 35 57 00
00 00 40 04 00 30 30 32 30 53 42 31 4d 54 53 32 39 30 35 31 33 41 35
20 53 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
20 20 20 20 20 20 20 10 80 00 00 00 2f 00 40 00 02 00 02 07 00 ff 3f
10 00 3f 00 10 fc fb 00 10 01 ff ff ff 0f 00 00 07 00 03 00 78 00 78
00 78 00 78 00 00 00 00 00 00 00 00 00 00 00 00 00 1f 00 02 05 00 00
48 00 40 00 f0 01 29 00 6b 34 09 7d 23 61 69 34 09 bc 23 61 7f 40 24
00 24 00 80 80 fe ff 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 70 59
1c 1d 00 00 00 00 00 00 00 00 00 00 00 00 00 50 00 c5 dc 32 73 79 00
00 00 00 00 00 00 00 00 00 00 00 00 00 1e 40 1c 40 00 00 00 00 00 00
00 00 00 00 00 00 00 00 21 00 70 59 1c 1d 70 59 1c 1d 20 20 02 00 40
01 00 01 00 50 06 3c 0a 3c 00 00 3c 00 00 00 08 00 00 00 00 00 1f 00
80 02 00 00 00 00 08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
3c 00 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 3b 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 18 15 00 00 00 00 00 00 00 00 10 10 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 a5 d4
SG_IO: desc[]: 00 00
ATA_16 stat=00 err=00 nsect=00 lbal=00 lbam=00 lbah=00 dev=00
ATA device, with non-removable media
Model Number: ST9250315AS
Serial Number: 6VCQ3NW5
Firmware Revision: 0002BSM1
Transport: Serial
Standards:
Used: unknown (minor revision code 0x0029)
Supported: 8 7 6 5
Likely used: 8
Configuration:
Logical max current
cylinders 16383 16383
heads 16 16
sectors/track 63 63
--
CHS current addressable sectors: 16514064
LBA user addressable sectors: 268435455
LBA48 user addressable sectors: 488397168
Logical/Physical Sector size: 512 bytes
device size with M = 1024*1024: 238475 MBytes
device size with M = 1000*1000: 250059 MBytes (250 GB)
cache/buffer size = 8192 KBytes
Nominal Media Rotation Rate: 5400
Capabilities:
LBA, IORDY(can be disabled)
Queue depth: 32
Standby timer values: spec'd by Standard, no device specific minimum
R/W multiple sector transfer: Max = 16 Current = 16
Advanced power management level: 128
Recommended acoustic management value: 254, current value: 0
DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 udma5 *udma6
Cycle time: min=120ns recommended=120ns
PIO: pio0 pio1 pio2 pio3 pio4
Cycle time: no flow control=120ns IORDY flow control=120ns
Commands/features:
Enabled Supported:
* SMART feature set
Security Mode feature set
* Power Management feature set
* Write cache
* Look-ahead
* Host Protected Area feature set
* WRITE_BUFFER command
* READ_BUFFER command
* DOWNLOAD_MICROCODE
* Advanced Power Management feature set
SET_MAX security extension
* 48-bit Address feature set
* Device Configuration Overlay feature set
* Mandatory FLUSH_CACHE
* FLUSH_CACHE_EXT
* SMART error logging
* SMART self-test
* General Purpose Logging feature set
* 64-bit World wide name
* IDLE_IMMEDIATE with UNLOAD
Write-Read-Verify feature set
* WRITE_UNCORRECTABLE_EXT command
* {READ,WRITE}_DMA_EXT_GPL commands
* Segmented DOWNLOAD_MICROCODE
* Gen1 signaling speed (1.5Gb/s)
* Native Command Queueing (NCQ)
* Phy event counters
Device-initiated interface power management
* Software settings preservation
* SMART Command Transport (SCT) feature set
* SCT Long Sector Access (AC1)
* SCT Error Recovery Control (AC3)
* SCT Features Control (AC4)
* SCT Data Tables (AC5)
unknown 206[12] (vendor specific)
Security:
Master password revision code = 65534
supported
not enabled
not locked
not frozen
not expired: security count
supported: enhanced erase
72min for SECURITY ERASE UNIT. 72min for ENHANCED SECURITY ERASE UNIT.
Logical Unit WWN Device Identifier: 5000c50032dc7973
NAA : 5
IEEE OUI : 000c50
Unique ID : 032dc7973
Checksum: correct
And the impact of Enabling/Disabling Cache can be seen in:
Commands/features:
Enabled Supported:
* SMART feature set
Security Mode feature set
* Power Management feature set
Write cache – Changes after doing ‘hdparm –W 0/1’
* Look-ahead
* Host Protected Area feature set
* WRITE_BUFFER command
* READ_BUFFER command
Looking at corresponding code in ‘hdparm’ to fetch this: an ioctl with
command ‘ATA_OP_IDENTIFY’ is passed to the device using SG_IO
interface (function – get_identify_data()) – which receives the buffer
data and that is passed to identify the device specification.
file:identify.c, function: void identify (__u16 *id_supplied)
printf("Commands/features:\n\tEnabled\tSupported:\n");
print_features(val[CMDS_SUPP_0] & 0x7fff,
val[CMDS_EN_0], feat_word82_str);
static const char *feat_word82_str[16] = {
"obsolete 82[15]", /* word 82 bit
15: obsolete */
"NOP cmd", /* word 82 bit 14 */
"READ_BUFFER command", /* word 82 bit 13 */
"WRITE_BUFFER command", /* word 82 bit 12 */
"WRITE_VERIFY command", /* word 82 bit
11: obsolete */
"Host Protected Area feature set", /* word 82 bit 10 */
"DEVICE_RESET command", /* word 82 bit 9 */
"SERVICE interrupt", /* word 82 bit 8 */
"Release interrupt", /* word 82 bit 7 */
"Look-ahead", /* word 82 bit 6 */
"Write cache", /* word 82 bit 5 */
"PACKET command feature set", /* word 82 bit 4 */
"Power Management feature set", /* word 82 bit 3 */
"Removable Media feature set", /* word 82 bit 2 */
"Security Mode feature set", /* word 82 bit 1 */
"SMART feature set" /* word 82 bit 0 */
};
static void print_features (__u16 supported, __u16 enabled, const char *names[])
{
int i;
for (i = 0; i < 16; ++i) {
__u16 mask = 1 << i;
if ((supported & mask) && names[15 - i])
printf("\t %c\t%s\n", (enabled & mask) ? '*'
: ' ', names[15 - i]);
}
}
In this, the corresponding ‘Words’ which are passed are:
011010001101011 – 34 6b -val[82] – Supported
011010001101001 – 34 69 -val[85] – When Write Cache is Enabled
011010001001001 – 34 49 -val[85] – When Write Cache is Disabled
Val[82], val[85] indicates Words from the buffer received in response
to the ATA_OP_IDENTIFY – IOCTL
For Disabled Write Cache:
Identify Data: 5a 0c ff 3f 37 c8 10 00 00 00 00 00 3f 00 00 00 00 00
00 00 20 20 20 20 20 20 20 20 20 20 20 20 56 36 51 43 4e 33 35 57 00
00 00 40 04 00 30 30 32 30 53 42 31 4d 54 53 32 39 30 35 31 33 41 35
20 53 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
20 20 20 20 20 20 20 10 80 00 00 00 2f 00 40 00 02 00 02 07 00 ff 3f
10 00 3f 00 10 fc fb 00 10 01 ff ff ff 0f 00 00 07 00 03 00 78 00 78
00 78 00 78 00 00 00 00 00 00 00 00 00 00 00 00 00 1f 00 02 05 00 00
48 00 40 00 f0 01 29 00 6b 34 09 7d 23 61 49 34 09 bc 23 61 7f 40 24
00 24 00 80 80 fe ff 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 70 59
1c 1d 00 00 00 00 00 00 00 00 00 00 00 00 00 50 00 c5 dc 32 73 79 00
00 00 00 00 00 00 00 00 00 00 00 00 00 1e 40 1c 40 00 00 00 00 00 00
00 00 00 00 00 00 00 00
For Enabled Write Cache:
Identify Data: 5a 0c ff 3f 37 c8 10 00 00 00 00 00 3f 00 00 00 00 00
00 00 20 20 20 20 20 20 20 20 20 20 20 20 56 36 51 43 4e 33 35 57 00
00 00 40 04 00 30 30 32 30 53 42 31 4d 54 53 32 39 30 35 31 33 41 35
20 53 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
20 20 20 20 20 20 20 10 80 00 00 00 2f 00 40 00 02 00 02 07 00 ff 3f
10 00 3f 00 10 fc fb 00 10 01 ff ff ff 0f 00 00 07 00 03 00 78 00 78
00 78 00 78 00 00 00 00 00 00 00 00 00 00 00 00 00 1f 00 02 05 00 00
48 00 40 00 f0 01 29 00 6b 34 09 7d 23 61 69 34 09 bc 23 61 7f 40 24
00 24 00 80 80 fe ff 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 70 59
1c 1d 00 00 00 00 00 00 00 00 00 00 00 00 00 50 00 c5 dc 32 73 79 00
00 00 00 00 00 00 00 00 00 00 00 00 00 1e 40 1c 40 00 00 00 00 00 00
00 00 00 00 00 00 00 00
So, probably the kernel code for sensing the disk and reading to check
for the presence of the cache is not working for these USB HDD’s, I
have tried with a number of hard-disk’s(different manufactures –
with/without write cache) just to make sure that the observation is
correct.
The corresponding effect of enabling/disabling the write cache can be
seen on the write performance also - .
Please share your opinion on this.
Thanks & Regards,
Amit Sahrawat
On Thu, Sep 29, 2011 at 2:59 AM, James Bottomley
<James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 2011-09-28 at 21:27 +0530, Amit Sahrawat wrote:
>> Marking mail to linux-scsi.
>>
>> Thanks Christoph.
>>
>> Regards,
>> Amit Sahrawat
>>
>> On Wed, Sep 28, 2011 at 9:12 PM, Amit Sahrawat
>> <amit.sahrawat83@xxxxxxxxx> wrote:
>> > When a USB HDD is connected to the device, it invokes slave_configure
>> > to configure the USB HDD. In this function, whenever there is a SCSI
>> > device of type TYPE_DISK, it sets:
>> > /* A number of devices have problems with MODE SENSE for
>> > * page x08, so we will skip it. */
>> > sdev->skip_ms_page_8 = 1;
>> >
>> > Now, as a part of SCSI device probing, in the function
>> > sd_revalidate_disk()-->sd_read_cache_type(), there is a condition
>> > if (sdp->skip_ms_page_8)
>> > goto defaults;
>> > which becomes always true for all the USB HDD’s – the net result is
>> > that the Write Cache is never considered for USB HDD(WCE = 0) –
>> > “Assuming drive cache: write through”
>> >
>> > What’s more – the QUEUE ordering which is marked for WCE=0 is
>> > QUEUE_ORDERED_DRAIN, instead of QUEUE_ORDERED_DRAIN_FLUSH
>> > This means there is no flushing of USB HDD internal cache (although
>> > SYNCHRONIZE_CACHE is implemented as passed as command in
>> > sd_prepare_flush) – queue_flush()(called in function
>> > blk_do_ordered()-->start_ordered()) does not gets called in case of
>> > QUEUE_ORDERED_DRAIN.
>> >
>> > This causes a serious impact on USB HDD’s.
>> >
>> > Please let me know in case I have missed something in my observations.
>
> This should be working in 3.0 ... what version of the kernel are you
> testing. The actual patch that relaxes the caching mode page check is
> this one:
>
> commit 0bcaa11154f07502e68375617e5650173eea8e50
> Author: Luben Tuikov <ltuikov@xxxxxxxxx>
> Date: Thu May 19 00:00:58 2011 -0700
>
> [SCSI] Retrieve the Caching mode page (version 2)
>
> James
>
>
>
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