On Thu, 13 Nov 2008 10:52:43 +1100
"Mark Harvey" <markh794@xxxxxxxxx> wrote:
Seems that the attached patch fixes the 512-byte read case, but not
256-byte. I guess that I still misunderstand something...
> >> Now test we can read in a 256k block from the tape.
> >> # dd if=/dev/st0 of=/tmp/block0 bs=256k count=1
> >> 1+0 records in
> >> 1+0 records out
> >> 262144 bytes (262 kB) copied, 0.00424289 s, 61.8 MB/s
> >>
> >> Now test if we can read in a partial block (this fails returning no
> >> data - we should have read in the 128k)
> >> # dd if=/dev/st0 of=/tmp/block0 bs=128k count=1
> >> dd: reading `/dev/st0': Input/output error
> >> 0+0 records in
> >> 0+0 records out
> >> 0 bytes (0 B) copied, 0.00249643 s, 0.0 kB/s
> >
> > Sorry for my dumb question here:
> >
> > What should stgt return? The first 128 KB of the first block and no
> > sense?
>
> The amount of data requested should be returned. In this example, 128k.
>
> The sense returned should be :NO SENSE | VALID | ILI (Illegal Length
> Indicator) and the overrun values (size of data block - size of data
> requested) filled in sense_buffer[3] -> sense_buffer[7].
With the patch, stgt returns CHECK CONDITION with a sense (NO SENSE |
VALID | ILI ) and the information field sets to 128K.
I got (actually, stgt returns 128KB data though...):
nemo:/home/fujita# dd if=/dev/st0 of=/tmp/block0 bs=128k count=1
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.0030381 seconds, 0.0 kB/s
But the last line should be something like:
131072 bytes (131 kB) copied...
Right?
> >> Now test if we can read in a more then a block (this fails returning
> >> no data - we should have read in the 256k)
> >> # dd if=/dev/st0 of=/tmp/block0 bs=512k count=1
> >> dd: reading `/dev/st0': Input/output error
> >> 0+0 records in
> >> 0+0 records out
> >> 0 bytes (0 B) copied, 0.00705821 s, 0.0 kB/s
> >
> > stgt should return the whole first block without sense, right?
> >
>
> The amount of data successfully read should be returned. In this example, 128k.
>
> The sense returned should be :NO SENSE | VALID | ILI (Illegal Length
> Indicator) and the amount of data NOT successfully returned -> filled
> in sense_buffer[3] -> sense_buffer[7]
With the patch, stgt returns CHECK CONDITION with a sense (NO SENSE |
VALID | ILI ) and the information field sets to 256K.
nemo:/home/fujita# dd if=/dev/st0 of=/tmp/block0 bs=512k count=1
0+1 records in
0+1 records out
262144 bytes (262 kB) copied, 0.019265 seconds, 13.6 MB/s
This is the right response?
> On a side note (real world implementation):
> NetBackup as part of its logic to determine if the media has valid
> NetBackup data performs a :
> - Request 64k data
> - NetBackup expects to see only 1k returned with the sense | ILI set.
> Otherwise it treats the media as something it did not create.
>
>
> SSC3-r04a reads as follows (page 91): - note 'SILI == Supress Illegal
> Length Indicator'
> If the SILI bit is zero and an incorrect-length logical block is read,
> CHECK CONDITION status shall be returned. The ILI and VALID bits shall
> be set to one in the sense data and the additional sense code shall be
> set to NO ADDITIONAL SENSE INFORMATION
>
> Upon termination, the logical position shall be after the
> incorrect-length logical block (end-of-partition side)
>
> If the FIXED bit is one, the INFORMATION field shall be set to the
> requested transfer length minus the actual number of logical blocks
> read (not including the incorrect-length logical block).
>
> If the FIXED bit is zero, the INFORMATION field shall be set to the
> requested transfer length minus the actual logical block length.
>
> Logical units that do not support negative values shall set the
> INFORMATION field to zero if the overlength condition exists.
Thanks!
I still need to learn lots about ssc...
This patch is against the latest git head:
commit c467cd60be224f62f8f28cb4f892578ad9848064
Author: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Date: Sun Nov 23 02:09:06 2008 +0900
ssc: fix the information field in sense
=
diff --git a/usr/bs_ssc.c b/usr/bs_ssc.c
index 0b9fedb..4aff96c 100644
--- a/usr/bs_ssc.c
+++ b/usr/bs_ssc.c
@@ -317,15 +317,29 @@ static int resp_var_read(struct scsi_cmd *cmd, uint8_t *buf, uint32_t length,
*transferred = 0;
if (length != h->blk_sz) {
+ uint8_t info[4];
+
+ if (length > h->blk_sz)
+ put_unaligned_be32(length - h->blk_sz, info);
+ else
+ put_unaligned_be32(h->blk_sz - length, info);
+
if (h->blk_type == BLK_EOD)
sense_data_build(cmd, 0x40 | BLANK_CHECK,
NO_ADDITIONAL_SENSE);
else
- sense_data_build(cmd, NO_SENSE, NO_ADDITIONAL_SENSE);
+ ssc_sense_data_build(cmd, NO_SENSE | 0x20,
+ NO_ADDITIONAL_SENSE,
+ info, sizeof(info));
+
+ if (length > h->blk_sz)
+ scsi_set_in_resid_by_actual(cmd, length - h->blk_sz);
+ else
+ scsi_set_in_resid_by_actual(cmd, 0);
length = min(length, h->blk_sz);
+
result = SAM_STAT_CHECK_CONDITION;
- scsi_set_in_resid_by_actual(cmd, length);
if (!length)
goto out;
--
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