A useful test case for error recovery is multiple,
consecutive medium errors. When scsi_debug is started
with "opts=2" a MEDIUM ERROR is generated when block
0x1234 (4660) is read. The patch extends that to
10 consecutive blocks from 0x1234 (i.e. blocks 4660 to
4669 inclusive).
# lsscsi -gs
[0:0:0:0] disk ATA INTEL SSD 2CV1 /dev/sda /dev/sg0 80.0GB
[10:0:0:0] disk Linux scsi_debug 0004 /dev/sdb /dev/sg1 1.09TB
# ddpt if=/dev/sg1 iflag=coe bs=512 count=4680
Output file not specified so no copy, just reading input
>> unrecovered read error at blk=4660, substitute zeros
...
>> unrecovered read error at blk=4669, substitute zeros
4670+10 records in
0+0 records out
10 unrecovered read errors
lowest unrecovered read lba=4660, highest unrecovered lba=4669
time to read data: 0.047943 secs at 49.87 MB/sec
BTW Change /dev/sg1 (bsg device works just as well) to
/dev/sdb to see why, with faulty media, you do not want
to use the block layer interface. Reason: time block
layer takes to do useless retries and collateral damage
to data in its 4 KB blocks (O_DIRECT mitigates the
latter).
This patch applies to lk 2.6.37 and also applies
to lk 2.6.38-rc8 including with Martin Petersen's
recent patch.
ChangeLog:
- extend opts=2 medium error generation at block
0x1234 to 10 consecutive blocks (i.e. blocks
0x1234 to 0x123d).
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
--- linux/drivers/scsi/scsi_debug.c 2011-01-05 09:36:01.496918857 -0500
+++ linux/drivers/scsi/scsi_debug.c2637mederr 2011-01-15 21:46:20.717085001 -0500
@@ -144,6 +144,7 @@ static const char * scsi_debug_version_d
/* when 1==SCSI_DEBUG_OPT_MEDIUM_ERR, a medium error is simulated at this
* sector on read commands: */
#define OPT_MEDIUM_ERR_ADDR 0x1234 /* that's sector 4660 in decimal */
+#define OPT_MEDIUM_ERR_NUM 10 /* number of consecutive medium errs */
/* If REPORT LUNS has luns >= 256 it can choose "flat space" (value 1)
* or "peripheral device" addressing (value 0) */
@@ -1791,15 +1792,15 @@ static int resp_read(struct scsi_cmnd *S
return ret;
if ((SCSI_DEBUG_OPT_MEDIUM_ERR & scsi_debug_opts) &&
- (lba <= OPT_MEDIUM_ERR_ADDR) &&
+ (lba <= (OPT_MEDIUM_ERR_ADDR + OPT_MEDIUM_ERR_NUM - 1)) &&
((lba + num) > OPT_MEDIUM_ERR_ADDR)) {
/* claim unrecoverable read error */
- mk_sense_buffer(devip, MEDIUM_ERROR, UNRECOVERED_READ_ERR,
- 0);
+ mk_sense_buffer(devip, MEDIUM_ERROR, UNRECOVERED_READ_ERR, 0);
/* set info field and valid bit for fixed descriptor */
if (0x70 == (devip->sense_buff[0] & 0x7f)) {
devip->sense_buff[0] |= 0x80; /* Valid bit */
- ret = OPT_MEDIUM_ERR_ADDR;
+ ret = (lba < OPT_MEDIUM_ERR_ADDR)
+ ? OPT_MEDIUM_ERR_ADDR : (int)lba;
devip->sense_buff[3] = (ret >> 24) & 0xff;
devip->sense_buff[4] = (ret >> 16) & 0xff;
devip->sense_buff[5] = (ret >> 8) & 0xff;
