Date: Tue, 04 Jan 2005 07:06:00 -0700 From: "James E. Flemer" <jflemer@uvm.edu> To: freebsd-scsi@freebsd.org Cc: James Flemer <jflemer@uvm.edu> Subject: Re: mtio/sa device response to bad blocks Message-ID: <41DAA2C8.7030303@uvm.edu> In-Reply-To: <7579f7fb05010323457bab1899@mail.gmail.com> References: <41DA2475.90509@uvm.edu> <7579f7fb05010323457bab1899@mail.gmail.com>
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I am using fixed block mode. Why is it that errors cannot propagate for
fixed block? After a little more looking in the code, perhaps this
patch in saerror() will do what I want. I have not tried this patch yet
though, since I compiled SCSI into the kernel (not module) and cannot
reboot the box at the moment.
-James
--- sys/cam/scsi/scsi_sa.c 16 Jun 2004 09:46:31 -0000 1.101
+++ sys/cam/scsi/scsi_sa.c 4 Jan 2005 13:56:50 -0000
@@ -2415,6 +2415,8 @@
} else {
error = EIO;
}
+ } else if (sense_key == SSD_KEY_MEDIUM_ERROR) {
+ error = EIO;
} else if (sense->flags & SSD_FILEMARK) {
if (softc->flags & SA_FLAG_FIXED) {
error = -1;
Matthew Jacob wrote:
> Are you using fixed block or variable block mode? I believe that
> errors propagate correctly for variable but can't for fixed block
> mode.
>
>
> On Mon, 03 Jan 2005 22:07:01 -0700, James E. Flemer <jflemer@uvm.edu> wrote:
>
>>I have a SCSI DAT drive and have had some problems reading tapes with
>>bad blocks. It seems that a read(2) from the sa device returns 0 when a
>>bad block is read from the tape. Note that read(2) also correctly
>>returns 0 when a filemark is read. A userland application (see below)
>>can tell the difference between a filemark and a read error by looking
>>at the io_sense part of the scsi_tape_errors struct (via the
>>MTIOCERRSTAT ioctl). However this is cumbersome and requires the
>>knowledge of the scsi_sense_data struct. It would seem more appropriate
>>for the read to return -1 and set errno to EIO when a bad block is read.
>> With such a change "dd conv=noerror,sync" could be used to dump a tape
>>with bad blocks. Unfortunately, I'm not familiar enough with the
>>SCSI/CAM layers to know where make this change, could someone point me
>>where to look?
>>
>>Thanks,
>>-James
>>
>>/* This code will check the real reason for read to return 0
>> * and change the return code to -1 and set errno to EIO if there
>> * was a MEDIUM_ERROR. Other non-SSD_FILEMARK/SSD_EOM flags
>> * should probably also be handled via -1/errno.
>> */
>>num_read = read(mtfd, buf, blk_size);
>>if (num_read == 0) {
>> ioctl(mtfd, MTIOCERRSTAT, &tape_err);
>> sense_data = (struct scsi_sense_data *)&tape_err.io_sense;
>> if (sense_data->flags & SSD_KEY_MEDIUM_ERROR) {
>> num_read = -1;
>> errno = EIO;
>> }
>>}
>>_______________________________________________
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>>
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