[stgt] [PATCH V2] Make virtual tapes more closely emulate physical ones

[Jay Fenlason]

On Thu, Jan 10, 2013 at 11:36:44AM -0500, Jay Fenlason wrote:
> On my physical drive (a Sony AIT-2 drive, if it matters) when
> userspace reads a file mark, it gets an EOF, and the tape is advanced
> past the file mark so that a subsequent read will return data from the
> next file on the tape.  With a virtual drive, the file mark is
> sticky--reads continue to return EOF until the tape is manually
> advanced with a FSF ioctl.  I wrote this quick patch to make the
> virtual tape behave like my physical one.

V2: Replace FIXME with correct error flow.  If the attempt to read the
next block fails, return ASC_MEDIUM_FORMAT_CORRUPT

Signed-off-by: Jay Fenlason <fenlason at redhat.com>


--- tgt-1.0.32/usr/bs_ssc.c.filemark	2012-09-30 18:39:21.000000000 -0400
+++ tgt-1.0.32/usr/bs_ssc.c	2013-01-17 14:39:54.000000000 -0500
@@ -325,6 +325,9 @@ static int resp_var_read(struct scsi_cmd
 		if (h->blk_type == BLK_EOD)
 			sense_data_build(cmd, 0x40 | BLANK_CHECK,
 					 NO_ADDITIONAL_SENSE);
+		else if (h->blk_type == BLK_FILEMARK)
+			ssc_sense_data_build(cmd, NO_SENSE | SENSE_FILEMARK,
+					     ASC_MARK, info, sizeof(info));
 		else
 			ssc_sense_data_build(cmd, NO_SENSE | 0x20,
 					     NO_ADDITIONAL_SENSE,
@@ -339,8 +342,11 @@ static int resp_var_read(struct scsi_cmd
 
 		result = SAM_STAT_CHECK_CONDITION;
 
-		if (!length)
+		if (!length) {
+			if (h->blk_type == BLK_FILEMARK)
+				goto skip_and_out;
 			goto out;
+		}
 	}
 
 	ret = pread64(cmd->dev->fd, buf, length, h->curr + SSC_BLK_HDR_SIZE);
@@ -351,6 +357,7 @@ static int resp_var_read(struct scsi_cmd
 	}
 	*transferred = length;
 
+skip_and_out:
 	ret = skip_next_header(cmd->dev);
 	if (ret) {
 		sense_data_build(cmd, MEDIUM_ERROR, ASC_MEDIUM_FORMAT_CORRUPT);
--
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