s390/dasd: fix no record found for raw_track_access

For DASD devices in raw_track_access mode only full track images are
read and written.
For this purpose it is not necessary to do search operation in the
locate record extended function. The documentation even states that
this might fail if the searched record is not found on a track.

Currently the driver sets a value of 1 in the search field for the first
record after record zero. This is the default for disks not in
raw_track_access mode but record 1 might be missing on a completely
empty track.

There has not been any problem with this on IBM storage servers but it
might lead to errors with DASD devices on other vendors storage servers.

Fix this by setting the search field to 0. Record zero is always available
even on a completely empty track.

Fixes: e4dbb0f ("[S390] dasd: Add support for raw ECKD access.")
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Link: https://lore.kernel.org/r/20221123160719.3002694-4-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/s390/block/dasd_eckd.c

@@ -4722,7 +4722,6 @@ static struct dasd_ccw_req *dasd_eckd_build_cp_raw(struct dasd_device *startdev,
 	struct dasd_device *basedev;
 	struct req_iterator iter;
 	struct dasd_ccw_req *cqr;
-	unsigned int first_offs;
 	unsigned int trkcount;
 	unsigned long *idaws;
 	unsigned int size;
@@ -4756,7 +4755,6 @@ static struct dasd_ccw_req *dasd_eckd_build_cp_raw(struct dasd_device *startdev,
 	last_trk = (blk_rq_pos(req) + blk_rq_sectors(req) - 1) /
 		DASD_RAW_SECTORS_PER_TRACK;
 	trkcount = last_trk - first_trk + 1;
-	first_offs = 0;
 
 	if (rq_data_dir(req) == READ)
 		cmd = DASD_ECKD_CCW_READ_TRACK;
@@ -4800,13 +4798,13 @@ static struct dasd_ccw_req *dasd_eckd_build_cp_raw(struct dasd_device *startdev,
 
 	if (use_prefix) {
 		prefix_LRE(ccw++, data, first_trk, last_trk, cmd, basedev,
-			   startdev, 1, first_offs + 1, trkcount, 0, 0);
+			   startdev, 1, 0, trkcount, 0, 0);
 	} else {
 		define_extent(ccw++, data, first_trk, last_trk, cmd, basedev, 0);
 		ccw[-1].flags |= CCW_FLAG_CC;
 
 		data += sizeof(struct DE_eckd_data);
-		locate_record_ext(ccw++, data, first_trk, first_offs + 1,
+		locate_record_ext(ccw++, data, first_trk, 0,
 				  trkcount, cmd, basedev, 0, 0);
 	}