block: remove support for the host aware zone model

When zones were first added the SCSI and ATA specs, two different
models were supported (in addition to the drive managed one that
is invisible to the host):

 - host managed where non-conventional zones there is strict requirement
   to write at the write pointer, or else an error is returned
 - host aware where a write point is maintained if writes always happen
   at it, otherwise it is left in an under-defined state and the
   sequential write preferred zones behave like conventional zones
   (probably very badly performing ones, though)

Not surprisingly this lukewarm model didn't prove to be very useful and
was finally removed from the ZBC and SBC specs (NVMe never implemented
it).  Due to to the easily disappearing write pointer host software
could never rely on the write pointer to actually be useful for say
recovery.

Fortunately only a few HDD prototypes shipped using this model which
never made it to mass production.  Drop the support before it is too
late.  Note that any such host aware prototype HDD can still be used
with Linux as we'll now treat it as a conventional HDD.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20231217165359.604246-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1 insertions, 15 deletions

diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
index a25215507668..26af5ab7d7c1 100644
--- a/drivers/scsi/sd_zbc.c
+++ b/drivers/scsi/sd_zbc.c
@@ -836,10 +836,7 @@ int sd_zbc_revalidate_zones(struct scsi_disk *sdkp)
 
 	/*
 	 * For all zoned disks, initialize zone append emulation data if not
-	 * already done. This is necessary also for host-aware disks used as
-	 * regular disks due to the presence of partitions as these partitions
-	 * may be deleted and the disk zoned model changed back from
-	 * BLK_ZONED_NONE to BLK_ZONED_HA.
+	 * already done.
 	 */
 	if (sd_is_zoned(sdkp) && !sdkp->zone_wp_update_buf) {
 		ret = sd_zbc_init_disk(sdkp);
@@ -932,17 +929,6 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, u8 buf[SD_BUF_SIZE])
 	sdkp->device->use_10_for_rw = 0;
 	sdkp->device->use_16_for_sync = 1;
 
-	if (!blk_queue_is_zoned(q)) {
-		/*
-		 * This can happen for a host aware disk with partitions.
-		 * The block device zone model was already cleared by
-		 * disk_set_zoned(). Only free the scsi disk zone
-		 * information and exit early.
-		 */
-		sd_zbc_free_zone_info(sdkp);
-		return 0;
-	}
-
 	/* Check zoned block device characteristics (unconstrained reads) */
 	ret = sd_zbc_check_zoned_characteristics(sdkp, buf);
 	if (ret)