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>

3 files changed, 13 insertions, 75 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 09e3a4d5e4d2..50e9efb59f67 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -56,7 +56,7 @@ void blk_set_default_limits(struct queue_limits *lim)
 	lim->alignment_offset = 0;
 	lim->io_opt = 0;
 	lim->misaligned = 0;
-	lim->zoned = BLK_ZONED_NONE;
+	lim->zoned = false;
 	lim->zone_write_granularity = 0;
 	lim->dma_alignment = 511;
 }
@@ -880,79 +880,30 @@ bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
 }
 EXPORT_SYMBOL_GPL(blk_queue_can_use_dma_map_merging);
 
-static bool disk_has_partitions(struct gendisk *disk)
-{
-	unsigned long idx;
-	struct block_device *part;
-	bool ret = false;
-
-	rcu_read_lock();
-	xa_for_each(&disk->part_tbl, idx, part) {
-		if (bdev_is_partition(part)) {
-			ret = true;
-			break;
-		}
-	}
-	rcu_read_unlock();
-
-	return ret;
-}
-
 /**
  * disk_set_zoned - configure the zoned model for a disk
  * @disk:	the gendisk of the queue to configure
- * @model:	the zoned model to set
- *
- * Set the zoned model of @disk to @model.
+ * @zoned:	zoned or not.
  *
- * When @model is BLK_ZONED_HM (host managed), this should be called only
- * if zoned block device support is enabled (CONFIG_BLK_DEV_ZONED option).
- * If @model specifies BLK_ZONED_HA (host aware), the effective model used
- * depends on CONFIG_BLK_DEV_ZONED settings and on the existence of partitions
- * on the disk.
+ * When @zoned is %true, this should be called only if zoned block device
+ * support is enabled (CONFIG_BLK_DEV_ZONED option).
  */
-void disk_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
+void disk_set_zoned(struct gendisk *disk, bool zoned)
 {
 	struct request_queue *q = disk->queue;
-	unsigned int old_model = q->limits.zoned;
 
-	switch (model) {
-	case BLK_ZONED_HM:
-		/*
-		 * Host managed devices are supported only if
-		 * CONFIG_BLK_DEV_ZONED is enabled.
-		 */
+	if (zoned) {
 		WARN_ON_ONCE(!IS_ENABLED(CONFIG_BLK_DEV_ZONED));
-		break;
-	case BLK_ZONED_HA:
-		/*
-		 * Host aware devices can be treated either as regular block
-		 * devices (similar to drive managed devices) or as zoned block
-		 * devices to take advantage of the zone command set, similarly
-		 * to host managed devices. We try the latter if there are no
-		 * partitions and zoned block device support is enabled, else
-		 * we do nothing special as far as the block layer is concerned.
-		 */
-		if (!IS_ENABLED(CONFIG_BLK_DEV_ZONED) ||
-		    disk_has_partitions(disk))
-			model = BLK_ZONED_NONE;
-		break;
-	case BLK_ZONED_NONE:
-	default:
-		if (WARN_ON_ONCE(model != BLK_ZONED_NONE))
-			model = BLK_ZONED_NONE;
-		break;
-	}
 
-	q->limits.zoned = model;
-	if (model != BLK_ZONED_NONE) {
 		/*
 		 * Set the zone write granularity to the device logical block
 		 * size by default. The driver can change this value if needed.
 		 */
+		q->limits.zoned = true;
 		blk_queue_zone_write_granularity(q,
 						queue_logical_block_size(q));
-	} else if (old_model != BLK_ZONED_NONE) {
+	} else if (q->limits.zoned) {
+		q->limits.zoned = false;
 		disk_clear_zone_settings(disk);
 	}
 }
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 63e481262336..d5e669a401b0 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -309,14 +309,9 @@ QUEUE_SYSFS_BIT_FNS(stable_writes, STABLE_WRITES, 0);
 
 static ssize_t queue_zoned_show(struct request_queue *q, char *page)
 {
-	switch (blk_queue_zoned_model(q)) {
-	case BLK_ZONED_HA:
-		return sprintf(page, "host-aware\n");
-	case BLK_ZONED_HM:
+	if (blk_queue_is_zoned(q))
 		return sprintf(page, "host-managed\n");
-	default:
-		return sprintf(page, "none\n");
-	}
+	return sprintf(page, "none\n");
 }
 
 static ssize_t queue_nr_zones_show(struct request_queue *q, char *page)
diff --git a/block/partitions/core.c b/block/partitions/core.c
index f47ffcfdfcec..e6ac73617f3e 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -305,18 +305,10 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
 	 * Partitions are not supported on zoned block devices that are used as
 	 * such.
 	 */
-	switch (disk->queue->limits.zoned) {
-	case BLK_ZONED_HM:
+	if (bdev_is_zoned(disk->part0)) {
 		pr_warn("%s: partitions not supported on host managed zoned block device\n",
 			disk->disk_name);
 		return ERR_PTR(-ENXIO);
-	case BLK_ZONED_HA:
-		pr_info("%s: disabling host aware zoned block device support due to partitions\n",
-			disk->disk_name);
-		disk_set_zoned(disk, BLK_ZONED_NONE);
-		break;
-	case BLK_ZONED_NONE:
-		break;
 	}
 
 	if (xa_load(&disk->part_tbl, partno))
@@ -613,7 +605,7 @@ static int blk_add_partitions(struct gendisk *disk)
 	/*
 	 * Partitions are not supported on host managed zoned block devices.
 	 */
-	if (disk->queue->limits.zoned == BLK_ZONED_HM) {
+	if (bdev_is_zoned(disk->part0)) {
 		pr_warn("%s: ignoring partition table on host managed zoned block device\n",
 			disk->disk_name);
 		ret = 0;