block: allow partitions on host aware zone devices

Host-aware SMR drives can be used with the commands to explicitly manage
zone state, but they can also be used as normal disks.  In the former
case it makes perfect sense to allow partitions on them, in the latter
it does not, just like for host managed devices.  Add a check to
add_partition to allow partitions on host aware devices, but give
up any zone management capabilities in that case, which also catches
the previously missed case of adding a partition vs just scanning it.

Because sd can rescan the attribute at runtime it needs to check if
a disk has partitions, for which a new helper is added to genhd.h.

Fixes: 5eac3eb30c9a ("block: Remove partition support for zoned block devices")
Reported-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 8bb63027e4d6..ea4c133b4139 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -245,6 +245,18 @@ static inline bool disk_part_scan_enabled(struct gendisk *disk)
 		!(disk->flags & GENHD_FL_NO_PART_SCAN);
 }
 
+static inline bool disk_has_partitions(struct gendisk *disk)
+{
+	bool ret = false;
+
+	rcu_read_lock();
+	if (rcu_dereference(disk->part_tbl)->len > 1)
+		ret = true;
+	rcu_read_unlock();
+
+	return ret;
+}
+
 static inline dev_t disk_devt(struct gendisk *disk)
 {
 	return MKDEV(disk->major, disk->first_minor);