[PATCH 5.10.y 6/7] block: don't set GENHD_FL_NO_PART for hidden gendisks

[Sasha Levin <sashal@kernel.org>]

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 9f18db572c97bc327b63528d195fdb252f47e9de ]

Hidden gendisks can't be opened using blkdev_get_*, so we can't really
reach any of the partition scanning paths or partitioning ioctls except
for the initial partition scan from add_disk.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211122130625.1136848-13-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Adapt the dependency to the 5.10 disk-registration layout.  Keep the void
disk_scan_partitions() interface and its capacity and partition-scan
checks, adding a direct GENHD_FL_HIDDEN check before requesting a scan.

Remove the implicit GENHD_FL_NO_PART assignment from __device_add_disk(),
where this branch handles hidden disks.  Preserve its existing BDI and
region registration, and keep register_disk()'s hidden-disk early return,
uevents and sysfs links intact.  No functions are added.

Verified that target 3f9c7a108c0e applies cleanly with a three-way merge,
placing its zoned-disk check in __device_add_disk() before partition
scanning.  The existing GENHD_FL_NO_PART ext_range handling is retained.

Stable-dep-of: 3f9c7a108c0e ("block: flag zoned disks with GENHD_FL_NO_PART")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/genhd.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 4ecab2f503719..ea81203f6a036 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -680,7 +680,8 @@ static void disk_scan_partitions(struct gendisk *disk)
 {
 	struct block_device *bdev;
 
-	if (!get_capacity(disk) || !disk_part_scan_enabled(disk))
+	if (!get_capacity(disk) || !disk_part_scan_enabled(disk) ||
+	    (disk->flags & GENHD_FL_HIDDEN))
 		return;
 
 	set_bit(GD_NEED_PART_SCAN, &disk->state);
@@ -745,12 +746,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
 
 	disk_alloc_events(disk);
 
-	if (disk->flags & GENHD_FL_HIDDEN) {
-		/*
-		 * Don't bother scanning for partitions.
-		 */
-		disk->flags |= GENHD_FL_NO_PART;
-	} else {
+	if (!(disk->flags & GENHD_FL_HIDDEN)) {
 		struct backing_dev_info *bdi = disk->queue->backing_dev_info;
 		struct device *dev = disk_to_dev(disk);
 		int ret;
-- 
2.53.0