block: add a disk_has_partscan helper

Add a helper to check if partition scanning is enabled instead of
open coding the check in a few places.  This now always checks for
the hidden flag even if all but one of the callers are never reachable
for hidden gendisks.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240502130033.1958492-2-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -345,9 +345,7 @@ int disk_scan_partitions(struct gendisk *disk, blk_mode_t mode)
 	struct file *file;
 	int ret = 0;
 
-	if (disk->flags & (GENHD_FL_NO_PART | GENHD_FL_HIDDEN))
-		return -EINVAL;
-	if (test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
+	if (!disk_has_partscan(disk))
 		return -EINVAL;
 	if (disk->open_partitions)
 		return -EBUSY;
@@ -503,8 +501,7 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
 			goto out_unregister_bdi;
 
 		/* Make sure the first partition scan will be proceed */
-		if (get_capacity(disk) && !(disk->flags & GENHD_FL_NO_PART) &&
-		    !test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
+		if (get_capacity(disk) && disk_has_partscan(disk))
 			set_bit(GD_NEED_PART_SCAN, &disk->state);
 
 		bdev_add(disk->part0, ddev->devt);

block/partitions/core.c

@@ -573,10 +573,7 @@ static int blk_add_partitions(struct gendisk *disk)
 	struct parsed_partitions *state;
 	int ret = -EAGAIN, p;
 
-	if (disk->flags & GENHD_FL_NO_PART)
-		return 0;
-
-	if (test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
+	if (!disk_has_partscan(disk))
 		return 0;
 
 	state = check_partition(disk);

include/linux/blkdev.h

@@ -230,6 +230,19 @@ static inline unsigned int disk_openers(struct gendisk *disk)
 	return atomic_read(&disk->part0->bd_openers);
 }
 
+/**
+ * disk_has_partscan - return %true if partition scanning is enabled on a disk
+ * @disk: disk to check
+ *
+ * Returns %true if partitions scanning is enabled for @disk, or %false if
+ * partition scanning is disabled either permanently or temporarily.
+ */
+static inline bool disk_has_partscan(struct gendisk *disk)
+{
+	return !(disk->flags & (GENHD_FL_NO_PART | GENHD_FL_HIDDEN)) &&
+		!test_bit(GD_SUPPRESS_PART_SCAN, &disk->state);
+}
+
 /*
  * The gendisk is refcounted by the part0 block_device, and the bd_device
  * therein is also used for device model presentation in sysfs.