[PATCH] dm: Implement set_read_only

["Łukasz Patron" <priv.luk@gmail.com>]

This lets us change the read-only flag for device mapper block devices
via the BLKROSET ioctl.

Signed-off-by: Łukasz Patron <priv.luk@gmail.com>
---
 drivers/md/dm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 87bb90303435..538a93e596d7 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -410,6 +410,12 @@ static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
 	return dm_get_geometry(md, geo);
 }
 
+static int dm_blk_set_read_only(struct block_device *bdev, bool ro)
+{
+	set_disk_ro(bdev->bd_disk, ro);
+	return 0;
+}
+
 static int dm_prepare_ioctl(struct mapped_device *md, int *srcu_idx,
 			    struct block_device **bdev)
 {
@@ -3666,6 +3672,7 @@ static const struct block_device_operations dm_blk_dops = {
 	.release = dm_blk_close,
 	.ioctl = dm_blk_ioctl,
 	.getgeo = dm_blk_getgeo,
+	.set_read_only = dm_blk_set_read_only,
 	.report_zones = dm_blk_report_zones,
 	.pr_ops = &dm_pr_ops,
 	.owner = THIS_MODULE
-- 
2.46.0