[PATCH] dm: Implement set_read_only

[Łukasz Patron]

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

Signed-off-by: Łukasz Patron <priv....@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