Add support for defining read-only partitions and complete support for
it in the cmdline partition parser as the additional "ro" after a
partition is scanned but never actually applied.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/blk.h                | 1 +
 block/partitions/cmdline.c | 3 +++
 block/partitions/core.c    | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/block/blk.h b/block/blk.h
index c718e4291db0..f300212d3e98 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -558,6 +558,7 @@ void blk_free_ext_minor(unsigned int minor);
 #define ADDPART_FLAG_NONE	0
 #define ADDPART_FLAG_RAID	1
 #define ADDPART_FLAG_WHOLEDISK	2
+#define ADDPART_FLAG_READONLY	4
 int bdev_add_partition(struct gendisk *disk, int partno, sector_t start,
 		sector_t length);
 int bdev_del_partition(struct gendisk *disk, int partno);
diff --git a/block/partitions/cmdline.c b/block/partitions/cmdline.c
index 152c85df92b2..da3e719d8e51 100644
--- a/block/partitions/cmdline.c
+++ b/block/partitions/cmdline.c
@@ -237,6 +237,9 @@ static int add_part(int slot, struct cmdline_subpart *subpart,
 	put_partition(state, slot, subpart->from >> 9,
 		      subpart->size >> 9);
 
+	if (subpart->flags & PF_RDONLY)
+		state->parts[slot].flags |= ADDPART_FLAG_READONLY;
+
 	info = &state->parts[slot].info;
 
 	strscpy(info->volname, subpart->name, sizeof(info->volname));
diff --git a/block/partitions/core.c b/block/partitions/core.c
index ab76e64f0f6c..abad6c83db8f 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -373,6 +373,9 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
 			goto out_del;
 	}
 
+	if (flags & ADDPART_FLAG_READONLY)
+		bdev_set_flag(bdev, BD_READ_ONLY);
+
 	/* everything is up and running, commence */
 	err = xa_insert(&disk->part_tbl, partno, bdev, GFP_KERNEL);
 	if (err)
-- 
2.45.2