[RFC PATCH 2/4] block: add new flag to add partitions read-only

[Daniel Golle <daniel@makrotopia.org>]

Add flag ADDPART_FLAG_READONLY to allow partition parsers marking a
partition to be set read-only.
This is needed for the uImage.FIT partition parser added by a follow-up
commit: we need to be sure the contents of uImage.FIT sub-images
remain unaltered they are validated using a hash within the uImage.FIT
structure which also serves as partition table.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 block/blk.h             | 1 +
 block/partitions/core.c | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/block/blk.h b/block/blk.h
index e85703ae81dd..05ac426350b2 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -414,6 +414,7 @@ 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/core.c b/block/partitions/core.c
index b8112f52d388..355646b0707d 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -398,6 +398,9 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
 			goto out_del;
 	}
 
+	if (flags & ADDPART_FLAG_READONLY)
+		bdev->bd_read_only = true;
+
 	/* everything is up and running, commence */
 	err = xa_insert(&disk->part_tbl, partno, bdev, GFP_KERNEL);
 	if (err)
-- 
2.38.1