From: Alasdair G Kergon Add a target feature flag to indicate that a target does not work in read-only mode. Signed-off-by: Alasdair G Kergon --- drivers/md/dm-table.c | 6 ++++++ include/linux/device-mapper.h | 5 ++++- 2 files changed, 10 insertions(+), 1 deletion(-) Index: linux-3.0-rc7/drivers/md/dm-table.c =================================================================== --- linux-3.0-rc7.orig/drivers/md/dm-table.c +++ linux-3.0-rc7/drivers/md/dm-table.c @@ -777,6 +777,12 @@ int dm_table_add_target(struct dm_table t->singleton = 1; } + if (dm_target_always_writeable(tgt->type) && !(t->mode & FMODE_WRITE)) { + DMERR("%s: target type %s may not be included in read-only tables", + dm_device_name(t->md), type); + return -EINVAL; + } + tgt->table = t; tgt->begin = start; tgt->len = len; Index: linux-3.0-rc7/include/linux/device-mapper.h =================================================================== --- linux-3.0-rc7.orig/include/linux/device-mapper.h +++ linux-3.0-rc7/include/linux/device-mapper.h @@ -162,9 +162,12 @@ struct target_type { /* * Any table that contains an instance of this target must have only one. */ -#define DM_TARGET_SINGLETON 0x00000001 +#define DM_TARGET_SINGLETON 0x00000001 #define dm_target_needs_singleton(type) ((type)->features & DM_TARGET_SINGLETON) +#define DM_TARGET_ALWAYS_WRITEABLE 0x00000002 +#define dm_target_always_writeable(type) ((type)->features & DM_TARGET_ALWAYS_WRITEABLE) + struct dm_target { struct dm_table *table; struct target_type *type;