system_id: make new VGs read-only for old lvm versions

Previous versions of lvm will not obey the restrictions
imposed by the new system_id, and would allow such a VG
to be written.  So, a VG with a new system_id is further
changed to force previous lvm versions to treat it as
read-only.  This is done by removing the WRITE flag from
the metadata status line of these VGs, and putting a new
WRITE_LOCKED flag in the flags line of the metadata.

Versions of lvm that recognize WRITE_LOCKED, also obey the
new system_id.  For these lvm versions, WRITE_LOCKED is
identical to WRITE, and the rules associated with matching
system_id's are imposed.

A new VG lock_type field is also added that causes the same
WRITE/WRITE_LOCKED transformation when set.  A previous
version of lvm will also see a VG with lock_type as read-only.

Versions of lvm that recognize WRITE_LOCKED, must also obey
the lock_type setting.  Until the lock_type feature is added,
lvm will fail to read any VG with lock_type set and report an
error about an unsupported lock_type.  Once the lock_type
feature is added, lvm will allow VGs with lock_type to be
used according to the rules imposed by the lock_type.

When both system_id and lock_type settings are removed, a VG
is written with the old WRITE status flag, and without the
new WRITE_LOCKED flag.  This allows old versions of lvm to
use the VG as before.

2 files changed, 16 insertions, 2 deletions

diff --git a/lib/format1/disk-rep.h b/lib/format1/disk-rep.h
index 9d1c8a5cc..37f728255 100644
--- a/lib/format1/disk-rep.h
+++ b/lib/format1/disk-rep.h
@@ -41,6 +41,7 @@
 #define	VG_WRITE             0x02	/*     "     */
 #define	VG_CLUSTERED         0x04	/*     "     */
 #define	VG_SHARED            0x08	/*     "     */
+#define	VG_WRITE_LOCKED      0x10	/*     "     */
 
 /* logical volume */
 #define	LV_ACTIVE            0x01	/* lv_status */
@@ -51,6 +52,7 @@
 #define	LV_WRITE             0x02	/*     "     */
 #define	LV_SNAPSHOT          0x04	/*     "     */
 #define	LV_SNAPSHOT_ORG      0x08	/*     "     */
+#define	LV_WRITE_LOCKED      0x10	/*     "     */
 
 #define	LV_BADBLOCK_ON       0x01	/* lv_badblock */
 
diff --git a/lib/format1/import-export.c b/lib/format1/import-export.c
index 9b387e2a1..b898e65b6 100644
--- a/lib/format1/import-export.c
+++ b/lib/format1/import-export.c
@@ -242,6 +242,9 @@ int import_vg(struct dm_pool *mem,
 	if (vgd->vg_access & VG_WRITE)
 		vg->status |= LVM_WRITE;
 
+	if (vgd->vg_access & VG_WRITE_LOCKED)
+		vg->status |= LVM_WRITE;
+
 	if (vgd->vg_access & VG_CLUSTERED)
 		vg->status |= CLUSTERED;
 
@@ -266,9 +269,12 @@ int export_vg(struct vg_disk *vgd, struct volume_group *vg)
 	if (vg->status & LVM_READ)
 		vgd->vg_access |= VG_READ;
 
-	if (vg->status & LVM_WRITE)
+	if ((vg->status & LVM_WRITE) && !vg_flag_write_locked(vg))
 		vgd->vg_access |= VG_WRITE;
 
+	if ((vg->status & LVM_WRITE) && vg_flag_write_locked(vg))
+		vgd->vg_access |= VG_WRITE_LOCKED;
+
 	if (vg_is_clustered(vg))
 		vgd->vg_access |= VG_CLUSTERED;
 
@@ -320,6 +326,9 @@ int import_lv(struct cmd_context *cmd, struct dm_pool *mem,
 	if (lvd->lv_access & LV_WRITE)
 		lv->status |= LVM_WRITE;
 
+	if (lvd->lv_access & LV_WRITE_LOCKED)
+		lv->status |= LVM_WRITE;
+
 	if (lvd->lv_badblock)
 		lv->status |= BADBLOCK_ON;
 
@@ -352,9 +361,12 @@ static void _export_lv(struct lv_disk *lvd, struct volume_group *vg,
 	if (lv->status & LVM_READ)
 		lvd->lv_access |= LV_READ;
 
-	if (lv->status & LVM_WRITE)
+	if ((lv->status & LVM_WRITE) && !vg_flag_write_locked(vg))
 		lvd->lv_access |= LV_WRITE;
 
+	if ((lv->status & LVM_WRITE) && vg_flag_write_locked(vg))
+		lvd->lv_access |= LV_WRITE_LOCKED;
+
 	if (lv->status & SPINDOWN_LV)
 		lvd->lv_status |= LV_SPINDOWN;