From 3791e2fc0e4b40d4188e79b0a99bfa6bce714a10 Mon Sep 17 00:00:00 2001
From: Alasdair G Kergon <agk@redhat.com>
Date: Mon, 31 Oct 2011 20:19:00 +0000
Subject: [PATCH] dm table: add singleton feature
Introduce the concept of a singleton table which contains exactly one target.
If a target type sets the DM_TARGET_SINGLETON feature bit device-mapper
will ensure that any table that includes that target contains no others.
The thin provisioning pool target uses this.
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
---
drivers/md/dm-table.c | 16 ++++++++++++++++
include/linux/device-mapper.h | 14 ++++++++++----
2 files changed, 26 insertions(+), 4 deletions(-)
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 81cbbf375bd7..2ec3482e942a 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -55,6 +55,7 @@ struct dm_table {
struct dm_target *targets;
unsigned integrity_supported:1;
+ unsigned singleton:1;
/*
* Indicates the rw permissions for the new logical
@@ -740,6 +741,12 @@ int dm_table_add_target(struct dm_table *t, const char *type,
char **argv;
struct dm_target *tgt;
+ if (t->singleton) {
+ DMERR("%s: target type %s must appear alone in table",
+ dm_device_name(t->md), t->targets->type->name);
+ return -EINVAL;
+ }
+
if ((r = check_space(t)))
return r;
@@ -758,6 +765,15 @@ int dm_table_add_target(struct dm_table *t, const char *type,
return -EINVAL;
}
+ if (dm_target_needs_singleton(tgt->type)) {
+ if (t->num_targets) {
+ DMERR("%s: target type %s must appear alone in table",
+ dm_device_name(t->md), type);
+ return -EINVAL;
+ }
+ t->singleton = 1;
+ }
+
tgt->table = t;
tgt->begin = start;
tgt->len = len;
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 622678ccb5e0..294e78a7fccd 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -128,10 +128,6 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d);
* Information about a target type
*/
-/*
- * Target features
- */
-
struct target_type {
uint64_t features;
const char *name;
@@ -160,6 +156,16 @@ struct target_type {
struct list_head list;
};
+/*
+ * Target features
+ */
+
+/*
+ * Any table that contains an instance of this target must have only one.
+ */
+#define DM_TARGET_SINGLETON 0x00000001
+#define dm_target_needs_singleton(type) ((type)->features & DM_TARGET_SINGLETON)
+
struct dm_target {
struct dm_table *table;
struct target_type *type;