From: Alasdair G Kergon <agk@redhat.com>
Date: Thu, 4 Aug 2011 00:24:36 +0000 (+1000)
Subject: Add a target feature flag to indicate that a target does not work in
X-Git-Tag: next-20110804~24^2~3
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=3348a38759322af14d5c4a4ed8ccaa11c552c3e8;p=karo-tx-linux.git

Add a target feature flag to indicate that a target does not work in
read-only mode.

The thin provisioning target uses this.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
---

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 26aef82a88d8..443d31a1f196 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -774,6 +774,12 @@ int dm_table_add_target(struct dm_table *t, const char *type,
 		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;
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 310d0a65d12e..ade1e695ad79 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -165,6 +165,10 @@ struct target_type {
 #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;