Date: Sat, 30 Sep 2006 21:17:02 +0100
From: Alasdair G Kergon <agk@redhat.com>
Subject: [RHEL5] dm: add feature flags to reduce future kABI impact

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=208543

This patch adds a 'feature flags' field to several structures that we
anticipate we may wish to extend for enhancements during the lifetime of the
product, to help us reduce the impact of future kABI changes.
(Mostly these are lists of function pointers that we might need to
extend if new features require new hooks, as happened several times
during RHEL4.)

Since 'struct exception_store' is included in 'struct dm_snapshot' we move
it to the end.

This patch deals with a problem peculiar to RHEL and is not currently
upstream.

Index: linux-2.6.18.noarch/drivers/md/dm-hw-handler.h
===================================================================
--- linux-2.6.18.noarch.orig/drivers/md/dm-hw-handler.h	2006-09-20 04:42:06.000000000 +0100
+++ linux-2.6.18.noarch/drivers/md/dm-hw-handler.h	2006-09-29 12:06:29.000000000 +0100
@@ -24,6 +24,7 @@ struct hw_handler {
  */
 /* Information about a hardware handler type */
 struct hw_handler_type {
+	uint64_t features;
 	char *name;
 	struct module *module;
 
Index: linux-2.6.18.noarch/drivers/md/dm-log.h
===================================================================
--- linux-2.6.18.noarch.orig/drivers/md/dm-log.h	2006-09-26 17:01:32.000000000 +0100
+++ linux-2.6.18.noarch/drivers/md/dm-log.h	2006-09-29 12:06:29.000000000 +0100
@@ -28,6 +28,7 @@ struct dirty_log {
 };
 
 struct dirty_log_type {
+	uint64_t features;
 	struct list_head list;
 	const char *name;
 	struct module *module;
Index: linux-2.6.18.noarch/drivers/md/dm-mpath.h
===================================================================
--- linux-2.6.18.noarch.orig/drivers/md/dm-mpath.h	2006-09-20 04:42:06.000000000 +0100
+++ linux-2.6.18.noarch/drivers/md/dm-mpath.h	2006-09-29 12:06:29.000000000 +0100
@@ -12,6 +12,7 @@
 struct dm_dev;
 
 struct path {
+	uint64_t features;
 	struct dm_dev *dev;	/* Read-only */
 	unsigned is_active;	/* Read-only */
 
Index: linux-2.6.18.noarch/drivers/md/dm-path-selector.h
===================================================================
--- linux-2.6.18.noarch.orig/drivers/md/dm-path-selector.h	2006-09-20 04:42:06.000000000 +0100
+++ linux-2.6.18.noarch/drivers/md/dm-path-selector.h	2006-09-29 12:06:29.000000000 +0100
@@ -28,6 +28,7 @@ struct path_selector {
 
 /* Information about a path selector type */
 struct path_selector_type {
+	uint64_t features;
 	char *name;
 	struct module *module;
 
Index: linux-2.6.18.noarch/drivers/md/dm-snap.h
===================================================================
--- linux-2.6.18.noarch.orig/drivers/md/dm-snap.h	2006-09-29 12:06:18.000000000 +0100
+++ linux-2.6.18.noarch/drivers/md/dm-snap.h	2006-09-29 12:06:29.000000000 +0100
@@ -42,6 +42,7 @@ struct exception {
  * COW device).
  */
 struct exception_store {
+	uint64_t features;
 
 	/*
 	 * Destroys this object when you've finished with it.
@@ -85,6 +86,7 @@ struct exception_store {
 };
 
 struct dm_snapshot {
+	uint64_t features;
 	struct rw_semaphore lock;
 	struct dm_table *table;
 
@@ -120,14 +122,14 @@ struct dm_snapshot {
 	 */
 	spinlock_t pe_lock;
 
-	/* The on disk metadata handler */
-	struct exception_store store;
-
 	struct kcopyd_client *kcopyd_client;
 
 	/* Queue of snapshot writes for ksnapd to flush */
 	struct bio_list queued_bios;
 	struct work_struct queued_bios_work;
+
+	/* The on disk metadata handler */
+	struct exception_store store;
 };
 
 /*
Index: linux-2.6.18.noarch/include/linux/device-mapper.h
===================================================================
--- linux-2.6.18.noarch.orig/include/linux/device-mapper.h	2006-09-29 12:06:18.000000000 +0100
+++ linux-2.6.18.noarch/include/linux/device-mapper.h	2006-09-29 12:06:29.000000000 +0100
@@ -90,6 +90,7 @@ void dm_put_device(struct dm_target *ti,
  * Information about a target type
  */
 struct target_type {
+	uint64_t features;
 	const char *name;
 	struct module *module;
 	unsigned version[3];