Re-read exceptions after acquiring the cluster lock.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-exception-store.h |    8 ++++++++
 drivers/md/dm-snap-persistent.c |   11 +++++++++++
 drivers/md/dm-snap.c            |   16 ++++++++++++++++
 3 files changed, 35 insertions(+)

Index: linux-2.6.31-fast/drivers/md/dm-exception-store.h
===================================================================
--- linux-2.6.31-fast.orig/drivers/md/dm-exception-store.h	2009-10-19 12:05:53.000000000 +0200
+++ linux-2.6.31-fast/drivers/md/dm-exception-store.h	2009-10-19 12:50:57.000000000 +0200
@@ -69,6 +69,14 @@ struct dm_exception_store_type {
 			      void *callback_context, int will_handover);
 
 	/*
+	 * Reread new exceptions after some other node added them.
+	 */
+	int (*reread_exceptions) (struct dm_exception_store *store,
+				  int (*callback)(void *callback_context,
+						  chunk_t old, chunk_t new),
+				  void *callback_context);
+
+	/*
 	 * Find somewhere to store the next exception.
 	 */
 	int (*prepare_exception) (struct dm_exception_store *store,
Index: linux-2.6.31-fast/drivers/md/dm-snap-persistent.c
===================================================================
--- linux-2.6.31-fast.orig/drivers/md/dm-snap-persistent.c	2009-10-19 12:50:46.000000000 +0200
+++ linux-2.6.31-fast/drivers/md/dm-snap-persistent.c	2009-10-19 12:50:57.000000000 +0200
@@ -616,6 +616,15 @@ static int persistent_read_metadata(stru
 	return r;
 }
 
+static int persistent_reread_exceptions(struct dm_exception_store *store,
+				    int (*callback)(void *callback_context,
+						    chunk_t old, chunk_t new),
+				    void *callback_context)
+{
+	struct pstore *ps = get_info(store);
+	return read_exceptions(ps, callback, callback_context, 1);
+}
+
 static int persistent_prepare_exception(struct dm_exception_store *store,
 					struct dm_exception *e)
 {
@@ -833,6 +842,7 @@ static struct dm_exception_store_type _p
 	.ctr = persistent_ctr,
 	.dtr = persistent_dtr,
 	.read_metadata = persistent_read_metadata,
+	.reread_exceptions = persistent_reread_exceptions,
 	.prepare_exception = persistent_prepare_exception,
 	.commit_exception = persistent_commit_exception,
 	.prepare_merge = persistent_prepare_merge,
@@ -848,6 +858,7 @@ static struct dm_exception_store_type _p
 	.ctr = persistent_ctr,
 	.dtr = persistent_dtr,
 	.read_metadata = persistent_read_metadata,
+	.reread_exceptions = persistent_reread_exceptions,
 	.prepare_exception = persistent_prepare_exception,
 	.commit_exception = persistent_commit_exception,
 	.prepare_merge = persistent_prepare_merge,
Index: linux-2.6.31-fast/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.31-fast.orig/drivers/md/dm-snap.c	2009-10-19 12:50:42.000000000 +0200
+++ linux-2.6.31-fast/drivers/md/dm-snap.c	2009-10-19 12:53:25.000000000 +0200
@@ -178,6 +178,9 @@ static int bdev_equal(struct block_devic
 	return lhs == rhs;
 }
 
+static void __invalidate_snapshot(struct dm_snapshot *s, int err);
+static int dm_add_exception(void *context, chunk_t old, chunk_t new);
+
 static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
 			       union map_info *map_context);
 
@@ -352,6 +355,12 @@ static void lock_snapshot(struct dm_snap
 		int r = dm_cluster_lock_by_str(lockspace_handle, s->lockid,
 				DM_CLUSTER_LOCK_EXCLUSIVE, NULL, NULL);
 		BUG_ON(r < 0);
+		if (s->valid && r) {
+			r = s->store->type->reread_exceptions(s->store,
+						dm_add_exception, (void *)s);
+			if (unlikely(r))
+				__invalidate_snapshot(s, r);
+		}
 	}
 #endif
 }
@@ -977,6 +986,12 @@ static int snapshot_ctr(struct dm_target
 	argv += args_used;
 	argc -= args_used;
 
+	if (is_clustered(s) && !s->store->type->reread_exceptions) {
+		ti->error = "This exception store doesn't support clustering";
+		r = -EINVAL;
+		goto bad_clustered_store;
+	}
+
 	r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
 	if (r) {
 		ti->error = "Cannot get origin device";
@@ -1111,6 +1126,7 @@ bad_hash_tables:
 	dm_put_device(ti, s->origin);
 
 bad_origin:
+bad_clustered_store:
 	dm_exception_store_destroy(s->store);
 
 bad_clustering: