[PATCH] dm table: add target flush

This patch adds support for a per-target dm_flush_fn method.  This is needed
to allow dm-loop to invalidate page cache mappings in response to BLKFLSBUF
ioctl commands.

Signed-off-by: Bryn Reeves <breeves@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/dm-table.c

@@ -1001,6 +1001,11 @@ int dm_table_flush_all(struct dm_table *t)
 {
 	struct list_head *d, *devices = dm_table_get_devices(t);
 	int ret = 0;
+	unsigned i;
+
+	for (i = 0; i < t->num_targets; i++)
+		if (t->targets[i].type->flush)
+			t->targets[i].type->flush(&t->targets[i]);
 
 	for (d = devices->next; d != devices; d = d->next) {
 		struct dm_dev *dd = list_entry(d, struct dm_dev, list);