commit 00c4fc3b1f590288cb3c42f36da50f49a513cfcf
author Mike Snitzer <snitzer@redhat.com> Tue Aug 27 18:57:03 2013 -0400
committer Mike Snitzer <snitzer@redhat.com> Thu Sep 05 20:46:06 2013 -0400
tree e185bc97fc6529d1299e5e13987fe5b86cf21868
parent c2b04824620f30b52bb2fdcdd14c758b8c62c70f

dm ioctl: increase granularity of type_lock when loading table

Hold the mapped device's type_lock before calling populate_table() since
it is where the table's type is determined based on the specified
targets.  There is no need to allow concurrent table loads to race to
establish the table's targets or type.

This eliminates the need to grab the lock in dm_table_set_type().

Also verify that the type_lock is held in both dm_set_md_type() and
dm_get_md_type().

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

drivers/md/dm.c

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ef095a9..7faeaa3 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2235,11 +2235,13 @@
 
 void dm_set_md_type(struct mapped_device *md, unsigned type)
 {
+	BUG_ON(!mutex_is_locked(&md->type_lock));
 	md->type = type;
 }
 
 unsigned dm_get_md_type(struct mapped_device *md)
 {
+	BUG_ON(!mutex_is_locked(&md->type_lock));
 	return md->type;
 }