[dm-devel] [PATCH] dm-mpath: Track invalid map_context

[Hannes Reinecke]

The map_context pointer should always be set. However, we
have reports that upon requeing it is not set correctly.
So add a BUG_ON() statement and clear the pointer to
track the issue properly.

Cc: Alasdair Kergon <agk at redhat.com>
Cc: Mike Snitzer <snitzer at redhat.com>
Signed-off-by: Hannes Reinecke <hare at suse.de>
Tested-by: Heiko Carstens <heiko.carstens at de.ibm.com>
Acked-by: Dave Wysochanski <dwysocha at redhat.com>
---
 drivers/md/dm-mpath.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 801d92d..2ed316e 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -441,11 +441,13 @@ static void dispatch_queued_ios(struct multipath *m)
 		r = map_io(m, clone, mpio, 1);
 		if (r < 0) {
 			mempool_free(mpio, m->mpio_pool);
+			info->ptr = NULL;
 			dm_kill_unmapped_request(clone, r);
 		} else if (r == DM_MAPIO_REMAPPED)
 			dm_dispatch_request(clone);
 		else if (r == DM_MAPIO_REQUEUE) {
 			mempool_free(mpio, m->mpio_pool);
+			info->ptr = NULL;
 			dm_requeue_unmapped_request(clone);
 		}
 	}
@@ -920,8 +922,10 @@ static int multipath_map(struct dm_target *ti, struct request *clone,
 	map_context->ptr = mpio;
 	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 	r = map_io(m, clone, mpio, 0);
-	if (r < 0 || r == DM_MAPIO_REQUEUE)
+	if (r < 0 || r == DM_MAPIO_REQUEUE) {
 		mempool_free(mpio, m->mpio_pool);
+		map_context->ptr = NULL;
+	}
 
 	return r;
 }
@@ -1261,6 +1265,8 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone,
 	struct path_selector *ps;
 	int r;
 
+	BUG_ON(!mpio);
+
 	r  = do_end_io(m, clone, error, mpio);
 	if (pgpath) {
 		ps = &pgpath->pg->ps;
@@ -1268,6 +1274,7 @@ static int multipath_end_io(struct dm_target *ti, struct request *clone,
 			ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
 	}
 	mempool_free(mpio, m->mpio_pool);
+	map_context->ptr = NULL;
 
 	return r;
 }
-- 
1.6.0.2