Btrfs: avoid null deref in unpin_extent_cache()
I re-orderred the checks to avoid dereferencing "em" if it was null.
Found by smatch static checker.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 2c726b7..ccbdcb5 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -208,7 +208,7 @@
write_lock(&tree->lock);
em = lookup_extent_mapping(tree, start, len);
- WARN_ON(em->start != start || !em);
+ WARN_ON(!em || em->start != start);
if (!em)
goto out;