Btrfs: fix oops on NULL trans handle in btrfs_truncate

If we fail to reserve space in the transaction during truncate, we can
error out with a NULL trans handle.  The cleanup code needs an extra
check to make sure we aren't trying to use the bad handle.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 9 insertions, 7 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 9d0eaa57d4e..f60e2490bd0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6529,14 +6529,16 @@ end_trans:
                 ret = btrfs_orphan_del(NULL, inode);
         }
 
-        trans->block_rsv = &root->fs_info->trans_block_rsv;
-        ret = btrfs_update_inode(trans, root, inode);
-        if (ret && !err)
-                err = ret;
+        if (trans) {
+                trans->block_rsv = &root->fs_info->trans_block_rsv;
+                ret = btrfs_update_inode(trans, root, inode);
+                if (ret && !err)
+                        err = ret;
 
-        nr = trans->blocks_used;
-        ret = btrfs_end_transaction_throttle(trans, root);
-        btrfs_btree_balance_dirty(root, nr);
+                nr = trans->blocks_used;
+                ret = btrfs_end_transaction_throttle(trans, root);
+                btrfs_btree_balance_dirty(root, nr);
+        }
 
 out:
         btrfs_free_block_rsv(root, rsv);