btrfs: avoid NULL deref in btrfs_reserve_extent with DEBUG_ENOSPC

 __find_space_info can return NULL but we don't check it before calling
 dump_space_info().

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 37e0a80..c32a9bf 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5838,7 +5838,8 @@ again:
                        printk(KERN_ERR "btrfs allocation failed flags %llu, "
                               "wanted %llu\n", (unsigned long long)data,
                               (unsigned long long)num_bytes);
-                       dump_space_info(sinfo, num_bytes, 1);
+                       if (sinfo)
+                               dump_space_info(sinfo, num_bytes, 1);
                }
        }