[patch] e4defrag: relevant file fragmentation: fix arithmetic error as non-root

[Andreas Rid <andreas@rid-net.de>]

hi Kazuya Mio,

I found a bug on your patch "[RFC][PATCH V2 5/5] e4defrag: add solving relevant file fragmentation mode"

The variable "blocks_per_group" is only initialized as root cause of restrict access to the super-block.
As a non root user this cause an arithmetic error in function relevant_balloc.

diff --git a/misc/e4defrag.c b/misc/e4defrag.c
index 3f1df05..6022758 100644
--- a/misc/e4defrag.c
+++ b/misc/e4defrag.c
@@ -1662,14 +1662,15 @@ static int relevant_balloc(const char *file, int donor_fd,
 
 		/* Allocating  all blocks in an extent group */
 		while (rest > 0) {
-			int grp_offset;
-			grp_offset = (pi.pi_pstart - first_data_block) % bpg;