From: Nick Dokos Subject: [PATCH 2/2][64-BIT] ext2fs_group_first_block2(): 32-bit truncation. Date: Sat, 18 Apr 2009 02:05:13 -0400 Message-ID: <30396.1240034713@gamaville.dokosmarshall.org> Reply-To: nicholas.dokos@hp.com Cc: nicholas.dokos@hp.com, Theodore Ts'o , Valerie Aurora To: linux-ext4@vger.kernel.org Return-path: Received: from qmta09.emeryville.ca.mail.comcast.net ([76.96.30.96]:49828 "EHLO QMTA09.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751023AbZDRGFA (ORCPT ); Sat, 18 Apr 2009 02:05:00 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: ext2fs_group_first_block2() returns the product of the group number and the number of blocks per group (from the superblock). Unfortunately, both of these are 32-bit quantities, so the multiplication result is also 32 bits wide. It is then returned as a 64-bit quantity, but by then, it's too late. Cast one of the operands to blk64_t, so the multiplication will be done in 64 bits. e2fsck was complaining about a group that was marked BLOCK_UNINIT, but had blocks in use (it turned out that a different group had blocks in use, but the block numbers of the two different groups differed by 2^32, so this bug conflated them). With this change, this complaint goes away. In addition, dumpe2fs produces the right blocks for all the groups, whereas it was wrapping them at the 32-bit boundary previously. Signed-off-by: Nick Dokos --- lib/ext2fs/blknum.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/lib/ext2fs/blknum.c b/lib/ext2fs/blknum.c index b9666fb..fd56d53 100644 --- a/lib/ext2fs/blknum.c +++ b/lib/ext2fs/blknum.c @@ -28,7 +28,7 @@ dgrp_t ext2fs_group_of_blk2(ext2_filsys fs, blk64_t blk) blk64_t ext2fs_group_first_block2(ext2_filsys fs, dgrp_t group) { return fs->super->s_first_data_block + - (group * fs->super->s_blocks_per_group); + ((blk64_t)group * fs->super->s_blocks_per_group); } /* -- 1.6.0.6