From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Darrick J. Wong" Subject: [PATCH] ext4: Find the group descriptors on a 1k-block bigalloc,meta_bg filesystem Date: Thu, 19 Dec 2013 16:15:42 -0800 Message-ID: <20131220001541.GA10189@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4 To: "Theodore Ts'o" Return-path: Received: from aserp1040.oracle.com ([141.146.126.69]:38991 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756672Ab3LTAPu (ORCPT ); Thu, 19 Dec 2013 19:15:50 -0500 Content-Disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: On a filesystem with a 1k block size, the group descriptors live in block 2, not block 1. If the filesystem has bigalloc,meta_bg set, however, the calculation of the group descriptor table location does not take this into account and returns the wrong block number. Fix the calculation to return the correct value for this case. Signed-off-by: Darrick J. Wong --- fs/ext4/super.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 7f52a54..d968c64 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2420,6 +2420,16 @@ static ext4_fsblk_t descriptor_loc(struct super_block *sb, if (ext4_bg_has_super(sb, bg)) has_super = 1; + /* + * If we have a meta_bg fs with 1k blocks, group 0's GDT is at + * block 2, not 1. If s_first_data_block == 0 (bigalloc is enabled + * on modern mke2fs or blksize > 1k on older mke2fs) then we must + * compensate. + */ + if (sb->s_blocksize == 1024 && nr == 0 && + le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block) == 0) + has_super++; + return (has_super + ext4_group_first_block_no(sb, bg)); }