From: Nick Dokos Subject: [PATCH 1/6][64-bit] Eliminate erroneous blk_t casts in ext2fs_get_free_blocks2(). Date: Fri, 01 May 2009 04:46:13 -0400 Message-ID: <15553.1241167573@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 qmta03.emeryville.ca.mail.comcast.net ([76.96.30.32]:48454 "EHLO QMTA03.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752542AbZEAIqA (ORCPT ); Fri, 1 May 2009 04:46:00 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: Running e2fsck -n -f on a brand-new, never-mounted 32Tib fs was producing checksum errors on half the groups (the lower half) before it got to pass1 and block or inode bitmap conflicts on some groups in the upper half. The checksum errors were actually caused by the conflicts: e2fsck does a sanity check on block allocations, finds a conflict, and uses the backup superblock at 32768. But when it does that, it assumes the worst: it clears the UNINIT FLAGS and zeroes the free inode count for each group, assuming that it will fix them up during the run. That triggers the checksum errors (although it's not clear to me why only the lower half of the groups get checksum errors.) dumpe2fs showed that the conflicts were not artifacts of e2fsck processing: they existed on disk. In fact, the block bitmap of a group conflicted with the inode bitmap of the group fifteen steps further along. That smelled like flex_bg, so I remade the fs with flex_bg off and then *every* group in the upper half (more precisely, with blocks above the 32-bit boundary) had a conflict with itself: the block bitmap and inode bitmap were allocated on top of each other. That led to ext2fs_get_free_blocks2() which was truncating 64-bit block numbers by casting them to blk_t. This patch eliminates the casts. The resulting file system is free of the conflicts (with or without flex_bg.) However, it does not fsck cleanly yet: there are block bitmap differences in the very last group. Signed-off-by: Nick Dokos --- lib/ext2fs/alloc.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/lib/ext2fs/alloc.c b/lib/ext2fs/alloc.c index b1d1f9c..9f11673 100644 --- a/lib/ext2fs/alloc.c +++ b/lib/ext2fs/alloc.c @@ -272,8 +272,7 @@ errcode_t ext2fs_get_free_blocks2(ext2_filsys fs, blk64_t start, blk64_t finish, do { if (b+num-1 > ext2fs_blocks_count(fs->super)) b = fs->super->s_first_data_block; - if (ext2fs_fast_test_block_bitmap_range2(map, (blk_t) b, - (blk_t) num)) { + if (ext2fs_fast_test_block_bitmap_range2(map, b, num)) { *ret = b; return 0; } -- 1.6.0.6