linux-ext4 - broken commit 25567a7b0fa98b390fd1ff0d4702b29c23a75bbb

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Message-Id: <7EF281B4-882D-4F81-AEF8-404D2C3C0B76@dilger.ca>
Date:	Fri, 8 Jul 2011 18:07:14 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: broken commit 25567a7b0fa98b390fd1ff0d4702b29c23a75bbb

In my pull from e2fsprogs git "master" branch, it contains commit
25567a7b0fa98b390fd1ff0d4702b29c23a75bbb "support for bigalloc
file systems with a blocksize of 1024" that deletes the initialization
of the flexbg_size variable from lib/ext2fs/alloc_tables.c::flexbg_offset():

-       flexbg_size = 1 << fs->super->s_log_groups_per_flex;
-       flexbg = group / flexbg_size;
+       size = rem_grp * elem_size;

but it continues to use flexbg_size later on in this function:

       start_blk = ext2fs_group_first_block2(fs, flexbg_size * flexbg);
       last_grp = group | (flexbg_size - 1);

This provokes an uninitialized compiler warning (I always use CFLAGS=-Wall),
but it isn't clear to me at first glance what the intention of this change
is or how to fix it.

It doesn't cause any "make check" errors, but that is almost certainly
only because very few tests run with flex_bg enabled, but it is definitely
a bug that would cause strange behaviour.

Cheers, Andreas





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