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    Subject[patch 128/164] ext4: check s_log_groups_per_flex in online resize code
    2.6.33-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Sandeen <sandeen@redhat.com>

    commit 42007efd569f1cf3bfb9a61da60ef6c2179508ca upstream.

    If groups_per_flex < 2, sbi->s_flex_groups[] doesn't get filled out,
    and every other access to this first tests s_log_groups_per_flex;
    same thing needs to happen in resize or we'll wander off into
    a null pointer when doing an online resize of the file system.

    Thanks to Christoph Biedl, who came up with the trivial testcase:

    # truncate --size 128M fsfile
    # mkfs.ext3 -F fsfile
    # tune2fs -O extents,uninit_bg,dir_index,flex_bg,huge_file,dir_nlink,extra_isize fsfile
    # e2fsck -yDf -C0 fsfile
    # truncate --size 132M fsfile
    # losetup /dev/loop0 fsfile
    # mount /dev/loop0 mnt
    # resize2fs -p /dev/loop0

    https://bugzilla.kernel.org/show_bug.cgi?id=13549

    Reported-by: Alessandro Polverini <alex@nibbles.it>
    Test-case-by: Christoph Biedl <bugzilla.kernel.bpeb@manchmal.in-ulm.de>
    Signed-off-by: Eric Sandeen <sandeen@redhat.com>
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/ext4/resize.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/fs/ext4/resize.c
    +++ b/fs/ext4/resize.c
    @@ -930,7 +930,8 @@ int ext4_group_add(struct super_block *s
    percpu_counter_add(&sbi->s_freeinodes_counter,
    EXT4_INODES_PER_GROUP(sb));

    - if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
    + if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
    + sbi->s_log_groups_per_flex) {
    ext4_group_t flex_group;
    flex_group = ext4_flex_group(sbi, input->group);
    atomic_add(input->free_blocks_count,



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