[Ocfs2-tools-devel] [PATCH 1/2] fsck: fix the first group desc in chain 0 when globalbitmap has only one chain

[Joseph Qi]

On 17/9/12 08:50, piaojun wrote:
> 
> 
> On 2017/9/11 19:19, Joseph Qi wrote:
>>
>> Hi Jun,
>>
>> On 17/9/10 11:15, piaojun wrote:
>>> fsck can't fix the first group desc in chain 0 when global_bitmap has
>>> only one chain, because we will get error when reading gd in
>>> maybe_fix_clusters_per_group(). so we need fix the corrupted gd in the
>>> following steps.
>>>
>>> Signed-off-by: Jun Piao <piaojun at huawei.com>
>>> ---
>>>  fsck.ocfs2/pass0.c | 14 +++++++++++---
>>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fsck.ocfs2/pass0.c b/fsck.ocfs2/pass0.c
>>> index 148877c..bfd11fb 100644
>>> --- a/fsck.ocfs2/pass0.c
>>> +++ b/fsck.ocfs2/pass0.c
>>> @@ -635,7 +635,15 @@ static errcode_t maybe_fix_clusters_per_group(o2fsck_state *ost,
>>>  	blkno = cl->cl_recs[0].c_blkno;
>>>
>>>  	ret = ocfs2_read_group_desc(ost->ost_fs, blkno, (char *)gd);
>>> -	if (ret) {
>>> +	if ((ret == OCFS2_ET_BAD_GROUP_DESC_MAGIC) ||
>>> +	    (!ret && gd->bg_generation != ost->ost_fs_generation)) {
>>
>> IIRC, ocfs2_read_group_desc will validate gd after read. So could you
>> please describe in which case the return value is 0 while generation is
>> corrupt?
>>
>> Thanks,
>> Joseph
>>
> ocfs2_read_group_desc() will only validate gd signature, so if
> the signature is normal but the generation is corrupt for some reasons,
> e.g., file system bug. the return value will be 0.
> 
> Thanks,
> Jun
> 
IC, thanks for the explanation.
One more question, if now let it go further, can we fix this corrupt in
current fsck logic?

Thanks,
Joseph