[Ocfs2-tools-devel] [PATCH] mount.ocfs2: return -EROFS if file system is readonly

[piaojun]

Hi Eric,

On 2017/12/28 13:17, Eric Ren wrote:
> Hi Jun,
> 
> 
> On 12/28/2017 11:58 AM, Joseph Qi wrote:
>>
>> On 17/12/28 10:01, piaojun wrote:
>>> Hi Joseph,
>>>
>>> On 2017/12/28 9:11, Joseph Qi wrote:
>>>>
>>>> On 17/12/27 17:12, piaojun wrote:
>>>>> If metadata is corrupted such as 'invalid inode block', we will get
>>>>> -EROFS by calling 'mount()'. In this situation we need fix it by fsck,
>>>>> and mount again rather than doing meaningless retry.
>>>>>
>>>>> Signed-off-by: Jun Piao <piaojun at huawei.com>
>>>>> ---
>>>>>   mount.ocfs2/mount.ocfs2.c | 13 ++++++++++---
>>>>>   1 file changed, 10 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/mount.ocfs2/mount.ocfs2.c b/mount.ocfs2/mount.ocfs2.c
>>>>> index e3d8871..1ab07ac 100644
>>>>> --- a/mount.ocfs2/mount.ocfs2.c
>>>>> +++ b/mount.ocfs2/mount.ocfs2.c
>>>>> @@ -434,8 +434,15 @@ int main(int argc, char **argv)
>>>>>               o2cb_complete_group_join(&cluster, &desc, errno);
>>>>>           }
>>>>>           block_signals (SIG_UNBLOCK);
>>>>> -        com_err(progname, ret, "while mounting %s on %s. Check 'dmesg' "
>>>>> -            "for more information on this error.", mo.dev, mo.dir);
>>>>> +        if (ret == -EROFS)
>>>>> +            com_err(progname, 0, "file system is now readonly due to "
>>>>> +                "on-disk corruption while mounting %s on %s, please "
>>>>> +                "fix this by fsck.ocfs2 and then retry mounting",
>>>>> +                mo.dev, mo.dir);
>>>> Could we use a meaningful error code instead of 0?
>>>>
>>>> Thanks,
>>>> Joseph
>>> I looked over 'ocfs2_err.et', and did not find a suitable error code.
>>> Should we define a new error code like this?
>>>
>>> -- 
>>> ec OCFS2_ET_CORRUPT_INODE_BLOCK,
>>> "Inode block is corrupt"
>>> -- 
>>>
>> Yes, I think it should be acceptable.
> 
> Does it mean we will always interpret EROFS code ( returned from kernel?) as
> "inode block corruption"? Is there some other internal error returning EROFS?
> 
> Thanks,
> Eric
> .
> 
Yes, when readonly device detected but readonly mount was not
specified, we will also get -EROFS from kernel as below:

ocfs2_fill_super
  ...
  if (bdev_read_only(sb->s_bdev)) {
      ...
      ocfs2_set_ro_flag(osb, 1);
      ...
  }

That is hard-ro error. Sadly we can hardly distinguish it from soft-ro,
and fsck seems useless. I just come up with a solution that we could
use -EACCES instead of -EROFS in this case. I'm glad to hear your
suggestion.

thanks,
Jun