On 2015-12-02 18:40, Qu Wenruo wrote:
>
>
> On 12/03/2015 06:48 AM, Eric Sandeen wrote:
>> On 12/2/15 11:48 AM, Austin S Hemmelgarn wrote:
>>
>>> On a side note, do either XFS or ext4 support removing the norecovery
>>> option from the mount flags through mount -o remount?  Even if they
>>> don't, that might be a nice feature to have in BTRFS if we can safely
>>> support it.
>>
>> It's not remountable today on xfs:
>>
>>          /* ro -> rw */
>>          if ((mp->m_flags & XFS_MOUNT_RDONLY) && !(*flags & MS_RDONLY)) {
>>                  if (mp->m_flags & XFS_MOUNT_NORECOVERY) {
>>                          xfs_warn(mp,
>>                  "ro->rw transition prohibited on norecovery mount");
>>                          return -EINVAL;
>>                  }
>>
>> not sure about ext4.
>>
>> -Eric
>
> Not remountable is very good to implement it.
> Makes things super easy to do.
>
> Or we will need to add log replay for remount time.
>
> I'd like to implement it first for non-remountable case as a try.
> And for the option name, I prefer something like "notreereplay", but I
> don't consider it the best one yet....
>
I entirely understand wanting a simple implementation first, my only 
point is that it would be a potentially useful feature to have if we 
could sanely implement it.