Re: [PATCH v5 0/2][PULL REQUEST] Unify 'norecovery' bahavior with other filesystems

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

David Sterba wrote on 2016/01/14 17:00 +0100:
> On Tue, Jan 12, 2016 at 10:05:11AM +0800, Qu Wenruo wrote:
>> 'Norecovery' mount option is almost a standard for all other
>> filesystems, including f2fs, ext4, gfs2, nilfs2, and xfs.
>> And since current 'recovery' mount option for btrfs is too generic, it's
>> better to change btrfs 'recovery' to 'usebackuproot' and then we can
>> safely add 'norecovery' and 'nologreplay' mount option for btrfs.
>>
>> The patch itself is not huge and already tested by others since v2.
>> Only mount option name is changing during all these version changes.
>
> So we have some kind of consensus about the options, but I think you
> need to split the patches further.
>
> * the new option 'nologreplay'
> * keep 'usebackuproot' as a new alias for 'recovery' (with the
>    deprecation warning)
> * new 'norecovery' that switches on 'nologreplay' and 'nousebackuproot'
>    (ie. the desired "no writes")

Hi David,

I'm curious about why 'norecovery' needs to imply 'nousebackuproot'.
As usebackuproot only affects where btrfs to read the tree/chunk roots.
It doesn't mean to change/write anything. RO will ensure superblock is 
not modified.

So I'll only add 'norecovery' as alias for 'nologreplay'.

Thanks,
Qu

>
> There is a case in remount, when we start with 'ro,nologreplay' then
> remount with just 'ro', the log should be replayed. The other
> combinations should be easy. I haven't looked at the patch if it's
> implemented that way though.
>
>