Re: [PATCH v2] btrfs: Introduce new mount option to disable tree log replay

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

Chandan Rajendra wrote on 2015/12/08 15:36 +0530:
> On Tuesday 08 Dec 2015 14:10:33 Qu Wenruo wrote:
>> Introduce a new mount option "nologreplay" to co-operate with "ro" mount
>> option to get real readonly mount, like "norecovery" in ext* and xfs.
>>
>> Since the new parse_options() need to check new flags at remount time,
>> so add a new parameter for parse_options().
>>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> ---
>> v2:
>>    Make RO check mandatory for btrfs_parse_options().
>>    Add btrfs_show_options() support for nologreplay.
>>
>>    Document for btrfs-mount(5) will follow after the patch being merged.
>> ---
>>   Documentation/filesystems/btrfs.txt |  7 +++++++
>>   fs/btrfs/ctree.h                    |  4 +++-
>>   fs/btrfs/disk-io.c                  |  7 ++++---
>>   fs/btrfs/super.c                    | 29 +++++++++++++++++++++++++----
>>   4 files changed, 39 insertions(+), 8 deletions(-)
>>
>> diff --git a/Documentation/filesystems/btrfs.txt
>> b/Documentation/filesystems/btrfs.txt index c772b47..7ad5b93 100644
>> --- a/Documentation/filesystems/btrfs.txt
>> +++ b/Documentation/filesystems/btrfs.txt
>> @@ -168,6 +168,13 @@ Options with (*) are default options and will not show
>> in the mount options. notreelog
>>   	Enable/disable the tree logging used for fsync and O_SYNC writes.
>>
>> +  nologreplay
>> +	Disable the log tree replay at mount time to prevent devices get
>> +	modified. Must be use with 'ro' mount option.
>> +	A filesystem mounted with the 'nologreplay' option cannot
>> +	transition to a read-write mount via remount,rw - the filesystem
>> +	must be unmounted and remounted if read-write access is desired.
>> +
>
> May be the following is slightly better ...
>
> Disable the log tree replay at mount time to prevent filesystem from getting
> modified. Must be used with 'ro' mount option.  A filesystem mounted with the
> 'nologreplay' option cannot transition to a read-write mount via remount,rw -
> the filesystem must be unmounted and mounted back again if read-write access
> is desired.

Thanks for the review and advice.

Since I'm not a native English speaker, I'll follow your advice.
(Yeah, remount in my patch is confusing.)

I'll update it to v3 with Document update only

Thank,
Qu
>
> Aside from above, everything else looks good to me.
>
> Reviewed-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
>