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

[Eric Sandeen <sandeen@redhat.com>]

On 12/7/15 12:06 AM, 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>
> ---
>  Documentation/filesystems/btrfs.txt |  5 +++++
>  fs/btrfs/ctree.h                    |  4 +++-
>  fs/btrfs/disk-io.c                  |  7 ++++---
>  fs/btrfs/super.c                    | 20 +++++++++++++++++---
>  4 files changed, 29 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt
> index c772b47..ac4ed68 100644
> --- a/Documentation/filesystems/btrfs.txt
> +++ b/Documentation/filesystems/btrfs.txt
> @@ -168,6 +168,11 @@ 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 for real read-only mount.
> +	Must be use with "ro" mount option and can't be disabled by mount
> +	option.

This documentation is not clear to me - "can't be disabled by mount option?"

I think you mean to talk about remount here?  Perhaps something like:

"... 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 remounted if read-write
access is desired."

Thanks,
-Eric