Re: [PATCH 4/5] Btrfs: cancel the scrub when remounting a fs to ro

[Miao Xie <miaox@cn.fujitsu.com>]

On Fri, 18 May 2012 14:52:07 +0200, David Sterba wrote:
> On Thu, May 17, 2012 at 07:58:21PM +0800, Miao Xie wrote:
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -1151,6 +1151,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
>>  		/* pause restriper - we want to resume on remount to r/w */
>>  		btrfs_pause_balance(root->fs_info);
>>  
>> +		btrfs_scrub_cancel(root);
> 
> Can we possibly switch scrub to readonly instead ? I'm not sure what's
> the 'least surprise here', whether to cancel everything on the
> filesystem upon ro-remount or just the minimal set of operations (and
> leave the rest running if possible).

I don't think it is better to switch scrub to readonly soundlessly, because
it is not the operation that the users expect if they don't choose the readonly
mode.

BTW, I think we needn't cancel the readonly scrub on the filesystem upon ro-remount.

Thanks
Miao

> 
> Looking at the scrub code, if dev->readonly is set, no repairs are done,
> so the only concern is to wait for any outstanding IOs and then switch
> to RO.
> 
> 
> david
>