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

[Stefan Behrens <sbehrens@giantdisaster.de>]

On Mon, 21 May 2012 13:34:05 +0800, Miao Xie wrote:
> 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.

Since David put me on CC for this thread, I state my humble opinion:
If I manually remount read-only, I would expect that scrub is switched
into read-only mode as well, not canceled. Plus a log message about this
change.


> 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