Re: [PATCH] f2fs: remove default option setting in remount

[Chao Yu <chao@kernel.org>]

On 2018/9/18 21:47, cgxu519 wrote:
> On 09/18/2018 09:20 PM, Chao Yu wrote:
>> On 2018/9/18 14:23, Chengguang Xu wrote:
>>> Currently we set default value to options before parsing remount options,
>>> it will cause unexpected change of options which were specified in first
>>> mount.
>> Can you check below commit? It looks w/o it we may lose default option after
>> remount.
>>
>> 498c5e9fcd10 ("f2fs: add default mount options to remount")
> 
> Hi Chao,

Hi Chengguang,

> 
> It looks like there was a bug in remount at that time, but I think the fix above
> is not correct.
> 
> from the patch '498c5e9fcd10', I think it was caused by clearing
> sbi->mount_opt.opt before
> 
> parsing. I think remount should not change the options which were specified by
> user in
> 
> previous mount unless user specifies in remount.

Can you check description in manual of mount.

IIRC, old mount option will be record into /etc/mtab or /proc/mounts (for
adapting namespace feature), with command of "mount -o remount,rw  /dir", old
mount options can be loaded from above config file, and merge them with new
specified options.

Even we kill old mount options by call default_options() in ->remount, user's
old mount option can still be set through parameters.

But the problem here is, some old parameter can be configured via sysfs, if we
reset them in default_options(), we will lose them forever after remount.

If you have no other opinion about this, could you adapt your commit log?

Thanks,

> 
> Thanks,
> Chengguang
> 
> 
> 
> 
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