[RFC] UBIFS recovery

[hujianyang]

Hi Steve,

On 2015/2/5 23:08, Steve deRosier wrote:
> On Thu, Feb 5, 2015 at 1:47 AM, hujianyang <hujianyang at huawei.com> wrote:
>> There are two ways for UBIFS recovery. One is repairing UBIFS image
>> in userspace via UBI interfaces, the other is repairing the corrupted
>> data during mount by default or via a special mount option.
>>
>> The userspace tool is the most effective way to repair a partition.
>> It could have enough time and resource to whole scan the target and
>> cleanup the corrupted while the file-system offline. But it's hard
>> to program: many structures and functions in kernel need to be copied
>> into this utility, current ubi-utils focus mostly on UBI device, not
>> UBIFS, and the subsequent updating of file-system should consider the
>> userspace tool. It's too complicated.
>>
> 
> I hear (and agree with) several valid arguments for a tool in
> userspace. And I'd like to throw my support towards an in-driver
> solution. 

Thanks~!

> Flash filesystems are different than on-disk filesystems, in
> particular in their usecase: they're generally both critical and
> exclusive to embedded systems. As such, the entire filesystem might be
> on the corrupted UBIFS, so even if the filesystem is recoverable, if
> we can't mount it and get at the userspace tool, then we're toast.
> Often the kernel itself is stored in a separate read-only partition as
> a blob directly on the flash, and thus the kernel itself would be
> fine. The better UBI & UBIFS can recover to a usable state in-kernel,
> the better off we are I think.
> 
> Just my thoughts on the matter.
> 
> - Steve
> 
> .
> 

I think it's a good standpoint you are providing. It's a problem like
filesystem dirver and filesystem partition. But it may not only exit
in UBIFS. A good user configuration is always needed to solve problems
like this.

Maybe an acceptable solution is mount the filesystem R/O first and then
perform other recoveries.

Thanks,
Hu