[PATCH]fs/jffs2/wbuf.c: add compatibility support for OOB data block

[Ferenc Havasi]

Artem B. Bityuckiy wrote:

> Ferenc Havasi wrote:
>
>> No. The task of this condition is to make sure that the summary was 
>> generated correctly. If the summary is generated by the filesystem, 
>> it will be always good, but you are also able to generate summary 
>> with the userspace tool 'sumtool'. If we do not recognise this 
>> mistake that can cause big problems and make the user confused.
>>
> Err, do you mean that sumtool may generate summary with wrong erase_size?

It means: the user called it with wrong parameters - because may not 
understood what is virtual erase block and how he should calculate it. I 
think it will be a typical mistake.

> Here the size of eraseblock depends on sizeof(struct 
> jffs2_eraseblock). You increase the size of 'struct jffs2_eraseblock'. 
> So, you may have a situation when one mounts an *old* image with *new* 
> JFFS2 with *summary enabled*, and JFFS2 uses *larger* virtual 
> eraseblock size, because
>
> blocks * sizeof (struct jffs2_eraseblock)) > (128 * 1024)
>
> condition is changed.
>
> How is this situation handled?

Now the user should know the virutal erase block size at summary 
generation time. If it recognized someshing is wrong it uses the 
original scanning method.

Ferenc