Module loading problem in joyride?

[Mitch Bradley]

Deepak Saxena wrote:
> On Nov 22 2008, at 08:40, Mitch Bradley was caught saying:
>   
>> There are two things that could have changed - either RTIME compression 
>> was added to the mkfs.jffs2 configuration, or it was removed from the 
>> kernel configuration (or both).  My best guess is that it was removed 
>> from the kernel at some point, because I know that, at least at one 
>> point in OLPC's past, RTIME compression was enabled.  I know this 
>> because there was an OFW bug in which OFW encountered an 
>> RTIME-compressed node and couldn't handle it.  OFW now supports RTIME 
>> decompression.
>>     
>
> Your guess is correct. I got overzealous when I disabled LZO and
> disabled RTIME in the config.
>
>   
>> The best solution would be:
>>
>> a) In mkfs.jffs2, turn off RTIME compression so it is never used in 
>> pristine filesystems
>> b) In the kernel, enable both CONFIG_JFFS2_RTIME and JFFS2_CMODE_PRIORITY
>>
>> The suggested kernel setting makes the RTIME decompressor available if 
>> needed, but ensures that when zlib (higher priority) succeeds, the 
>> kernel won't waste time on RTIME.  There's still some time wasted when 
>> zlib can't reduce the size - instead of just punting and storing an 
>> uncompressed node, it will try RTIME.  Ideally, it would be better to 
>> disable RTIME decompression entirely, so as not to waste that time.  
>> While there is a #define to do that - JFFS2_RTIME_DISABLED - I see no 
>> Kconfig option to control it at that .config level.
>>     
>
> There is CONFIG_JFFS2_RTIME option. Will re-enable it and and push to 
> master.  I agree that ideally we should just disable it but as per Daniel's
> experience this will break unless we change the mkfs.jffs2 option.
> Even if we do the later, it will lead to issues if someone tries to 
> mix and match new kernels with older builds.
>   

Note that there is a distinction between CONFIG_JFFS2_RTIME and 
JFFS2_RTIME_DISABLED - the former removes all support for RTIME - 
compression and decompression - while the latter just turns off RTIME 
compression.  So, were there a config option that controlled the latter 
#define, it would be possible to handle existing JFFS2 images that 
include some RTIME nodes, while avoiding the creation of new such nodes.


> ~Deepak
>
>
>