Module loading problem in joyride?
wmb at laptop.org
Mon Nov 24 01:50:32 EST 2008
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
> 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.
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