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 > > > _______________________________________________ Devel mailing list [email protected] http://lists.laptop.org/listinfo/devel
