> commit 24b584240a0006ea7436cd35f5e8983eb76f1e6f > Author: Theodore Ts'o <tytso@xxxxxxx> > Date: Mon Dec 7 14:08:51 2009 -0500 > > ext4: Use ext4 file system driver for ext2/ext3 file system mounts > > Add a new config option, CONFIG_EXT4_USE_FOR_EXT23 which if enabled, > will cause ext4 to be used for either ext2 or ext3 file system mounts > when ext2 or ext3 is not enabled in the configuration. > > This allows minimalist kernel fanatics to drop to file system drivers > from their compiled kernel with out losing functionality. > > Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx> > > > So now we have this thing, and people are using it, and running into trouble: > > http://bugzilla.kernel.org/show_bug.cgi?id=15420 > Bug 15420 - EXT4_USE_FOR_EXT23 causes wrong free space calculation on ext2 and ext3 > > and now we propose turning off delalloc if we mount ext3 as ext4; however, > migrated ext3->ext4 filesystems, which initially may have no difference other > than a superblock feature flag, will not get this behavior, I guess. > > Jan suggests that we not surprise users by having delalloc enabled when ext3 > is mounted with the ext4 driver. However there are other behavior differences > as well, mballoc behavior comes to mind at least. What about the 32000 subdir > limit? If we go back to ext3 is it ok with the subsecond timestamps and > creation time etc? Maybe so... have we tested any of this? Yeah, this is a good point... Honestly, I don't quite understand what's the problem with "minimalist kernel fanatics" going and mounting all the devices as ext4 (when they decided to compile kernel without ext2/3) - no need for special kernel option. It will probably need some tweaks in automounters but still... Honza -- Jan Kara <jack@xxxxxxx> SuSE CR Labs -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
