Hi, Ted and Jan! tytso@xxxxxxx wrote: > On Tue, Feb 16, 2010 at 04:41:23PM +0900, Toshiyuki Okajima wrote: > > > > > > jbd2 has new features from jbd. For example, it includes the > > > integrity improvement features. The body of ext3 is already enough > > > quality. If ext3 changes the journaling interface from jbd into > > > jbd2, ext3 filesystem with jbd2 interface may get better integrity > > > than with the jbd interface. (jbd2 is aggressively being developed > > > now, so I think we are glad if we can get the effect of the > > > development of jbd2 for ext3.) > > > > > > And ext3 is as de facto standard filesystem, so jbd2 component will > > > be used by more people than now if ext3 has the jbd2 interface. If > > > many people used the jbd2 interface of ext3, the jbd2 component > > > would get more chances to improve the quality and performance and so > > > on. > > Jbd2 is development attention because it is part of ext4. And you > don't get to use the data integrity features of jbd2 without OK. I understand. (jbd2 is now developing.) > backporting required changes from ext4 to ext3. At which point, why > not have people use ext4? The reason that I wanted to change the journaling interface into jbd2 were: - the most of my customers use linux for Mission Critical (M.C.). - M.C. users want the filesystems which have more integrity for their data. - I think we should not recommend ext4 to M.C. users because for M.C. users, ext4 is still unstable filesystem. Therefore I want to let M.C. users use ext3 for the present. - it is not easy to maintain both jbd and jbd2, so I thought it was easy to solve it by unifying the journaling interfaces into ext4. > > Ext4 is format compatible with ext3, and with the proper kernel > configuration options, starting with 2.6.33, it's possible to > seemlessly allow people who use "mount -t ext3 /dev/sda1 /u1" to have > /dev/sda1 mounted using the ext4 file system driver. So we even have > a way that we can seemlessly upgrade existing userspace setups to > using ext4 without having to make any system configuration changes > (except installing a new kernel, of course). I know this feature. But I wanted not to let M.C. users use it now because this feature is based on ext4. > > The whole point of creating the ext3/ext4 fork was to not disturb ext3 > users while ext4 was under development. This was done by effectively > putting ext3 into a bug-fix-only development mode. Changing ext3 so > it could use jbd2 would seem to violate the stability process that we > have made to the ext3 users; if people want new features and > performance improvements, they can use ext4. Jan Kara wrote: > Hello, > > On Tue 16-02-10 16:41:23, Toshiyuki Okajima wrote: > > > I will try to change the journaling interface of ext3 from jbd into jbd2. > > > > > > jbd2 has new features from jbd. For example, it includes the integrity > > > improvement features. The body of ext3 is already enough quality. If ext3 > > > changes the journaling interface from jbd into jbd2, ext3 filesystem with jbd2 > > > interface may get better integrity than with the jbd interface. > > > (jbd2 is aggressively being developed now, so I think we are glad if we can > > > get the effect of the development of jbd2 for ext3.) > > > > > > And ext3 is as de facto standard filesystem, so jbd2 component will be used > > > by more people than now if ext3 has the jbd2 interface. If many people used > > > the jbd2 interface of ext3, the jbd2 component would get more chances to > > > improve the quality and performance and so on. > > > > > > Besides, ext3 is now the only user of jbd. > > > (ocfs2 which was the user of jbd is now the user of jbd2.) > > > > > > Do you want the jbd2 interface of ext3? > > > If you want the jbd2 interface, I will try to implement one. > Yes, as Ted pointed out, the main reason why we have a separate codebase for > ext3 and ext4 and similarly jbd and jbd2 is that we didn't want the changes > in ext4/jbd2 to influence (and possibly destabilize) ext3 filesystem. So > switching ext3 to jbd2 would be directly against this logic... OK. I see. (ext3 is already stable filesystem, so, we should not change ext3 drastically.) Thanks, Toshiyuki Okajima -- 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
