> -----Original Message----- > From: Theodore Ts'o [mailto:tytso@xxxxxxx] > Sent: Friday, September 19, 2014 3:18 AM > To: Dexuan Cui > Cc: linux-ext4@xxxxxxxxxxxxxxx > Subject: Re: Is ext2 freezable? > > On Thu, Sep 18, 2014 at 06:46:21AM +0000, Dexuan Cui wrote: > > > > I've got the answer: > > ext2.ko itself does support fsfreeze, but typical linux distros don't supply > > ext2.ko at all now -- instead, they usually supply ext3.ko and have ext4 > builtin. > > > > So when I mount an ext2 partition, actually the kernel is registering the ext4 > > driver as an ext2 driver and in this case the ext2's s_op->freeze_fs is NULL -- > > but, why did ext4 choose this behavior for ext2? > > It wasn't a deliberate design choice. It was just that when > no-journal mode was added to ext4, freeeze support was never > implemented, and up until now, no one had asked for it. We can add it > to ext4; thanks for calling it to our attention. > - Ted Hi Ted, Thanks very much for the clarification! And thanks a lot for implementing this -- I've seen the patches you sent out several hours ago. IMO it's useful to have such compatibility, e.g., Hyper-V guest has a fsfreeze-based feature to back up the data; the feature works fine for ext4 partition, but Ubuntu's installer can create /boot of ext2 partition by default and hence the feature can't work: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1362574 I believe the bug will go away after Ubuntu integrates your patches. Thanks! -- Dexuan -- 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
