On Sun, Jan 31, 2010 at 09:54:27PM -0800, Michael Rubin wrote: > On Sun, Jan 31, 2010 at 2:31 PM, Thomas Kupper <thomas@xxxxxxxxxx> wrote: > > Consider the following scenario: Assume I have a partition > > formated with ext2 on a computer with some 2.4.x kernel. Now I > > mount this ext2 partition on another computer as ext4 using a > > 2.6.29+ kernel. After that I take the disk back to the older > > computer and mount the ext2 on the 2.4.x kernel with the ext2 > > driver. > > I have seen this work as long as you don't add the "extents" or other > ext4 specific mount options. Our kernels are not quite as up to date > as 2.6.29 and we have not done extensive testing with that kernel. Not > sure anyone has tested this case thoroughly. Yep, it's a supported feature that mounting a file system previously intended for ext2 or ext3 on ext4 shouldn't cause it to become unmountable elsewhere. Note however that the "extents" ext4 mount options has gone away; if you want to enable extents on kernels, the supported way to do this is: tune2fs -O extents /dev/sda1 Once you do this (and you can do this on a live-mounted ext4 filesystem and it will take effect immediately), any new inodes that are created will be extent-mapped. We currently don't have a way of converting extent-mapped inodes back to the legacy indirect block mapping scheme (a patch to do an off-line conversion wouldn't be _that_ hard; patches gratefully accepted), so this is currently a one-way conversion. - Ted -- 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
