On 4/28/11 3:14 PM, Peter Uchno wrote: > Hello, > I recently converted an ext3 filesystem to ext4 in the hopes of > performance increases. However, I ran into a snag: > > In theory, chattr can be used to convert a file to extents using > "chattr +e foo". However, on my system (Archlinux, kernel 2.6.37.4), > the behavior of this command is unexpected. Given a file baz created > when the filesystem was still ext3 (and thus not using extents), > "chattr +e baz" returns zero but "lsattr baz" reveals the file is not > using extents. Run "chattr +e baz" a second time, the same thing > happens. A third time, however, it comes back with: > "chattr: Input/output error while setting flags on baz" > and an error in the kernel log: > attempt to access beyond end of device > loop1: rw=0, want=204802, limit=204800 > The file is still not using extents and remounting the filesystem > doesn't seem to change much. Running e2fsck on the filesystem after > unmounting it comes back with some errors. Letting it fix them and > then mounting the FS up again shows that the file is now using > extents. > I attempted this on an Arch system with both kernels 2.6.37.4 and > 2.6.38.4 and was able to recreate it by creating a small loopback > filesystem using dd, making a few files on it, converting the FS to > ext4 using "tune2fs -O extents,uninit_bg,dir_index /tmp/fs.ext; e2fsck > -fDC0 /tmp/fs.ext", and then mounting it again as ext4 and attempting > the conversion to extents with chattr. However, on a debian system > with kernel 2.6.32.5, it works as intended (chattr +e bar; lsattr bar > reveals the file converted to extents). I ran strace on the chattr > command on the Arch system and came up with the following: > > http://pastebin.com/EpwhLF3t > for the first attempt at running the command; > http://pastebin.com/qB7DiDgF > for the second try; and > http://pastebin.com/jjAdPtBr > for the final attempt. > > After doing so, running e2fsck on the filesystem revealed the following: > > http://pastebin.com/83q60Wik > > And after mounting the filesystem again, the file is now using extents. > > My kernel config, if it is of interest, is at: > http://pastebin.com/uk1Hs53P > > I'm using e2fsprogs 1.41.14. The Debian system (where it works > normally) has e2fsprogs 1.41.12. > > I'm not sure what would cause the filesystem to behave in this > fashion. Does anyone have any insights? I can't speak directly to the problem because I haven't investigated, but I can tell you that chattr +e foo is probably almost never tested. If any other ext4 dev does test it, speak up. :) And I would strongly suggest that if you want an ext4 filesystem, mkfs.ext4 and migratind data to it is the best route to a consistent, featureful, well-tested setup. -Eric > Regards, > Peter -- 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
