On Thu, Sep 3, 2009 at 9:48 PM, Greg Freemyer<greg.freemyer@xxxxxxxxx> wrote: > On Thu, Sep 3, 2009 at 1:13 AM, Peng Tao<bergwolf@xxxxxxxxx> wrote: >> Hi, Greg, >> >> On Thu, Sep 3, 2009 at 4:59 AM, Greg Freemyer<greg.freemyer@xxxxxxxxx> wrote: >>> Peng, >>> >>> I have not looked at the code very closely, but can you tell me where >>> a file corruption can take place? Not completing the replacement of >>> extents with donor extents is one thing. Corrupting the original file >>> contents is another. >> The file corruption is mainly because of the half done replacement. >> >> My test case is here: >> http://marc.info/?l=linux-ext4&m=124992522305319&w=2 >> >> With Akira's previous patch >> (http://marc.info/?l=linux-ext4&m=124937430627867&w=2), >> EXT4_IOC_MOVE_EXT does not panic the kernel any more. But it leaves >> the orig file's extent tree corrupted. > > Is this highly repeatable, e4defrag using EXT4_IOC_MOVE_EXT corrupts > sparse files? It is the EXT4_IOC_MOVE_EXT ioctl corrupts sparse files because it doesn't handle well with file holes. The e4defrag program loops to call EXT4_IOC_MOVE_EXT for each non-continuous parts of a file, so it doesn't expose file holes to kernel. But since the ioctl interface is publicly usable, I do suggest making it behave better, at lease don't bug the kernel, because I did hit null pointer reference in my last time testing the new ioctl. So IMHO, Akira's previous patch (http://patchwork.ozlabs.org/patch/30707/) is really necessary. > > If so, it seems like a pretty major bug that will be exposed to > userspace when 2.6.31 goes final. > > It seems to me at a minimum a Kconfig option should be added to enable > the ioctl to userspace and that it should have depends on EXPERIMENTAL > and default to NO for now. > > We don't want people thinking that this feature is stable in 2.6.31. I do agree that the feature is still unstable ATM. > > Greg > -- > Greg Freemyer > Head of EDD Tape Extraction and Processing team > Litigation Triage Solutions Specialist > http://www.linkedin.com/in/gregfreemyer > Preservation and Forensic processing of Exchange Repositories White Paper - > <http://www.norcrossgroup.com/forms/whitepapers/tng_whitepaper_fpe.html> > > The Norcross Group > The Intersection of Evidence & Technology > http://www.norcrossgroup.com > -- Cheers, Peng Tao State Key Laboratory of Networking and Switching Technology Beijing Univ. of Posts and Telecoms. -- 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
