On 02/10/2014 04:56 PM, Zdenek Kabelac wrote: > Dne 10.2.2014 15:37, Christian Hesse napsal(a): >> Peter Rajnoha <prajnoha@redhat.com> on Mon, 2014/02/10 15:12: >>> On 02/10/2014 02:48 PM, Christian Hesse wrote: >>>> Zdenek Kabelac <zkabelac@redhat.com> on Mon, 2014/02/10 13:20: >>>>> Dne 10.2.2014 10:30, Christian Hesse napsal(a): >>>>>> Zdenek Kabelac <zkabelac@redhat.com> on Mon, 2014/02/10 09:33: >>>>>>> Dne 8.2.2014 00:55, Christian Hesse napsal(a): >>>>>>>> Christian Hesse <list@eworm.de> on Sat, 2014/02/08 00:36: >>>>>>>>> Hello everybody, >>>>>>>>> >>>>>>>>> I think I nailed it down with git bisect. My first bad commit is: >>>>>>>>> >>>>>>>>> 75628f341ad38b68aae33eae0b5700be2a6e5769 >>>>>>>>> configure: enable blkid_wiping by default if the blkid library is >>>>>>>>> present >>>>>>>>> >>>>>>>>> Looks like this wipes data that is still needed... Building a >>>>>>>>> package >>>>>>>>> with '--disable-blkid_wipe' now to verify on another system. >>>>>>>> >>>>>>>> Uh, this only helps part of... >>>>>>>> >>>>>>>> I changed my test setup and used writable snapshots. After that >>>>>>>> I got: >>>>>>>> >>>>>>>> WARNING: DM_snapshot_cow signature detected on >>>>>>>> /dev/cvg/snap-home at >>>>>>>> offset 0. Wipe it? [y/n] >>>>>>>> >>>>>>>> (see https://bbs.archlinux.org/viewtopic.php?id=176504 for another >>>>>>>> report) >>>>>>>> >>>>>>>> Looks like disabling blkid_wiping fixes this. My snapshot >>>>>>>> corruption >>>>>>>> still occurs though. :-/ >>>>>>>> Bad thing about it is that the corruption does not occur >>>>>>>> reliable when >>>>>>>> doing simple tests in 'git bisect'... Out of ideas for now - >>>>>>>> Will go >>>>>>>> to bed now. >>>>>>> >>>>>>> Now this was helpful, I guess I think what is going on. >>>>>> >>>>>> Great! Waiting for patches then. :D >>>>>> >>>>>> I could provide some more information when needed: >>>>>> >>>>>> * This happens with read only snapshots only. >>>>>> * I could reproduce with commit >>>>>> eaa23d32732c9bc3dd4f948781b5764cf21d84ba >>>>>> (wiping: add support for blkid wiping), so it was introduced >>>>>> there or >>>>>> before. >>>>>> >>>>>> Should I investigate further or wait for something to test from you? >>>>> >>>>> Is the patch bellow fixing your problem ? >>>>> (It's still not final - but should help) >>>>> >>>>> Zdenek >>>>> >>>>> >>>>> diff --git a/tools/lvcreate.c b/tools/lvcreate.c >>>>> index 638a868..e8b1a7f 100644 >>>>> --- a/tools/lvcreate.c >>>>> +++ b/tools/lvcreate.c >>>>> @@ -772,7 +772,7 @@ static int _read_activation_params(struct >>>>> lvcreate_params *lp, LVM_READ | LVM_WRITE); >>>>> >>>>> /* Must not zero/wipe read only volume */ >>>>> - if (!(lp->permission & LVM_WRITE)) { >>>>> + if (!lp->snapshot && !(lp->permission & LVM_WRITE)) { >>>>> lp->zero = 0; >>>>> lp->wipe_signatures = 0; >>>>> } >>>> >>>> This looks good to me. I've made some backups now without any >>>> corruption. >>>> >>>> But with blkid_wiping enabled I do have this warning/question now >>>> for read >>>> only snapshots as well: >>>> >>>> WARNING: DM_snapshot_cow signature detected on /dev/cvg/snap-home >>>> at offset 0. Wipe it? [y/n] >>>> >>>> lvm works perfectly only with your patch applied and compiled with >>>> --disable-blkid_wiping. >>> >>> Also, try this patch in addition: >>> >>> https://git.fedorahosted.org/cgit/lvm2.git/commit/?id=ed166a3b1d3290ad887d8f83c24a8d8877713d3c >>> >> >> That did the trick. Thanks a lot! >> >> If anybody is interested... These are the patches updated to apply >> against >> version 2.02.105: >> >> http://www.eworm.de/download/linux/lvm2-snapshot.patch >> http://www.eworm.de/download/linux/lvm2-snapshot-wiping.patch >> > > > We need to resolve the logic behind the query for wiping. We will most > probably go with this logic: > > We query for wipe of 'known' signatures, before passing newly allocated > 'normal' LV (visible). > Any other so called 'private/hidden' LV will do either wipe or > unconditional zeroing of 1st. 4kb - which is usually the only thing > needed here. > MD can write its signature beyond 4K. Just an example... > Current logic is somewhat overcomplicated. Current logic is simple - we do the wiping first (not asking about any special LV signatures that we directly produce - for now its only the DM_snapshot_cow that libblkid recognizes). And after wiping, zeroing happens. Simple as that, nothing overcomplicated actually... -- Peter _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
