From: Marc MERLIN <marc@merlins.org>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: btrfs check --repair: ERROR: cannot read chunk root
Date: Sun, 30 Oct 2016 23:37:37 -0700 [thread overview]
Message-ID: <20161031063737.GP28648@merlins.org> (raw)
In-Reply-To: <0c9e25b1-c8e1-6300-0c79-e9e3e8fd0f52@cn.fujitsu.com>
On Mon, Oct 31, 2016 at 02:32:53PM +0800, Qu Wenruo wrote:
>
>
> At 10/31/2016 02:25 PM, Marc MERLIN wrote:
> >On Mon, Oct 31, 2016 at 02:04:10PM +0800, Qu Wenruo wrote:
> >>>Sorry for asking, am I doing this wrong?
> >>>myth:~# dd if=/dev/mapper/crypt_bcache0 of=/tmp/dump1 bs=512 count=32
> >>>skip=26367830208
> >>>dd: reading `/dev/mapper/crypt_bcache0': Invalid argument
> >>>0+0 records in
> >>>0+0 records out
> >>>0 bytes (0 B) copied, 0.000401393 s, 0.0 kB/s
> >>
> >>So, the underlying MD RAID5 are complaining about some wrong data, and
> >>refuse to read out.
> >>
> >>It seems that btrfs-progs can't handle read failure?
> >>Maybe dm-error could emulate it.
> >>
> >>And what about the 2nd range?
> >
> >they both fail the same, but I wasn' tsure if I typed the wrong dd command
> >or not.
>
> Strange, your command seems OK to me.
>
> Does it has anything to do with your security setup or something like that?
> Or is it related to dm-crypt or bcache?
>
>
> But this reminds me, if dd can't read it, maybe btrfs-progs is the same.
>
> Maybe only kernel can read dm-crypt device while user space tools can't
> access dm-crypt devices directly?
It can, it's just the offset seems wrong:
myth:~# dd if=/dev/mapper/crypt_bcache0 of=/tmp/dump1 bs=512 count=32 skip=26367830208
dd: reading `/dev/mapper/crypt_bcache0': Invalid argument
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000421662 s, 0.0 kB/s
If I divide by 1000, it works:
myth:~# dd if=/dev/mapper/crypt_bcache0 of=/tmp/dump1 bs=512 count=32 skip=26367830
32+0 records in
32+0 records out
16384 bytes (16 kB) copied, 0.139005 s, 118 kB/s
so that's why I was asking you if I counted the offset wrong. I took the
value you asked and divided by 512, but it seems too big
13500329066496 / 512 = 26367830208
Marc
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/
next prev parent reply other threads:[~2016-10-31 6:37 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-30 18:34 btrfs check --repair: ERROR: cannot read chunk root Marc MERLIN
2016-10-31 1:02 ` Qu Wenruo
2016-10-31 2:06 ` Marc MERLIN
2016-10-31 4:21 ` Marc MERLIN
2016-10-31 5:27 ` Qu Wenruo
2016-10-31 5:47 ` Marc MERLIN
2016-10-31 6:04 ` Qu Wenruo
2016-10-31 6:25 ` Marc MERLIN
2016-10-31 6:32 ` Qu Wenruo
2016-10-31 6:37 ` Marc MERLIN [this message]
2016-10-31 7:04 ` Qu Wenruo
2016-10-31 8:44 ` Hugo Mills
2016-10-31 15:04 ` Marc MERLIN
2016-11-01 3:48 ` Marc MERLIN
2016-11-01 4:13 ` Qu Wenruo
2016-11-01 4:21 ` Marc MERLIN
2016-11-04 8:01 ` Marc MERLIN
2016-11-04 9:00 ` Roman Mamedov
2016-11-04 17:59 ` Marc MERLIN
2016-11-07 1:11 ` Qu Wenruo
[not found] ` <87lgwwnnyf.fsf@notabene.neil.brown.name>
2016-11-07 1:20 ` clearing blocks wrongfully marked as bad if --update=no-bbl can't be used? Marc MERLIN
2016-11-07 1:39 ` Qu Wenruo
2016-11-07 4:18 ` Qu Wenruo
2016-11-07 5:36 ` btrfs support for filesystems >8TB on 32bit architectures Marc MERLIN
2016-11-07 6:16 ` Qu Wenruo
2016-11-07 14:55 ` Marc MERLIN
2016-11-08 0:35 ` Qu Wenruo
2016-11-08 0:39 ` Marc MERLIN
2016-11-08 0:43 ` Qu Wenruo
2016-11-08 1:06 ` Marc MERLIN
2016-11-08 1:17 ` Qu Wenruo
2016-11-08 15:24 ` Marc MERLIN
2016-11-09 1:50 ` Qu Wenruo
2016-11-09 2:05 ` Marc MERLIN
2016-11-11 3:48 ` Marc MERLIN
2016-11-11 3:55 ` Qu Wenruo
2016-11-12 3:17 ` when btrfs scrub reports errors and btrfs check --repair does not Marc MERLIN
2016-11-13 15:06 ` Marc MERLIN
2016-11-13 15:13 ` Roman Mamedov
2016-11-13 15:52 ` Marc MERLIN
-- strict thread matches above, loose matches on Subject: below --
2016-10-31 1:29 btrfs check --repair: ERROR: cannot read chunk root Janos Toth F.
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