Got 10 csum errors according to dmesg but 0 errors according to dev stats

Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

I have installed a new virtual machine (VirtualBox) with Arch on btrfs 
(just a root fs and swap partition, no other partitions).
I suddenly noticed 10 checksum errors in the kernel log:
$ dmesg | grep csum
[  736.283506] BTRFS warning (device sda1): csum failed ino 1704363 off 
761856 csum 1145980813 expected csum 2566472073
[  736.283605] BTRFS warning (device sda1): csum failed ino 1704363 off 
1146880 csum 1961240434 expected csum 2566472073
[  745.583064] BTRFS warning (device sda1): csum failed ino 1704346 off 
393216 csum 4035064017 expected csum 2566472073
[  752.324899] BTRFS warning (device sda1): csum failed ino 1705927 off 
2125824 csum 3638986839 expected csum 2566472073
[  752.333115] BTRFS warning (device sda1): csum failed ino 1705927 off 
2588672 csum 176788087 expected csum 2566472073
[  752.333303] BTRFS warning (device sda1): csum failed ino 1705927 off 
3276800 csum 1891435134 expected csum 2566472073
[  752.333397] BTRFS warning (device sda1): csum failed ino 1705927 off 
3964928 csum 3304112727 expected csum 2566472073
[ 2761.889460] BTRFS warning (device sda1): csum failed ino 1705927 off 
2125824 csum 3638986839 expected csum 2566472073
[ 9054.226022] BTRFS warning (device sda1): csum failed ino 1704363 off 
761856 csum 1145980813 expected csum 2566472073
[ 9054.226106] BTRFS warning (device sda1): csum failed ino 1704363 off 
1146880 csum 1961240434 expected csum 2566472073

This is a new vm, it hasn't crashed (which might have caused filesystem 
corruption). The virtual disk is on a RAID storage on the host, which is 
healthy. All corrupted files are Firefox data files:
$ dmesg | grep csum | grep -Eo 'csum failed ino [0-9]* ' | awk '{print 
$4}' | xargs -I{} find -inum {}
./.mozilla/firefox/nfh217zw.default/cookies.sqlite
./.mozilla/firefox/nfh217zw.default/cookies.sqlite
./.mozilla/firefox/nfh217zw.default/webappsstore.sqlite
./.mozilla/firefox/nfh217zw.default/places.sqlite
./.mozilla/firefox/nfh217zw.default/places.sqlite
./.mozilla/firefox/nfh217zw.default/places.sqlite
./.mozilla/firefox/nfh217zw.default/places.sqlite
./.mozilla/firefox/nfh217zw.default/places.sqlite
./.mozilla/firefox/nfh217zw.default/cookies.sqlite
./.mozilla/firefox/nfh217zw.default/cookies.sqlite

How could this possibly happen?

And more importantly: Why doesn't the btrfs stat(u)s output tell me that 
errors have occurred?
$ sudo btrfs dev stats /
[/dev/sda1].write_io_errs   0
[/dev/sda1].read_io_errs    0
[/dev/sda1].flush_io_errs   0
[/dev/sda1].corruption_errs 0
[/dev/sda1].generation_errs 0

If the filesystem health was monitored using btrfs dev stats (cronjob) 
(like checking a zpool using zpool status), the admin would not have 
been notified:
$ sudo btrfs dev stats / | grep -v 0 -c
0

Is my understanding of the stats command wrong, does "corruption_errs" 
not mean corruption errors?



-- 
Philip

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

Forgot to mention kernel version: Linux 4.0.1-1-ARCH

$ sudo btrfs fi show
Label: none  uuid: 3e8973d3-83ce-4d93-8d50-2989c0be256a
     Total devices 1 FS bytes used 19.87GiB
     devid    1 size 45.00GiB used 21.03GiB path /dev/sda1

btrfs-progs v3.19.1



On 05/10/2015 04:37 PM, Philip Seeger wrote:
> I have installed a new virtual machine (VirtualBox) with Arch on btrfs
> (just a root fs and swap partition, no other partitions).
> I suddenly noticed 10 checksum errors in the kernel log:
> $ dmesg | grep csum
> [  736.283506] BTRFS warning (device sda1): csum failed ino 1704363 off
> 761856 csum 1145980813 expected csum 2566472073
> [  736.283605] BTRFS warning (device sda1): csum failed ino 1704363 off
> 1146880 csum 1961240434 expected csum 2566472073
> [  745.583064] BTRFS warning (device sda1): csum failed ino 1704346 off
> 393216 csum 4035064017 expected csum 2566472073
> [  752.324899] BTRFS warning (device sda1): csum failed ino 1705927 off
> 2125824 csum 3638986839 expected csum 2566472073
> [  752.333115] BTRFS warning (device sda1): csum failed ino 1705927 off
> 2588672 csum 176788087 expected csum 2566472073
> [  752.333303] BTRFS warning (device sda1): csum failed ino 1705927 off
> 3276800 csum 1891435134 expected csum 2566472073
> [  752.333397] BTRFS warning (device sda1): csum failed ino 1705927 off
> 3964928 csum 3304112727 expected csum 2566472073
> [ 2761.889460] BTRFS warning (device sda1): csum failed ino 1705927 off
> 2125824 csum 3638986839 expected csum 2566472073
> [ 9054.226022] BTRFS warning (device sda1): csum failed ino 1704363 off
> 761856 csum 1145980813 expected csum 2566472073
> [ 9054.226106] BTRFS warning (device sda1): csum failed ino 1704363 off
> 1146880 csum 1961240434 expected csum 2566472073
>
> This is a new vm, it hasn't crashed (which might have caused filesystem
> corruption). The virtual disk is on a RAID storage on the host, which is
> healthy. All corrupted files are Firefox data files:
> $ dmesg | grep csum | grep -Eo 'csum failed ino [0-9]* ' | awk '{print
> $4}' | xargs -I{} find -inum {}
> ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
> ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
> ./.mozilla/firefox/nfh217zw.default/webappsstore.sqlite
> ./.mozilla/firefox/nfh217zw.default/places.sqlite
> ./.mozilla/firefox/nfh217zw.default/places.sqlite
> ./.mozilla/firefox/nfh217zw.default/places.sqlite
> ./.mozilla/firefox/nfh217zw.default/places.sqlite
> ./.mozilla/firefox/nfh217zw.default/places.sqlite
> ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
> ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>
> How could this possibly happen?
>
> And more importantly: Why doesn't the btrfs stat(u)s output tell me that
> errors have occurred?
> $ sudo btrfs dev stats /
> [/dev/sda1].write_io_errs   0
> [/dev/sda1].read_io_errs    0
> [/dev/sda1].flush_io_errs   0
> [/dev/sda1].corruption_errs 0
> [/dev/sda1].generation_errs 0
>
> If the filesystem health was monitored using btrfs dev stats (cronjob)
> (like checking a zpool using zpool status), the admin would not have
> been notified:
> $ sudo btrfs dev stats / | grep -v 0 -c
> 0
>
> Is my understanding of the stats command wrong, does "corruption_errs"
> not mean corruption errors?
>
>
>

-- 
Philip

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

(Again, last message was rejected.)

Hi Richard,

thank you for this tip, I didn't notice that btrfs-progs didn't match 
the kernel version.
I've updated btrfs-progs (from the repository, not manually installed), 
btrfs --version now shows v4.0.

However, it seems strange to me that a bunch of files is corrupted 
simply because btrfs-progs is older than the kernel.
To trigger more csum errors, I ran a script that basically finds all 
files and runs cat $file >/dev/null. I also scrubbed the filesystem.
It's getting worse. The number of corrupted files has grown to 79 - all 
in /home. Some of these files have not been modified in 3 years. I have 
copied them into this Arch vm from another vm, which runs Fedora (kernel 
3.19). The Fedora vm also uses btrfs, so it has the right checksums for 
all of those files. There are no csum errors in dmesg on that Fedora 
system. I've also started a scrub there, which has not generated any 
error yet. To be clear, we're talking about 50k something files (about 
11 GB) that I've copied onto this vm; I have used a handful of them and 
created <10.

So after copying a lot of files onto this Arch vm, many of them have 
been corrupted for unknown reasons (mostly old files, not changed on 
this Arch system).

Scrub:
# time btrfs scrub start -B / ; echo scrub $? done

scrub done for 3e8973d3-83ce-4d93-8d50-2989c0be256a
     scrub started at Sun May 10 17:47:34 2015 and finished after 427 
seconds
     total bytes scrubbed: 19.87GiB with 21941 errors
     error details: csum=21941
     corrected errors: 0, uncorrectable errors: 21941, unverified errors: 0
ERROR: There are uncorrectable errors.

During the scrub, I also saw several of these:
[19935.898678] __readpage_endio_check: 14 callbacks suppressed

I have started another scrub (now with v4.0), I still get errors but the 
affected file names are mentioned in dmesg, which is nice. Is there a 
btrfs status command that will list permanently damaged files as well 
(like zpool status -v), since dmesg will be empty after a reboot or crash?

I believe, thanks to Richard, I can now answer my second question: The 
old version 3.19 failed to increase the error counter(s) in dev stats, 
but this is apparently fixed in 4.0 (so a monitoring job would now be 
able to notify an admin):
$ sudo btrfs dev stats / | grep -v 0
[/dev/sda1].corruption_errs 43882



Thanks
Philip

On 05/10/2015 05:33 PM, Richard Michael wrote:
> Hi Philip,
>
> Have you tried latest btrfs-progs?
>
> The progs release version has sync'd up with the kernel version, so 
> your kernel v4.0.1 with progs v3.19.1 could be taken as a "mismatch".
>
> I haven't read the progs v3.19.1 v4.0 commit diff, and the wiki 
> doesn't mention csum fixes/work related to corruption, but, in your 
> situation, I'd probably try out v4.0 progs to be sure.
>
> https://btrfs.wiki.kernel.org/index.php/Main_Page#News
>
> Sorry I don't have more than this to offer.
>
>
> Regards,
> Richard
>
>
> On Sun, May 10, 2015 at 10:58 AM, Philip Seeger <p0h0i0l0i0p@gmail.com 
> <mailto:p0h0i0l0i0p@gmail.com>> wrote:
>
>     Forgot to mention kernel version: Linux 4.0.1-1-ARCH
>
>     $ sudo btrfs fi show
>     Label: none  uuid: 3e8973d3-83ce-4d93-8d50-2989c0be256a
>         Total devices 1 FS bytes used 19.87GiB
>         devid    1 size 45.00GiB used 21.03GiB path /dev/sda1
>
>     btrfs-progs v3.19.1
>
>
>
>
>     On 05/10/2015 04:37 PM, Philip Seeger wrote:
>
>         I have installed a new virtual machine (VirtualBox) with Arch
>         on btrfs
>         (just a root fs and swap partition, no other partitions).
>         I suddenly noticed 10 checksum errors in the kernel log:
>         $ dmesg | grep csum
>         [  736.283506] BTRFS warning (device sda1): csum failed ino
>         1704363 off
>         761856 csum 1145980813 expected csum 2566472073
>         [  736.283605] BTRFS warning (device sda1): csum failed ino
>         1704363 off
>         1146880 csum 1961240434 expected csum 2566472073
>         [  745.583064] BTRFS warning (device sda1): csum failed ino
>         1704346 off
>         393216 csum 4035064017 expected csum 2566472073
>         [  752.324899] BTRFS warning (device sda1): csum failed ino
>         1705927 off
>         2125824 csum 3638986839 expected csum 2566472073
>         [  752.333115] BTRFS warning (device sda1): csum failed ino
>         1705927 off
>         2588672 csum 176788087 expected csum 2566472073
>         [  752.333303] BTRFS warning (device sda1): csum failed ino
>         1705927 off
>         3276800 csum 1891435134 expected csum 2566472073
>         [  752.333397] BTRFS warning (device sda1): csum failed ino
>         1705927 off
>         3964928 csum 3304112727 expected csum 2566472073
>         [ 2761.889460] BTRFS warning (device sda1): csum failed ino
>         1705927 off
>         2125824 csum 3638986839 expected csum 2566472073
>         [ 9054.226022] BTRFS warning (device sda1): csum failed ino
>         1704363 off
>         761856 csum 1145980813 expected csum 2566472073
>         [ 9054.226106] BTRFS warning (device sda1): csum failed ino
>         1704363 off
>         1146880 csum 1961240434 expected csum 2566472073
>
>         This is a new vm, it hasn't crashed (which might have caused
>         filesystem
>         corruption). The virtual disk is on a RAID storage on the
>         host, which is
>         healthy. All corrupted files are Firefox data files:
>         $ dmesg | grep csum | grep -Eo 'csum failed ino [0-9]* ' | awk
>         '{print
>         $4}' | xargs -I{} find -inum {}
>         ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>         ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>         ./.mozilla/firefox/nfh217zw.default/webappsstore.sqlite
>         ./.mozilla/firefox/nfh217zw.default/places.sqlite
>         ./.mozilla/firefox/nfh217zw.default/places.sqlite
>         ./.mozilla/firefox/nfh217zw.default/places.sqlite
>         ./.mozilla/firefox/nfh217zw.default/places.sqlite
>         ./.mozilla/firefox/nfh217zw.default/places.sqlite
>         ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>         ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>
>         How could this possibly happen?
>
>         And more importantly: Why doesn't the btrfs stat(u)s output
>         tell me that
>         errors have occurred?
>         $ sudo btrfs dev stats /
>         [/dev/sda1].write_io_errs   0
>         [/dev/sda1].read_io_errs    0
>         [/dev/sda1].flush_io_errs   0
>         [/dev/sda1].corruption_errs 0
>         [/dev/sda1].generation_errs 0
>
>         If the filesystem health was monitored using btrfs dev stats
>         (cronjob)
>         (like checking a zpool using zpool status), the admin would
>         not have
>         been notified:
>         $ sudo btrfs dev stats / | grep -v 0 -c
>         0
>
>         Is my understanding of the stats command wrong, does
>         "corruption_errs"
>         not mean corruption errors?
>
>
>
>
>     -- 
>     Philip
>     --
>     To unsubscribe from this list: send the line "unsubscribe
>     linux-btrfs" in
>     the body of a message to majordomo@vger.kernel.org
>     <mailto:majordomo@vger.kernel.org>
>     More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Russell Coker]

On Mon, 11 May 2015 03:32:45 AM Philip Seeger wrote:
> However, it seems strange to me that a bunch of files is corrupted 
> simply because btrfs-progs is older than the kernel.

That won't happen.

> To trigger more csum errors, I ran a script that basically finds all 
> files and runs cat $file >/dev/null. I also scrubbed the filesystem.
> It's getting worse. The number of corrupted files has grown to 79 - all 
> in /home. Some of these files have not been modified in 3 years. I have 

Sounds like you are having errors in your RAM, CPU, motherboard, or hard drive 
cabling.  Turn the machine off ASAP and plug the disks into a different system, 
if you keep it running you will make it worse.

-- 
My Main Blog         http://etbe.coker.com.au/
My Documents Blog    http://doc.coker.com.au/

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

> Sounds like you are having errors in your RAM, CPU, motherboard, or hard drive
> cabling.  Turn the machine off ASAP and plug the disks into a different system,
> if you keep it running you will make it worse.
>
I know it sounds like it, but the host is fine. The host filesystem (on 
which the vm virtual hdd resides) is healthy. Other vms are running on 
the same host, no problems there. Just to be sure, I will run memtest, 
but I'm pretty sure that's not it. The system is under high load a lot, 
but I don't think btrfs would fail because of a slow system.

So I have deleted all those corrupted files in this Arch vm, ran a 
scrub, 0 errors, all fixed. I restored them, fixed some other things and 
now - I get checksum errors again. Interestingly, it looks like the 
corruption is not happening randomly, because the same sqlite files are 
affected under ~/.mozilla/ and exactly one library file (ghostscript).
Meanwhile, other vms (not Arch but Fedora and Debian) are running 
without a problem (one of them using btrfs as well).

Is it possible that systemd isn't unmounting the filesystem properly, so 
it gets corrupted on shutdown? (Juest a wild guess.) Although I'm not 
sure if all this happened between reboots.


Philip

RE: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Paul Jones]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 2060 bytes --]

> -----Original Message-----
> From: linux-btrfs-owner@vger.kernel.org [mailto:linux-btrfs-
> owner@vger.kernel.org] On Behalf Of Philip Seeger
> Sent: Tuesday, 12 May 2015 10:15 AM
> To: linux-btrfs@vger.kernel.org
> Subject: Re: Got 10 csum errors according to dmesg but 0 errors according to
> dev stats
> 
> > Sounds like you are having errors in your RAM, CPU, motherboard, or
> > hard drive cabling.  Turn the machine off ASAP and plug the disks into
> > a different system, if you keep it running you will make it worse.
> >
> I know it sounds like it, but the host is fine. The host filesystem (on which the
> vm virtual hdd resides) is healthy. Other vms are running on the same host,
> no problems there. Just to be sure, I will run memtest, but I'm pretty sure
> that's not it. The system is under high load a lot, but I don't think btrfs would
> fail because of a slow system.
> 
> So I have deleted all those corrupted files in this Arch vm, ran a scrub, 0
> errors, all fixed. I restored them, fixed some other things and now - I get
> checksum errors again. Interestingly, it looks like the corruption is not
> happening randomly, because the same sqlite files are affected under
> ~/.mozilla/ and exactly one library file (ghostscript).
> Meanwhile, other vms (not Arch but Fedora and Debian) are running without
> a problem (one of them using btrfs as well).
> 
> Is it possible that systemd isn't unmounting the filesystem properly, so it gets
> corrupted on shutdown? (Juest a wild guess.) Although I'm not sure if all this
> happened between reboots.

Are you using KVM with some form of disk caching? I had a windows vm that was constantly creating errors on the host filesystem (btrfs) somewhere within the disk image. I changed the caching option (I can't remember from/to what) and it fixed the error. It didn't seem to be causing any errors on the windows guest, but it's windows so you never know :)

Paul.
ÿôèº{.nÇ+‰·Ÿ®‰­†+%ŠËÿ±éݶ\x17¥Šwÿº{.nÇ+‰·¥Š{±ý»k~ÏâžØ^n‡r¡ö¦zË\x1aëh™¨è­Ú&£ûàz¿äz¹Þ—ú+€Ê+zf£¢·hšˆ§~†­†Ûiÿÿïêÿ‘êçz_è®\x0fæj:+v‰¨þ)ߣøm

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Chris Murphy]

There are two file systems involved, guest and host. What are their
file systems? I know one of them is Btrfs but I can't tell if they're
both Btrfs.

There is a regression somewhere, I don't know where yet, when libvirt
cache=none or cache=directsync, and the disk image (qcow2 in my case)
is on Btrfs. The guest file system doesn't matter, it'll eventually
spew some corruption related errors.
https://bugzilla.redhat.com/show_bug.cgi?id=1204569


Chris Murphy

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

The host filesystem (where the virtual hdd is stored) is ZFS (no 
errors). It's a bit slower recently because I am moving a lot of data 
around while other vms are running. But that shouldn't be a problem.

This Arch vm appears to be the only one having problems. Again, I have 
even scrubbed one other vm, which also uses btrfs (but 3.19, not 4.0) 
and found no errors. This is the vm from which I have copied the 11 GB 
directory, which now keeps getting corrupted in the Arch vm.

I'd just like to repeat that I have copied one directory from an older 
vm, which uses btrfs, to a new Arch vm, which also used btrfs, and while 
that older vm has worked fine (still does), the same files in that 
copied directory are getting corrupted in the new Arch vm...

The bug report mentions Gnome Boxes, but I'm using VirtualBox. Don't 
know if both are affected in the same way.
If it makes a difference: The Arch vm has an IDE controller (host cache 
enabled) for the virtual optical drive and one SATA controller (host 
cache disabled) for the virtual hard drive.

I will try to get this vm in a healthy state again by deleting all 
affected files and copying them back again.

Also, should I try to use a specific mount option, maybe a lower commit 
interval?


Philip

On 05/12/2015 03:37 AM, Chris Murphy wrote:
> There are two file systems involved, guest and host. What are their
> file systems? I know one of them is Btrfs but I can't tell if they're
> both Btrfs.
>
> There is a regression somewhere, I don't know where yet, when libvirt
> cache=none or cache=directsync, and the disk image (qcow2 in my case)
> is on Btrfs. The guest file system doesn't matter, it'll eventually
> spew some corruption related errors.
> https://bugzilla.redhat.com/show_bug.cgi?id=1204569
>
>
> Chris Murphy
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

The SATA controller used for the virtual hard drive of this vm does not 
have host caching enabled (checkbox not checked). So, no, VirtualBox 
should not be using any form of disk caching.

Also, there is no Windows involved.

Philip

On 05/12/2015 03:04 AM, Paul Jones wrote:
>> -----Original Message-----
>> From: linux-btrfs-owner@vger.kernel.org [mailto:linux-btrfs-
>> owner@vger.kernel.org] On Behalf Of Philip Seeger
>> Sent: Tuesday, 12 May 2015 10:15 AM
>> To: linux-btrfs@vger.kernel.org
>> Subject: Re: Got 10 csum errors according to dmesg but 0 errors according to
>> dev stats
>>
>>> Sounds like you are having errors in your RAM, CPU, motherboard, or
>>> hard drive cabling.  Turn the machine off ASAP and plug the disks into
>>> a different system, if you keep it running you will make it worse.
>>>
>> I know it sounds like it, but the host is fine. The host filesystem (on which the
>> vm virtual hdd resides) is healthy. Other vms are running on the same host,
>> no problems there. Just to be sure, I will run memtest, but I'm pretty sure
>> that's not it. The system is under high load a lot, but I don't think btrfs would
>> fail because of a slow system.
>>
>> So I have deleted all those corrupted files in this Arch vm, ran a scrub, 0
>> errors, all fixed. I restored them, fixed some other things and now - I get
>> checksum errors again. Interestingly, it looks like the corruption is not
>> happening randomly, because the same sqlite files are affected under
>> ~/.mozilla/ and exactly one library file (ghostscript).
>> Meanwhile, other vms (not Arch but Fedora and Debian) are running without
>> a problem (one of them using btrfs as well).
>>
>> Is it possible that systemd isn't unmounting the filesystem properly, so it gets
>> corrupted on shutdown? (Juest a wild guess.) Although I'm not sure if all this
>> happened between reboots.
> Are you using KVM with some form of disk caching? I had a windows vm that was constantly creating errors on the host filesystem (btrfs) somewhere within the disk image. I changed the caching option (I can't remember from/to what) and it fixed the error. It didn't seem to be causing any errors on the windows guest, but it's windows so you never know :)
>
> Paul.

Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

I deleted and restored the corrupted files again. One of those files 
(not a new one) got corrupted again.

I think I forgot to mention that this btrfs filesystem was converted 
from ext4 (not initially created as btrfs).
Could this cause this corruption?

Also, does this df output look weird to anyone, shouldn't metadata be 
duplicated?
# btrfs fi df /
Data, single: total=21.00GiB, used=20.82GiB
System, single: total=32.00MiB, used=4.00KiB
Metadata, single: total=1.25GiB, used=901.21MiB
GlobalReserve, single: total=304.00MiB, used=0.00B


Philip

On 05/10/2015 04:58 PM, Philip Seeger wrote:
> Forgot to mention kernel version: Linux 4.0.1-1-ARCH
>
> $ sudo btrfs fi show
> Label: none  uuid: 3e8973d3-83ce-4d93-8d50-2989c0be256a
>     Total devices 1 FS bytes used 19.87GiB
>     devid    1 size 45.00GiB used 21.03GiB path /dev/sda1
>
> btrfs-progs v3.19.1
>
>
>
> On 05/10/2015 04:37 PM, Philip Seeger wrote:
>> I have installed a new virtual machine (VirtualBox) with Arch on btrfs
>> (just a root fs and swap partition, no other partitions).
>> I suddenly noticed 10 checksum errors in the kernel log:
>> $ dmesg | grep csum
>> [  736.283506] BTRFS warning (device sda1): csum failed ino 1704363 off
>> 761856 csum 1145980813 expected csum 2566472073
>> [  736.283605] BTRFS warning (device sda1): csum failed ino 1704363 off
>> 1146880 csum 1961240434 expected csum 2566472073
>> [  745.583064] BTRFS warning (device sda1): csum failed ino 1704346 off
>> 393216 csum 4035064017 expected csum 2566472073
>> [  752.324899] BTRFS warning (device sda1): csum failed ino 1705927 off
>> 2125824 csum 3638986839 expected csum 2566472073
>> [  752.333115] BTRFS warning (device sda1): csum failed ino 1705927 off
>> 2588672 csum 176788087 expected csum 2566472073
>> [  752.333303] BTRFS warning (device sda1): csum failed ino 1705927 off
>> 3276800 csum 1891435134 expected csum 2566472073
>> [  752.333397] BTRFS warning (device sda1): csum failed ino 1705927 off
>> 3964928 csum 3304112727 expected csum 2566472073
>> [ 2761.889460] BTRFS warning (device sda1): csum failed ino 1705927 off
>> 2125824 csum 3638986839 expected csum 2566472073
>> [ 9054.226022] BTRFS warning (device sda1): csum failed ino 1704363 off
>> 761856 csum 1145980813 expected csum 2566472073
>> [ 9054.226106] BTRFS warning (device sda1): csum failed ino 1704363 off
>> 1146880 csum 1961240434 expected csum 2566472073
>>
>> This is a new vm, it hasn't crashed (which might have caused filesystem
>> corruption). The virtual disk is on a RAID storage on the host, which is
>> healthy. All corrupted files are Firefox data files:
>> $ dmesg | grep csum | grep -Eo 'csum failed ino [0-9]* ' | awk '{print
>> $4}' | xargs -I{} find -inum {}
>> ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>> ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>> ./.mozilla/firefox/nfh217zw.default/webappsstore.sqlite
>> ./.mozilla/firefox/nfh217zw.default/places.sqlite
>> ./.mozilla/firefox/nfh217zw.default/places.sqlite
>> ./.mozilla/firefox/nfh217zw.default/places.sqlite
>> ./.mozilla/firefox/nfh217zw.default/places.sqlite
>> ./.mozilla/firefox/nfh217zw.default/places.sqlite
>> ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>> ./.mozilla/firefox/nfh217zw.default/cookies.sqlite
>>
>> How could this possibly happen?
>>
>> And more importantly: Why doesn't the btrfs stat(u)s output tell me that
>> errors have occurred?
>> $ sudo btrfs dev stats /
>> [/dev/sda1].write_io_errs   0
>> [/dev/sda1].read_io_errs    0
>> [/dev/sda1].flush_io_errs   0
>> [/dev/sda1].corruption_errs 0
>> [/dev/sda1].generation_errs 0
>>
>> If the filesystem health was monitored using btrfs dev stats (cronjob)
>> (like checking a zpool using zpool status), the admin would not have
>> been notified:
>> $ sudo btrfs dev stats / | grep -v 0 -c
>> 0
>>
>> Is my understanding of the stats command wrong, does "corruption_errs"
>> not mean corruption errors?
>>
>>
>>
>

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Duncan]

Philip Seeger posted on Sun, 17 May 2015 03:53:20 +0200 as excerpted:
> 
> On 05/10/2015 04:58 PM, Philip Seeger wrote:
>> 
>> Forgot to mention kernel version: Linux 4.0.1-1-ARCH
>>
>> $ sudo btrfs fi show Label: none  uuid:
>> 3e8973d3-83ce-4d93-8d50-2989c0be256a
>>     Total devices 1 FS bytes used 19.87GiB
>>     devid    1 size 45.00GiB used 21.03GiB path /dev/sda1
>>
>> btrfs-progs v3.19.1
>>
> I think I forgot to mention that this btrfs filesystem was converted
> from ext4 (not initially created as btrfs).
> Could this cause this corruption?
> 
> Also, does this df output look weird to anyone, shouldn't metadata be
> duplicated?
> # btrfs fi df /
> Data, single: total=21.00GiB, used=20.82GiB
> System, single: total=32.00MiB, used=4.00KiB
> Metadata, single: total=1.25GiB, used=901.21MiB
> GlobalReserve, single: total=304.00MiB, used=0.00B

[Reordered to standard quote/reply order, so replies have proper 
context.  Top posting... not so fun to reply to! =:^( ]

I can't answer the corruption bit, but answering the df metadata 
question...

Normally, btrfs on a single device defaults to dup metadata type, single 
data type.  The one /normal/ exception to that is when mkfs.btrfs detects 
an ssd, where it defaults to single data due to ssd firmware often 
canceling out the intended redundancy of dup anyway.[1]

However, conversion from ext* is a bit of a different ball game, and 
while it /should/ default to dup metadata as well, on 4.0 and into 4.1-rcs 
as a proper fix hasn't been posted, there's a balance-conversion bug 
that's keeping type conversion from occurring, both in the normal btrfs 
balance convert case and in the ext* conversion case.  Thus, ext* 
conversions remain metadata-single mode and cannot be converted to 
metadata-dup until this bug is fixed.

I said that a /proper/ fix hasn't yet been posted.  There has been a 
bisect trace to the commit that killed balance-convert, and that can be 
reverted, as I guess some distros are doing in their current releases.  
However, that commit happened to fix an ext* to btrfs conversion fault, 
that would cause ext* conversions to fail entirely.  So reverting that 
commit does fix normal btrfs balance conversions, but it breaks the 
ability to convert from ext* at all.  I don't know when /that/ was 
broken, but apparently it was further back.

So right now, the only way to get a desired btrfs chunk redundancy type 
is to use mkfs.btrfs to create it that way in the first place.  Which 
means no ext* conversion unless you're happy with single-data/single-
metadata, since that's what it ends up with, and balance-convert is ATM 
currently broken and can't convert to other redundancy types.

Well, unless you want to do the ext* to btrfs convert with the current 
tools as they are (with the commit in question so the ext*-conversion 
actually works), then rebuild with that commit reverted, so balance-
convert works...

Chris Mason has stated he has what he believes to be the correct fix in 
his head, but he hasn't posted it yet.  Either it turned out to have 
other problems, or he simply hasn't had time to write it out and properly 
test that it /doesn't/ have other problems.

Either way, as I said above, until that patch appears, the only /current/ 
way (other than jumping thru rebuild and revert hoops) to get other than 
single data/metadata both on data that's currently on ext4, is to either 
back it up or use it as a backup, and create a /new/ btrfs of the 
intended chunk redundancy layout using mkfs.btrfs, mount it and copy the 
data into it from that backup.

---
[1] Ssd firmware canceling out dup redundancy: This can happen in two 
ways.  First, some common ssd firmware (sandforce, IIRC, perhaps others) 
does its own dedup, such that two identical copies only get written once 
anyway, thus directly canceling out the benefits of filesystem dup.  
Second, even for firmware that actually writes two copies, because they 
are written one right after the other, they may well be written into the 
same erase block, and since the fail-pattern of ssds normally fails 
entire erase-blocks at the same time or very close to it, dup won't 
provide the intended redundancy protection anyway.  Thus, on ssds one 
really needs two physically separate devices in raid1 mode to provide the 
redundancy single-device dup is intended to provide.  Some ssds /may/ 
provide dup protection as intended, but it's sufficiently unreliable on 
available ssds that simply defaulting to single and not pretending 
otherwise was seen to be the wiser path, particularly since users can 
still specify dup mode at mkfs.btrfs time if they like, or (normally, 
when balance-convert is working) convert to it later if necessary.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Omar Sandoval]

On Sun, May 17, 2015 at 08:19:48AM +0000, Duncan wrote:
> Philip Seeger posted on Sun, 17 May 2015 03:53:20 +0200 as excerpted:
> > 
> > On 05/10/2015 04:58 PM, Philip Seeger wrote:
> >> 
> >> Forgot to mention kernel version: Linux 4.0.1-1-ARCH
> >>
> >> $ sudo btrfs fi show Label: none  uuid:
> >> 3e8973d3-83ce-4d93-8d50-2989c0be256a
> >>     Total devices 1 FS bytes used 19.87GiB
> >>     devid    1 size 45.00GiB used 21.03GiB path /dev/sda1
> >>
> >> btrfs-progs v3.19.1
> >>
> > I think I forgot to mention that this btrfs filesystem was converted
> > from ext4 (not initially created as btrfs).
> > Could this cause this corruption?
> > 
> > Also, does this df output look weird to anyone, shouldn't metadata be
> > duplicated?
> > # btrfs fi df /
> > Data, single: total=21.00GiB, used=20.82GiB
> > System, single: total=32.00MiB, used=4.00KiB
> > Metadata, single: total=1.25GiB, used=901.21MiB
> > GlobalReserve, single: total=304.00MiB, used=0.00B
> 
> [Reordered to standard quote/reply order, so replies have proper 
> context.  Top posting... not so fun to reply to! =:^( ]
> 
> I can't answer the corruption bit, but answering the df metadata 
> question...
> 
> Normally, btrfs on a single device defaults to dup metadata type, single 
> data type.  The one /normal/ exception to that is when mkfs.btrfs detects 
> an ssd, where it defaults to single data due to ssd firmware often 
> canceling out the intended redundancy of dup anyway.[1]
> 
> However, conversion from ext* is a bit of a different ball game, and 
> while it /should/ default to dup metadata as well, on 4.0 and into 4.1-rcs 
> as a proper fix hasn't been posted, there's a balance-conversion bug 
> that's keeping type conversion from occurring, both in the normal btrfs 
> balance convert case and in the ext* conversion case.  Thus, ext* 
> conversions remain metadata-single mode and cannot be converted to 
> metadata-dup until this bug is fixed.
> 
> I said that a /proper/ fix hasn't yet been posted.  There has been a 
> bisect trace to the commit that killed balance-convert, and that can be 
> reverted, as I guess some distros are doing in their current releases.  
> However, that commit happened to fix an ext* to btrfs conversion fault, 
> that would cause ext* conversions to fail entirely.  So reverting that 
> commit does fix normal btrfs balance conversions, but it breaks the 
> ability to convert from ext* at all.  I don't know when /that/ was 
> broken, but apparently it was further back.
> 
> So right now, the only way to get a desired btrfs chunk redundancy type 
> is to use mkfs.btrfs to create it that way in the first place.  Which 
> means no ext* conversion unless you're happy with single-data/single-
> metadata, since that's what it ends up with, and balance-convert is ATM 
> currently broken and can't convert to other redundancy types.
> 
> Well, unless you want to do the ext* to btrfs convert with the current 
> tools as they are (with the commit in question so the ext*-conversion 
> actually works), then rebuild with that commit reverted, so balance-
> convert works...

Duncan is referring to the commit reverted here:
https://patchwork.kernel.org/patch/6238111/

Just to clarify, reverting 2f0810880f082fa8ba66ab2c33b02e4ff9770a5e does
not break ext4 conversion. If you revert it, you can btrfs-convert, do a
btrfs balance to finalize the conversion, then do another btrfs balance
-dconvert=... -mconvert=... to convert the profile. I should have been
clearer in that other thread: conversion from ext4 to Btrfs works, its
just that the commit that caused the regression did not actually
accomplish what it set out to do: allow converting the data/metadata
profile of a freshly btrfs-converted ext4 filesystem.

-- 
Omar

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Duncan]

Omar Sandoval posted on Sun, 17 May 2015 01:36:54 -0700 as excerpted:

> I should have been clearer in that other thread: conversion from ext4 to
> Btrfs works, its just that the commit that caused the regression did not
> actually accomplish what it set out to do: allow converting the
> data/metadata profile of a freshly btrfs-converted ext4 filesystem.

Thank you.  Clearer now. =:^)

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

On Sun, 2015-05-17 at 08:19 +0000, Duncan wrote:
> 
> I can't answer the corruption bit, but answering the df metadata 
> question...
> 
> Normally, btrfs on a single device defaults to dup metadata type, 
> single 
> data type.  The one /normal/ exception to that is when mkfs.btrfs 
> detects 
> an ssd, where it defaults to single data due to ssd firmware often 
> canceling out the intended redundancy of dup anyway.[1]
> 
> However, conversion from ext* is a bit of a different ball game, and 
> while it /should/ default to dup metadata as well, on 4.0 and into 
> 4.1-rcs 
> as a proper fix hasn't been posted, there's a balance-conversion bug 
> that's keeping type conversion from occurring, both in the normal 
> btrfs 
> balance convert case and in the ext* conversion case.  Thus, ext* 
> conversions remain metadata-single mode and cannot be converted to 
> metadata-dup until this bug is fixed.
> 

Thanks for the detailed explanation. I might take a look at the commit
you're referring to when I have some more time. For now, I simply used
an older live system (3.16) to balance the filesystem (btrfs balance
start), which worked. Before that, I deleted the corrupted files.

Arch after balance:
# btrfs fi df /
Data, single: total=25.72GiB, used=19.47GiB
System, DUP: total=32.00MiB, used=12.00KiB
Metadata, DUP: total=1.25GiB, used=742.27MiB
GlobalReserve, single: total=248.00MiB, used=0.00B

I have copied my files back (that were corrupted in this vm) and this
system is working fine now, no more corruption (so far). It seems the
balance has fixed it.

Is this a known side effect, that files could get corrupted if no
balance is run (not counting the balance with 4.0 which doesn't work
due to that commit) after an ext4 conversion?



-- 
Philip

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Duncan]

Philip Seeger posted on Sat, 23 May 2015 14:49:50 +0200 as excerpted:

> Is this a known side effect, that files could get corrupted if no
> balance is run (not counting the balance with 4.0 which doesn't work due
> to that commit) after an ext4 conversion?

I'm not sure.

What I am sure of is that I'd not trust a btrfs converted from ext* until 
the saved subvol is deleted, and a defrag and balance run.  Even then, 
I'd personally be more comfortable with a fresh mkfs.btrfs, and copy over 
from backup, tho I know reality is that btrfs /needs/ a working 
conversion program or it'll never take off as the default successor to 
the ext* crown, as it wants to be.  I simply don't trust that conversion, 
as I've seen too many people have problems with their btrfs after doing 
the conversion from ext*.

Balance-conversions between raid modes of btrfs are a little different, 
and somewhat more trustworthy... to me, anyway.

To be fair, it might well be a personal bias of mine against ext* in the 
first place, as I never really was comfortable with it for various 
reasons.  Among others, I think enough kernel devs see ext* as simple 
enough to meddle with that it gets more changes than it really should 
have, ext3's period with data=writeback as the default being a primary 
example.  Reiserfs, my personal favorite, and xfs, and now btrfs, all 
seem to be different enough that the hacking is left to the folks that 
really know the filesystem, with others leaving it to the experts as 
they're afraid to touch it, at least more so than ext*.  Anyway, it's 
quite possible I have enough of a bias there that it taints anything 
converted from it more than it should as well.  Either way, I personally 
just don't trust ext* conversions, and would rather see people do 
mkfs.btrfs and copy over from backup, as I think the filesystem is 
cleanly native btrfs that way, and has less problems as a result.

But you really need a second opinion before trusting /that/, because as I 
said, it might simply be my personal bias talking.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

Re: Got 10 csum errors according to dmesg but 0 errors according to dev stats

[Philip Seeger]

On Sat, 2015-05-23 at 16:52 +0000, Duncan wrote:
> Philip Seeger posted on Sat, 23 May 2015 14:49:50 +0200 as excerpted:
> 
> > Is this a known side effect, that files could get corrupted if no
> > balance is run (not counting the balance with 4.0 which doesn't 
> > work due
> > to that commit) after an ext4 conversion?
> 
> I'm not sure.
> 
> What I am sure of is that I'd not trust a btrfs converted from ext* 
> until 
> the saved subvol is deleted, and a defrag and balance run.  Even 


I agree. I did delete the saved subvolume right away, but given that I
effectively did not run a balance (due to this bug, the balance had no
effect) and then had new files corrupted (repeatedly) as a consequence
makes this pretty clear.

Maybe there should be a warning in the wiki ("run a complete balance
before you start using the converted fs, otherwise your files might get
corrupted.")?

Though I'd be more interested in some details as to how this might have
happened. It seems wrong that corruption occurs after a successful
conversion (before a proper balance). Is there anyone else who has had
this issue? Maybe someone who's converted to btrfs, using a btrfs
version with the balance bug?



Philip