btrfs fi df "unknown"

btrfs fi df "unknown"

[Chris Murphy]

kernel 3.15.0-0.rc1.git0.1.fc21.x86_64
btrfs-progs v3.14

One 80GB virtual disk, formatted btrfs by installer and Fedora Rawhide installed to it. Post-install I see:

[root@localhost ~]# btrfs fi show
Label: 'fedora'  uuid: d372e5d1-386f-460c-b036-611469e0155e
	Total devices 1 FS bytes used 4.00GiB
	devid    1 size 79.31GiB used 6.04GiB path /dev/sda3

Btrfs v3.14
[root@localhost ~]# btrfs fi df /
Data, single: total=4.01GiB, used=3.79GiB
System, DUP: total=8.00MiB, used=16.00KiB
System, single: total=4.00MiB, used=0.00
Metadata, DUP: total=1.00GiB, used=215.69MiB
Metadata, single: total=8.00MiB, used=0.00
unknown, single: total=80.00MiB, used=0.00


What is unknown?


Chris Murphy

Re: btrfs fi df "unknown" chunk type

[Chris Murphy]

On Apr 20, 2014, at 2:18 PM, Chris Murphy <lists@colorremedies.com> wrote:
> What is unknown?


/dev/sd[bcd] are 2GB, 3GB, and 4GB respectively.

[root@localhost ~]# mkfs.btrfs -d raid0 -m raid1 /dev/sd[bcd]

WARNING! - Btrfs v3.14 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using

Performing full device TRIM (2.00GiB) ...
Turning ON incompat feature 'extref': increased hardlink limit per file to 65536
Performing full device TRIM (3.00GiB) ...
adding device /dev/sdc id 2
Performing full device TRIM (4.00GiB) ...
adding device /dev/sdd id 3
fs created label (null) on /dev/sdb
	nodesize 16384 leafsize 16384 sectorsize 4096 size 9.00GiB

[root@localhost ~]# mount /dev/sdb /mnt
[root@localhost ~]# btrfs fi show
Label: none  uuid: ff85abb0-3398-40a0-b06c-8146cb1bfda0
	Total devices 3 FS bytes used 112.00KiB
	devid    1 size 2.00GiB used 787.94MiB path /dev/sdb
	devid    2 size 3.00GiB used 315.19MiB path /dev/sdc
	devid    3 size 4.00GiB used 775.94MiB path /dev/sdd

[root@localhost ~]# btrfs fi df /mnt
Data, RAID0: total=921.56MiB, used=256.00KiB
Data, single: total=8.00MiB, used=0.00
System, RAID1: total=8.00MiB, used=16.00KiB
System, single: total=4.00MiB, used=0.00
Metadata, RAID1: total=460.75MiB, used=112.00KiB
Metadata, single: total=8.00MiB, used=0.00
unknown, single: total=16.00MiB, used=0.00

[root@localhost ~]# btrfs balance start /mnt
Done, had to relocate 6 out of 6 chunks

[root@localhost ~]# btrfs fi show
Label: none  uuid: ff85abb0-3398-40a0-b06c-8146cb1bfda0
	Total devices 3 FS bytes used 384.00KiB
	devid    1 size 2.00GiB used 0.00 path /dev/sdb
	devid    2 size 3.00GiB used 288.00MiB path /dev/sdc
	devid    3 size 4.00GiB used 1.19GiB path /dev/sdd

[root@localhost ~]# btrfs fi df /mnt
Data, single: total=928.00MiB, used=256.00KiB
System, RAID1: total=32.00MiB, used=16.00KiB
Metadata, RAID1: total=256.00MiB, used=112.00KiB
unknown, single: total=16.00MiB, used=0.00


An unknown chunk type here too, exists even after a balance. Along with a weird allocation different merely due to balancing an empty file system.


Chris Murphy

Re: btrfs fi df "unknown" chunk type

[Duncan]

Chris Murphy posted on Sun, 20 Apr 2014 14:26:37 -0600 as excerpted:

> On Apr 20, 2014, at 2:18 PM, Chris Murphy <lists@colorremedies.com> wrote:
>> What is unknown?
> 
> 
> /dev/sd[bcd] are 2GB, 3GB, and 4GB respectively.
> 
> [root@localhost ~]# mkfs.btrfs -d raid0 -m raid1 /dev/sd[bcd]

[...]

> [root@localhost ~]# mount /dev/sdb /mnt
> [root@localhost ~]# btrfs fi show
> Label: none  uuid: ff85abb0-3398-40a0-b06c-8146cb1bfda0
> 	Total devices 3 FS bytes used 112.00KiB
> 	devid    1 size 2.00GiB used 787.94MiB path /dev/sdb
> 	devid    2 size 3.00GiB used 315.19MiB path /dev/sdc
> 	devid    3 size 4.00GiB used 775.94MiB path /dev/sdd
> 
> [root@localhost ~]# btrfs fi df /mnt
> Data, RAID0: total=921.56MiB, used=256.00KiB
> Data, single: total=8.00MiB, used=0.00
> System, RAID1: total=8.00MiB, used=16.00KiB
> System, single: total=4.00MiB, used=0.00
> Metadata, RAID1: total=460.75MiB, used=112.00KiB
> Metadata, single: total=8.00MiB, used=0.00
> unknown, single: total=16.00MiB, used=0.00

I have no clue /what/ that unknown is.  If I didn't see the
mkfs.btrfs right above, I'd guess it was filesystem damage
of some sort, but with the mkfs.btrfs, and with all three
devices very specifically trimmed, I haven't the foggiest.

Meanwhile...

> [root@localhost ~]# btrfs balance start /mnt
> Done, had to relocate 6 out of 6 chunks

Count.  There's 7 items listed above including unknown.
Only 6 of 6 chunks relocated.

Conclusion given the below, balance didn't touch that
unknown at all!

> [root@localhost ~]# btrfs fi show
> Label: none  uuid: ff85abb0-3398-40a0-b06c-8146cb1bfda0
> 	Total devices 3 FS bytes used 384.00KiB
> 	devid    1 size 2.00GiB used 0.00 path /dev/sdb
> 	devid    2 size 3.00GiB used 288.00MiB path /dev/sdc
> 	devid    3 size 4.00GiB used 1.19GiB path /dev/sdd
> 
> [root@localhost ~]# btrfs fi df /mnt
> Data, single: total=928.00MiB, used=256.00KiB
> System, RAID1: total=32.00MiB, used=16.00KiB
> Metadata, RAID1: total=256.00MiB, used=112.00KiB
> unknown, single: total=16.00MiB, used=0.00
> 
> 
> An unknown chunk type here too, exists even after a balance.
> Along with a weird allocation different merely due to
> balancing an empty file system.

As I concluded above, unknown untouched by the balance.

The different allocation (raid0 to single) with the
empty-filesystem balance is I believe a known issue.

Meanwhile, based on those numbers, we have

* data single 928 MiB, as one chunk on the 4G (largest) device

* system and metadata raid1 32 + 256 = 288 MiB on each of the
two largest devices (3G and 4G).

* 928 + 256 + 32 = 1216 MiB / 1024 = 1.1875 GiB
= show reported usage, 4G device

* 256 + 32 = 288 MiB, show reported usage, 3G device

* show doesn't seem to report the 16 MiB "unknown" on
any of the three



Out of curiosity...

What does a btrfs balance start -v (verbose) report?

What about btrfs scrub  start -BdR (no-background,
per-device, raw stats)?

What about btrfs check?  (Obviously without the --repair,
so it's read-only)

Of course both the command output and the related dmesg,
if any, for all the above.

And... given the existence of that strange unknown
even after the mkfs.btrfs trims... Does a badblocks
run (with either -n or -w and -v) turn up anything strange?

I'd ask about smartctl -A if it wasn't virtual...

-- 
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: btrfs fi df "unknown"

[Chris Mason]

On 04/20/2014 04:18 PM, Chris Murphy wrote:
> kernel 3.15.0-0.rc1.git0.1.fc21.x86_64
> btrfs-progs v3.14
> 
> One 80GB virtual disk, formatted btrfs by installer and Fedora Rawhide installed to it. Post-install I see:
> 
> [root@localhost ~]# btrfs fi show
> Label: 'fedora'  uuid: d372e5d1-386f-460c-b036-611469e0155e
> 	Total devices 1 FS bytes used 4.00GiB
> 	devid    1 size 79.31GiB used 6.04GiB path /dev/sda3
> 
> Btrfs v3.14
> [root@localhost ~]# btrfs fi df /
> Data, single: total=4.01GiB, used=3.79GiB
> System, DUP: total=8.00MiB, used=16.00KiB
> System, single: total=4.00MiB, used=0.00
> Metadata, DUP: total=1.00GiB, used=215.69MiB
> Metadata, single: total=8.00MiB, used=0.00
> unknown, single: total=80.00MiB, used=0.00
> 
> 
> What is unknown?
> 


3.15 has this commit, it's the cause of the unknown.  We'll roll the progs patch 
into the next progs release, but it's nothing at all to worry about.

-chris

Author: David Sterba <dsterba@suse.cz>
Date:   Fri Feb 7 14:34:12 2014 +0100

    btrfs: export global block reserve size as space_info
    
    Introduce a block group type bit for a global reserve and fill the space
    info for SPACE_INFO ioctl. This should replace the newly added ioctl
    (01e219e8069516cdb98594d417b8bb8d906ed30d) to get just the 'size' part
    of the global reserve, while the actual usage can be now visible in the
    'btrfs fi df' output during ENOSPC stress.
    
    The unpatched userspace tools will show the blockgroup as 'unknown'.
    
    CC: Jeff Mahoney <jeffm@suse.com>
    CC: Josef Bacik <jbacik@fb.com>
    Signed-off-by: David Sterba <dsterba@suse.cz>
    Signed-off-by: Chris Mason <clm@fb.com>

Re: btrfs fi df "unknown"

[Duncan]

Chris Mason posted on Mon, 21 Apr 2014 08:41:34 -0400 as excerpted:

> 3.15 has this commit, it's the cause of the unknown.

[Since I already replied to thread.]

That would explain why I haven't seen it yet.  I'm still running kernel 
3.14 as I'm trying to catch up on some other stuff before I upgrade to 
3.15-rc.  Tho I try to upgrade before rc4 at the latest, so if I spot any 
bugs I can report 'em with some time to fix before release.  Which gives 
me a week or so...

-- 
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