On 2012-10-14 20:35, Tommy Pettersson wrote:
The problem has been resolved, but I think it will be impossible
to figure out what went wrong. The root cause was I accidentally
messed up my initrd so that btrfs was mounted without prior dev
scan (which I think didn't work with earlier kernels, but now
(3.4.9-gentoo) it "worked" in a very bad way it seems), and
possibly that I also mounted subvolid=0 (containing the subvol I
previously mounted as / ) with conflicting mount options for
space_cache.
This is a very strange behaviour; I am not aware of any bug which could
justify this.
But after I had realized and fixed that, it was too late. Both
Scrub and Balance, and reading from the filesystem, behaved
strange. The output of df jumped between 95 % and 12 %, while I
got many lines about wrong checksums, unexpected tree parent
generation something, and free space inode generation (0) did
not match free space cache. It sometimes said it corrected
things, but it didn't seem to help, and at random points I would
get a kernel panic.
# uname -a
Linux fruit64 3.4.9-gentoo #2 SMP PREEMPT Sat Sep 1 17:34:38 CEST 2012 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ AuthenticAMD GNU/Linux
The 3.4.9 is a quite old kernel. I am guessing if a recent kernel would
still behave as you described.
# btrfs --version
Btrfs Btrfs v0.19
It would have been nice to debug this mess so that btrfs could
handled it in the future, and not do all the strange things with
the free space and cause kernel panics, but I had to get my
system back up.
The good news is that even this torture of my bits didn't
actually kill them. I eventually cleared the btrfs master record
on one of the disks, mounted in degraded mode, added it back,
waited seven hours for balance to finish, and now my filesystem
is consistent again, and everything is back to normal. So no
need to restore from my daily backup yet. :-)
Good !
Regards,
Tommy
On Sun, Oct 14, 2012 at 06:11:58PM +0200, Goffredo Baroncelli wrote:
Hi,
did you used the latest kernel version ?
The other thing that you could try is a scrub looking for a defective
page.. but I don't think so....
BR
G.Baroncelli
On 2012-10-14 02:19, Tommy Pettersson wrote:
Hi,
(I'm not subscribed to the list, so please CC me.)
I have a btrfs with raid1 on two identical unpartitioned disks.
Today I noticed that df (normal df) said I am 77 % full. This
was a chock, because since forever it has been around 12 %.
# btrfs fi show
Label: 'green' uuid: dd83031c-2447-4736-a8f6-9bd9cdeea879
Total devices 2 FS bytes used 212.88GB
devid 2 size 1.82TB used 356.04GB path /dev/sdb
devid 1 size 1.82TB used 356.06GB path /dev/sda
# btrfs fi df /
Data, RAID1: total=276.00GB, used=209.02GB
Data: total=8.00M, used=0.00
System, RAID1: total=40.00MB, used=64.00KB
System: total=4.00MB, used=0.00
Metadata, RAID1: total=80.00GB, used=3.88GB
Metadata: total=8.00MB, used=0.00
# df -h
Filesystem Size Used Avail Use% Mounted on
rootfs 3.7T 426G 134G 77% /
The thing that has drastically changed is Avail in the output
from df.
I tried a btrfs balance, which self-aborted after some hours
with No space left on device. I deleted two snapshots, so I got
some free space and could use the system again.
The balance, although it didn't finish, seems to have reduced
the used space, but it also reduced the "available" space:
# btrfs fi show
Label: 'green' uuid: dd83031c-2447-4736-a8f6-9bd9cdeea879
Total devices 2 FS bytes used 212.88GB
devid 2 size 1.82TB used 356.04GB path /dev/sdb
devid 1 size 1.82TB used 215.01GB path /dev/sda
# btrfs fi df /
Data, RAID1: total=210.00GB, used=197.97GB
System, RAID1: total=8.00MB, used=44.00KB
System: total=4.00MB, used=0.00
Metadata, RAID1: total=5.00GB, used=3.41GB
# df -h
Filesystem Size Used Avail Use% Mounted on
rootfs 3.7T 403G 25G 95% /
I made an unqualified guess that the space cache was corrupted,
and tried to mount with option clear_cache and nospace_cache.
Both of them caused btrfs to scan my disks for a couple of
minutes at boot, but the amount of available space did not
improve.
What can I do to help locate the cause of this problem?
Regards,
Tommy
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