On 10/10/2018 10:51 PM, Chris Murphy wrote:
On Wed, Oct 10, 2018 at 8:12 PM, Larkin Lowrey
<llowrey@xxxxxxxxxxxxxxxxx> wrote:
On 10/10/2018 7:55 PM, Hans van Kranenburg wrote:
On 10/10/2018 07:44 PM, Chris Murphy wrote:
I'm pretty sure you have to umount, and then clear the space_cache
with 'btrfs check --clear-space-cache=v1' and then do a one time mount
with -o space_cache=v2.
The --clear-space-cache=v1 is optional, but recommended, if you are
someone who do not likes to keep accumulated cruft.
The v2 mount (rw mount!!!) does not remove the v1 cache. If you just
mount with v2, the v1 data keeps being there, doing nothing any more.
Theoretically I have the v2 space_cache enabled. After a clean umount...
# mount -onospace_cache /backups
[ 391.243175] BTRFS info (device dm-3): disabling free space tree
[ 391.249213] BTRFS error (device dm-3): cannot disable free space tree
[ 391.255884] BTRFS error (device dm-3): open_ctree failed
"free space tree" is the v2 space cache, and once enabled it cannot be
disabled with nospace_cache mount option. If you want to run with
nospace_cache you'll need to clear it.
# mount -ospace_cache=v1 /backups/
mount: /backups: wrong fs type, bad option, bad superblock on
/dev/mapper/Cached-Backups, missing codepage or helper program, or other
error
[ 983.501874] BTRFS info (device dm-3): enabling disk space caching
[ 983.508052] BTRFS error (device dm-3): cannot disable free space tree
[ 983.514633] BTRFS error (device dm-3): open_ctree failed
You cannot go back and forth between v1 and v2. Once v2 is enabled,
it's always used regardless of any mount option. You'll need to use
btrfs check to clear the v2 cache if you want to use v1 cache.
# btrfs check --clear-space-cache v1 /dev/Cached/Backups
Opening filesystem to check...
couldn't open RDWR because of unsupported option features (3).
ERROR: cannot open file system
You're missing the '=' symbol for the clear option, that's why it fails.
# btrfs check --clear-space-cache=v2 /dev/Cached/Backups
Opening filesystem to check...
Checking filesystem on /dev/Cached/Backups
UUID: acff5096-1128-4b24-a15e-4ba04261edc3
Clear free space cache v2
Segmentation fault (core dumped)
[ 109.686188] btrfs[2429]: segfault at 68 ip 0000555ff6394b1c sp
00007ffcc4733ab0 error 4 in btrfs[555ff637c000+ca000]
[ 109.696732] Code: ff e8 68 ed ff ff 8b 4c 24 58 4d 8b 8f c7 01 00 00
4c 89 fe 85 c0 0f 44 44 24 40 45 31 c0 89 44 24 40 48 8b 84 24 90 00 00
00 <8b> 40 68 49 29 87 d0 00 00 00 6a 00 55 48 8b 54 24 18 48 8b 7c 24
That's btrfs-progs v4.17.1 on 4.18.12-200.fc28.x86_64.
I appreciate the help and advice from everyone who has contributed to
this thread. At this point, unless there is something for the project to
gain from tracking down this trouble, I'm just going to nuke the fs and
start over.
--Larkin
