Hello,
I'm encountering weird enospc problem while writing to filesystem and
creating snapshot at a same time:
Steps to reproduce:
start writing data to filesystem:
# LC_ALL=C dd if=/dev/zero of=/foobar
dd: writing to '/foobar': No space left on device
3003803+0 records in
3003802+0 records out
1537946624 bytes (1.5 GB, 1.4 GiB) copied, 10.8072 s, 142 MB/s
in other terminal create read-only (or r/w - results are the same)
# btrfs sub snap -r / /.snap1
Create a readonly snapshot of '/' in '//.snap1'
while creating this snapshot, ENOSPC is produced.
Interesting is that I can reproduce this on some filesystems but not on
others while all of available information are the same. There IS free
space in data, metadata and global reserve.
I've tried balancing and defragmenting with no success. I've tried
debugging by using enospc_debug but nothing is written to dmesg or any
system log
Does anybody have a clue what may be the cause?
# uname -a
Linux interceptor 4.4.3-1-ARCH #1 SMP PREEMPT Fri Feb 26 15:09:29 CET
2016 x86_64 GNU/Linux
# btrfs --version
btrfs-progs v4.4.1
# btrfs fi show
Label: none uuid: 859dec5c-850c-4660-ad99-bc87456aa309
Total devices 1 FS bytes used 116.72GiB
devid 1 size 200.00GiB used 121.03GiB path
/dev/mapper/vg0-btrfsroot
# btrfs fi df /
Data, single: total=117.00GiB, used=113.68GiB
System, single: total=32.00MiB, used=16.00KiB
Metadata, single: total=4.00GiB, used=3.04GiB
GlobalReserve, single: total=512.00MiB, used=0.00B
# dmesg | tail
[ 15.618995] cfg80211: DFS Master region: ETSI
[ 15.618996] cfg80211: (start_freq - end_freq @ bandwidth),
(max_antenna_gain, max_eirp), (dfs_cac_time)
[ 15.618998] cfg80211: (2400000 KHz - 2483500 KHz @ 40000 KHz),
(N/A, 2000 mBm), (N/A)
[ 15.619000] cfg80211: (5150000 KHz - 5250000 KHz @ 80000 KHz,
200000 KHz AUTO), (N/A, 2301 mBm), (N/A)
[ 15.619001] cfg80211: (5250000 KHz - 5350000 KHz @ 80000 KHz,
200000 KHz AUTO), (N/A, 2000 mBm), (0 s)
[ 15.619002] cfg80211: (5470000 KHz - 5725000 KHz @ 160000 KHz),
(N/A, 2698 mBm), (0 s)
[ 15.619003] cfg80211: (57000000 KHz - 66000000 KHz @ 2160000 KHz),
(N/A, 4000 mBm), (N/A)
[ 15.792765] brcmsmac bcma0:1: brcms_ops_bss_info_changed: arp
filtering: 1 addresses (implement)
[ 20.411931] tun: Universal TUN/TAP device driver, 1.6
[ 20.411938] tun: (C) 1999-2004 Max Krasnyansky <m...@qualcomm.com>
# mount | grep root
/dev/mapper/vg0-btrfsroot on / type btrfs
(rw,noatime,nodatasum,nodatacow,ssd,discard,space_cache,enospc_debug,commit=900,subvolid=5,subvol=/)
Thanks for any insight!
Best regards,
Martin Mlynar
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