Re: [PATCH] btrfs: do not zero f_bavail if we have available space

Marc MERLIN
2020-02-20T21:46:58Z

Well, turns out this was a more serious bug than we thought.
With dm-thin overcommit, it causes this:
[1324107.675334] BTRFS info (device dm-13): forced readonly
[1324107.692909] BTRFS warning (device dm-13): Skipping commit of aborted transaction.
[1324107.717141] BTRFS: error (device dm-13) in cleanup_transaction:1828: errno=-5 IO failure
[1324107.743298] BTRFS info (device dm-13): delayed_refs has NO entry
[1324107.817671] device-mapper: thin: 252:9: switching pool to write mode
[1324108.662095] BTRFS error (device dm-13): bad tree block start, want 9050645626880 have 0
[1324108.694286] BTRFS error (device dm-13): bad tree block start, want 9050645626880 have 0

In other words, this broke my filesystem. I didn't try to see if it's damaged or just read-only,
but obviously, this isn't good.

New kernel should stop this from happening hopefully.

VG/dm details if you care:
VG Name vgds2
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 88
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 8
Open LV 7
Max PV 0
Cur PV 1
Act PV 1
VG Size 14.55 TiB
PE Size 4.00 MiB
Total PE 3815316
Alloc PE / Size 3801146 / 14.50 TiB
Free PE / Size 14170 / 55.35 GiB
VG UUID pc1cTH-kFo7-g0Kz-dELp-j51s-1yOO-v20WIV

--- Logical volume ---
LV Name thinpool2
VG Name vgds2
LV UUID rxJCsT-ImNv-ibvM-zOS0-Xzqv-O8AU-1STUH9
LV Write Access read/write
LV Creation host, time gargamel.svh.merlins.org, 2018-07-26 08:42:51 -0700
LV Pool metadata thinpool2_tmeta
LV Pool data thinpool2_tdata
LV Status available
# open 8
LV Size 14.50 TiB
Allocated pool data 99.99%
Allocated metadata 59.88%
Current LE 3801088
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 252:9

LV Path /dev/vgds2/ubuntu
LV Name ubuntu
VG Name vgds2
LV UUID y42AA8-5zfq-Vbmr-TNo9-g7rn-UbGf-KOnFrf
LV Write Access read/write
LV Creation host, time gargamel.svh.merlins.org, 2018-07-26 23:22:18 -0700
LV Pool name thinpool2
LV Status available
# open 1
LV Size 14.00 TiB
Mapped size 60.26%
Current LE 3670016
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 252:13

--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.

Home page: http://marc.merlins.org/ | PGP 7F55D5F27AAF9D08