corruption with btrfs on nocow loop file

corruption with btrfs on nocow loop file

[Jan Killius]

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Hello,
I get corruption with btrfs in a loop device with linux-3.16.3
(https://git.kernel.org/cgit/linux/kernel/git/mason/linux-btrfs.git/
for-linus applied).
I never had a problem with this setup until 3.16.

This happened just after unpacking a few thousand small files and
reading them back with an IDE (phpstorm).
The loop file is a 50GB nocow file with LUKS on it.

mount options for the main btrfs filesystem:
/dev/sda2 on / type btrfs
(rw,noatime,compress-force=lzo,ssd,discard,noacl,space_cache)
mount options for the loop device:
/dev/mapper/myvolume on /mnt/volume type btrfs
(rw,noatime,compress-force=lzo,ssd,noacl,space_cache)



btrfsck:
Checking filesystem on /dev/mapper/npoa
UUID: 3a869f74-2a05-4ea2-9950-a6be5e4a9691
checking extents
checking free space cache
checking fs roots
checking csums
checking root refs
found 197030750 bytes used err is 0
total csum bytes: 1245628
total tree bytes: 133332992
total fs tree bytes: 127696896
total extent tree bytes: 3997696
btree space waste bytes: 22086930
file data blocks allocated: 1277382656
referenced 2252468224
Btrfs v0.20-rc1-592-ge11a9ae-dirty

I also got a btrfs-image of the loop file system if needed.
If more information's are needed to investigate the issue just ask.



Kindly regards
Jan Killius

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