test-script.sh fails 1/11: Failed to run synchronizer: Operation not supported

[martinpitt]

I'm testing current casync git master on current Debian unstable. Building is fine and it generally works, but ninja -C build test fails: one test:

 1/11 test-script.sh                          FAIL    40.53 s
[...]
+ /home/martin/upstream/casync/build/casync -v --without=privileged extract /var/tmp/test-casync.25039/test.caidx --seed=/var/tmp/test-casync.25039/extract-caidx /
var/tmp/test-casync.25039/extract-caidx2
[...]
Can't reproduce name table for GOODBYE record, ignoring.
Extracting casync/.git/logs/refs/remotes
Extracting casync/.git/logs/refs/remotes/origin
Extracting casync/.git/logs/refs/remotes/origin/HEAD
Extracted casync/.git/logs/refs/remotes/origin/HEAD
Extracted casync/.git/logs/refs/remotes/origin
Extracted casync/.git/logs/refs/remotes
Extracted casync/.git/logs/refs
Extracted casync/.git/logs
Extracting casync/.git/objects
Extracting casync/.git/objects/info
Extracted casync/.git/objects/info
Extracting casync/.git/objects/pack
Extracting casync/.git/objects/pack/pack-7fd33197e2a8fce8f83843897392f59b4933d3fb.idx
Extracted casync/.git/objects/pack/pack-7fd33197e2a8fce8f83843897392f59b4933d3fb.idx
Failed to run synchronizer: Operation not supported

[martinpitt]

The test keeps the temp files around, so I can run this manually. stracing it says:

$ strace -fvvs1024 /home/martin/upstream/casync/build/casync -v --without=privileged extract /var/tmp/test-casync.25039/test.caidx --seed=/var/tmp/test-casync.25039/extract-caidx /var/tmp/test-casync.25039/extract-caidx2

29292 openat(21, ".#pack-7fd33197e2a8fce8f83843897392f59b4933d3fb.idx16ff5668928d5fa4", O_WRONLY|O_CREAT|O_EXCL|O_NOCTTY|O_NOFOLLOW|O_CLOEXEC, 0100666) = 25
[...]
29292 ioctl(25, BTRFS_IOC_CLONE_RANGE or FICLONERANGE, {src_fd=23, src_offset=16384, src_length=8192, dest_offset=16384}) = -1 EOPNOTSUPP (Operation not supported)

This happens in a chroot which is on a tmpfs (within the host's /tmp).

[martinpitt]

This also happens in PPA builds which most likely don't have /tmp or /var/tmp/ on tmpfs. Does this maybe only work with /var/tmp/ being on btrfs?

[poettering]

Ah, thanks for the bug report. I figure there might be a fallback missing for the case where the backing fs doesn't do reflinks...