Hi,
I tried just what you did, and use "btrfs receive --dump" to exam the
send stream.
And things works quite well:
$ sudo mount /dev/sda6 /mnt/btrfs/
$ sudo btrfs subvolume create /mnt/btrfs/subv1
$ sudo xfs_io -f -c "pwrite 0 2M" /mnt/btrfs/subv1/file1
$ sudo xfs_io -f -c "reflink /mnt/btrfs/subv1/file1 0 0 2M"
/mnt/btrfs/subv1/file1.ref
$ sudo btrfs subv snap -r /mnt/btrfs/subv1/ /mnt/btrfs/ro_snap
$ sudo btrfs send /mnt/btrfs/ro_snap/ > /tmp/output
$ sudo btrfs receive --dump < /tmp/output
And the output shows like this:
subvol ./ro_snap
uuid=e788bb6e-8ec6-dd47-a452-e26196d22699 transid=9
chown ./ro_snap/ gid=0 uid=0
chmod ./ro_snap/ mode=755
utimes ./ro_snap/
atime=2016-12-29T13:46:00+0800 mtime=2016-12-29T13:46:50+0800
ctime=2016-12-29T13:46:50+0800
mkfile ./ro_snap/o257-8-0rename ./ro_snap/o257-8-0
dest=./ro_snap/file1
utimes ./ro_snap/
atime=2016-12-29T13:46:00+0800 mtime=2016-12-29T13:46:50+0800
ctime=2016-12-29T13:46:50+0800
write ./ro_snap/file1 offset=0 len=49152
write ./ro_snap/file1 offset=49152 len=49152
<snip normal write for file1>
write ./ro_snap/file1 offset=2064384 len=32768
truncate ./ro_snap/file1 size=2097152
chown ./ro_snap/file1 gid=0 uid=0
chmod ./ro_snap/file1 mode=600
utimes ./ro_snap/file1
atime=2016-12-29T13:46:24+0800 mtime=2016-12-29T13:46:24+0800
ctime=2016-12-29T13:46:24+0800
mkfile ./ro_snap/o258-8-0rename ./ro_snap/o258-8-0
dest=./ro_snap/file1.ref
utimes ./ro_snap/
atime=2016-12-29T13:46:00+0800 mtime=2016-12-29T13:46:50+0800
ctime=2016-12-29T13:46:50+0800
clone ./ro_snap/file1.ref offset=0 len=2097152
from=./ro_snap/file1 clone_offset=0
^^^ Here is the clone operation
truncate ./ro_snap/file1.ref size=2097152
chown ./ro_snap/file1.ref gid=0 uid=0
chmod ./ro_snap/file1.ref mode=600
utimes ./ro_snap/file1.ref
atime=2016-12-29T13:46:50+0800 mtime=2016-12-29T13:47:07+0800
ctime=2016-12-29T13:47:07+0800
And in fact, btrfs send can even handle reflink to parent subvolume.
(Although this behavior can be deadly for heavily reflinked files)
So, would you please upload the send stream for us to check?
Thanks,
Qu
At 12/29/2016 10:44 AM, Glenn Washburn wrote:
I'm having a hard time getting btrfs receive to create reflinked files
and have a trivial example that I believe *should* work but doesn't.
I've attached a script that I used to perform this test, so others can
try to reproduce. The text file is the output of the shell script
except the last command, which is a tool I wrote to print the extent
info from FIEMAP. "btrfs fi du" would work just as well, but I'm on
Ubuntu 16.04, whose btrfs progs doesn't have that command yet. I've
also tested on Ubuntu 16.10 with similar results, except that "btrfs fi
du" is on that version and confirms what my tool displays.
So, can send not do what I'm trying to get it to do? If it can now,
when did that feature get introduced (must have been after kernel
4.8)? I'm very surprised that this feature wouldn't have already
been done and if not that no one seems to be complaining about it. I've
done a decent amount of searching on this and have come up with
nothing. Any help would be greatly appreciated.
Thanks,
Glenn
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