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
Attachment:
sending-reflinked-files.sh
Description: application/shellscript
+ BVOL1=/media/tmp1 + BVOL2=/media/tmp2 + uname -a Linux crass-Ideapad-Z570 4.4.0-53-generic #74-Ubuntu SMP Fri Dec 2 15:59:10 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux + btrfs --version btrfs-progs v4.4 + cd /media/tmp1 + btrfs sub create C Create subvolume './C' + dd if=/dev/urandom of=C/test count=100 100+0 records in 100+0 records out 51200 bytes (51 kB, 50 KiB) copied, 0.00485396 s, 10.5 MB/s + cp --reflink=always -vp C/test C/test.ref 'C/test' -> 'C/test.ref' + btrfs property set C ro true + btrfs send -v C + btrfs receive /media/tmp2 At subvol C BTRFS_IOC_SEND returned 0 joining genl thread At subvol C + ~/development/reflink_tools.git/fmaptool.py print -P C/test C/test.ref /media/tmp2/C/test /media/tmp2/C/test.ref C/test ------ 0+53248: 12845056 C/test.ref ---------- 0+53248: 12845056 /media/tmp2/C/test ------------------ 0+49152: NULL 49152+4096: 12845056 /media/tmp2/C/test.ref ---------------------- 0+49152: NULL 49152+4096: 12849152
