[Bugs] [Bug 1591634] New: Snapshots fail when underlying bricks are btrfs

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1591634

            Bug ID: 1591634
           Summary: Snapshots fail when underlying bricks are btrfs
           Product: GlusterFS
           Version: 4.0
         Component: snapshot
          Severity: high
          Assignee: bugs at gluster.org
          Reporter: evili.del.rio at gmail.com
                CC: bugs at gluster.org



Created attachment 1451792
  --> https://bugzilla.redhat.com/attachment.cgi?id=1451792&action=edit
Relevant part of local node glusterd.log

Description of problem:

I have a disperse volume [1 x (4 + 2) = 6] with 3 servers 2 bricks each. Each  
brick is a thin LV with a BTRFS filesystem on it. When I try to make a gluster
snapshot of the volume:

gluster snapshot create web_data-24 web_data no-timestamp description
Backup_snapshot

it fails with the following error:

snapshot create: failed: Commit failed on localhost. Please check log file for
details.
Snapshot command failed

Then the local node has strange mounts on the volume bricks:

 /dev/mapper/vg_brickN-SOMEUUID_1

The other nodes on the cluster are unaffected.

If I make the same setup (servers, volume, mount points) but with xfs bricks
everything works as it should.

Version-Release number of selected component (if applicable):

4.0.2

How reproducible: Whenever there are btrfs bricks in a volume:

Steps to Reproduce:

1. Setup a gluster cluster.
2. For each node create 2 vg with 2 thin pools, and 2 thin volumes as stated in 
https://docs.gluster.org/en/latest/Administrator%20Guide/Managing%20Snapshots/
3. Mount all bricks
4. Create the volume:
gluster volume create web_data  redundancy 2
gluster0.storage:/srv/glusterfs/web/brick0/brick
gluster0.storage:/srv/glusterfs/web/brick3/brick
gluster1.storage:/srv/glusterfs/web/brick1/brick
gluster1.storage:/srv/glusterfs/web/brick4/brick 
gluster2.storage:/srv/glusterfs/web/brick2/brick
gluster2.storage:/srv/glusterfs/web/brick5/brick force
5. Try to make a snapshot:
gluster snapshot create web_data-24 web_data no-timestamp description
Backup_snapshot

Actual results: The snapshot fails on local node:
snapshot create: failed: Commit failed on localhost. Please check log file for
details.

And there are strange mounts on system like:

/dev/mapper/vg_web5-95d900edd0564a8296ea63bd6886ba73_1 on
/srv/glusterfs/web/brick5 type btrfs
(rw,noatime,nodiratime,seclabel,nobarrier,compress=lzo,space_cache,autodefrag,commit=60,subvolid=5,subvol=/)

instead of the original one:

/dev/mapper/vg_web5-brick on /srv/glusterfs/web/brick5 type btrfs
(rw,noatime,nodiratime,seclabel,nobarrier,compress=lzo,space_cache,autodefrag,commit=60,subvolid=5,subvol=/)

Expected results:
Creation of the gluster snapshot.

Additional info:

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