Please attach the complete virt-v2v -v -x output.

Actually forget that, this is fixed upstream already:

https://github.com/libguestfs/libguestfs/commit/738c3bf4fdce569858369b2d2ce3879bf4b75f50

I can reproduce this bug with below builds:
virt-v2v-1.32.7-3.el7_3.2.x86_64
libguestfs-1.32.7-3.el7_3.2.x86_64
libvirt-2.0.0-10.el7_3.4.x86_64
qemu-kvm-rhev-2.6.0-28.el7_3.3.x86_64

Reproduce steps:
1.Prepare a linux guest on ESXi6.0 host and add below to /etc/fatab

/dev/sda4 /home btrfs rw,user,subvol=foo 0 0

2.Use virt-v2v convert this guest to kvm
# virt-v2v -ic vpx://root.75.182/data/10.73.72.61/?no_verify=1 mxie-rhel6.8 --password-file /tmp/passwd
[   0.0] Opening the source -i libvirt -ic vpx://root.75.182/data/10.73.72.61/?no_verify=1 mxie-rhel6.8
[   1.2] Creating an overlay to protect the source from being modified
[   1.9] Initializing the target -o libvirt -os default
[   1.9] Opening the overlay
[  14.8] Inspecting the overlay
virt-v2v: error: libguestfs error: aug_get: aug_get: 
/files/etc/fstab/8/opt: Too many matches for path expression: There are 3 
nodes matching /files/etc/fstab/8/opt

If reporting bugs, run virt-v2v with debugging enabled and include the 
complete output:

  virt-v2v -v -x [...]

Verify the bug with builds:
virt-v2v-1.36.1-1.el7.x86_64
libguestfs-1.36.1-1.el7.x86_64
libvirt-3.1.0-1.el7.x86_64
qemu-kvm-1.5.3-132.el7.x86_64

Steps:
Scenario1:
1.Prepare a linux guest on ESXi6.0 host and add below to /etc/fatab
/dev/sda4 /home btrfs rw,user,subvol 0 0

2.Use virt-v2v convert this guest to kvm, but the conversion is failed with below error, details pls refer to virt-v2v-1.36.1-1.log
# virt-v2v -ic vpx://root.75.182/data/10.73.72.61/?no_verify=1 mxie-rhel6.8 --password-file /tmp/passwd
[   0.0] Opening the source -i libvirt -ic vpx://root.75.182/data/10.73.72.61/?no_verify=1 mxie-rhel6.8
[   1.2] Creating an overlay to protect the source from being modified
[   1.8] Initializing the target -o libvirt -os default
[   1.8] Opening the overlay
[  14.4] Inspecting the overlay
virt-v2v: error: libguestfs error: aug_get: no matching node

If reporting bugs, run virt-v2v with debugging enabled and include the 
complete output:

  virt-v2v -v -x [...]


Scenario2:
1.Prepare a linux guest on ESXi6.0 host and add below to /etc/fatab
/dev/sda4 /home btrfs rw,user,subvol=foo 0 0

2.Use virt-v2v convert this guest to kvm, the conversion can be finished but with warning
#  virt-v2v -ic vpx://root.75.182/data/10.73.72.61/?no_verify=1 mxie-rhel6.8 --password-file /tmp/passwd
[   0.0] Opening the source -i libvirt -ic vpx://root.75.182/data/10.73.72.61/?no_verify=1 mxie-rhel6.8
[   1.3] Creating an overlay to protect the source from being modified
[   1.9] Initializing the target -o libvirt -os default
[   1.9] Opening the overlay
[  14.3] Inspecting the overlay
virt-v2v: warning: mount: mount_stub: btrfsvol:/dev/sda4/foo: expecting a 
btrfs volume (ignored)
[  99.8] Checking for sufficient free disk space in the guest
[  99.8] Estimating space required on target for each disk
[  99.8] Converting Red Hat Enterprise Linux Server release 6.8 (Santiago) to run on KVM
virt-v2v: This guest has virtio drivers installed.
[ 786.2] Mapping filesystem data to avoid copying unused and blank areas
[ 787.4] Closing the overlay
[ 787.5] Checking if the guest needs BIOS or UEFI to boot
[ 787.5] Assigning disks to buses
[ 787.5] Copying disk 1/1 to /var/lib/libvirt/images/mxie-rhel6.8-sda (raw)
    (100.00/100%)
[ 936.4] Creating output metadata
Pool default refreshed

Domain mxie-rhel6.8 defined from /tmp/v2vlibvirtc26e53.xml

[ 936.5] Finishing off


Hi rjones,
Could you help to see scenario1, why the conversion will be failed when not set subvol=foo in guest's /etc/fstab?

pls also help see the warning in scenario2, whether the warning is accepted?
Thanks

Created attachment 1261074 [details]
virt-v2v-1.36.1-1.log

> /dev/sda4 /home btrfs rw,user,subvol 0 0

is incorrect syntax (it should always be subvol=PATH), so
virt-v2v is entitled to fail on this.

The error message (from lib/inspect-fs-unix.c:check_fstab)
isn't that great, but with the virt-v2v -v -x output it would
be trivial to see why it's failing so debugging this wouldn't
be too hard.

Thanks for Richard's explanation, I just got the meaning of the line "/dev/sda4 /home btrfs rw,user,subvol=foo 0 0"


Verify the bug with builds again:
virt-v2v-1.36.2-1.el7.x86_64
libguestfs-1.36.2-1.el7.x86_64
libvirt-3.1.0-2.el7.x86_64
qemu-kvm-rhev-2.8.0-6.el7.x86_64

Steps:
1.Install a rhel7 guest and configure the /home as a single partition and device type is btrfs

2.Check the /etc/fstab after finishing os installation
#cat fstab 
....
UUID=b138e4bc-c35c-4917-976a-a00135b3d3e1 /                       ext4    defaults        1 1
UUID=23d0f88f-a199-418d-9e68-cfd9ad35b332 /home                   btrfs   subvol=home     0 0
UUID=5ead36b0-9556-49c3-81a1-01b7f560126f swap                    swap    defaults        0 0

3.Because /home is mounted by /dev/sda2, add below line into /etc/fstab

/dev/sda2  /home btrfs	rw,root,subvol=foo 0 0

4.Guest could rebooted normally after editting /etc/fstab

5.Power off the guest and then using virt-v2v convert the guest to rhvm,the conversion could be finished but with warning 

# virt-v2v rhel7.3 -o rhv -os 10.73.131.93:/home/nfs_export -on foo
[   0.0] Opening the source -i libvirt rhel7.3
[   0.0] Creating an overlay to protect the source from being modified
[   0.2] Initializing the target -o rhv -os 10.73.131.93:/home/nfs_export
[   0.4] Opening the overlay
[  15.4] Inspecting the overlay
virt-v2v: warning: mount: /dev/sda2 on /home (options: ''): mount: mount(2) 
failed: No such file or directory (ignored)
[  32.3] Checking for sufficient free disk space in the guest
[  32.3] Estimating space required on target for each disk
[  32.3] Converting Red Hat Enterprise Linux Server 7.3 (Maipo) to run on KVM
virt-v2v: This guest has virtio drivers installed.
[ 105.6] Mapping filesystem data to avoid copying unused and blank areas
[ 105.7] Closing the overlay
[ 105.8] Checking if the guest needs BIOS or UEFI to boot
[ 105.8] Assigning disks to buses
[ 105.8] Copying disk 1/1 to /tmp/v2v.hUiFiT/165c1942-70e7-4691-aa63-9184a0569bf2/images/085112d2-9901-4a4a-8da3-9f36a2b5ea18/b2c6f33f-a866-42c3-8fc6-b273531f07fa (qcow2)
    (100.00/100%)
[ 538.4] Creating output metadata
[ 538.5] Finishing off

6.Import the guest from export domain to data domain, power on the guest and checkpoints of guest are passed


Hi rjones,

Could you pls help check whether verify steps are enough and warning of conversion is correct?

Thanks

Looks good to me.

According to comment 9 and comment 10, move the bug from ON_QA to VERIFIED

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2017:2023