The warning is only emitted when in verbose mode (which was
the precise fix for bug 1168144).  The current code is:

        try g#fstrim "/"
        with G.Error msg ->
          (* Only emit this warning when debugging, because otherwise
           * it causes distress (RHBZ#1168144).
           *)
          if verbose () then
            warning (f_"%s (ignored)") msg

If this warning is hidden when not verbose, then this is NOTABUG.

(In reply to Richard W.M. Jones from comment #2)
> The warning is only emitted when in verbose mode (which was
> the precise fix for bug 1168144).  The current code is:
> 
>         try g#fstrim "/"
>         with G.Error msg ->
>           (* Only emit this warning when debugging, because otherwise
>            * it causes distress (RHBZ#1168144).
>            *)
>           if verbose () then
>             warning (f_"%s (ignored)") msg
> 
> If this warning is hidden when not verbose, then this is NOTABUG.

From https://bugzilla.redhat.com/show_bug.cgi?id=1167623#c12,"Enable server-side debugging" button is removed.

So I just launch virt-p2v client and use the default configuration,the warning info shows just in the virt-p2v client.I think the info shows on virt-p2v client is not in debug mode,the log from virt-p2v server is in debug mode.

Pls check the screenshot from virt-p2v client.

Created attachment 1190321 [details]
screenshot from virt-p2v client

OK I see this is a virt-p2v transfer.  Yes, debugging is
always enabled "behind the scenes" now.

This warning indicates a real problem.  During any conversion
the fstrim is used to reduce the amount of data that needs to
be copied.  If the fstrim cannot be done then conversion will
run more slowly (in some cases much much more slowly).

Perhaps we should always display the warning (reverting
bug 1168144) but change the wording to make it clear what
is happening.

Patches posted:

https://www.redhat.com/archives/libguestfs/2016-August/thread.html#00087

Note this reverts the fix for bug 1168144.  The warning is
always enabled with these patches.

This warning also will be shown when convert rhel7.3-sata-uefi host to libvirt by virt-p2v

Upstream:
https://github.com/libguestfs/libguestfs/commit/66816e11332b07a07efd6821e7ecf090691ce441
https://github.com/libguestfs/libguestfs/commit/dd22e376c4ec8fd7c78c78f94c60bb763ddcf08f

I can reproduce the bug as comment7 said

Verify this bug with below builds:
virt-v2v-1.32.7-2.el7.x86_64
libguestfs-1.32.7-2.el7.x86_64
virt-p2v-1.32.7-2.el7.x86_64


Steps:

1.Convert uefi guest from vmware to libvirt
# virt-v2v -ic vpx://root.145.47/data/10.73.3.19/?no_verify=1 juzhou-test-efi -of qcow2 --password-file /tmp/passwd
[   0.0] Opening the source -i libvirt -ic vpx://root.145.47/data/10.73.3.19/?no_verify=1 juzhou-test-efi
[   0.8] Creating an overlay to protect the source from being modified
[   1.5] Initializing the target -o libvirt -os default
[   1.5] Opening the overlay
[  23.0] Inspecting the overlay
[  83.2] Checking for sufficient free disk space in the guest
[  83.2] Estimating space required on target for each disk
[  83.2] Converting Windows Server 2012 R2 Standard to run on KVM
virt-v2v: warning: there is no QXL driver for this version of Windows (6.3 
x86_64).  virt-v2v looks for this driver in /usr/share/virtio-win

The guest will be configured to use a basic VGA display driver.
virt-v2v: This guest has virtio drivers installed.
[  93.4] Mapping filesystem data to avoid copying unused and blank areas
virt-v2v: warning: fstrim on guest filesystem /dev/sda2 failed.  Usually 
you can ignore this message.  To find out more read "Trimming" in 
virt-v2v(1).

Original message: fstrim: fstrim: /sysroot/: the discard operation is not 
supported
[  94.0] Closing the overlay
[  94.0] Checking if the guest needs BIOS or UEFI to boot
virt-v2v: This guest requires UEFI on the target to boot.
[  94.0] Assigning disks to buses
[  94.0] Copying disk 1/1 to /var/lib/libvirt/images/juzhou-test-efi-sda (qcow2)
    (100.00/100%)
[ 596.7] Creating output metadata
Pool default refreshed

Domain juzhou-test-efi defined from /tmp/v2vlibvirtb2b963.xml

[ 597.1] Finishing off

2.Convert rhel7.3-sata-uefi host to libvirt by virt-p2v, the warning about  fstrim shows as step1

Hi rjones,

Why need to reserve original message: fstrim: fstrim: /sysroot/: the discard operation is not supported in warning? 

Thanks

I don't want to lose the original error message.  It might be something
important.

According to comment 10 and comment 11, move this 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://rhn.redhat.com/errata/RHSA-2016-2576.html