We need to pass the 'trim' requests through the copy-on-read filter so
if a user configures a discard policy on the disk the requests get
through to the appropriate format layer in the blockdev tree.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1986509
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
---
 src/qemu/qemu_block.c                                       | 1 +
 tests/qemuxml2argvdata/disk-copy_on_read.x86_64-latest.args | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_block.c b/src/qemu/qemu_block.c
index 1610f72d07..4691dff4f7 100644
--- a/src/qemu/qemu_block.c
+++ b/src/qemu/qemu_block.c
@@ -2157,6 +2157,7 @@ qemuBlockStorageGetCopyOnReadProps(virDomainDiskDef *disk)
                                           "s:driver", "copy-on-read",
                                           "s:node-name", priv->nodeCopyOnRead,
                                           "s:file", disk->src->nodeformat,
+                                          "s:discard", "unmap",
                                           NULL));

     return ret;
diff --git a/tests/qemuxml2argvdata/disk-copy_on_read.x86_64-latest.args b/tests/qemuxml2argvdata/disk-copy_on_read.x86_64-latest.args
index 93d3a06c88..690d4f3ea1 100644
--- a/tests/qemuxml2argvdata/disk-copy_on_read.x86_64-latest.args
+++ b/tests/qemuxml2argvdata/disk-copy_on_read.x86_64-latest.args
@@ -30,7 +30,7 @@ XDG_CONFIG_HOME=/tmp/lib/domain--1-test/.config \
 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x6 \
 -blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/f14.img","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-2-format","read-only":false,"driver":"qcow2","file":"libvirt-2-storage"}' \
--blockdev '{"driver":"copy-on-read","node-name":"libvirt-CoR-vda","file":"libvirt-2-format"}' \
+-blockdev '{"driver":"copy-on-read","node-name":"libvirt-CoR-vda","file":"libvirt-2-format","discard":"unmap"}' \
 -device virtio-blk-pci,bus=pci.0,addr=0x4,drive=libvirt-CoR-vda,id=virtio-disk0,bootindex=2 \
 -blockdev '{"driver":"file","filename":"/var/lib/libvirt/Fedora-14-x86_64-Live-KDE.iso","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"node-name":"libvirt-1-format","read-only":true,"driver":"raw","file":"libvirt-1-storage"}' \
-- 
2.31.1

On Wed, Jul 28, 2021 at 09:51:38AM +0200, Peter Krempa wrote:
> We need to pass the 'trim' requests through the copy-on-read filter so
> if a user configures a discard policy on the disk the requests get
> through to the appropriate format layer in the blockdev tree.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1986509
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Tested-by: Richard W.M. Jones <rjones@redhat.com>
> Signed-off-by: Peter Krempa <pkrempa@redhat.com>
> ---
>  src/qemu/qemu_block.c                                       | 1 +
>  tests/qemuxml2argvdata/disk-copy_on_read.x86_64-latest.args | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


Regards,
Daniel
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