[Bug 1523246] Re: Virtio-blk does not support TRIM

[mohammadreza nasrabadi]

On which version of qemu the discard option is supported?

I have emulated a VM with below qemu options related to disk type:

-drive file=disk.img,if=none,id=disk0,l2-cache-
size=8M,format=qcow2,discard=on,detect-zeroes=unmap,aio=io_uring -device
virtio-blk-pci,drive=disk0,scsi=off,bootindex=2

the disk file on the host side is located on xfs mountpoint on RAID
level 10 array.

After I downloaded a file with 1GB size on the guest OS, I saw the size
of the disk file on the host has been increased as well.

But when I delete the downloaded file and issue fstrim --all -v command,
the disk file on host has not been decreased.

The version of qemu I'm using is 5.2.0

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https://bugs.launchpad.net/bugs/1523246

Title:
  Virtio-blk does not support TRIM

Status in QEMU:
  Fix Released

Bug description:
  When model=virtio is used, TRIM is not supported.

  # mount -o discard /dev/vda4 /mnt
  # mount | tail -1
  /dev/vda4 on /mnt type fuseblk 
(rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other,blksize=4096)
  # fstrim /mnt/
  fstrim: /mnt/: the discard operation is not supported

  Booting without model=virtio allows using TRIM (in Windows as well).

  Full QEMU line:

  qemu-system-x86_64 -enable-kvm -cpu host -bios
  /usr/share/ovmf/ovmf_x64.bin -smp 2 -m 7G -vga qxl -usbdevice tablet
  -net nic,model=virtio -net user -drive discard=unmap,detect-
  zeroes=unmap,cache=none,file=vms/win10.hd.img.vmdk,format=vmdk,if=virtio

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