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+x86: 0.512
+graphic: 0.496
+device: 0.409
+performance: 0.386
+architecture: 0.330
+hypervisor: 0.244
+files: 0.242
+ppc: 0.212
+KVM: 0.202
+semantic: 0.165
+boot: 0.147
+PID: 0.131
+kernel: 0.127
+mistranslation: 0.120
+register: 0.119
+user-level: 0.107
+network: 0.100
+i386: 0.099
+debug: 0.090
+peripherals: 0.086
+socket: 0.080
+vnc: 0.073
+permissions: 0.067
+risc-v: 0.066
+virtual: 0.057
+arm: 0.054
+VMM: 0.047
+TCG: 0.043
+assembly: 0.037
+
+detect-zeroes=unmap fails to discard in some cases
+
+Under certain circumstances, QEMU 2.1.2 fails to discard the underlaying block. The command to start QEMU is:
+
+qemu-system-x86_64 -machine pc,accel=kvm -m 2G -smp 2 -vga std -usb -usbdevice tablet -drive if=none,id=ff,aio=native,discard=unmap,detect-zeroes=unmap,file=/tmp/test.qcow2 -device virtio-scsi-pci -device scsi-disk,drive=ff -cdrom /media/iso/archlinux-2014.06.01-dual.iso -vnc :1
+
+Steps to reproduce:
+
+ 0. qemu-img create -f qcow2 /tmp/test.qcow2 4G
+ 1. Boot in the guest (Arch Linux x86_64 with Linux 3.14.4)
+ 2. cat /dev/zero > /dev/sda. Observe a file of 4109M (size measured with `du -m`
+ 3. cat /dev/zero > /dev/sda
+ 4. blkdiscard /dev/sda
+ 5. Observe that test.qcow2 grows larger than 1M (13M in my testing).
+
+The results are more severe when you write other kind of data in step 2, for instance `base64 /dev/zero > /dev/sda` and then continuing with step 3 and 4 will result in a file of 3642M, after blkdiscard.
+
+It makes not much of a difference if I create an ext4 filesystem on top of it and use fstrim (or rm).
+
+Note that `cat /dev/zero` followed by `blkdiscard` has no issues.
+
+Triaging old bug tickets... can you still reproduce this issue with the latest version of QEMU? Or could we close this ticket nowadays?
+
+[Expired for QEMU because there has been no activity for 60 days.]
+