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Description of problem: A one line reproducer is from the libguestfs source directory is: ./run guestfish -N fs:btrfs:1G -m /dev/sda1 txz-in test-data/files/filesanddirs-10M.tar.xz / -v -x Version-Release number of selected component (if applicable): libguestfs 1.35.2 kernel-4.8.0-0.rc4.git0.1.fc26.x86_64 qemu-2.7.0-0.2.rc3.fc26.x86_64 btrfs-progs-4.7.1-1.fc26.x86_64 How reproducible: 100% Steps to Reproduce: 1. As above. Additional info: It only happens on one of my machines. It happens with either KVM or TCG. The same pattern is found in tests/btrfs/test-btrfs-devices,sh, where it causes the test suite to hang
Created attachment 1196488 [details] log up to the point where it hangs
I'm fairly sure this is a kernel/qemu/something bug. In fact the command proceeds, but very very slowly, taking about 10 minutes to unpack that 8K tar.xz file. Here is an even simpler demonstration of the problem: ./run guestfish -N fs:btrfs:1G -m /dev/sda1 -v -x \ upload test-data/files/filesanddirs-10M.tar.xz /test.tar.xz : \ debug sh "cd /sysroot && tar --xz -xvf test.tar.xz"
Making the virtual disk larger (eg. 10G) improves the performance, so I suspect that btrfs is having problems coping with lack of free space.