[Libguestfs] Fwd: [Qemu-devel] debugging qemu-nbd.c

---------- Forwarded message ---------- From: Skippy VonDrake <skippyvondrake(a)gmail.com&gt; Date: Tue, Apr 9, 2013 at 11:38 AM Subject: Re: [Qemu-devel] debugging qemu-nbd.c To: "Richard W.M. Jones" <rjones(a)redhat.com&gt; With both LIBGUESTFS_DEBUG and LIBGUESTFS_TRACE set and guestfs_set_verbose(g,1) and guestfs_set_trace(g,1). Below is the output. Some messages may look unfamiliar because I placed some statements in libguestfs just for a 'crude' tracing into the library. The initial 'nbd_client_thread' message is one I placed in the qemu sources. executing 'system(sudo rmmod nbd) executing 'system(sudo modprobe nbd max_part=16) setupNbdServer - size: 77824 setupNbdServer - system(serverCmd) string: qemu-nbd -v -n -o 77824 -t -p 3000 -c /dev/nbd0 /home/skippy/mnt/mnt0/win7x64amdHP.vdi nbd_client_thread:line 260::12806|939447:: qemu-NBD device /dev/nbd0 is NOWWW connected to /home/skippy/mnt/mnt0/win7x64amdHP.vdi libguestfs: trace: add_drive "" "format:raw" "protocol:nbd" "server:localhost:3000" libguestfs: trace: add_drive = 0 guestfs is launching the appliance libguestfs: trace: launch libguestfs: trace: get_tmpdir libguestfs: trace: get_tmpdir = "/tmp" libguestfs: launch: attach-method=appliance libguestfs: launch: tmpdir=/tmp/libguestfsscRysl libguestfs: launch: umask=0022 libguestfs: launch: euid=0 libguestfs: [00000ms] begin testing qemu features libguestfs: command: run: /home/skippy/Downloads/qemu/latest-build/install_dir/bin/qemu-system-x86_64 libguestfs: command: run: \ -nographic libguestfs: command: run: \ -help libguestfs: command: run: /home/skippy/Downloads/qemu/latest-build/install_dir/bin/qemu-system-x86_64 libguestfs: command: run: \ -nographic libguestfs: command: run: \ -version libguestfs: qemu version 1.4 libguestfs: command: run: /home/skippy/Downloads/qemu/latest-build/install_dir/bin/qemu-system-x86_64 libguestfs: command: run: \ -nographic libguestfs: command: run: \ -machine accel=kvm:tcg libguestfs: command: run: \ -device ? libguestfs: [00025ms] finished testing qemu features libguestfs: [00025ms] r from fork: 13658 \n \ libguestfs: error: appliance closed the connection unexpectedly, see earlier error messages libguestfs: child_cleanup: 0x11f4ba0: child process died libguestfs: sending SIGTERM to process 13658 libguestfs: error: /home/skippy/Downloads/qemu/latest-build/install_dir/bin/qemu-system-x86_64 exited with error status 1, see debug messages above libguestfs: error: guestfs_launch failed, see earlier error messages libguestfs: trace: launch = -1 (error) ERROR from setupGuestfs-> guestfs_launch, errnum: 0 Last error msg: guestfs_launch failed, see earlier error messages main thread exiting libguestfs: trace: close libguestfs: closing guestfs handle 0x11f4ba0 (state 0) libguestfs: command: run: rm libguestfs: command: run: \ -rf /tmp/libguestfsscRysl As you can see, the output looks similar to my previous post. At which you suggested that qemu might be failing. So that is when I started trying to pinpoint the problem in qemu. And the 'chdir' command was the final point at which my file-log statements ended. For that logging I'd open the log, write a string and close the log each time. One bit that might be of interest - my app does a fork/system command to launch the ndb server. When I give the disconnect command (after the error output above), I see this displayed from qemu: $ nbd.c:nbd_trip():L1106: From: 18446744073709551104, Len: 0, Size: 20003880960, Offset: 77824 nbd.c:nbd_trip():L1107: requested operation past EOF--bad client? The image is 20GB with a VDI header prepended to it. The size of the header is displayed with "setupNbdServer - size: 77824" and used for the offset parameter for qemu-nbd. I don't know what to make of the "From" value nor the 'Len' of zero in the last output.