Re: [libvirt] [PATCH 0/2] Two simple sparse streams fixes

On Tue, May 30, 2017 at 12:44:21PM +0200, Michal Privoznik wrote: I'm also getting confusing errors when there is no space on the destination: error: cannot receive data from volume fedora.img error: An error occurred, but the cause is unknown But that's not related to the sparse streams (unless it was caused by making the iohelper a thread). ... few moments later after /me tries just a thing or two ... Well, this made me try out few more things and I've found out few things. I'm not sure what's related to your patches and what's not, so here's the rundown, and I'll let you decide: - vol-download --sparse --offset $source_file_size --length 1 /path/to/source.file destination.file - Every now and then (not always) it gets stuck waiting for the daemon to receive data (see backtrace below), but the daemon is not waiting for anything, it's just some weird race. We can try debugging it with wireshark later. That file ends with a hole. Thread 1 (Thread 0x7f1d2b434880 (LWP 28584)): #0 0x00007f1d2796efbd in poll () at ../sysdeps/unix/syscall-template.S:84 #1 0x00007f1d2a806ee3 in poll (__timeout=5000, __nfds=2, __fds=0x7ffe9effd640) at /usr/include/bits/poll2.h:46 #2 virNetClientIOEventLoop (client=client@entry=0x563525bb06d0, thiscall=thiscall@entry=0x563525badc00) at rpc/virnetclient.c:1664 #3 0x00007f1d2a8074d3 in virNetClientIO (client=client@entry=0x563525bb06d0, thiscall=0x563525badc00) at rpc/virnetclient.c:1957 #4 0x00007f1d2a80780e in virNetClientSendInternal (client=client@entry=0x563525bb06d0, msg=msg@entry=0x563525bb03d0, expectReply=expectReply@entry=true, nonBlock=nonBlock@entry=false) at rpc/virnetclient.c:2132 #5 0x00007f1d2a808dfc in virNetClientSendWithReplyStream (client=client@entry=0x563525bb06d0, msg=msg@entry=0x563525bb03d0, st=st@entry=0x563525bade10) at rpc/virnetclient.c:2236 #6 0x00007f1d2a80ab2d in virNetClientStreamRecvPacket (st=st@entry=0x563525bade10, client=0x563525bb06d0, data=data@entry=0x7f1d20686010 "", nbytes=nbytes@entry=262120, nonblock=false, flags=32766, flags@entry=1) at rpc/virnetclientstream.c:499 #7 0x00007f1d2a7e0e3e in remoteStreamRecvFlags (st=0x563525badc60, data=0x7f1d20686010 "", nbytes=262120, flags=1) at remote/remote_driver.c:5664 #8 0x00007f1d2a7c8347 in virStreamRecvFlags (stream=stream@entry=0x563525badc60, data=0x7f1d20686010 "", nbytes=nbytes@entry=262120, flags=flags@entry=1) at libvirt-stream.c:361 #9 0x00007f1d2a7c9b7f in virStreamSparseRecvAll (stream=stream@entry=0x563525badc60, handler=0x563525760196 <virshStreamSink>, holeHandler=0x56352576020b <virshStreamSkip>, opaque=opaque@entry=0x7ffe9effd954) at libvirt-stream.c:964 #10 0x000056352576232e in cmdVolDownload (ctl=0x7ffe9effda40, cmd=<optimized out>) at virsh-volume.c:834 #11 0x00005635257662f1 in vshCommandRun (ctl=0x7ffe9effda40, cmd=0x563525bacf40) at vsh.c:1327 #12 0x000056352572aee2 in main (argc=9, argv=<optimized out>) at virsh.c:929 Trying to reproduce yet another one, the command gets stuck even with different offsets. - vol-download --sparse --offset $X --length 1 /path/to/source.file destination.file - This does not respect the length if: X > $source_file_size - $last_hole_size The size ends up being $source_file_size - $X I'm afraid to try more things, but I can provide more info for these if you want. Have a nice day, Martin