I would appreciate this patch being committed as I *think* it's affecting a system i'm building now.
I have a backup host with 2 VMs. For business reasons they need to be network isolated from each other and the host, so each is passed through a physical NIC. Each VM does need access to a variable size datastore on the host so I am using virtfs /9p to expose a mountpoint to each VM. The VMs each backup servers to their respective mountpoint to this virtfs mount using rsync. Just backing up one server with ~4000 files and 3 large sparse VM images saw the open files on the backup host increase to over *800000* and the rsync progressively get slower. Shutting down these VMs then takes hours as it can't unlock the files it has open on the backup host. I understand rsync does use open-unlink-fstat extensively, hence why I think this is the issue. This is a deal breaker for any production use of virtfs. Does anybody know if this is fixed in other builds of qemu? tl;dr - to recreate this on 16.04 - create a VM with a virtfs/9p mount to the host. Do lots of rsyncs to this mount within the VM, watch 'lsof | wc -l' go higher and higher on the host. Thanks, /Sean -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1336794 Title: 9pfs does not honor open file handles on unlinked files Status in QEMU: New Bug description: This was originally filed over here: https://bugzilla.redhat.com/show_bug.cgi?id=1114221 The open-unlink-fstat idiom used in some places to create an anonymous private temporary file does not work in a QEMU guest over a virtio-9p filesystem. Version-Release number of selected component (if applicable): qemu-kvm-1.6.2-6.fc20.x86_64 qemu-system-x86-1.6.2-6.fc20.x86_64 (those are fedora RPMs) How reproducible: Always. See this example C program: https://bugzilla.redhat.com/attachment.cgi?id=913069 Steps to Reproduce: 1. Export a filesystem with virt-manager for the guest. (type: mount, driver: default, mode: passthrough) 2. Start guest and mount that filesystem (mount -t 9p -o trans=virtio,version=9p2000.L ...) 3. Run a program that uses open-unlink-fstat (in my case it was trying to compile Perl 5.20) Actual results: fstat fails: open("/home/tst/filename", O_RDWR|O_CREAT|O_EXCL, 0600) = 3 unlink("/home/tst/filename") = 0 fstat(3, 0x23aa1a8) = -1 ENOENT (No such file or directory) close(3) Expected results: open("/home/tst/filename", O_RDWR|O_CREAT|O_EXCL, 0600) = 3 unlink("/home/tst/filename") = 0 fstat(3, {st_mode=S_IFREG|0600, st_size=0, ...}) = 0 fcntl(3, F_SETFD, FD_CLOEXEC) = 0 close(3) Additional info: There was a patch put into the kernel back in '07 to handle this very problem for other filesystems; maybe its helpful: http://lwn.net/Articles/251228/ There is also a thread on LKML from last December specifically about this very problem: https://lkml.org/lkml/2013/12/31/163 There was a discussion on the QEMU list back in '11 that doesn't seem to have come to a conclusion, but did provide the test program that i've attached to this report: http://marc.info/?l=qemu-devel&m=130443605720648&w=2 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1336794/+subscriptions
