[Qemu-devel] [Bug 648128] Re: VirtFS: Cannot mount 9p during boot

[Venkateswararao Jujjuri \(JV\)]

** Changed in: qemu
       Status: In Progress => Fix Committed

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https://bugs.launchpad.net/bugs/648128

Title:
  VirtFS: Cannot mount 9p during boot

Status in QEMU:
  Fix Committed

Bug description:
  I use as client Debian squeeze i386 with a custom kernel:
  Linux (none) 2.6.35.5 #3 Thu Sep 23 18:36:02 UTC 2010 i686 GNU/Linux

  And as host Debian squeeze amd64
  Linux asd 2.6.32-5-amd64 #1 SMP Fri Sep 17 21:50:19 UTC 2010 x86_64 GNU/Linux

  kvm version is:
  kvm-88-5908-gdd67374

  Started the client using:
  sudo /usr/local/kvm/bin/qemu-system-x86_64 -m 1024 -kernel 
linux-2.6.35.5.qemu -drive file=root.img,if=virtio -net 
nic,macaddr=02:ca:ff:ee:ba:be,model=virtio,vlan=1 -net 
tap,ifname=tap1,vlan=1,script=no -virtfs 
local,path=/host,security_model=passthrough,mount_tag=host -nographic

  I noticed that I cannot mount it (mapped or passthrough) using
  /etc/rc.local or /etc/fstab, but after login as root using

  mount /mnt

  or

  mount -t 9p -o trans=virtio host /mnt

  (the same stuff i tried inside /etc/rc.local)

  The only output on a failed mount in rc.local/fstab I get is

  [ 15.035920] device: '9p-1': device_add
  [ 15.038180] 9p: no channels available
  [ 15.038937] device: '9p-1': device_unregister
  [ 15.049123] device: '9p-1': device_create_release

  The stuff in /etc/fstab is:
  host            /mnt   9p      trans=virtio 0 0


  I intercepted the boot by adding `set -v; set +e; mount -t 9p -o trans=virtio 
host_share /mnt; /bin/sh` on top of my /etc/rc.local:
  ... but than it works quite well... well that is not what I expected. So I 
changed it to `set -v; mount /mnt || true; /bin/sh`.. and then it doesn't work 
anymore... mysterios but hey, did you notice that the share is actually called 
host and not host_share as I wrote inside the rc.local. So why does it work at 
all? Let me change it to `set -v; set +e; mount -t 9p -o trans=virtio host 
/mnt; /bin/sh` and reboot again.

  What should i say: it says:
  [    8.004754] device: '9p-1': device_add
  [    8.006446] 9p: no channels available
  [    8.007156] device: '9p-1': device_unregister
  [    8.008650] device: '9p-1': device_create_release
  mount: No such file or directory

  But i have a shell now and can type the mount stuff inside it:
  $ mount -v -t 9p -o trans=virtio host /mnt
  mount -v -t 9p -o trans=virtio host /mnt
  [   70.982688] device: '9p-2': device_add
  [   70.986508] 9p: no channels available
  [   70.987969] device: '9p-2': device_unregister
  [   70.992937] device: '9p-2': device_create_release
  mount: No such file or directory
  $ ls -l /sys/bus/virtio/drivers/9pnet_virtio
  total 0
  --w------- 1 root root 4096 Sep 26 12:58 bind
  --w------- 1 root root 4096 Sep 26 12:58 uevent
  --w------- 1 root root 4096 Sep 26 12:58 unbind
  lrwxrwxrwx 1 root root    0 Sep 26 12:58 virtio1 -> 
../../../../devices/virtio-pci/virtio1
  $ ls -l /sys/devices/virtio-pci/virtio1
  total 0
  lrwxrwxrwx 1 root root    0 Sep 26 13:00 bus -> ../../../bus/virtio
  -r--r--r-- 1 root root 4096 Sep 26 13:00 device
  lrwxrwxrwx 1 root root    0 Sep 26 13:00 driver -> 
../../../bus/virtio/drivers/9pnet_virtio
  -r--r--r-- 1 root root 4096 Sep 26 13:00 features
  -r--r--r-- 1 root root 4096 Sep 26 13:00 modalias
  -r--r--r-- 1 root root 4096 Sep 26 13:00 mount_tag
  drwxr-xr-x 2 root root    0 Sep 26 12:58 power
  -r--r--r-- 1 root root 4096 Sep 26 13:00 status
  lrwxrwxrwx 1 root root    0 Sep 26 13:00 subsystem -> ../../../bus/virtio
  -rw-r--r-- 1 root root 4096 Sep 26 13:00 uevent
  -r--r--r-- 1 root root 4096 Sep 26 13:00 vendor
  $ cat /sys/devices/virtio-pci/virtio1/mount_tag
  host$ mount -v -t 9p -o trans=virtio host /mnt
  [  340.559853] device: '9p-3': device_add
  [  340.563699] 9p: no channels available
  [  340.565602] device: '9p-3': device_unregister
  [  340.569201] device: '9p-3': device_create_release
  mount: No such file or director
  $ mount  -v -t 9p -o trans=virtio hostA /mnt
  [  406.218462] device: '9p-4': device_add
  hostA on /mnt type 9p (rw,trans=virtio)
  $ env
  CONSOLE=/dev/console
  HOME=/
  runlevel=2
  INIT_VERSION=sysvinit-2.88
  COLUMNS=80
  TERM=linux
  PATH=/sbin:/usr/sbin:/bin:/usr/bin
  RUNLEVEL=2
  PREVLEVEL=N
  SHELL=/bin/sh
  PWD=/
  previous=N
  LINES=24
  VERBOSE=no
  $ id
  uid=0(root) gid=0(root) groups=0(root)
  $ hexdump asd
  0000000 6f68 7473 0000 0000 0000 0000 0000 0000
  0000010 0000 0000                              
  0000014

  I rebooted again and now just ctrl+d in my rc.local shell to get to my real 
root login with zsh:
  $ cat /sys/devices/virtio-pci/virtio1/mount_tag > asd
  $ hexdump asd
  0000000 6f68 7473 0000 0000 0000 0000 0000 0000
  0000010 0000 0000                              
  0000014
  $ id
  uid=0(root) gid=0(root) groups=0(root)
  $ env
  TERM=linux
  HOME=/root
  SHELL=/bin/zsh
  USER=root
  LOGNAME=root
  
PATH=/host/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
  MAIL=/var/mail/root
  HUSHLOGIN=FALSE
  SHLVL=1
  PWD=/root
  OLDPWD=/root
  COLORTERM=yes
  LINKS_XTERM=screen
  EDITOR=vim
  PAGER=less -r
  BROWSER=iceweasel
  LESS=-RIM
  
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lz=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.rar=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.axa=00;36:*.oga=00;36:*.spx=00;36:*.xspf=00;36:
  HISTFILE=/root/.zsh_history
  HISTSIZE=10000
  SAVEHIST=10000
  _=/usr/bin/env
  $ mount  -v -t 9p -o trans=virtio host /mnt
  [  224.087952] device: '9p-2': device_add
  host on /mnt type 9p (rw,trans=virtio)

  So the next step was to change my login shell to /bin/sh (dash) and reboot:
  $ id
  uid=0(root) gid=0(root) groups=0(root)
  $ env
  USER=root
  MAIL=/var/mail/root
  OLDPWD=/root
  HOME=/root
  HUSHLOGIN=FALSE
  PS1=\h:\w\$ 
  LOGNAME=root
  TERM=linux
  
PATH=/host/usr/bin:/host/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
  SHELL=/bin/sh
  PWD=/host
  $ mount  -v -t 9p -o trans=virtio host /mnt
  [   15.330643] device: '9p-2': device_add
  host on /mnt type 9p (rw,trans=virtio)

  Next step was to boot up, change my env and then use the correct mount:
  $ for i in USER MAIL OLDPWD HOME HUSHLOGIN PS1 LOGNAME TERM PATH SHELL PWD; 
do unset $i; done
  $ env
  $ /bin/mount  -v -t 9p -o trans=virtio host /mnt
  [  431.742839] device: '9p-2': device_add
  host on /mnt type 9p (rw,trans=virtio)