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qemuDomainBuildNamespace: Move /dev/* mountpoints later

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When setting up mount namespace for a qemu domain the following
steps are executed:

1) get list of mountpoints under /dev/
2) move them to /var/run/libvirt/qemu/$domName.ext
3) start constructing new device tree under /var/run/libvirt/qemu/$domName.dev
4) move the mountpoint of the new device tree to /dev
5) restore original mountpoints from step 2)

Note the problem with this approach is that if some device in step
3) requires access to a mountpoint from step 2) it will fail as
the mountpoint is not there anymore. For instance consider the
following domain disk configuration:

    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/dev/shm/vhostmd0'/>
      <target dev='vdb' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
    </disk>

In this case operation fails as we are unable to create vhostmd0
in the new device tree because after step 2) there is no /dev/shm
anymore. Leave aside fact that we shouldn't try to create devices
living in other mountpoints. That's a separate bug that will be
addressed later.

Currently, the order described above is rearranged to:

1) get list of mountpoints under /dev/
2) start constructing new device tree under /var/run/libvirt/qemu/$domName.dev
3) move them to /var/run/libvirt/qemu/$domName.ext
4) move the mountpoint of the new device tree to /dev
5) restore original mountpoints from step 3)

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Cedric Bosdonnat <cbosdonnat@suse.com>
This commit is contained in:
Michal Privoznik 2017-04-27 16:29:21 +02:00
parent 624bc92661
commit a7cc039dc7
1 changed files with 24 additions and 24 deletions
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48
src/qemu/qemu_domain.c
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@ -8029,6 +8029,30 @@ qemuDomainBuildNamespace(virQEMUDriverConfigPtr cfg,
if (qemuDomainSetupDev(cfg, mgr, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllDisks(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllHostdevs(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllMemories(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllChardevs(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupTPM(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllGraphics(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllInputs(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllRNGs(cfg, vm, devPath) < 0)
goto cleanup;
/* Save some mount points because we want to share them with the host */
for (i = 0; i < ndevMountsPath; i++) {
struct stat sb;
@ -8056,30 +8080,6 @@ qemuDomainBuildNamespace(virQEMUDriverConfigPtr cfg,
goto cleanup;
}
if (qemuDomainSetupAllDisks(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllHostdevs(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllMemories(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllChardevs(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupTPM(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllGraphics(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllInputs(cfg, vm, devPath) < 0)
goto cleanup;
if (qemuDomainSetupAllRNGs(cfg, vm, devPath) < 0)
goto cleanup;
if (virFileMoveMount(devPath, "/dev") < 0)
goto cleanup;