[libvirt] [RFC] [PATCH v3 2/6] add fuse support for libvirt lxc

[Gao feng]

于 2012年09月26日 02:37, Daniel P. Berrange 写道:
> On Tue, Sep 11, 2012 at 10:54:48AM +0800, Gao feng wrote:
>> this patch addes fuse support for libvirt lxc.
>> we can use fuse filesystem to generate sysinfo dynamically,
>> So we can isolate /proc/meminfo,cpuinfo and so on through
>> fuse filesystem.
>>
>> we mount fuse filesystem for every container.the mount name
>> is Lxc-containename-fuse,mount point is
>> localstatedir/run/libvirt/lxc/containername.
>>
>> Signed-off-by: Gao feng <gaofeng at cn.fujitsu.com>
> 
>> diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
>> index e5aea11..c5f4951 100644
>> --- a/src/lxc/lxc_controller.c
>> +++ b/src/lxc/lxc_controller.c
>> @@ -1657,6 +1659,14 @@ int main(int argc, char *argv[])
>>          }
>>      }
>>  
>> +    rc = virThreadCreate(&thread, true, lxcRegisterFuse,
>> +                         (void *)ctrl->def);
>> +    if (rc < 0) {
>> +        virReportSystemError(-rc, "%s",
>> +                             _("Create Fuse filesystem failed"));
>> +        goto cleanup;
>> +    }
>> +
> 
> This is the wrong place to start FUSE. At this point the LXC
> controller is still sharing its mount namespace with the host
> OS. This causes the FUSE mount for each container to become
> visible in the host, which is not what we want.
sorry for the delay.

I think it's correct,because host can see container's meminfo
through cgroup too.NOW the container's cgroup can be seen and
modified in container too,I don't know why this is necessary?

> 
> We must only start FUSE, after, we have done the unshare()
> call while setting up /dev/pts.
> 
> 
>> +void lxcRegisterFuse(void *DomainDef)
> 
> More conventional naming would be  'void *opaque'
> 

will fix this.

>> +{
>> +    int argc = 4;
>> +    char *argv[argc];
>> +    char *path = NULL;
>> +    char *name = NULL;
>> +    virDomainDefPtr def = (virDomainDefPtr) DomainDef;
>> +
>> +    if (virAsprintf(&name, "Lxc-%s-fuse", def->name) < 0) {
>> +        virReportOOMError();
>> +        goto cleanup;
>> +    }
>> +
>> +    if (virAsprintf(&path, "%s/%s/", LXC_STATE_DIR, def->name) < 0) {
>> +        virReportOOMError();
>> +        goto cleanup;
>> +    }
>> +
>> +    if (virFileMakePath(path) < 0) {
>> +        virReportSystemError(errno, _("Cannot create %s"), path);
>> +        goto cleanup;
>> +    }
>> +
>> +    argv[0] = name;
>> +    argv[1] = path;
>> +    argv[2] = (char *)"-odirect_io";
>> +    argv[3] = (char *)"-f";
>> +
>> +    if (fuse_main(argc, argv, &lxcProcOper, def) < 0)
>> +        virReportSystemError(errno, "%s", _("Cannot start fuse"));
>> +
>> +cleanup:
>> +    VIR_FREE(name);
>> +    VIR_FREE(path);
>> +    return;
>> +}
>> +
>> +void lxcUnregisterFuse(virDomainDefPtr def)
>> +{
>> +    char *path = NULL;
>> +
>> +    if (virAsprintf(&path, "%s/%s/", LXC_STATE_DIR, def->name) < 0) {
>> +        virReportOOMError();
>> +        return;
>> +    }
>> +
>> +    if (umount(path) < 0)
>> +         virReportSystemError(errno, "%s",
>> +                              _("umount fuse filesystem failed"));
>> +
>> +    VIR_FREE(path);
>> +}
>> +
>> +#else
>> +void lxcRegisterFuse(void *DomainDef ATTRIBUTE_UNUSED)
>> +{
>> +}
>> +
>> +void lxcUnregisterFuse(virDomainDefPtr def ATTRIBUTE_UNUSED)
>> +{
>> +}
>> +#endif
> 
>> diff --git a/src/lxc/lxc_process.c b/src/lxc/lxc_process.c
>> index bcd59cb..d5e1822 100644
>> --- a/src/lxc/lxc_process.c
>> +++ b/src/lxc/lxc_process.c
>> @@ -28,6 +28,7 @@
>>  #include "lxc_process.h"
>>  #include "lxc_domain.h"
>>  #include "lxc_container.h"
>> +#include "lxc_fuse.h"
>>  #include "datatypes.h"
>>  #include "virfile.h"
>>  #include "virpidfile.h"
>> @@ -232,7 +233,7 @@ static void virLXCProcessCleanup(virLXCDriverPtr driver,
>>                      NULL, xml, NULL);
>>          VIR_FREE(xml);
>>      }
>> -
>> +    lxcUnregisterFuse(vm->def);
>>      /* Stop autodestroy in case guest is restarted */
>>      virLXCProcessAutoDestroyRemove(driver, vm);
> 
> If you delayed starting FUSE until after we do unshare(), then the mount
> point will automatically go away when the LXC controller process exits,
> so we won't need any manual unmount in lxcUnregisterFuse()
> 
> 
> Daniel
>