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Re: [libvirt] [PATCH v2 5/8] LXC: Creating devices for container on host side



On 05/10/2013 06:28 PM, Richard RW. Weinberger wrote:
> ----- Urspr√ľngliche Mail -----
>> user namespace doesn't allow to create devices in
>> uninit userns. We should create devices on host side.
>>
>> Signed-off-by: Gao feng <gaofeng cn fujitsu com>
>> ---
>>  src/lxc/lxc_container.c  | 47 +++++++----------------------
>>  src/lxc/lxc_controller.c | 77
>>  ++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 87 insertions(+), 37 deletions(-)
>>
>> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
>> index eabaa34..540246f 100644
>> --- a/src/lxc/lxc_container.c
>> +++ b/src/lxc/lxc_container.c
>> @@ -833,22 +833,10 @@ cleanup:
>>      return ret;
>>  }
>>  
>> -static int lxcContainerPopulateDevices(char **ttyPaths, size_t
>> nttyPaths)
>> +static int lxcContainerSetupDevices(char **ttyPaths, size_t
>> nttyPaths)
>>  {
>>      size_t i;
>>      const struct {
>> -        int maj;
>> -        int min;
>> -        mode_t mode;
>> -        const char *path;
>> -    } devs[] = {
>> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_NULL, 0666, "/dev/null" },
>> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_ZERO, 0666, "/dev/zero" },
>> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_FULL, 0666, "/dev/full" },
>> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_RANDOM, 0666,
>> "/dev/random" },
>> -        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_URANDOM, 0666,
>> "/dev/urandom" },
>> -    };
>> -    const struct {
>>          const char *src;
>>          const char *dst;
>>      } links[] = {
>> @@ -858,18 +846,6 @@ static int lxcContainerPopulateDevices(char
>> **ttyPaths, size_t nttyPaths)
>>          { "/proc/self/fd", "/dev/fd" },
>>      };
>>  
>> -    /* Populate /dev/ with a few important bits */
>> -    for (i = 0 ; i < ARRAY_CARDINALITY(devs) ; i++) {
>> -        dev_t dev = makedev(devs[i].maj, devs[i].min);
>> -        if (mknod(devs[i].path, S_IFCHR, dev) < 0 ||
>> -            chmod(devs[i].path, devs[i].mode)) {
>> -            virReportSystemError(errno,
>> -                                 _("Failed to make device %s"),
>> -                                 devs[i].path);
>> -            return -1;
>> -        }
>> -    }
>> -
>>      for (i = 0 ; i < ARRAY_CARDINALITY(links) ; i++) {
>>          if (symlink(links[i].src, links[i].dst) < 0) {
>>              virReportSystemError(errno,
>> @@ -882,22 +858,13 @@ static int lxcContainerPopulateDevices(char
>> **ttyPaths, size_t nttyPaths)
>>      if (access("/dev/pts/ptmx", W_OK) == 0) {
>>          /* We have private devpts capability, so bind that */
>>          if (virFileTouch("/dev/ptmx", 0666) < 0)
>> -            return -1;
>> +           return -1;
>>  
>>          if (mount("/dev/pts/ptmx", "/dev/ptmx", "ptmx", MS_BIND,
>>          NULL) < 0) {
>>              virReportSystemError(errno, "%s",
>>                                   _("Failed to bind /dev/pts/ptmx on
>>                                   to /dev/ptmx"));
>>              return -1;
>>          }
>> -    } else {
>> -        /* Legacy devpts, so we need to just use shared one */
>> -        dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
>> -        if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 ||
>> -            chmod("/dev/ptmx", 0666)) {
>> -            virReportSystemError(errno, "%s",
>> -                                 _("Failed to make device
>> /dev/ptmx"));
>> -            return -1;
>> -        }
>>      }
>>  
>>      for (i = 0 ; i < nttyPaths ; i++) {
>> @@ -1825,8 +1792,8 @@ static int
>> lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
>>      if (lxcContainerMountFSDevPTS(vmDef, "/.oldroot") < 0)
>>          goto cleanup;
>>  
>> -    /* Populates device nodes in /dev/ */
>> -    if (lxcContainerPopulateDevices(ttyPaths, nttyPaths) < 0)
>> +    /* Sets up device nodes in /dev/ */
>> +    if (lxcContainerSetupDevices(ttyPaths, nttyPaths) < 0)
>>          goto cleanup;
>>  
>>      /* Sets up any non-root mounts from guest config */
>> @@ -2037,6 +2004,12 @@ static int lxcContainerChild(void *data)
>>          goto cleanup;
>>      }
>>  
>> +    if (lxcContainerWaitForContinue(argv->monitor) < 0) {
>> +        virReportSystemError(errno, "%s",
>> +                             _("Failed to read the container
>> continue message"));
>> +        goto cleanup;
>> +    }
>> +
>>      ret = 0;
>>  cleanup:
>>      VIR_FREE(ttyPath);
>> diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
>> index e9b90bf..2072e9a 100644
>> --- a/src/lxc/lxc_controller.c
>> +++ b/src/lxc/lxc_controller.c
>> @@ -1103,6 +1103,73 @@ cleanup:
>>  }
>>  
>>  
>> +static int virLXCControllerPopulateDevices(virLXCControllerPtr ctrl)
>> +{
>> +    size_t i;
>> +    int ret = -1;
>> +    char *ptmx = NULL;
>> +    char *path = NULL;
>> +    const struct {
>> +        int maj;
>> +        int min;
>> +        mode_t mode;
>> +        const char *path;
>> +    } devs[] = {
>> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_NULL, 0666, "/dev/null" },
>> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_ZERO, 0666, "/dev/zero" },
>> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_FULL, 0666, "/dev/full" },
>> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_RANDOM, 0666,
>> "/dev/random" },
>> +        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_URANDOM, 0666,
>> "/dev/urandom" },
>> +    };
>> +
>> +    /* Populate /dev/ with a few important bits */
>> +    for (i = 0 ; i < ARRAY_CARDINALITY(devs) ; i++) {
>> +        if (virAsprintf(&path, "/proc/%llu/root/%s",
>> +                        (unsigned long long)ctrl->initpid,
>> +                        devs[i].path) < 0) {
>> +            virReportOOMError();
>> +            goto out;
>> +        }
>> +
>> +        dev_t dev = makedev(devs[i].maj, devs[i].min);
>> +        if (mknod(path, S_IFCHR, dev) < 0 ||
>> +            chmod(path, devs[i].mode)) {
>> +            virReportSystemError(errno,
>> +                                 _("Failed to make device %s"),
>> +                                 devs[i].path);
>> +            goto out;
>> +        }
>> +    }
>> +
>> +    if (virAsprintf(&ptmx, "/proc/%llu/root/dev/pts/ptmx",
>> +                    (unsigned long long)ctrl->initpid) < 0) {
>> +        virReportOOMError();
>> +        goto out;
>> +    }
>> +
>> +    if (access(ptmx, W_OK)) {
>> +        VIR_FREE(path);
>> +
>> +        if (virAsprintf(&path, "/proc/%llu/root/dev/ptmx",
>> +                        (unsigned long long)ctrl->initpid) < 0) {
>> +            virReportOOMError();
>> +            goto out;
>> +        }
>> +        /* Legacy devpts, so we need to just use shared one */
>> +        dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
>> +        if (mknod(path, S_IFCHR, dev) < 0 ||
>> +            chmod(path, 0666)) {
>> +            virReportSystemError(errno,  _("Failed to make device
>> %s"), path);
>> +            goto out;
>> +        }
>> +    }
>> +
>> +    ret = 0;
>> +out:
>> +    VIR_FREE(ptmx);
>> +    VIR_FREE(path);
>> +    return ret;
>> +}
>>  
>>  /**
>>   * virLXCControllerMoveInterfaces
>> @@ -1552,6 +1619,16 @@ virLXCControllerRun(virLXCControllerPtr ctrl)
>>          goto cleanup;
>>      }
>>  
>> +    /* Populate devices for container */
>> +    if (virLXCControllerPopulateDevices(ctrl) < 0)
>> +        goto cleanup;
> 
> systemd will be not happy with this.
> If /dev/ is not already a mountpoint it will try to mount devtmpfs which
> will fail an systemd stops booting.
> 
> It would be nice to have:
> a) A way to disable virLXCControllerPopulateDevices(), i.e. one bind mounts his own lxc-/dev to /dev
> b) libvirt mounts a tmpfs onto /dev and then creates the devices nodes.
> 

Thanks for you pointing it out, I will pay attention to this problem in my next round patchset.

Thanks,
Gao


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