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Re: [libvirt] [PATCH 2/2] virDomainUndefineFlags: Allow NVRAM unlinking



some comments below

On 09/11/14 14:09, Michal Privoznik wrote:
> When a domain is undefined, there are options to remove it's
> managed save state or snapshots. However, there's another file
> that libvirt creates per domain: the NVRAM variable store file.
> Make sure that the file is not left behind if the domain is
> undefined.
> 
> Signed-off-by: Michal Privoznik <mprivozn redhat com>
> ---
>  include/libvirt/libvirt.h.in |  2 ++
>  src/qemu/qemu_driver.c       | 19 ++++++++++++++++++-
>  tools/virsh-domain.c         | 15 ++++++++++++---
>  tools/virsh.pod              |  6 +++++-
>  4 files changed, 37 insertions(+), 5 deletions(-)
> 
> diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
> index 94b942c..3c2a51a 100644
> --- a/include/libvirt/libvirt.h.in
> +++ b/include/libvirt/libvirt.h.in
> @@ -2257,6 +2257,8 @@ typedef enum {
>      VIR_DOMAIN_UNDEFINE_SNAPSHOTS_METADATA = (1 << 1), /* If last use of domain,
>                                                            then also remove any
>                                                            snapshot metadata */
> +    VIR_DOMAIN_UNDEFINE_NVRAM              = (1 << 2), /* Also remove any
> +                                                          nvram file */
>  
>      /* Future undefine control flags should come here. */
>  } virDomainUndefineFlagsValues;
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index a8cda43..7f17fee 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -6403,7 +6403,8 @@ qemuDomainUndefineFlags(virDomainPtr dom,
>      virQEMUDriverConfigPtr cfg = NULL;
>  
>      virCheckFlags(VIR_DOMAIN_UNDEFINE_MANAGED_SAVE |
> -                  VIR_DOMAIN_UNDEFINE_SNAPSHOTS_METADATA, -1);
> +                  VIR_DOMAIN_UNDEFINE_SNAPSHOTS_METADATA |
> +                  VIR_DOMAIN_UNDEFINE_NVRAM, -1);
>  
>      if (!(vm = qemuDomObjFromDomain(dom)))
>          return -1;
> @@ -6452,6 +6453,22 @@ qemuDomainUndefineFlags(virDomainPtr dom,
>          }
>      }
>  

Seems okay and consistent with the rest of the code thus far. OK.

> +    if (!virDomainObjIsActive(vm) &&
> +        vm->def->os.loader && vm->def->os.loader->nvram) {
> +        if (!(flags & VIR_DOMAIN_UNDEFINE_NVRAM)) {
> +            virReportError(VIR_ERR_OPERATION_INVALID, "%s",
> +                           _("cannot delete inactive domain with nvram"));
> +            goto cleanup;
> +        }
> +
> +        if (unlink(vm->def->os.loader->nvram) < 0) {
> +            virReportSystemError(errno,
> +                                 _("failed to remove nvram: %s"),
> +                                 vm->def->os.loader->nvram);
> +            goto cleanup;
> +        }
> +    }
> +

Again, this seems consistent with the rest of the code, eg. with the
"cannot delete inactive domain with %d snapshots".

I slightly wonder what happens when you succeed in the above, bute then
the following fails:

>      if (virDomainDeleteConfig(cfg->configDir, cfg->autostartDir, vm) < 0)
>          goto cleanup;

I guess the full undefine operation will fail in this case. And if the
user retries the undefine, then even the unlink() will fail (because the
nvram file won't exist any longer).

(1) After staring a bit longer at qemuDomainUndefineFlags(): can you
please *further* restrict this code with a check for virFileExists()?

Namely, the VIR_DOMAIN_UNDEFINE_MANAGED_SAVE flag does something very
similar (including an unlink()), and that one is protected with a
virFileExists().

I'll leave it up to you if you add the && to the top IF, or if you just
short-circuit the unlink() with it (as in, (!virFileExists() && unlink()
< 0)). I think it would be more useful to restrict the outer condition
with it -- there's no point in complaining about the lack of
VIR_DOMAIN_UNDEFINE_NVRAM of the nvram file doesn't exist anyway.

>  
> diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
> index 6aa8631..db52271 100644
> --- a/tools/virsh-domain.c
> +++ b/tools/virsh-domain.c
> @@ -3248,6 +3248,10 @@ static const vshCmdOptDef opts_undefine[] = {
>       .type = VSH_OT_BOOL,
>       .help = N_("remove all domain snapshot metadata, if inactive")
>      },
> +    {.name = "nvram",
> +     .type = VSH_OT_BOOL,
> +     .help = N_("remove nvram file, if inactive")
> +    },
>      {.name = NULL}
>  };
>  
> @@ -3270,6 +3274,7 @@ cmdUndefine(vshControl *ctl, const vshCmd *cmd)
>      bool snapshots_metadata = vshCommandOptBool(cmd, "snapshots-metadata");
>      bool wipe_storage = vshCommandOptBool(cmd, "wipe-storage");
>      bool remove_all_storage = vshCommandOptBool(cmd, "remove-all-storage");
> +    bool nvram = vshCommandOptBool(cmd, "nvram");
>      /* Positive if these items exist.  */
>      int has_managed_save = 0;
>      int has_snapshots_metadata = 0;
> @@ -3313,6 +3318,9 @@ cmdUndefine(vshControl *ctl, const vshCmd *cmd)
>          flags |= VIR_DOMAIN_UNDEFINE_SNAPSHOTS_METADATA;
>          snapshots_safe = true;
>      }
> +    if (nvram) {
> +        flags |= VIR_DOMAIN_UNDEFINE_NVRAM;
> +    }
>  
>      if (!(dom = vshCommandOptDomain(ctl, cmd, &name)))
>          return false;

Seems reasonable. OK.

> @@ -3504,10 +3512,11 @@ cmdUndefine(vshControl *ctl, const vshCmd *cmd)
>       * VIR_DOMAIN_UNDEFINE_SNAPSHOTS_METADATA flag was not present
>       * until 0.9.5; skip to piecewise emulation if we couldn't prove
>       * above that the new API is safe.  */
> -    if (managed_save_safe && snapshots_safe) {
> +    if ((managed_save_safe && snapshots_safe) || nvram) {
>          rc = virDomainUndefineFlags(dom, flags);
> -        if (rc == 0 || (last_error->code != VIR_ERR_NO_SUPPORT &&
> -                        last_error->code != VIR_ERR_INVALID_ARG))
> +        if (rc == 0 || nvram ||
> +            (last_error->code != VIR_ERR_NO_SUPPORT &&
> +             last_error->code != VIR_ERR_INVALID_ARG))
>              goto out;
>          vshResetLibvirtError();
>      }

If I understand correctly, if the user requests virsh to undefine the
nvram too, then that's grounds enough to try the "new API" first. Okay.

Then, pre-patch, the "new API" used to be considered *sufficient* if:
- it succeeded,
- or it failed, but the error code was different from both NO_SUPPORT
  and INVALID_ARG

Post-patch, the "new API" is considered sufficient if:
- it succeeded,
- or failed, but the error code was different from both NO_SUPPORT and
  INVALID_ARG,
- or it did fail with either  NO_SUPPORT or INVALID_ARG, but the user
  requested to undefine the nvram. Namely, in this case there's no "old
  API" to fall back to.

Good.

> diff --git a/tools/virsh.pod b/tools/virsh.pod
> index 60ee515..ae396d2 100644
> --- a/tools/virsh.pod
> +++ b/tools/virsh.pod
> @@ -2083,7 +2083,7 @@ Output the device used for the TTY console of the domain. If the information
>  is not available the processes will provide an exit code of 1.
>  
>  =item B<undefine> I<domain> [I<--managed-save>] [I<--snapshots-metadata>]
> -[ {I<--storage> B<volumes> | I<--remove-all-storage>} I<--wipe-storage>]
> +[I<--nvram>} [ {I<--storage> B<volumes> | I<--remove-all-storage>} I<--wipe-storage>]
                ^
                |
(2) I think this is a small typo -- didn't you mean "|" (pipe symbol,
meaning "alternatively")?

>  
>  Undefine a domain. If the domain is running, this converts it to a
>  transient domain, without stopping it. If the domain is inactive,
> @@ -2099,6 +2099,10 @@ domain.  Without the flag, attempts to undefine an inactive domain with
>  snapshot metadata will fail.  If the domain is active, this flag is
>  ignored.
>  
> +The I<--nvram> flag ensures no nvram (/domain/os/nvram/) file is
> +left behind. If the domain has a nvram file and the flag is

(3) "an nvram" (well it depends on how people read it out -- "an ENN VEE
RAM" vs. "a non-volatile RAM").

> +omitted the undefine will fail.

(4) please add a comma before "the undefine".

> +
>  The I<--storage> flag takes a parameter B<volumes>, which is a comma separated
>  list of volume target names or source paths of storage volumes to be removed
>  along with the undefined domain. Volumes can be undefined and thus removed only
> 

(5) Unrelated, please include a separate patch for it: yesterday both
Alex Williamson and myself independently noticed that you updated the
*code* according to Eric's request, ie. that the domain XML say
readonly="yes", but the *example* in the docs still says readonly='on'.
(The flowing text in the docs is correct.)

Thank you!
Laszlo


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