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Re: [libvirt] [PATCH v3 14/16] Track symlinks for co-mounted cgroup controllers



On 10.04.2013 12:08, Daniel P. Berrange wrote:
> From: "Daniel P. Berrange" <berrange redhat com>
> 
> If a cgroup controller is co-mounted with another, eg
> 
>    /sys/fs/cgroup/cpu,cpuacct
> 
> Then it is a requirement that there exist symlinks at
> 
>    /sys/fs/cgroup/cpu
>    /sys/fs/cgroup/cpuacct
> 
> pointing to the real mount point. Add support to virCgroupPtr
> to detect and track these symlinks
> 
> Signed-off-by: Daniel P. Berrange <berrange redhat com>
> ---
>  src/util/vircgroup.c     | 56 ++++++++++++++++++++++++++++++++++++++++++----
>  src/util/vircgrouppriv.h |  5 +++++
>  tests/vircgroupmock.c    | 58 ++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/vircgrouptest.c    | 36 +++++++++++++++++++++++-------
>  4 files changed, 143 insertions(+), 12 deletions(-)
> 
> diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
> index 6202614..14af16e 100644
> --- a/src/util/vircgroup.c
> +++ b/src/util/vircgroup.c

> @@ -157,9 +166,46 @@ static int virCgroupDetectMounts(virCgroupPtr group)
>                   * first entry only
>                   */
>                  if (typelen == len && STREQLEN(typestr, tmp, len) &&
> -                    !group->controllers[i].mountPoint &&
> -                    !(group->controllers[i].mountPoint = strdup(entry.mnt_dir)))
> -                    goto no_memory;
> +                    !group->controllers[i].mountPoint) {
> +                    char *linksrc;
> +                    struct stat sb;
> +                    char *tmp2;
> +
> +                    if (!(group->controllers[i].mountPoint = strdup(entry.mnt_dir)))
> +                        goto no_memory;
> +
> +                    tmp2 = strrchr(entry.mnt_dir, '/');
> +                    if (!tmp2) {
> +                        errno = EINVAL;
> +                        goto error;
> +                    }
> +                    *tmp2 = '\0';
> +                    /* If it is a co-mount it has a filename like "cpu,cpuacct"
> +                     * and we must identify the symlink path */
> +                    if (strchr(tmp2 + 1, ',')) {
> +                        if (virAsprintf(&linksrc, "%s/%s",
> +                                        entry.mnt_dir, typestr) < 0)
> +                            goto no_memory;
> +                        *tmp2 = '/';
> +
> +                        if (lstat(linksrc, &sb) < 0) {
> +                            if (errno == ENOENT) {
> +                                VIR_WARN("Controller %s co-mounted at %s is missing symlink at %s",
> +                                         typestr, entry.mnt_dir, linksrc);
> +                                VIR_FREE(linksrc);
> +                            } else {
> +                                goto error;
> +                            }
> +                        } else {
> +                            if (!S_ISLNK(sb.st_mode)) {
> +                                VIR_WARN("Expecting a symlink at %s for controller %s",
> +                                         linksrc, typestr);
> +                            } else {
> +                                group->controllers[i].linkPoint = linksrc;
> +                            }
> +                        }
> +                    }
> +                }
>                  tmp = next;
>              }
>          }
> @@ -170,8 +216,10 @@ static int virCgroupDetectMounts(virCgroupPtr group)
>      return 0;
>  
>  no_memory:
> +    errno = ENOENT;

Any reason for not returning ENOMEM here? I don't see any.

> +error:
>      VIR_FORCE_FCLOSE(mounts);
> -    return -ENOMEM;
> +    return -errno;
>  }
>  

ACK if errno fixed.

Michal


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