[libvirt] [PATCH 03/47] vircgroup: extract virCgroupV1Available

[Fabiano Fidêncio]

On Tue, Sep 18, 2018 at 5:45 PM, Pavel Hrdina <phrdina at redhat.com> wrote:

> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> ---
>  src/util/vircgroup.c        | 28 +++++++++-------------------
>  src/util/vircgroupbackend.h |  7 +++++++
>  src/util/vircgroupv1.c      | 35 +++++++++++++++++++++++++++++++++++
>  3 files changed, 51 insertions(+), 19 deletions(-)
>
> diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
> index e85e0bde24..a5478a3fa4 100644
> --- a/src/util/vircgroup.c
> +++ b/src/util/vircgroup.c
> @@ -51,6 +51,7 @@
>
>  #include "virutil.h"
>  #include "viralloc.h"
> +#include "vircgroupbackend.h"
>  #include "virerror.h"
>  #include "virlog.h"
>  #include "virfile.h"
> @@ -64,8 +65,6 @@
>
>  VIR_LOG_INIT("util.cgroup");
>
> -#define CGROUP_MAX_VAL 512
> -
>  #define VIR_FROM_THIS VIR_FROM_CGROUP
>
>  #define CGROUP_NB_TOTAL_CPU_STAT_PARAM 3
> @@ -132,29 +131,20 @@ virCgroupGetDevicePermsString(int perms)
>  bool
>  virCgroupAvailable(void)
>  {
> -    bool ret = false;
> -    FILE *mounts = NULL;
> -    struct mntent entry;
> -    char buf[CGROUP_MAX_VAL];
> +    size_t i;
> +    virCgroupBackendPtr *backends = virCgroupBackendGetAll();
>
> -    if (!virFileExists("/proc/cgroups"))
> +    if (!backends)
>          return false;
>
> -    if (!(mounts = fopen("/proc/mounts", "r")))
> -        return false;
> -
> -    while (getmntent_r(mounts, &entry, buf, sizeof(buf)) != NULL) {
> -        /* We're looking for at least one 'cgroup' fs mount,
> -         * which is *not* a named mount. */
> -        if (STREQ(entry.mnt_type, "cgroup") &&
> -            !strstr(entry.mnt_opts, "name=")) {
> -            ret = true;
> -            break;
> +    for (i = 0; i < VIR_CGROUP_BACKEND_TYPE_LAST; i++) {
> +        if (backends[i] && backends[i]->available &&
> +            backends[i]->available()) {
>

A little bit down in this patch I see the following comment about the
"available" callback:
/* Mandatory callbacks that need to be implemented for every backend. */

Considering this is part of the mandatory ones, do we really need to do the
`backends[i]->available` check?


> +            return true;
>          }
>      }
>
> -    VIR_FORCE_FCLOSE(mounts);
> -    return ret;
> +    return false;
>  }
>
>
> diff --git a/src/util/vircgroupbackend.h b/src/util/vircgroupbackend.h
> index db052485a8..88f51416b0 100644
> --- a/src/util/vircgroupbackend.h
> +++ b/src/util/vircgroupbackend.h
> @@ -25,14 +25,21 @@
>
>  # include "vircgroup.h"
>
> +# define CGROUP_MAX_VAL 512
>
>  typedef enum {
>      VIR_CGROUP_BACKEND_TYPE_V1 = 0,
>      VIR_CGROUP_BACKEND_TYPE_LAST,
>  } virCgroupBackendType;
>
> +typedef bool
> +(*virCgroupAvailableCB)(void);
> +
>  struct _virCgroupBackend {
>      virCgroupBackendType type;
> +
> +    /* Mandatory callbacks that need to be implemented for every backend.
> */
> +    virCgroupAvailableCB available;
>  };
>  typedef struct _virCgroupBackend virCgroupBackend;
>  typedef virCgroupBackend *virCgroupBackendPtr;
> diff --git a/src/util/vircgroupv1.c b/src/util/vircgroupv1.c
> index 711ebf1128..c5bd2f6a3b 100644
> --- a/src/util/vircgroupv1.c
> +++ b/src/util/vircgroupv1.c
> @@ -20,6 +20,10 @@
>   */
>  #include <config.h>
>
> +#if defined HAVE_MNTENT_H && defined HAVE_GETMNTENT_R
> +# include <mntent.h>
> +#endif
> +
>  #include "internal.h"
>
>  #define __VIR_CGROUP_ALLOW_INCLUDE_PRIV_H__
> @@ -29,6 +33,7 @@
>  #include "vircgroup.h"
>  #include "vircgroupbackend.h"
>  #include "vircgroupv1.h"
> +#include "virfile.h"
>  #include "virlog.h"
>
>  VIR_LOG_INIT("util.cgroup");
> @@ -43,8 +48,38 @@ VIR_ENUM_IMPL(virCgroupV1Controller,
> VIR_CGROUP_CONTROLLER_LAST,
>                "name=systemd");
>
>
> +/* We're looking for at least one 'cgroup' fs mount,
> + * which is *not* a named mount. */
> +static bool
> +virCgroupV1Available(void)
> +{
> +    bool ret = false;
> +    FILE *mounts = NULL;
> +    struct mntent entry;
> +    char buf[CGROUP_MAX_VAL];
> +
> +    if (!virFileExists("/proc/cgroups"))
> +        return false;
> +
> +    if (!(mounts = fopen("/proc/mounts", "r")))
> +        return false;
> +
> +    while (getmntent_r(mounts, &entry, buf, sizeof(buf)) != NULL) {
> +        if (STREQ(entry.mnt_type, "cgroup") && !strstr(entry.mnt_opts,
> "name=")) {
> +            ret = true;
> +            break;
> +        }
> +    }
> +
> +    VIR_FORCE_FCLOSE(mounts);
> +    return ret;
> +}
> +
> +
>  virCgroupBackend virCgroupV1Backend = {
>      .type = VIR_CGROUP_BACKEND_TYPE_V1,
> +
> +    .available = virCgroupV1Available,
>  };
>
>
> --
> 2.17.1
>
> --
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>
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