[libvirt] [PATCH 1/6] Add virFileIsMountPoint function

[Chen Hanxiao]

Reviewed-by: Chen Hanxiao <chenhanxiao at cn.fujitsu.com>

> -----Original Message-----
> From: libvir-list-bounces at redhat.com
[mailto:libvir-list-bounces at redhat.com]
> On Behalf Of Daniel P. Berrange
> Sent: Monday, October 07, 2013 9:07 PM
> To: libvir-list at redhat.com
> Subject: [libvirt] [PATCH 1/6] Add virFileIsMountPoint function
> 
> From: "Daniel P. Berrange" <berrange at redhat.com>
> 
> Add a function for efficiently checking if a path is a filesystem
> mount point.
> 
> NB will not work for bind mounts, only true filesystem mounts.
> 
> Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
> ---
>  src/libvirt_private.syms |  1 +
>  src/util/virfile.c       | 58
> ++++++++++++++++++++++++++++++++++++++++++++++++
>  src/util/virfile.h       |  2 ++
>  3 files changed, 61 insertions(+)
> 
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index fe40834..31fa604 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1182,6 +1182,7 @@ virFileIsAbsPath;
>  virFileIsDir;
>  virFileIsExecutable;
>  virFileIsLink;
> +virFileIsMountPoint;
>  virFileLinkPointsTo;
>  virFileLock;
>  virFileLoopDeviceAssociate;
> diff --git a/src/util/virfile.c b/src/util/virfile.c
> index e10de5a..fa21aeb 100644
> --- a/src/util/virfile.c
> +++ b/src/util/virfile.c
> @@ -1513,6 +1513,64 @@ virFileIsExecutable(const char *file)
>      return false;
>  }
> 
> +
> +/*
> + * Check that a file refers to a mount point. Trick is that for
> + * a mount point, the st_dev field will differ from the parent
> + * directory.
> + *
> + * Note that this will not detect bind mounts of dirs/files,
> + * only true filesystem mounts.
> + */
> +int virFileIsMountPoint(const char *file)
> +{
> +    char *parent = NULL;
> +    char *tmp;
> +    int ret = -1;
> +    struct stat sb1, sb2;
> +
> +    if (VIR_STRDUP_QUIET(parent, file) < 0)
> +        goto cleanup;
> +
> +    if (!(tmp = strrchr(parent, '/'))) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR,
> +                       _("Could not find '/' in '%s'"),
> +                       file);
> +        goto cleanup;
> +    }
> +
> +    *tmp = '\0';
> +
> +    VIR_DEBUG("Comparing '%s' to '%s'", file, parent);
> +
> +    if (stat(file, &sb1) < 0) {
> +        if (errno == ENOENT)
> +            ret = 0;
> +        else
> +            virReportSystemError(errno,
> +                                 _("Cannot stat '%s'"),
> +                                 file);
> +        goto cleanup;
> +    }
> +
> +    if (stat(parent, &sb2) < 0) {
> +        virReportSystemError(errno,
> +                             _("Cannot stat '%s'"),
> +                             parent);
> +        goto cleanup;
> +    }
> +
> +    if (!S_ISDIR(sb1.st_mode))
> +        return false;
> +
> +    ret = sb1.st_dev != sb2.st_dev;
> +    VIR_DEBUG("Is mount %d", ret);
> +
> + cleanup:
> +    VIR_FREE(parent);
> +    return ret;
> +}
> +
>  #ifndef WIN32
>  /* Check that a file is accessible under certain
>   * user & gid.
> diff --git a/src/util/virfile.h b/src/util/virfile.h
> index 72d35ce..ff84719 100644
> --- a/src/util/virfile.h
> +++ b/src/util/virfile.h
> @@ -156,6 +156,8 @@ bool virFileIsDir (const char *file)
> ATTRIBUTE_NONNULL(1);
>  bool virFileExists(const char *file) ATTRIBUTE_NONNULL(1);
>  bool virFileIsExecutable(const char *file) ATTRIBUTE_NONNULL(1);
> 
> +int virFileIsMountPoint(const char *file) ATTRIBUTE_NONNULL(1);
> +
>  char *virFileSanitizePath(const char *path);
> 
>  enum {
> --
> 1.8.3.1
> 
> --
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