[CRIU] [PATCH] mount: Create target of bind mount if it doesn't exist

[Saied Kazemi]

I have seen a similar case where /dev/null is missing (Docker using
UnionFS).  While this patch fixes the issue, I am wondering why the target
file should be missing to start with and whether *always* recreating
missing target files could be masking more serious issues.  Any thoughts?

--Saied



On Thu, Aug 28, 2014 at 8:27 AM, Tycho Andersen <
tycho.andersen at canonical.com> wrote:

> If the target of a bind mount doesn't exist, create it. In particular, this
> happens with /dev/ptmx across hosts under LXC. We could also mkdir -p any
> path
> to the target, although I'm not sure if that is a case that occurrs in the
> wild.
>
> Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> ---
>  mount.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/mount.c b/mount.c
> index 9bb8a17..2108907 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -1346,6 +1346,24 @@ static int do_bind_mount(struct mount_info *mi)
>                 root = rpath;
>  do_bind:
>                 pr_info("\tBind %s to %s\n", root, mi->mountpoint);
> +
> +               if (access(mi->mountpoint, F_OK)) {
> +                       if (errno == ENOENT) {
> +                               FILE *f;
> +
> +                               f = fopen(mi->mountpoint, "w");
> +                               if (!f) {
> +                                       pr_perror("couldn't write 0 length
> %s", mi->mountpoint);
> +                                       return -1;
> +                               }
> +
> +                               fclose(f);
> +                       } else {
> +                               pr_perror("Couldn't access %s",
> mi->mountpoint);
> +                               return -1;
> +                       }
> +               }
> +
>                 if (mount(root, mi->mountpoint, NULL,
>                                         MS_BIND, NULL) < 0) {
>                         pr_perror("Can't mount at %s", mi->mountpoint);
> --
> 1.9.1
>
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