[CRIU] [PATCH] mount: detect the newinstance option for devpts

[Pavel Emelyanov]

On 04/01/2014 02:44 PM, Andrey Vagin wrote:
> The devpts instance was mounted w/o the newinstance option if,
> the device number is equal to the root /dev/pts.
> 
> I think this condition is strong enough to not mount devpts in a
> temporary place.
> 
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  include/fs-magic.h |  4 ++++
>  mount.c            | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 61 insertions(+)
> 
> diff --git a/include/fs-magic.h b/include/fs-magic.h
> index d31a939..9db3ee9 100644
> --- a/include/fs-magic.h
> +++ b/include/fs-magic.h
> @@ -29,4 +29,8 @@
>  # define SOCKFS_MAGIC		0x534f434b
>  #endif
>  
> +#ifndef DEVPTS_SUPER_MAGIC
> +#define DEVPTS_SUPER_MAGIC	0x1cd1
> +#endif
> +
>  #endif /* __CR_FS_MAGIC_H__ */
> diff --git a/mount.c b/mount.c
> index 10d1378..71fbf97 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -23,6 +23,7 @@
>  #include "proc_parse.h"
>  #include "image.h"
>  #include "namespaces.h"
> +#include "fs-magic.h"
>  #include "protobuf.h"
>  #include "protobuf/mnt.pb-c.h"
>  
> @@ -578,6 +579,61 @@ out:
>  	return NULL;
>  }
>  
> +/* Is it mounted w or w/o the newinstance option */
> +static int devpts_dump(struct mount_info *pm)
> +{
> +	static const char newinstance[] = ",newinstance";
> +	static struct stat host_st = {};
> +	struct stat st;
> +	DIR *fdir = NULL;
> +	char *buf;
> +	int len;
> +
> +	if (host_st.st_dev == 0) {
> +		struct statfs fst;
> +
> +		if (statfs("/dev/pts", &fst)) {
> +			pr_perror("Unable to statefs /dev/pts");
> +			return -1;
> +		}
> +		if (fst.f_type != DEVPTS_SUPER_MAGIC) {
> +			pr_err("devpts isn't mount on the host\n");
> +			return -1;
> +		}
> +
> +		/* The root /dev/pts is mounted w/o newinstance, isn't it? */
> +		if (stat("/dev/pts", &host_st)) {
> +			pr_perror("Unable to state /dev/pts");
> +			return -1;
> +		}
> +	}

The host.bla-bla-bla should be in kerndat.c

> +
> +	fdir = open_mountpoint(pm);
> +	if (fdir == NULL)
> +		return -1;
> +
> +	if (fstat(dirfd(fdir), &st)) {
> +		pr_perror("Unable to statfs %d:%s",
> +				pm->mnt_id, pm->mountpoint);
> +		close_mountpoint(fdir);
> +		return -1;
> +	}
> +	close_mountpoint(fdir);
> +
> +	if (host_st.st_dev == st.st_dev)
> +		return 0;
> +
> +	len = strlen(pm->options);
> +	buf = xrealloc(pm->options, len + sizeof(newinstance));
> +	if (buf == NULL)
> +		return -1;
> +	memcpy(buf, newinstance, sizeof(newinstance));
> +
> +	pm->options = buf;
> +
> +	return 0;
> +}
> +
>  static int tmpfs_dump(struct mount_info *pm)
>  {
>  	int ret = -1;
> @@ -694,6 +750,7 @@ static struct fstype fstypes[] = {
>  		.restore = tmpfs_restore,
>  	}, {
>  		.name = "devpts",
> +		.dump = devpts_dump,
>  		.code = FSTYPE__DEVPTS,
>  	}, {
>  		.name = "simfs",
>