[CRIU] [PATCH] files: predump_one_fd -- Use direct read of pid's fd link

[Andrew Vagin]

On Mon, Mar 31, 2014 at 11:04:25PM +0400, Cyrill Gorcunov wrote:
> Using O_PATH known to be buggy on 3.11 kernel so use
> direct link reading procedure here.

Acked-by: Andrew Vagin <avagin at parallels.com>

> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  files.c | 35 +++++++++++------------------------
>  1 file changed, 11 insertions(+), 24 deletions(-)
> 
> diff --git a/files.c b/files.c
> index 3cf5e470c5c0..5140d8edc1b0 100644
> --- a/files.c
> +++ b/files.c
> @@ -405,34 +405,22 @@ err:
>  
>  static int predump_one_fd(int pid, int fd)
>  {
> -	int lfd, ret = 0;
> -	struct statfs buf;
>  	const struct fdtype_ops *ops;
> -	char link[32];
> -
> -	/*
> -	 * This should look like the dump_task_files_seized,
> -	 * but since we pre-dump only *notify-s, we use the
> -	 * enightened version without fds draining.
> -	 */
> -
> -	lfd = __open_proc(pid, O_PATH | O_RDONLY, "fd/%d", fd);
> -	if (lfd < 0)
> -		return 0; /* That's OK, it can be a socket */
> +	char link[PATH_MAX], t[32];
> +	int ret = 0;
>  
> -	if (fstatfs(lfd, &buf)) {
> -		pr_perror("Can't fstatfs file");
> +	snprintf(t, sizeof(t), "/proc/%d/fd/%d", pid, fd);
> +	ret = readlink(t, link, sizeof(link));
> +	if (ret < 0) {
> +		pr_perror("Can't read link of fd %d", fd);
> +		return -1;
> +	} else if ((size_t)ret == sizeof(link)) {
> +		pr_err("Buffer for read link of fd %d is too small\n", fd);
>  		return -1;
>  	}
> +	link[ret] = 0;
>  
> -	if (buf.f_type != ANON_INODE_FS_MAGIC)
> -		goto out;
> -
> -	if (read_fd_link(lfd, link, sizeof(link)) < 0) {
> -		ret = -1;
> -		goto out;
> -	}
> -
> +	ret = 0;
>  	if (is_inotify_link(link))
>  		ops = &inotify_dump_ops;
>  	else if (is_fanotify_link(link))
> @@ -443,7 +431,6 @@ static int predump_one_fd(int pid, int fd)
>  	pr_debug("Pre-dumping %d's %d fd\n", pid, fd);
>  	ret = ops->pre_dump(pid, fd);
>  out:
> -	close(lfd);
>  	return ret;
>  }
>  
> -- 
> 1.8.3.1
>