[CRIU] [PATCH] files-reg: discover file system type only if file is going to be dumped

[Andrew Vagin]

On Tue, Aug 02, 2016 at 07:05:18PM +0300, Stanislav Kinsburskiy wrote:
> Instead of calling it in fill_fd_params_special (which is called for any found
> path).
> This reduces amount of system calls on dump.
> 
> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
> ---
>  criu/cr-dump.c |   47 +++++++++++++++++++++++++++--------------------
>  1 file changed, 27 insertions(+), 20 deletions(-)
> 
> diff --git a/criu/cr-dump.c b/criu/cr-dump.c
> index 2288908..e51e258 100644
> --- a/criu/cr-dump.c
> +++ b/criu/cr-dump.c
> @@ -215,8 +215,6 @@ static int collect_fds(pid_t pid, struct parasite_drain_fd **dfds)
>  
>  static int fill_fd_params_special(int fd, struct fd_parms *p)
>  {
> -	struct statfs fst;
> -
>  	*p = FD_PARMS_INIT;
>  
>  	if (fstat(fd, &p->stat) < 0) {
> @@ -227,13 +225,28 @@ static int fill_fd_params_special(int fd, struct fd_parms *p)
>  	if (get_fd_mntid(fd, &p->mnt_id))
>  		return -1;
>  
> -	if (fstatfs(fd, &fst)) {
> -		pr_perror("Unable to statfs fd %d", fd);
> +	return 0;
> +}
> +
> +static int get_fs_type(int lfd)
> +{
> +	struct statfs fst;
> +
> +	if (fstatfs(lfd, &fst)) {
> +		pr_perror("Unable to statfs fd %d", lfd);
>  		return -1;
>  	}
> +	return fst.f_type;
> +}
>  
> -	p->fs_type = fst.f_type;
> -
> +static int dump_one_reg_file_cond(int lfd, u32 *id, struct fd_parms *parms)
> +{
> +	if (fd_id_generate_special(parms, id)) {
> +		parms->fs_type = get_fs_type(lfd);
> +		if (parms->fs_type < 0)
> +			return -1;

Why do we get fs_type here. Can we move it in dump_one_reg_file?

> +		return dump_one_reg_file(lfd, *id, parms);
> +	}
>  	return 0;
>  }
>  
> @@ -249,8 +262,7 @@ static int dump_task_exe_link(pid_t pid, MmEntry *mm)
>  	if (fill_fd_params_special(fd, &params))
>  		return -1;
>  
> -	if (fd_id_generate_special(&params, &mm->exe_file_id))
> -		ret = dump_one_reg_file(fd, mm->exe_file_id, &params);
> +	ret = dump_one_reg_file_cond(fd, &mm->exe_file_id, &params);
>  
>  	close(fd);
>  	return ret;
> @@ -272,11 +284,9 @@ static int dump_task_fs(pid_t pid, struct parasite_dump_misc *misc, struct cr_im
>  	if (fill_fd_params_special(fd, &p))
>  		return -1;
>  
> -	if (fd_id_generate_special(&p, &fe.cwd_id)) {
> -		ret = dump_one_reg_file(fd, fe.cwd_id, &p);
> -		if (ret < 0)
> -			return ret;
> -	}
> +	ret = dump_one_reg_file_cond(fd, &fe.cwd_id, &p);
> +	if (ret < 0)
> +		return ret;
>  
>  	close(fd);
>  
> @@ -287,11 +297,9 @@ static int dump_task_fs(pid_t pid, struct parasite_dump_misc *misc, struct cr_im
>  	if (fill_fd_params_special(fd, &p))
>  		return -1;
>  
> -	if (fd_id_generate_special(&p, &fe.root_id)) {
> -		ret = dump_one_reg_file(fd, fe.root_id, &p);
> -		if (ret < 0)
> -			return ret;
> -	}
> +	ret = dump_one_reg_file_cond(fd, &fe.root_id, &p);
> +	if (ret < 0)
> +		return ret;
>  
>  	close(fd);
>  
> @@ -398,8 +406,7 @@ static int dump_filemap(struct vma_area *vma_area, int fd)
>  
>  	/* Flags will be set during restore in open_filmap() */
>  
> -	if (fd_id_generate_special(&p, &id))
> -		ret = dump_one_reg_file(fd, id, &p);
> +	ret = dump_one_reg_file_cond(fd, &id, &p);
>  
>  	vma->shmid = id;
>  	return ret;
>