Re: [PATCH 2/4] proc: Simplify proc_get_sb.

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

Eric W. Biederman wrote:
> The idle_thread now has a struct pid, so we can always find out know
> the pid of the child_reaper before we mount proc.
> 
> Therefore we can remove the special cases for getting the pid of the
> child_reaper from proc_get_sb.
> 
> Signed-off-by: Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
> ---
>  fs/proc/root.c |   17 +----------------
>  1 files changed, 1 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/proc/root.c b/fs/proc/root.c
> index 81f99e6..f442967 100644
> --- a/fs/proc/root.c
> +++ b/fs/proc/root.c
> @@ -46,17 +46,6 @@ static int proc_get_sb(struct file_system_type *fs_type,
>  	struct pid_namespace *ns;
>  	struct proc_inode *ei;
>  
> -	if (proc_mnt) {
> -		/* Seed the root directory with a pid so it doesn't need
> -		 * to be special in base.c.  I would do this earlier but
> -		 * the only task alive when /proc is mounted the first time
> -		 * is the init_task and it doesn't have any pids.
> -		 */
> -		ei = PROC_I(proc_mnt->mnt_sb->s_root->d_inode);
> -		if (!ei->pid)
> -			ei->pid = find_get_pid(1);
> -	}
> -
>  	if (flags & MS_KERNMOUNT)
>  		ns = (struct pid_namespace *)data;
>  	else
> @@ -76,11 +65,7 @@ static int proc_get_sb(struct file_system_type *fs_type,
>  		}
>  
>  		ei = PROC_I(sb->s_root->d_inode);
> -		if (!ei->pid) {
> -			rcu_read_lock();
> -			ei->pid = get_pid(find_pid_ns(1, ns));
> -			rcu_read_unlock();
> -		}
> +		ei->pid = get_pid(ns->child_reaper);

That's not git-bisect safe - you move the child_reaper initialization
before the call to prepare_proc only in the 4th patch.

>  		sb->s_flags |= MS_ACTIVE;
>  		ns->proc_mnt = mnt;