Issue
I know clone function creates /proc/[pid]/ns/mnt link. But I couldn’t find where it calls something like proc_mkdir to create such directory.
Solution
clone() doesn't create anything in /proc.
When you open /proc/[pid]/ns/mnt, the path lookup logic in VFS finds /proc and then gets to proc_root_lookup().
From there it goes to proc_pid_lookup() to proc_pid_instantiate(), which creates, on the fly, an in-memory directory inode for /proc/[pid] via proc_pid_make_inode().
Answered By - root Answer Checked By - David Marino (WPSolving Volunteer)