Hello! > The struct file that is used appears impossible for user space > to get at directly. Therefore I believe we can instead increment > and decrement the namespace count at the same places we increment > and decrement shm_nattach. Ideally we would only increment the > namespace count when shm_nattach goes from 0 to 1 and we would > only decrement the namespace count when shm_nattach goes from 1 to 0. > > Does that make sense? Yes, this would save the day. Indeed, shm_file_ns() is required only when the segment is already mapped, except for shm_mmap() and even there shm_nattch is incremented before do_mmap() is used. It will work. Possibility to use this file directly will be lost. It is a little unpleasant; openvz checkpointing used it to restore sysv shm mappings like another file mappings, it was nice, but this code can be a little uglified to treat those mapping specially. No harm either. Alexey
