On Tue, May 21, 2019 at 05:30:27PM +0100, David Howells wrote: > Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > Umm... That's going to be very painful if you dup2() something to MAX_INT and > > then run that; roughly 2G iterations of bouncing ->file_lock up and down, > > without anything that would yield CPU in process. > > > > If anything, I would suggest something like > > > > fd = *start_fd; > > grab the lock > > fdt = files_fdtable(files); > > more: > > look for the next eviction candidate in ->open_fds, starting at fd > > if there's none up to max_fd > > drop the lock > > return NULL > > *start_fd = fd + 1; > > if the fscker is really opened and not just reserved > > rcu_assign_pointer(fdt->fd[fd], NULL); > > __put_unused_fd(files, fd); > > drop the lock > > return the file we'd got > > if (unlikely(need_resched())) > > drop lock > > cond_resched(); > > grab lock > > fdt = files_fdtable(files); > > goto more; > > > > with the main loop being basically > > while ((file = pick_next(files, &start_fd, max_fd)) != NULL) > > filp_close(file, files); > > If we can live with close_from(int first) rather than close_range(), then this > can perhaps be done a lot more efficiently by: Yeah, you mentioned this before. I do like being able to specify an upper bound to have the ability to place fds strategically after said upper bound. I have used this quite a few times where I know that given task may have inherited up to m fds and I want to inherit a specific pipe who's fd I know. Then I'd dup2(pipe_fd, <upper_bound + 1>) and then close all other fds. Is that too much of a corner case? Christian
