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
