[src/trunk]: src/sys/kern Remove the slop code. Suggested by mrg@

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d643d3a086b0
branches:  trunk
changeset: 456370:d643d3a086b0
user:      christos <christos%NetBSD.org@localhost>
date:      Sun May 05 20:45:08 2019 +0000

description:
Remove the slop code. Suggested by mrg@

diffstat:

 sys/kern/sys_select.c |  18 +++++++++++-------
 1 files changed, 11 insertions(+), 7 deletions(-)

diffs (42 lines):

diff -r afdd884d4fc0 -r d643d3a086b0 sys/kern/sys_select.c
--- a/sys/kern/sys_select.c     Sun May 05 20:10:57 2019 +0000
+++ b/sys/kern/sys_select.c     Sun May 05 20:45:08 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_select.c,v 1.42 2019/05/04 15:46:58 christos Exp $ */
+/*     $NetBSD: sys_select.c,v 1.43 2019/05/05 20:45:08 christos Exp $ */
 
 /*-
  * Copyright (c) 2007, 2008, 2009, 2010 The NetBSD Foundation, Inc.
@@ -84,7 +84,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_select.c,v 1.42 2019/05/04 15:46:58 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_select.c,v 1.43 2019/05/05 20:45:08 christos Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -488,14 +488,18 @@
        int             error;
        size_t          ni;
 
-       if (nfds > MAX(1000 + curlwp->l_fd->fd_dt->dt_nfiles,
-           curlwp->l_proc->p_rlimit[RLIMIT_NOFILE].rlim_cur)) {
+       if (nfds > curlwp->l_proc->p_rlimit[RLIMIT_NOFILE].rlim_cur) {
                /*
-                * Either the user passed in a very sparse 'fds' or junk!
-                * The kmem_alloc() call below would be bad news.
-                * We could process the 'fds' array in chunks, but that
+                * Prevent userland from causing over-allocation.
+                * Raising the default limit too high can still cause
+                * a lot of memory to be allocated, but this also means
+                * that the file descriptor array will also be large.
+                *
+                * To reduce the memory requirements here, we could 
+                * process the 'fds' array in chunks, but that
                 * is a lot of code that isn't normally useful.
                 * (Or just move the copyin/out into pollscan().)
+                *
                 * Historically the code silently truncated 'fds' to
                 * dt_nfiles entries - but that does cause issues.
                 */