[src/trunk]: src/sys/miscfs/specfs Hang a warning banner on some nasty code I...

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

details:   https://anonhg.NetBSD.org/src/rev/93f9d115fc9e
branches:  trunk
changeset: 787416:93f9d115fc9e
user:      dholland <dholland%NetBSD.org@localhost>
date:      Sun Jun 16 20:46:24 2013 +0000

description:
Hang a warning banner on some nasty code I just found.

diffstat:

 sys/miscfs/specfs/spec_vnops.c |  20 ++++++++++++++++++--
 1 files changed, 18 insertions(+), 2 deletions(-)

diffs (47 lines):

diff -r 0631f05c1ccc -r 93f9d115fc9e sys/miscfs/specfs/spec_vnops.c
--- a/sys/miscfs/specfs/spec_vnops.c    Sun Jun 16 19:05:00 2013 +0000
+++ b/sys/miscfs/specfs/spec_vnops.c    Sun Jun 16 20:46:24 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: spec_vnops.c,v 1.137 2013/02/13 14:03:48 hannken Exp $ */
+/*     $NetBSD: spec_vnops.c,v 1.138 2013/06/16 20:46:24 dholland Exp $        */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -58,7 +58,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.137 2013/02/13 14:03:48 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.138 2013/06/16 20:46:24 dholland Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -683,12 +683,28 @@
                if (uio->uio_offset < 0)
                        return (EINVAL);
                bsize = BLKDEV_IOSIZE;
+
+               /*
+                * dholland 20130616: XXX this logic should not be
+                * here. It is here because the old buffer cache
+                * demands that all accesses to the same blocks need
+                * to be the same size; but it only works for FFS and
+                * nowadays I think it'll fail silently if the size
+                * info in the disklabel is wrong. (Or missing.) The
+                * buffer cache needs to be smarter; or failing that
+                * we need a reliable way here to get the right block
+                * size; or a reliable way to guarantee that (a) the
+                * fs is not mounted when we get here and (b) any
+                * buffers generated here will get purged when the fs
+                * does get mounted.
+                */
                if (bdev_ioctl(vp->v_rdev, DIOCGPART, &dpart, FREAD, l) == 0) {
                        if (dpart.part->p_fstype == FS_BSDFFS &&
                            dpart.part->p_frag != 0 && dpart.part->p_fsize != 0)
                                bsize = dpart.part->p_frag *
                                    dpart.part->p_fsize;
                }
+
                bscale = bsize >> DEV_BSHIFT;
                do {
                        bn = (uio->uio_offset >> DEV_BSHIFT) &~ (bscale - 1);