[src/trunk]: src/sys/rump/librump/rumpvfs * set winsize to memwinsize in init...

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

details:   https://anonhg.NetBSD.org/src/rev/09a519234fa3
branches:  trunk
changeset: 747969:09a519234fa3
user:      pooka <pooka%NetBSD.org@localhost>
date:      Wed Oct 07 09:42:14 2009 +0000

description:
* set winsize to memwinsize in initial getwindow().  makes no functional
  difference, but looks less like a debug hack leftover.
* explain memory windows vs. directio a little better in comment

diffstat:

 sys/rump/librump/rumpvfs/rumpblk.c |  15 ++++++++++++---
 1 files changed, 12 insertions(+), 3 deletions(-)

diffs (39 lines):

diff -r 01779ed8000d -r 09a519234fa3 sys/rump/librump/rumpvfs/rumpblk.c
--- a/sys/rump/librump/rumpvfs/rumpblk.c        Wed Oct 07 09:24:27 2009 +0000
+++ b/sys/rump/librump/rumpvfs/rumpblk.c        Wed Oct 07 09:42:14 2009 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: rumpblk.c,v 1.28 2009/10/07 09:23:03 pooka Exp $       */
+/*     $NetBSD: rumpblk.c,v 1.29 2009/10/07 09:42:14 pooka Exp $       */
 
 /*
  * Copyright (c) 2009 Antti Kantee.  All Rights Reserved.
@@ -40,10 +40,19 @@
  * I/O operation.  It also gives finer-grained control of how to
  * flush data.  Additionally, in case the rump kernel dumps core,
  * we get way less carnage.
+ *
+ * However, it is quite costly in writing large amounts of
+ * file data, since old contents cannot merely be overwritten, but
+ * must be paged in first before replacing (i.e. r/m/w).  Ideally,
+ * we should use directio.  The problem is that directio can fail
+ * silently causing improper file system semantics (i.e. unflushed
+ * data).  Therefore, default to mmap for now.  Even so, directio
+ * _should_ be safe and can be enabled by compiling this module
+ * with -DHAS_DIRECTIO.
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: rumpblk.c,v 1.28 2009/10/07 09:23:03 pooka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: rumpblk.c,v 1.29 2009/10/07 09:42:14 pooka Exp $");
 
 #include <sys/param.h>
 #include <sys/buf.h>
@@ -448,7 +457,7 @@
                         * make sure a) we can mmap at all b) we have the
                         * necessary VA available
                         */
-                       winsize = 1;
+                       winsize = memwinsize;
                        win = getwindow(rblk, off + i*memwinsize, &winsize,
                            &error); 
                        if (win) {