[src/trunk]: src/sys/miscfs/genfs when zeroing pages past EOF, don't zero the...

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

details:   https://anonhg.NetBSD.org/src/rev/54c3cb15cf69
branches:  trunk
changeset: 515270:54c3cb15cf69
user:      chs <chs%NetBSD.org@localhost>
date:      Fri Sep 21 07:52:25 2001 +0000

description:
when zeroing pages past EOF, don't zero the page containing EOF if it
already contains valid data.  should fix PRs 13361 and 13436.

diffstat:

 sys/miscfs/genfs/genfs_vnops.c |  14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diffs (32 lines):

diff -r 2f4b6108a300 -r 54c3cb15cf69 sys/miscfs/genfs/genfs_vnops.c
--- a/sys/miscfs/genfs/genfs_vnops.c    Fri Sep 21 07:11:33 2001 +0000
+++ b/sys/miscfs/genfs/genfs_vnops.c    Fri Sep 21 07:52:25 2001 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: genfs_vnops.c,v 1.37 2001/09/15 20:36:38 chs Exp $     */
+/*     $NetBSD: genfs_vnops.c,v 1.38 2001/09/21 07:52:25 chs Exp $     */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -640,12 +640,20 @@
 
        /*
         * if EOF is in the middle of the range, zero the part past EOF.
+        * if the page including EOF is not PG_FAKE, skip over it since
+        * in that case it has valid data that we need to preserve.
         */
 
        if (tailbytes > 0) {
+               size_t tailstart = bytes;
+
+               if ((pgs[bytes >> PAGE_SHIFT]->flags & PG_FAKE) == 0) {
+                       tailstart = round_page(tailstart);
+                       tailbytes -= tailstart - bytes;
+               }
                UVMHIST_LOG(ubchist, "tailbytes %p 0x%x 0x%x",
-                           kva, bytes, tailbytes,0);
-               memset((void *)(kva + bytes), 0, tailbytes);
+                           kva, tailstart, tailbytes,0);
+               memset((void *)(kva + tailstart), 0, tailbytes);
        }
 
        /*