[src/trunk]: src/sys/ufs/lfs Lock buffers with B_BUSY between data checksum c...

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

details:   https://anonhg.NetBSD.org/src/rev/38f443743c6a
branches:  trunk
changeset: 467549:38f443743c6a
user:      perseant <perseant%NetBSD.org@localhost>
date:      Thu Mar 25 22:02:36 1999 +0000

description:
Lock buffers with B_BUSY between data checksum calculation and write, so
some other process doesn't change the data after it was checksummed.

diffstat:

 sys/ufs/lfs/lfs_segment.c |  30 ++++++++++++++++++++++++++++--
 1 files changed, 28 insertions(+), 2 deletions(-)

diffs (45 lines):

diff -r c90664c20f88 -r 38f443743c6a sys/ufs/lfs/lfs_segment.c
--- a/sys/ufs/lfs/lfs_segment.c Thu Mar 25 21:55:17 1999 +0000
+++ b/sys/ufs/lfs/lfs_segment.c Thu Mar 25 22:02:36 1999 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: lfs_segment.c,v 1.17 1999/03/25 21:54:10 perseant Exp $        */
+/*     $NetBSD: lfs_segment.c,v 1.18 1999/03/25 22:02:36 perseant Exp $        */
 
 /*-
  * Copyright (c) 1999 The NetBSD Foundation, Inc.
@@ -1119,8 +1119,34 @@
                if (((*++bpp)->b_flags & (B_CALL|B_INVAL)) == (B_CALL|B_INVAL)) {
                        if (copyin((*bpp)->b_saveaddr, dp++, sizeof(u_long)))
                                panic("lfs_writeseg: copyin failed [1]: ino %d blk %d", VTOI((*bpp)->b_vp)->i_number, (*bpp)->b_lblkno);
-               } else
+               } else {
+                       if( !((*bpp)->b_flags & B_CALL) ) {
+                               /*
+                                * Before we record data for a checksm,
+                                * make sure the data won't change in between
+                                * the checksum calculation and the write,
+                                * by marking the buffer B_BUSY.  It will
+                                * be freed later by brelse().
+                                */
+                       again:
+                               s = splbio();
+                               if((*bpp)->b_flags & B_BUSY) {
+#ifdef DEBUG
+                                       printf("lfs_writeseg: avoiding potential data summary corruption for ino %d, lbn %d\n",
+                                              VTOI((*bpp)->b_vp)->i_number,
+                                              bp->b_lblkno);
+#endif
+                                       (*bpp)->b_flags |= B_WANTED;
+                                       tsleep((*bpp), (PRIBIO + 1),
+                                              "lfs_writeseg", 0);
+                                       splx(s);
+                                       goto again;
+                               }
+                               (*bpp)->b_flags |= B_BUSY;
+                               splx(s);
+                       }
                        *dp++ = ((u_long *)(*bpp)->b_data)[0];
+               }
        }
        ssp->ss_create = time.tv_sec;
        ssp->ss_datasum = cksum(datap, (nblocks - 1) * sizeof(u_long));