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in vtruncbuf(), use a "synchronous freeing" flush to prevent a race

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between write i/os in a disk-based filesystem vs. the disk block being
freed by a truncation, allocated to a new file, and written again with
different data.  if the disk driver reorders the requests and does
the second i/o first, the old data will clobber the new, corrupting
the new file.
This commit is contained in:
chs 2001-01-08 07:05:47 +00:00
parent 9bbe5b85ca
commit 6717a2ac1b
1 changed files with 2 additions and 2 deletions
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4
sys/kern/vfs_subr.c
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@ -1,4 +1,4 @@
/* $NetBSD: vfs_subr.c,v 1.143 2000/12/31 03:13:51 sommerfeld Exp $ */
/* $NetBSD: vfs_subr.c,v 1.144 2001/01/08 07:05:47 chs Exp $ */
/*-
* Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
@ -748,7 +748,7 @@ vtruncbuf(vp, lbn, slpflag, slptimeo)
simple_lock(&uobj->vmobjlock);
rv = (uobj->pgops->pgo_flush)(uobj,
round_page(lbn << vp->v_mount->mnt_fs_bshift),
vp->v_uvm.u_size, PGO_FREE);
vp->v_uvm.u_size, PGO_FREE|PGO_SYNCIO);
simple_unlock(&uobj->vmobjlock);
if (!rv) {
splx(s);