Date: Thu, 13 Aug 1998 18:00:01 -0700 (PDT) From: Matthew Dillon <dillon@backplane.com> To: freebsd-bugs@FreeBSD.ORG Subject: Re: kern/7422: FreeBSD-current VM systems do not properly remove mapped Message-ID: <199808140100.SAA11729@freefall.freebsd.org>
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The following reply was made to PR kern/7422; it has been noted by GNATS.
From: Matthew Dillon <dillon@backplane.com>
To: Luoqi Chen <luoqi@chen.ml.org>
Cc: freebsd-gnats-submit@freebsd.org, luoqi@watermarkgroup.com
Subject: Re: kern/7422: FreeBSD-current VM systems do not properly remove mapped
Date: Thu, 13 Aug 1998 17:48:38 -0700 (PDT)
Great! That's one down! I was hoping someone would be able to fix
that one quickly and, indeed, so it happens!
I'll run the patch on our -current test box (running a news system) to
life-test it.
The mmap-reading/file-writing corruption is going to be a much stickier
problem to solve. I think the key item is that the only thing writing
to the file is write(), and a shared+RO mmap() is capable of causing the
written file data to become corrupted as of the time of the write or
as of a slightly later time. I've been concentrating on the page fault
code trying to figure out how it could corrupt the buffer cache, but
it's virtual black magic to me.
-Matt
Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet
Communications
<dillon@backplane.com> (Please include original email in any response)
:This is a one-line bug in vnode_pager_setsize() function. Below is
:the fix, note that the higher end of page index range in function
:vm_object_page_remove() is not inclusive (I got rid of some auto
:variables and unused calculation, so the fix is more than one line).
:This bug should exist in -stable also, not sure why it behaved
:correctly (I don't have a -stable machine to test with).
:
:-lq
:
:Index: sys/vm/vnode_pager.c
:===================================================================
:RCS file: /fun/cvs/src/sys/vm/vnode_pager.c,v
:retrieving revision 1.94
:diff -u -r1.94 vnode_pager.c
:...
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