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Date: Sat, 23 Feb 2002 22:21:20 -0800 (PST)
From: Luigi Rizzo <rizzo@icir.org>
Reply-To: Luigi Rizzo <rizzo@icir.org>
To: FreeBSD-gnats-submit@freebsd.org
Cc:
Subject: possible panics with 4:1 filesystem ratios
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>Number:         35269
>Category:       kern
>Synopsis:       possible panics with 4:1 filesystem ratios
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kris
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Feb 23 22:30:01 PST 2002
>Closed-Date:    Sat May 07 23:17:32 GMT 2005
>Last-Modified:  Sat May 07 23:17:32 GMT 2005
>Originator:     Luigi Rizzo
>Release:        FreeBSD 4.5-RELEASE i386
>Organization:
>Environment:
System: FreeBSD iguana.icir.org 4.5-RELEASE FreeBSD 4.5-RELEASE #0: Mon Feb 4 15:00:58 PST 2002 root@iguana.icir.org:/usr/src/sys/compile/ACIRI-4.5-USB i386


	
>Description:
There are likely problems with filesystems having 4:1 block:frag
ratios, possibly leading to panics trying to access unmapped pages.

My suspect is that some part of the code assumes a 8:1 ratio,
so when givne a fragment size, it tries to access an entire
"block" 8 times the size of the fragment.

>How-To-Repeat:
One way is to try and use an NFS-mounted filesystem with 4k:1k blocks/fragments.(e.g. changing the defaults in mount_md in /etc/rc.diskless{1,2} and
using them on a diskless client).
If you are lucky, the faulty code will try to access a block of 8-1k
fragments, the second part of which will be unmapped and thus result in
a panic.
I suspect that you won't be able to reproduce the problem with 2k/512
layouts as the 8 fragments will still be within a page.

>Fix:

source code browsing...


>Release-Note:
>Audit-Trail:
State-Changed-From-To: open->feedback 
State-Changed-By: kris 
State-Changed-When: Mon Jul 14 04:19:03 PDT 2003 
State-Changed-Why:  
Is this still an issue in 5.x? 

http://www.freebsd.org/cgi/query-pr.cgi?pr=35269 
Responsible-Changed-From-To: freebsd-bugs->kris 
Responsible-Changed-By: kris 
Responsible-Changed-When: Fri Aug 15 22:23:46 PDT 2003 
Responsible-Changed-Why:  
I am attempting to verify this 

http://www.freebsd.org/cgi/query-pr.cgi?pr=35269 
State-Changed-From-To: feedback->closed 
State-Changed-By: kris 
State-Changed-When: Sat May 7 23:17:00 GMT 2005 
State-Changed-Why:  
I've been running extensively with 4:1 ratios on the package machines 
without incident.  This seems to be fixed. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=35269 
>Unformatted:
