From pb@fasterix.freenix.fr  Sun May 28 06:01:13 1995
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Date: Sun, 28 May 1995 14:56:52 +0200
From: Pierre Beyssac <pb@fasterix.freenix.fr>
Reply-To: pb@fasterix.freenix.fr
To: FreeBSD-gnats-submit@freebsd.org
Subject: page fault in pagedaemon on vnode swapping
X-Send-Pr-Version: 3.2

>Number:         452
>Category:       kern
>Synopsis:       vnode swapping panics
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    davidg
>State:          closed
>Quarter:
>Keywords:
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun May 28 06:10:01 1995
>Closed-Date:    Wed Oct 23 18:26:16 PDT 1996
>Last-Modified:  Wed Oct 23 18:27:12 PDT 1996
>Originator:     Pierre Beyssac
>Release:        FreeBSD 2.0-BUILT-19950528 i386
>Organization:
Pierre Beyssac
>Environment:

	Diskless 486 PC.
	RAM : 4Mb
	Swap : 8Mb vnconfig'd in /swp

>Description:

	Swapping works for awhile (swapinfo indicates 10-15% used).
	After some short time (apparently when a big amount of pages
	is swapped out at the same time to make room, e.g. to start
	"vi") the same panic occurs.

Hand-copied from DDB :

trap 12
page fault while in kernel mode
supervisor read, page not present
process 2 (pagedaemon)

Stack trace:

bcopy		(apparently in macro nfsm_fhtom() in nfs_vnops.c:912)
nfs_writerpc
nfs_doio
nfs_strategy
vnstrategy
spec_strategy
swstrategy
spec_strategy
swap_pager_output
swap_pager_putmulti
vm_pager_put_pages
vm_pageout_clean
vm_pageout_scan
vm_pageout
getpbuf

>How-To-Repeat:

	Make /swp a 8Mb file.

	Boot the diskless (4Mb) PC.

	# vnconfig -e /dev/vn0c /swp swap
	# swapinfo
	# vi something

>Fix:
	
	None known.
	Direct NFS-swap doesn't help : many processes get a SIGSEGV
	and the kernel quickly panics too.
	Probably local swap works, I'll try that next.
>Release-Note:
>Audit-Trail:
State-Changed-From-To: open->feedback 
State-Changed-By: pst 
State-Changed-When: Wed Feb 7 15:45:54 PST 1996 
State-Changed-Why:  
Please verify that this problem has been addressed in released code. 


Responsible-Changed-From-To: freebsd-bugs->davidg 
Responsible-Changed-By: pst 
Responsible-Changed-When: Wed Feb 7 15:45:54 PST 1996 
Responsible-Changed-Why:  
State-Changed-From-To: feedback->closed 
State-Changed-By: scrappy 
State-Changed-When: Wed Oct 23 18:26:16 PDT 1996 
State-Changed-Why:  

Originator confirms closure 
>Unformatted:


