*BSD News Article 80491


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From: zeno@serv.net (Sean T. Lamont .)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: single to multiple IP address mapping
Date: 12 Oct 1996 03:38:38 -0700
Organization: ServNet Internet Services, Seattle, WA
Lines: 35
Message-ID: <53nsfe$28c@itchy.serv.net>
NNTP-Posting-Host: itchy.serv.net

I"m not sure if this is a bug or not. In the example I have a 2.1.5 system
mounting an nfs disk from a 2.1.0 system.

cp /kernel /nfs/kernel

mv /nfs/kernel /nfs/kernel.old ; cp /kernel /nfs/kernel
mv /nfs/kernel /nfs/kernel.old ; cp /kernel /nfs/kernel
mv /nfs/kernel /nfs/kernel.old ; cp /kernel /nfs/kernel
......

Each time this is executed, a chunk of disk the size of /kernel is consumed
by the system ; I thought it was an open file descriptor by nfsd or mountd, 
but killing nfsd doesn't seem to free the space. Of course, this above 
operation doesn't lose anything on the local disk.

This is unfortunate, because I'm using something similar to this to manage
our password system. removing /nfs/kernel.old before executing 'mv' seems
to fix the problem, but this bothers me because rename() is an autonomous
operation, and I don't believe you can be left at any point with a nonexistent
/kernel.old file. executing unlink() before rename() is close, but there
still exists the possibility that the unlink() can be called, and then a 
process be swapped in which accesses this (nonexistent) file before the
rename() is called. I don't believe the memory-leaking example has this
possibility.






-- 
Sean T. Lamont, President / Chief NetNerd, Abstract Software, Inc. (ServNet)  
- Internet access * WWW hosting * TCP/IP * UNIX * NEXTSTEP * WWW Development -
email: lamont@abstractsoft.com              WWW:  http://www.serv.net
"...There's no moral, it's just a lot of stuff that happens". - H. Simpson