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From: sadler@heurikon.UUCP (Jon Sadler)
Newsgroups: comp.protocols.nfs
Subject: Re: WHat is "Stale NFS handle"?
Message-ID: <292@heurikon.UUCP>
Date: 20 Jan 89 16:19:51 GMT
References: <1747@valhalla.ee.rochester.edu>
Reply-To: sadler@heurikon.UUCP (Jon Sadler)
Organization: Heurikon Corp., Madison WI
Lines: 34

In article <495@larry.UUCP> jwp@larry.uucp asks about "Stale NFS handle"

To answer this requires some murking around in how NFS really works.

     For example, I create a file called /export/foo, give full world permi-
sions to it.  Whenever I open this file on a NFS client machine, a "file-
handle" (a local structure containing info on the file ranging from the current
position in the file, to the machine it lives on, etc.) is created in-core (in
the kernal).  All access to the file reference this structure, and then are
sent to the remote machine via Sun's RPC.

Now, imagine the following scenerio:

     Say I run /bin/more on the file /export/foo.  Since NFS is stateless,
the server does not know that the file is being accessed, only that there are
requests coming in for data inside the file.  Now say I pause for a half-minute,
while more is prompting me, and someone on the server deletes /export/foo.
When bin/more does to ask for more data (because I hit a key, and it needs more
data), the file will not exist anymore.  Further, the head-inode for
/export/foo may have been re-used in another file.  At this point, /bin/more
will return an error, and the client will say "Stale-File Handle".  Why?
Because the file-handle created for referencing /export/foo is no longer
"up-to-date".  (In other words, it is stale.)

I hope this answers your questions.

Jonathan Sadler
Heurikon Corp.
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