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From: Terry Lambert <terry@lambert.org>
Message-Id: <199601231751.KAA17851@phaeton.artisoft.com>
Subject: Re: NFS trouble ?
To: m_tanaka@pa.yokogawa.co.jp (Mihoko Tanaka)
Date: Tue, 23 Jan 1996 10:51:12 -0700 (MST)
Cc: freebsd-hackers@freebsd.org
In-Reply-To: <9601231404.AA28044@cabbage.pa.yokogawa.co.jp> from "Mihoko Tanaka" at Jan 23, 96 11:04:54 pm
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> Hello All,
> 
> My friend is developping a program which seek a file and read it.
> Her program seeks a file with a wrong offset (i.e the offset size is larger
> than the file size). It occurs panic.
> 
> When a file is on a local disk, nothing happens.
> But when a file is on NFS, it occurs panic everytime.

Does it panic the NFS client or the NFS server?

>      off_t lseek(int fd, off_t offset, int whence)
> 
> off_t is defined in /usr/include/sys/types.h : 
>     typedef long long     off_t
> 
> then
> 	off_t offset = 0x90000000 > 0

I am suspiscious of > 31 bit offset values over NFS.  I suspect that
there would be problems, since I believe the protocol limit is 32 bits
with one bit for the sign bit for the return of error codes.

I believe this is your problem.

> I guess that lseek should return a error (EINVAL) when 'offset' is
> larger then the file size . 
> What do you think ?

No.  A seek to a valid location not in the file is perfectly legal,
even when followed by a read or a write (the first should return an
EOF error, the second should cause the file to be sparse).


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.