kern/120869: [procfs] 'stat' shows that all files have 0-length when they are actually not empty

[Bruce Evans]

The following reply was made to PR kern/120869; it has been noted by GNATS.

From: Bruce Evans <brde at optusnet.com.au>
To: Robert Watson <rwatson at freebsd.org>
Cc: remko at freebsd.org, freebsd-fs at freebsd.org, yuri at tsoft.com,
        bug-followup at freebsd.org
Subject: Re: kern/120869: [procfs] 'stat' shows that all files have 0-length
 when they are actually not empty
Date: Thu, 21 Feb 2008 20:24:13 +1100 (EST)

 On Wed, 20 Feb 2008, Robert Watson wrote:
 
 > On Wed, 20 Feb 2008, remko at FreeBSD.org wrote:
 >
 >> After a bit of discussion, this is not something which we are going to fix. 
 >> It is not worth the hassle. If you think this should be different, we do 
 >> welcome patches. Thanks fo rusing FreeBSD!
 >
 > Just as two data points here: Solaris attempts to provide coherent file sizes 
 > in /proc (at least to the extent that tried a few for objects where it is 
 > remotely possible), and the Linux 2.6.12 kernel I have on a box locally 
 > basically doesn't.
 >
 > My view is that it's a synthetic file system with data that varies 
 > dynamically at runtime, and that while it wouldn't hurt to produce file size 
 > information that's correct, it's quite a bit of work to do so and that I 
 > wouldn't prioritize it above other, more critical things that need to happen. 
 > We should certainly evaluate any patches that come in for possible inclusion, 
 > assuming they don't muck up the internals of procfs too much; it's not clear 
 > to me if they necessarily do so or not.
 
 The bug is mainly that stat() claims that the files are regular when
 they highly irregular (they are more like fifos).  This confuses naive
 applications into thinking that normal access methods for regular files
 actually work.
 
 Bruce