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Date: Fri, 22 Dec 2000 09:35:13 -0800
From: Alfred Perlstein <bright@wintelcom.net>
To: "G. Adam Stanislav" <adam@whizkidtech.net>
Cc: hackers@FreeBSD.ORG
Subject: Re: A bug in mmap?
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* G. Adam Stanislav <adam@whizkidtech.net> [001222 09:30] wrote:
> I think I have just discovered a bug... (FreeBSD 3.1).
> 
> Here is the scenario: The program (I have written) opens a file as O_RDWR,
> then uses mmap with PROT_READ | PROT_WRITE and MAP_SHARED. It works on
> the data, optionally reduces the file size, then unmaps and closes it.
> 
> Everything works fine as long as the file is on a native FreeBSD disk.
> But if it is on a Windows formatted hard drive mounted under FreeBSD,
> *sometimes* the file ends up filled with NULs.
> 
> Could it be mmap may get confused by a Windows formated drive? It does NOT
> return an error, but it fills the mapped area with zeros. It overwrites
> the contents of the file with zeros, but does not change the directory
> information (i.e., the time of the last access, and such).
> 
> It never happens on a FreeBSD drive, only on a Windows formated drive,
> which makes it rather spooky.

Most likely a result of a bug in the msdosfs code, perhaps you can
help track it down?  I don't use msdosfs. :(

-- 
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."


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