Subject: buf/msdosfs problem
To: None <>
From: Jaromir Dolecek <>
List: tech-kern
Date: 02/10/2000 10:27:45
I'm investigating strange issue I have with msdosfs. Basically,
when a file of "proper" size was copied to directory deep on
filesystem (say /dos/b/c/), that directory suddenly appeared to be
same as root directory - ls /dos/b/c/ was same as ls /dos. /dos/b/c/.
didn't exist at that stage. After umount/mount everything was ok
again, just the file was copied in root directory instead of the
original destination directory.

After quite some time of hunting, I found out that this bug appears
when the code in msdosfs_write() get's a buf (size 8192 if it matters)
and writes whole 8192 bytes into it at once (I tried to replace
the uiomove() with memset() and got same results). I didn't find what are
other coencidences needed, but found out that if I write
only 8191 or less bytes into the buffer, everything is happy.

I'm not sure whether this is some bug in buf handling code (i.e.
buf alloc problem ? or b*write() problem ?) or prolly other problem
in msdosfs (though the latter seems unlikely).

Has anyone an idea what the real problem might be ? Note that I never
had such problem with 1.4.*, it appeared after I upgraded the machine
to -current (1.4P I think).

Jaromir Dolecek <>
@@@@  Wanna a real operating system ? Go and get NetBSD, damn!  @@@@