Re: PROBLEM: umountfs and shutting down linux 2.3.99-pre5

From: Hadmut Danisch (hadmut@danisch.de)
Date: Mon Apr 24 2000 - 05:28:33 EST


On Mon, Apr 24, 2000 at 09:55:26AM +1000, Keith Owens wrote:

>
> Even with 2.3.99-pre6-5, file systems do not unmount correctly, it
> turned out to be a user space problem. /etc/rc.d/init.d/halt (Redhat)
> excludes some tasks from the kill list. Either devfs or shmfs changed
> the filter criteria, with the old init.d/halt, the shutdown task gets
> killed before it has a chance to do a clean unmount.
>

I yesterday tried to find the problem by calling all shutdown
procedures in /etc/rc0.d manually. Everything was shut down well.
The last procedure before actually halting the kernel was the
umount call. I found that I couldn't unmount one of the file
systems (in this case where /usr/local was mounted).

There were only about 6 or 7 processes left over
(init, kflushd, kupdate,..., my own shell, two gettys, since
init still was in level 3), but none of these processes was
actually using this filesystem (lsof also didn't show anything
using that filesystem).

I assume that there is some kind of reference counter of open file
descriptors in writing mode, and this ref counter isn't decremented
properly.

You should check the part of the kernel which avoids a filesystem
beeing unmounted (or remounted read only) while there is still write
access. There must be a bug.

regards
Hadmut

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