Subject: Re: raidframe, cgd and parity errors
To: None <tech-kern@NetBSD.org>
From: Alan Barrett <firstname.lastname@example.org>
Date: 05/09/2005 11:52:43
On Mon, 09 May 2005, Daniel Carosone wrote:
> > It might be worse to consider raid on cgd on vnd on ffs. The raid's
> > shutdown hooks will be run [potentially?] after the ffs is unmounted.
> If this is a problem, perhaps the solution is to make the filesystem
> unmounts be shutdown hooks too (added at mount time) so the ordering
> is appropriately preserved.
This is the problem that I was worried about when I asked whether the
shutdownhook mechanism was adequate to the task. I now believe that
the shutdownhook mechanism is fine, but the vfs_shutdown() mechanism is
At present, filesystems are unmounted using a mechanism that
predates shutdownhooks. See the MD cpu_reboot() functions in
src/sys/arch/*/*/*machdep.c, which call vfs_shutdown() before calling
doshutdownhooks(). I think it would make sense to change that, and use
shutdownhooks for unmounting. To match current behaviour, the unmount
hooks would have to honour the RB_NOSYNC flag.
My proposal is:
Every mount of every filesystem registers a shutdownhook which will
unmount the filesystem with or without syncing, depending on the
RB_NOSYNC flag. (One shutdownhook per mount, not one per filesystem
type.) vfs_shutdown() is replaced by these shutdownhooks.
Every cgd, raidframe, ccd, vnd, and similar device registers a
shutdownhook which will unconfigure the device cleanly or quickly,
depending on the RB_NOSYNC flag. (One shutdownhook per device, not
one per driver.)
Every swap partition registers a shutdownhook which will unconfigure
the device. (One shutdownhook per partition.)
Most of the other stuff that is done by MD cpu_reboot() is also moved
to shutdownhooks. For stuff that is currently invoked conditionally,
move the conditional test from cpu_reboot() into the shutdownhook.
--apb (Alan Barrett)