linux-kernel - Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...?

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Date:	Wed, 11 Jul 2007 13:05:08 -0700
From:	Daniel Phillips <phillips@...nq.net>
To:	Zan Lynx <zlynx@....org>
Cc:	Jesper Juhl <jesper.juhl@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...?

On Wednesday 11 July 2007 10:54, Zan Lynx wrote:
> Jesper Juhl wrote:
> > Hi,
> >
> > I'm wondering if it's time to make 4K stacks the default and to start
> > considering removing the 8K stack option alltogether soon?
> >
> > One of the big problem spots was XFS, but that got some stack usage
> > fixes recently, and the 4K stack option has been around for quite a
> > while now, so people really should have gotten around to fixing any
> > code that can't handle it.   Are there still any big problem areas
> > remaining?
>
> Has anyone fixed the infrequent crashes with 4K stacks and ext3 -> LVM
> snapshot -> LVM -> DM mirror -> libata?

Ahem: ext3 -> LVM snapshot -> LVM -> DM mirror -> DM crypt -> md -> libata,
or worse.

No, it's not fixed.  The model is wrong.  Virtual block drivers should not
be callling submit_bio.  The recursive IO submissions should be handled
on a dedicated stack, most probably allocated as part of the request queue.
This could be done easily in device mapper and md, or better, in
submit_bio.

Regards,

Daniel
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