linux-kernel - Re: x86: 4kstacks default

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Message-ID: <480B4390.4010907@rtr.ca>
Date:	Sun, 20 Apr 2008 09:22:24 -0400
From:	Mark Lord <lkml@....ca>
To:	Adrian Bunk <bunk@...nel.org>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Shawn Bohrer <shawn.bohrer@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: x86: 4kstacks default

Adrian Bunk wrote:
>
> The code in the kernel that gets the fewest coverage at all are our 
> error paths, and some vendor might try 4k stacks, validate it works in 
> all use cases - and then it will blow up in some error condition he 
> didn't test.
..

That's exactly the worry.

If anyone want's to take a crack at testing some of the more likely
fail paths there, just introduce a media error onto a SATA disk
that's buried at the bottom of a stacked RAID1 over RAID0 over LVM,
with XFS and nfsd on top.

Or something like that.
And then experiment with corrupting meta data rather than simply file data.
How-to introduce a media error?  hdparm --make-bad-sector nnnnnn /dev/sdX

This catches the most likely (IMHO) failure scenarios,
but still comes nowhere near 100% code coverage.  :(

Cheers
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