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ADD 804570 - The elevator bug

To: nb@xxxxxxx
Subject: ADD 804570 - The elevator bug
From: pv@xxxxxxxxxxxxxxxxxxxxxx (cattelan@xxxxxxxxxxx)
Date: Fri, 1 Dec 2000 23:20:03 -0800 (PST)
Cc: raa@xxxxxxx, huovinen@xxxxxxx, cattelan@xxxxxxx, mann@xxxxxxx, tbd@xxxxxxx, rrl@xxxxxxx, alaffin@xxxxxxx, linux-xfs@xxxxxxxxxxx
Reply-to: sgi.bugs.xfs@xxxxxxxxxxxxxxxxx
Sender: owner-linux-xfs@xxxxxxxxxxx
 Submitter : coreym                    Status : open                        
 Assigned Engineer : nb                Priority : 3                         
*Modified Date : 12/01/00             *Modified User : cattelan             
*Modified User Domain : thebarn.com   *Description :
I ran rwtest on a xfs-linux filesystem on the machine permit:

rwtest 100000000:/mnt1/file_1 >/tmp/file_1.out 2>&1 &

This caused df, ls -l, fdisk, and top all to hang.

Permit is running Redhat 6.2 with a 2.4.0-test5 kernel

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ADDITIONAL INFORMATION (ADD)

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ADDITIONAL INFORMATION (ADD)
From: russell cattelan <cattelan@xxxxxxxxxxx>
Date: Dec 01 2000 11:20:03PM
[pvnews version: 1.71]
==========================
"ananth@xxxxxxxxxxxx" wrote:

> View Incident: 
> http://co-op.engr.sgi.com/BugWorks/code/bwxquery.cgi?search=Search&wlong=1&view_type=Bug&wi=804570
>
>  Status : open                         Priority : 3
>  Assigned Engineer : nb                Submitter : coreym
> *Modified User : ananth               *Modified User Domain : engr
> *Description :
> I ran rwtest on a xfs-linux filesystem on the machine permit:
>
> rwtest 100000000:/mnt1/file_1 >/tmp/file_1.out 2>&1 &
>
> This caused df, ls -l, fdisk, and top all to hang.
>
> Permit is running Redhat 6.2 with a 2.4.0-test5 kernel
>
> ==========================
> ADDITIONAL INFORMATION (ADD)
>
> .....
>
> ==========================
> ADDITIONAL INFORMATION (ADD)
> From: ananth@engr (BugWorks)
> Date: Dec 01 2000 09:13:37PM
> ==========================
>
> Just so there is no confusion, this is only
> in Linux 2.4 ... here it has been observed
> only with XFS but elsewhere there also reports
> with ext2. Jens Axboe has some fixes for it.
> For XFS we are hoping the changes make it into
> the next 2.4 patch, test12.

Yes this is a know problem in the latest 2.4 kernels.
It has been observed on other file  systems as well not just XFS.

I have do have a kernel with Jens elevator patch, that does
appear to fix the starvation problem. Unfortunately it appears to either
have problems itself or is exposing  problems in the XFS code.

Currently XFS kiobuf based io causes a lockup that eventually cause the
kernel to through an NMI.

Non kiobuf io causes pagebuf to panic under heavy load.

I got this running late friday and haven't had much
of a chance to investigate.

Since this is a linux bug we are  waiting for the official
fix to show up in the linux tree.

--
Russell Cattelan
cattelan@xxxxxxxxxxx

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