Re: [PATCH 0/2] Improvements for barrier-test scheduler

[Chris Mason <chris.mason@oracle.com>]

On Wed, Jan 11, 2012 at 01:44:05AM +0100, Jan Kara wrote:
> 
>   Hello Chris,
> 
>   I was hunting one ext3/4 barrier related bug and so I used your barrier-test
> IO scheduler. It was quite helpful so thank you for it. For my purposes, I
> had to tweak it a bit to trigger my problem. I'm not sure if you keep the
> scheduler somewhere but if yes, I hope my patches could be of use.
> 
> Patch 1 implements raw support for handling reads - we don't have to flush
> our delayed writes everytime a read comes. It is enough to do so when some
> delayed write overlaps with a read. Scanning the list of delayed writes is slow
> but who really cares for barrier-test :)

Perfect ;)

> 
> Patch 2 implements another criteria for reordering requests and triggering
> reboot. Filesystem can flag certain bios as special. These bios will go
> directly to the backing storage and when they complete, reboot is triggered
> if there are enough pending writes. Filesystem can use the flag when writing
> commit blocks, superblocks or similarly sensitive metadata to verify whether
> barriers are issued in all the necessary places.

Great idea, I'll fold this in.

Jens, is this something you want in 3.3, or would you like to let it
cook for another release cycle?

-chris