linux-kernel - Re: New TRIM/UNMAP tree published (2009-05-02)

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Message-Id: <200905032048.04219.bzolnier@gmail.com>
Date:	Sun, 3 May 2009 20:48:03 +0200
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Boaz Harrosh <bharrosh@...asas.com>,
	Hugh Dickins <hugh@...itas.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jeff Garzik <jgarzik@...hat.com>, linux-scsi@...r.kernel.org,
	Jens Axboe <jens.axboe@...cle.com>, Mark Lord <lkml@....ca>
Subject: Re: New TRIM/UNMAP tree published (2009-05-02)

On Sunday 03 May 2009 17:42:16 Matthew Wilcox wrote:
> On Sun, May 03, 2009 at 06:02:51PM +0300, Boaz Harrosh wrote:
> > I agree with Hugh. The allocation is done at, too-low in the food chain.
> > (And that free of buffer at upper layer allocated by lower layer).
> > 
> > I think you need to separate the: "does lld need buffer, what size"
> > from the "here is buffer prepare", so upper layer that can sleep does
> > sleep.
> 
> So you want two function pointers in the request queue relating to discard?
> 
> > In all other buffer needing operations the allocation is done before
> > submission of request, No?
> 
> It's not true for the flush request (the example I quoted).  Obviously,
> the solution adopted here by IDE is Bad and Wrong ...

When speaking about "the solution" do you mean that quick & ugly hack
that I needed to fix the unexpected regression during late -rc cycle? ;)

The proper solution would involve adding 'struct ide_cmd flush_cmd' to
ide_drive_t but I never got to verify/inquiry that is OK with the block
layer (if there can be only one flush rq outstanding or if we can have
both q->pre_flush_rq and q->post_flush_rq queued at the same time)...

Thanks,
Bart
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