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Date: Thu, 20 Aug 2009 02:10:04 +0100
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [PATCH, RFC] xfs: batched discard support
Message-ID: <20090820011004.GC14005@shareable.org>
References: <20090816004705.GA7347@infradead.org>
	<20090819203916.GA25296@elte.hu>
	<20090820010552.GA22107@infradead.org>
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To: Christoph Hellwig <hch@infradead.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-scsi@vger.kernel.org, jens.axboe@oracle.com, linux-kernel@vger.kernel.org, xfs@oss.sgi.com, Paul Mackerras <paulus@samba.org>, liml@rtr.ca, linux-fsdevel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>, Linus Torvalds <torvalds@linux-foundation.org>

Christoph Hellwig wrote:
> > So i'm torn about the 'syscall versus ioctl' issue, i'd 
> > like to avoid making interface design mistakes and i'd 
> > like to solicit some opinions about this. I've attached 
> > the perfcounters ioctl patch below.
> 
> Only add a syscall if it has _one_ clear defined purpose,
> which has kernel-wide meaning.

One clear defined purpose which comes to mind is a "trim" or "punch"
system call, for making holes in files as well as trimming block
devices.  Several other OSes have that capability on files.

I don't remember - does TRIM guarantee the blocks read zeros afterwards?

It would be tidy if it does, as it could have the same meaning with files.

-- Jamie

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