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Re: [PATCH, RFC] xfs: batched discard support

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH, RFC] xfs: batched discard support
From: Jamie Lokier <jamie@xxxxxxxxxxxxx>
Date: Thu, 20 Aug 2009 02:10:04 +0100
Cc: Ingo Molnar <mingo@xxxxxxx>, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>, Paul Mackerras <paulus@xxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-scsi@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, liml@xxxxxx, jens.axboe@xxxxxxxxxx
In-reply-to: <20090820010552.GA22107@xxxxxxxxxxxxx>
References: <20090816004705.GA7347@xxxxxxxxxxxxx> <20090819203916.GA25296@xxxxxxx> <20090820010552.GA22107@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.13 (2006-08-11)
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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