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Date: Sat, 5 Mar 2016 12:57:28 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
	Jens Axboe <axboe@kernel.dk>,
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	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 3/3] block: implement (some of) fallocate for block
 devices
Message-ID: <20160305205728.GA4834@infradead.org>
References: <20160305005556.29738.66782.stgit@birch.djwong.org>
 <20160305005617.29738.85316.stgit@birch.djwong.org>
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On Fri, Mar 04, 2016 at 07:06:38PM -0800, Linus Torvalds wrote:
> > +       if ((mode & FALLOC_FL_PUNCH_HOLE) &&
> > +           (!blk_queue_discard(q) || !q->limits.discard_zeroes_data))
> > +               return -EOPNOTSUPP;
> 
> I'm ok with this, but suspect that some users would prefer to just
> turn this into ZERO_RANGE silently.
> 
> Comments from people who would be expected to use this?

A hole punch should be a hole punch, and not silently allocate blocks
isntead of deallocating them.  It's not even a fallback, it's pretty
much the opposite for some workloads.