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Date: Mon, 21 Nov 2011 14:13:22 -0800 (PST)
From: Hugh Dickins <hughd@google.com>
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To: Christoph Hellwig <hch@infradead.org>
cc: Josef Bacik <josef@redhat.com>, Kay Sievers <kay.sievers@vrfy.org>,
        Cong Wang <amwang@redhat.com>, linux-kernel@vger.kernel.org,
        akpm@linux-foundation.org, Pekka Enberg <penberg@kernel.org>,
        Dave Hansen <dave@linux.vnet.ibm.com>,
        Lennart Poettering <lennart@poettering.net>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, linux-mm@kvack.org
Subject: Re: [V2 PATCH] tmpfs: add fallocate support
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On Mon, 21 Nov 2011, Christoph Hellwig wrote:
> On Sun, Nov 20, 2011 at 01:39:12PM -0800, Hugh Dickins wrote:
> 
> > But since the present situation is that tmpfs has one interface to
> > punching holes, madvise(MADV_REMOVE), that IBM were pushing 5 years ago;
> > but ext4 (and others) now a fallocate(FALLOC_FL_PUNCH_HOLE) interface
> > which IBM have been pushing this year: we do want to normalize that
> > situation and make them all behave the same way.
> 
> FALLOC_FL_PUNCH_HOLE was added by Josef Bacik, who happens to work for
> Red Hat, but I doubt he was pushing any corporate agenda there, he was
> mostly making btrfs catch up with the 15 year old XFS hole punching
> ioctl.

Yeah, my apologies to Josef and to IBM and to XFS
for my regrettable little outburst of snarkiness :(

> 
> 
> > And if tmpfs is going to support fallocate(FALLOC_FL_PUNCH_HOLE),
> > looking at Amerigo's much more attractive V2 patch, it would seem
> > to me perverse to permit the deallocation but fail the allocation.
> 
> Agreed.

Thanks a lot for useful info, and saving me looking up the ENOSPC issue.

Hugh