linux-kernel - Re: [PATCH] tmpfs: support SEEK_DATA and SEEK

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Date:	Wed, 28 Nov 2012 20:22:09 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Dave Chinner <david@...morbit.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Theodore Ts'o <tytso@....edu>,
	Zheng Liu <wenqing.lz@...bao.com>,
	Jeff liu <jeff.liu@...cle.com>,
	Jim Meyering <jim@...ering.net>,
	Paul Eggert <eggert@...ucla.edu>,
	Christoph Hellwig <hch@...radead.org>,
	Josef Bacik <josef@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andreas Dilger <adilger@...ger.ca>,
	Marco Stornelli <marco.stornelli@...il.com>,
	Chris Mason <chris.mason@...ionio.com>,
	Sunil Mushran <sunil.mushran@...cle.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH] tmpfs: support SEEK_DATA and SEEK_HOLE (reprise)

On Thu, 29 Nov 2012, Dave Chinner wrote:
> On Wed, Nov 28, 2012 at 05:22:03PM -0800, Hugh Dickins wrote:
> > Revert 3.5's f21f8062201f ("tmpfs: revert SEEK_DATA and SEEK_HOLE")
> > to reinstate 4fb5ef089b28 ("tmpfs: support SEEK_DATA and SEEK_HOLE"),
> > with the intervening additional arg to generic_file_llseek_size().
> > 
> > In 3.8, ext4 is expected to join btrfs, ocfs2 and xfs with proper
> > SEEK_DATA and SEEK_HOLE support; and a good case has now been made
> > for it on tmpfs, so let's join the party.
> > 
> > It's quite easy for tmpfs to scan the radix_tree to support llseek's new
> > SEEK_DATA and SEEK_HOLE options: so add them while the minutiae are still
> > on my mind (in particular, the !PageUptodate-ness of pages fallocated but
> > still unwritten).
> > 
> > [akpm@...ux-foundation.org: fix warning with CONFIG_TMPFS=n]
> > Signed-off-by: Hugh Dickins <hughd@...gle.com>
> > ---
> 
> Does it pass the seek hole/data tests (285, 286) in xfstests?

It did before and ... [install this, install that, install tother]
... yes, it still passes those tests - using Boris Ranto's patch
extending xfstests to include tmpfs.

Though I'd have even more confidence if they gave a little pat on
the back for doing better than the no-op default, which also passes.

Hugh
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