From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx111.postini.com [74.125.245.111]) by kanga.kvack.org (Postfix) with SMTP id 8867D6B005A for ; Wed, 28 Nov 2012 21:02:21 -0500 (EST) Received: by mail-qc0-f169.google.com with SMTP id t2so12931612qcq.14 for ; Wed, 28 Nov 2012 18:02:20 -0800 (PST) Date: Wed, 28 Nov 2012 18:02:21 -0800 (PST) From: Hugh Dickins Subject: Re: [PATCH] tmpfs: support SEEK_DATA and SEEK_HOLE (reprise) In-Reply-To: <20121129012933.GA9112@kernel> Message-ID: References: <20121129012933.GA9112@kernel> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Jaegeuk Hanse Cc: Andrew Morton , Theodore Ts'o , Zheng Liu , Jeff liu , Jim Meyering , Paul Eggert , Christoph Hellwig , Josef Bacik , Andi Kleen , Andreas Dilger , Dave Chinner , Marco Stornelli , Chris Mason , Sunil Mushran , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org On Thu, 29 Nov 2012, Jaegeuk Hanse 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. > > > > Hi Hugh, > > IIUC, several months ago you revert the patch. You said, > > "I don't know who actually uses SEEK_DATA or SEEK_HOLE, and whether it > would be of any use to them on tmpfs. This code adds 92 lines and 752 > bytes on x86_64 - is that bloat or worthwhile?" YUC. > > But this time in which scenario will use it? I was not very convinced by the grep argument from Jim and Paul: that seemed to be grep holding on to a no-arbitrary-limits dogma, at the expense of its users, causing an absurd line-length issue, which use of SEEK_DATA happens to avoid in some cases. The cp of sparse files from Jeff and Dave was more convincing; but I still didn't see why little old tmpfs needed to be ahead of the pack. But at LinuxCon/Plumbers in San Diego in August, a more convincing case was made: I was hoping you would not ask, because I did not take notes, and cannot pass on the details - was it rpm building on tmpfs? I was convinced enough to promise support on tmpfs when support on ext4 goes in. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org