From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: BLKZEROOUT + pread should return zeroes, right? Date: Tue, 14 Oct 2014 02:32:10 -0400 Message-ID: <20141014063210.GK9738@thunk.org> References: <20141014030132.GA12013@birch.djwong.org> <20141014042711.GJ5267@dastard> <20141014060242.GA22878@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Dave Chinner , Jens Axboe , "Martin K. Petersen" , linux-fsdevel@vger.kernel.org, linux-ext4 To: "Darrick J. Wong" Return-path: Received: from imap.thunk.org ([74.207.234.97]:51004 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754975AbaJNGcR (ORCPT ); Tue, 14 Oct 2014 02:32:17 -0400 Content-Disposition: inline In-Reply-To: <20141014060242.GA22878@birch.djwong.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: The bottom line is for most of the use cases we are talking about, we're only zero'ing one or two 4k blocks at a time, so I've never been convinced that it's worth it to use BLKZEROOUT. We could add page cache coherency features to BLKZEROOUT, but I'm not entirely sure it's worth the effort. No user space program would be able to take advantage of adding coherency for several years, or adding feature tests, etc., and is it worth the upside of being able to use WRITE SAME for a few 4k or 8k writes? (Which the vast majority of storage devices don't support anyway....) Cheers, - Ted