From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id 27B7B7CA3 for ; Wed, 30 Mar 2016 20:20:43 -0500 (CDT) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay2.corp.sgi.com (Postfix) with ESMTP id E855F304082 for ; Wed, 30 Mar 2016 18:20:42 -0700 (PDT) Received: from ipmail06.adl2.internode.on.net (ipmail06.adl2.internode.on.net [150.101.137.129]) by cuda.sgi.com with ESMTP id 25p85I1pglEUl7LQ for ; Wed, 30 Mar 2016 18:20:36 -0700 (PDT) Date: Thu, 31 Mar 2016 12:18:13 +1100 From: Dave Chinner Subject: Re: fallocate mode flag for "unshare blocks"? Message-ID: <20160331011813.GJ30721@dastard> References: <20160302155007.GB7125@infradead.org> <20160330182755.GC2236@birch.djwong.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160330182755.GC2236@birch.djwong.org> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: "Darrick J. Wong" Cc: Christoph Hellwig , linux-fsdevel , linux-api@vger.kernel.org, linux-btrfs , xfs@oss.sgi.com On Wed, Mar 30, 2016 at 11:27:55AM -0700, Darrick J. Wong wrote: > Or is it ok that fallocate could block, potentially for a long time as > we stream cows through the page cache (or however unshare works > internally)? Those same programs might not be expecting fallocate to > take a long time. Yes, it's perfectly fine for fallocate to block for long periods of time. See what gfs2 does during preallocation of blocks - it ends up calling sb_issue_zerout() because it doesn't have unwritten extents, and hence can block for long periods of time.... Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs