From: "Darrick J. Wong" Subject: Re: [PATCH 10/22] ext4: Verify and calculate checksums for extent tree blocks Date: Mon, 5 Dec 2011 11:50:16 -0800 Message-ID: <20111205195016.GE7137@tux1.beaverton.ibm.com> References: <20111128232615.19194.80081.stgit@elm3c44.beaverton.ibm.com> <20111128232725.19194.12626.stgit@elm3c44.beaverton.ibm.com> <20111205164015.GD32031@thunk.org> Reply-To: djwong@us.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: "Ted Ts'o" , Andreas Dilger , Sunil Mushran , Martin K Petersen , Greg Freemyer , Amir Goldstein , linux-kernel , Andi Kleen , Mingming Cao , Joel Becker , linux-fsdevel , linux-ext4@vger.kernel.org, Coly Li Return-path: Received: from e7.ny.us.ibm.com ([32.97.182.137]:43893 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756122Ab1LETua (ORCPT ); Mon, 5 Dec 2011 14:50:30 -0500 Received: from /spool/local by e7.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 5 Dec 2011 14:50:29 -0500 Content-Disposition: inline In-Reply-To: <20111205164015.GD32031@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Dec 05, 2011 at 11:40:15AM -0500, Ted Ts'o wrote: > On Mon, Nov 28, 2011 at 03:27:25PM -0800, Darrick J. Wong wrote: > > /* > > + * This is the extent tail on-disk structure. > > + * All other extent structures are 12 bytes long. It turns out that > > + * block_size % 12 >= 4 for all valid block sizes (1k, 2k, 4k). > > More generally, block_size % 12 is >= 4 for all powers of 2 greater > than 12 bytes. I'd probably remove (1k, 2k, 4k) because that might > scare people who might say, "hey! I'm using a 16k block size on my > HPC system running on a Power or Itanium box --- am I going to be OK?". > Valid block sizes go up to the page size of the hardware in question... Ok. --D