From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754608Ab0A0MKy (ORCPT ); Wed, 27 Jan 2010 07:10:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754578Ab0A0MKx (ORCPT ); Wed, 27 Jan 2010 07:10:53 -0500 Received: from ey-out-2122.google.com ([74.125.78.24]:21795 "EHLO ey-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753197Ab0A0MKw (ORCPT ); Wed, 27 Jan 2010 07:10:52 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=M5nhotv94+BL/nIuVZf7UeRWauYMmFrOAQ9qfhOji0Dx3MDq6YmZ7DpJD/DmcbZHcA eh3LzWEFnGcj7W8uUMRx2ZEEmhm9THYQjZBRvvd0xJ8wfVDHdGI3w/swIDXQWzw2QBFY pKcV6chzEAQnPsu2P6WfptXpn3FVg7PrqDfp8= MIME-Version: 1.0 Date: Wed, 27 Jan 2010 12:10:50 +0000 Message-ID: <6278d2221001270410k1493582fvccdf23bed14cc0ff@mail.gmail.com> Subject: file/extent checksums for dedup/sync... From: Daniel J Blueman To: Linux BTRFS , Linux Kernel Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For purposes of data deduplication and data synchronisation, it would be a powerful tool to expose file data checksums. Since eg BTRFS uses the crc32c algorithm [1], it's possible to compute the file's overall CRC from the accumulation of the CRCs from all it's extents' CRCs. For now, exposing this via an IOCTL may be sufficient, though any ideas for introducing it in a more standard way? (it's a pity that when stat64 was introduced, reserved fields weren't added) Thanks, Daniel [1] http://www.research.ibm.com/haifa/satran/ips/Vince-Luben-crc32c-01.pdf -- Daniel J Blueman