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 (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q43JgCAH195650 for ; Thu, 3 May 2012 14:42:12 -0500 Message-ID: <4FA2DF94.2050805@sgi.com> Date: Thu, 03 May 2012 14:42:12 -0500 From: Mark Tinguely MIME-Version: 1.0 Subject: Re: [PATCH 07/10] xfs: support discontiguous buffers in the xfs_buf_log_item References: <1335249220-22274-1-git-send-email-david@fromorbit.com> <1335249220-22274-8-git-send-email-david@fromorbit.com> In-Reply-To: <1335249220-22274-8-git-send-email-david@fromorbit.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: xfs@oss.sgi.com On 04/24/12 01:33, Dave Chinner wrote: > From: Dave Chinner > >> From the perspective of the log, we need to keep each segment of a > discontigous buffer in separate buffer format structures. This means log > recovery will recover all the changes on a per segment basis without > requiring any knowledge of the fact that it was logged from a > compound buffer. > > To do this, we need to be able to determine what buffer segment any > given offset into the compound buffer sits over. This enables us to > translate the dirty bitmap in the number of separate buffer format > structures required. > > We also need to be able to determine the number of bitmap elements > that a given buffer segment has, as this determines the size of the > buffer format structure. Hence we need to be able to determine the > both the start offset into the buffer and the length of a given > segment to be able to calculate this. > > With this information, we can preallocate, build and format the > correct log vector array for each segment in a compound buffer to > appear exactly the same as individually logged buffers in the log. > > Signed-off-by: Dave Chinner Looks good. Reviewed-by: Mark Tinguely _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs