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 6F99E7F3F for ; Tue, 15 Apr 2014 19:42:01 -0500 (CDT) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay2.corp.sgi.com (Postfix) with ESMTP id 59B4730404E for ; Tue, 15 Apr 2014 17:42:01 -0700 (PDT) Received: from ipmail07.adl2.internode.on.net (ipmail07.adl2.internode.on.net [150.101.137.131]) by cuda.sgi.com with ESMTP id wJLgwg9CFJBDlilt for ; Tue, 15 Apr 2014 17:41:58 -0700 (PDT) Date: Wed, 16 Apr 2014 10:41:45 +1000 From: Dave Chinner Subject: Re: [PATCH 3/9] repair: ensure prefetched buffers have CRCs validated Message-ID: <20140416004145.GB15995@dastard> References: <1397550301-31883-1-git-send-email-david@fromorbit.com> <1397550301-31883-4-git-send-email-david@fromorbit.com> <20140415194000.GB3470@laptop.bfoster> <20140415214642.GN15995@dastard> <20140415220559.GE3470@laptop.bfoster> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20140415220559.GE3470@laptop.bfoster> 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: Brian Foster Cc: xfs@oss.sgi.com On Tue, Apr 15, 2014 at 06:06:00PM -0400, Brian Foster wrote: > On Wed, Apr 16, 2014 at 07:46:42AM +1000, Dave Chinner wrote: > > On Tue, Apr 15, 2014 at 03:40:00PM -0400, Brian Foster wrote: > > > Should we always expect an unchecked buffer to be read with an ops > > > vector before being written? Even if so, this might look cleaner if we > > > didn't encode the possibility of running a read verifier on a dirty > > > buffer. I presume that would always fail as the crc is updated in the > > > write verifier. > > > > It should fail, and that's a good thing because writing to an > > unchecked buffer would indicate that we didn't validate it properly > > in the first place. Hence I thought that doing it this way leaves > > a canary that traps other problem usage with unchecked buffers. > > > > Realistically, we shouldn't be writing unchecked buffers - prefetch > > doesn't touch buffers, it just does IO, and so someone else has to > > read the buffers before they can be dirtied. If it's read without an > > ops structure then modified and read again with an ops structure, > > we'll catch it... > > > > Ah, I see. That sounds good, but a small comment there with the > reasoning to allow a read verifier to run on a dirty buffer would be > nice. :) Ok, I'll add one. Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs