From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Clements Subject: Re: md: persistent (file-backed) bitmap Date: Wed, 10 Nov 2004 13:28:41 -0500 Message-ID: <41925DD9.4070704@steeleye.com> References: <40198E85.29EBC8E0@SteelEye.com> <16422.62911.755570.855200@notabene.cse.unsw.edu.au> <4027E342.D02202F1@SteelEye.com> <16424.8182.876520.280031@notabene.cse.unsw.edu.au> <402D3A86.97CF894F@SteelEye.com> <16456.2775.641721.204171@notabene.cse.unsw.edu.au> <4048F9AA.1BBD67F@SteelEye.com> <406B1024.7BF88C@SteelEye.com> <16528.49083.998593.199805@cse.unsw.edu.au> <40C6273B.2060200@steeleye.com> <16590.38597.170409.499394@cse.unsw.edu.au> <40D9FA9E.9010003@steeleye.com> <40F7E50F.2040308@steeleye.com> <16649.61212.310271.36561@cse.unsw.edu.au> <4119400A.40307@steeleye.com> <16668.12228.187383.596856@cse.unsw.edu.au> <414F9FD4.4070308@steeleye.com> <41507EA7.1000905@steeleye.com> <16747.15933.68499.915859@cse.unsw.edu.au> <16785.25306.475922.200700@cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <16785.25306.475922.200700@cse.unsw.edu.au> Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: jejb@steeleye.com, linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi Neil, Neil Brown wrote: > I would like to change the "RESYNC_MASK" bit to mean: > At least one block in this chunk is out-of-sync. OK > Then: > - When we read the bitmap from disk we set this bit and the > SHADOW_MASK, but leave the counter at zero. > - When we get a failed write, we set this bit, but still decrement > the counter. > - When we are performing a resync, we periodically clear the bit on > recently completed chunks. I assume that this also means that the counter will get incremented before each read-for-resync is submitted. Perhaps you've already considered that? > - We only clear the SHADOW_MASK and on-disk bit when the counter > hits zero *and* this bit is clear. > > I would find this approach a lot easier to understand. Are you OK > with it? It sounds reasonable. Probably a little simpler too... > Also, I would like to move the bitmap_testbit in md_do_sync down into > the personality. This should make life easier for other > personalities like raid10 which use a very different approach for > resync than for recovery. OK, that sounds fine. -- Paul