From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f174.google.com ([209.85.223.174]:36610 "EHLO mail-io0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932171AbcLSVx2 (ORCPT ); Mon, 19 Dec 2016 16:53:28 -0500 Received: by mail-io0-f174.google.com with SMTP id 136so164299364iou.3 for ; Mon, 19 Dec 2016 13:53:28 -0800 (PST) Date: Mon, 19 Dec 2016 12:53:21 -0900 From: Kent Overstreet To: Josef Bacik Cc: "linux-fsdevel@vger.kernel.org" , "david@fromorbit.com" , "hch@lst.de" Subject: Re: Simulating disk failure with a writeback cache Message-ID: <20161219215306.vmkhgwifrj5ph2qr@moria.home.lan> References: <079409FD-B1CB-460B-AA1E-77EF0107B424@fb.com> <20161218201253.wv4bsheg4ook4bdx@kmo-pixel> <1482093534.17731.1@smtp.office365.com> <20161218204623.gea7u4d3pb7k3zhw@kmo-pixel> <05A4E7E7-E733-4AE9-BDC7-FEE9F66E387D@fb.com> <20161219025111.g2nayb3xtxvfbasu@kmo-pixel> <20161219030725.3kmsfu23sjypcnek@kmo-pixel> <1482161254.17731.2@smtp.office365.com> <20161219205514.dntaogt3vjos37w2@kmo-pixel> <1482181240.24490.9@smtp.office365.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1482181240.24490.9@smtp.office365.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Dec 19, 2016 at 04:00:40PM -0500, Josef Bacik wrote: > Ok that works fine in the short term for you, but ideally you wouldn't have > to fix the test every time you wanted to run it on bcachefs. Do you have a > suggestion of how to make this generic enough to support you as well without > dd'ing the whole drive? Thanks, Yes, but it'd be a lot of work :) Change log-writes so that instead of replaying the log, you have it create a block device representing that specific point in the log - and then service read requests by looking them up however you like. So, it'd be just like mounting snapshots. It might not be too difficult since we can deal with crappy performance or memory usage here, but I don't know if it's really worth the effort.