From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 2/9] md: override md superblock recovery_offset for cache device Date: Tue, 4 Aug 2015 07:30:07 -0700 Message-ID: <20150804143007.GB8204@infradead.org> References: <42ac39ae4466dda63b1dee827c2bd3741d669860.1438215986.git.shli@fb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <42ac39ae4466dda63b1dee827c2bd3741d669860.1438215986.git.shli@fb.com> Sender: linux-raid-owner@vger.kernel.org To: Shaohua Li Cc: linux-raid@vger.kernel.org, Kernel-team@fb.com, songliubraving@fb.com, hch@infradead.org, dan.j.williams@intel.com, neilb@suse.de List-Id: linux-raid.ids On Wed, Jul 29, 2015 at 05:38:42PM -0700, Shaohua Li wrote: > Cache device stores data in a log structure. We need record the log > start. Here we override md superblock recovery_offset for this purpose. > This field of a cache device is meaningless otherwise. Just reusing the field for a different purpose without a different name or comment is highly confusing. I'd suggest to create unions in both the on-disk and in-memory structures and properly document that new usage for cache devices.