From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 1/2] block: add support for discard limits Date: Fri, 30 Oct 2009 01:05:58 -0400 Message-ID: <20091030050558.GC17714@infradead.org> References: <20091029150830.497006534@bombadil.infradead.org> <20091029151127.257902381@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:57180 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754284AbZJ3FFz (ORCPT ); Fri, 30 Oct 2009 01:05:55 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Martin K. Petersen" Cc: Christoph Hellwig , linux-scsi@vger.kernel.org, axboe@kernel.dk, matthew@wil.cx On Thu, Oct 29, 2009 at 11:19:43PM -0400, Martin K. Petersen wrote: > ACS-2 doesn't currently have a notion of unmap granularity and all array > vendors I have talked to appear to happily process any unmap request we > throw at them. So I'm leaning towards keeping things simple and just > sending things down verbatim... We have all the granularity and alignment information avilable and keeping track of it is simple enough. Yes md/dm will need to update the first aligned unmap sector, but they'll also need to update the first aligned LBA for I/O purposes and adding more more is simple enough. Given that these bits are in the standard vendors will use them sooner or later and I'd rather be prepared if it's simple enough.