From mboxrd@z Thu Jan 1 00:00:00 1970 From: Douglas Gilbert Subject: Re: [PATCH] scsi_debug: Thin provisioning Date: Sat, 03 Oct 2009 09:49:49 -0400 Message-ID: <4AC7567D.2080507@interlog.com> References: Reply-To: dgilbert@interlog.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.infotech.no ([82.134.31.41]:48496 "EHLO elrond.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932139AbZJCNtu (ORCPT ); Sat, 3 Oct 2009 09:49:50 -0400 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org Martin K. Petersen wrote: > scsi_debug: Thin provisioning support > > Implement support for thin provisioning in scsi_debug. No actual memory > de-allocation is taking place. The intent is to emulate a thinly > provisioned storage device, not to be one. > > There are four new module options: > > - unmap_granularity specifies the granularity at which to track mapped > blocks (specified in number of logical blocks). 2048 (1 MB) is a > realistic value for disk arrays although some may have a finer > granularity. > > - unmap_alignment specifies the first LBA which is naturally aligned on > an unmap_granularity boundary. > > - unmap_max_desc specifies the maximum number of ranges that can be > unmapped using one UNMAP command. If this is 0, only WRITE SAME is > supported and UNMAP will cause a check condition. > > - unmap_max_blocks specifies the maximum number of blocks that can be > unmapped using a single UNMAP command. Default is 0xffffffff. > > These parameters are reported in the new and extended block limits VPD. > > If unmap_granularity is specified the device is tagged as thin > provisioning capable in READ CAPACITY(16). A bitmap is allocated to > track whether blocks are mapped or not. A WRITE request will cause a > block to be mapped. So will WRITE SAME unless the UNMAP bit is set. > > Blocks can be unmapped using either WRITE SAME or UNMAP. No accounting > is done to track partial blocks. This means that only whole blocks will > be marked free. This is how the array people tell me their firmwares > work. > > GET LBA STATUS is also supported. This command reports whether a block > is mapped or not, and how long the adjoining mapped/unmapped extent is. > > The block allocation bitmap can also be viewed from user space via: > > /sys/bus/pseudo/drivers/scsi_debug/map > > Signed-off-by: Martin K. Petersen Acked-by: Douglas Gilbert