From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Problem w/ CONFIG_DEBUG_BLOCK_EXT_DEVT Date: Tue, 02 Sep 2008 12:47:13 +0200 Message-ID: <48BD19B1.9040207@kernel.org> References: <48BD173B.3090600@hp.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <48BD173B.3090600@hp.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: "Alan D. Brunelle" Cc: device-mapper development , "linux-kernel@vger.kernel.org" , Jens Axboe List-Id: dm-devel.ids Hello, Alan D. Brunelle wrote: > I have found two problems in LVM2/DM w/ a potential new "experimental > feature" in 2.6.28: CONFIG_DEBUG_BLOCK_EXT_DEVT (this is from Jens > Axboe's origin/for-2.6.28 git branch) It's a debug option and I don't expect it to be enabled in any production kernel. > "Conventionally, block device numbers are allocated from predetermined > contiguous area. However, extended block area may introduce > non-contiguous block device numbers. This option forces most block > device numbers to be allocated from the extended space and spreads them > to discover kernel or userland code paths which assume predetermined > contiguous device number allocation." > > W/ LVM2 & DM there are (at least) two issues: > > (1) Device major numbers for some reason are /not/ being entered > correctly into /proc/devices -- w/ CONFIG_DEBUG_BLOCK_EXT_DEVT=y I am > seeing some devices w/ major "259" (a SATA controller) but no entry in > /proc/devices. LVM2/DM will not find the entry in /proc/devices, and not > allow any device w/ that major to be used with LVM commands. Hmmm.. Adding a call to register_blkdev(), which will create the corresponding entry in /proc/devices, isn't difficult at all but which name would it use? It'll be mix of block devices (hd and sds currently). If we introduce a new name there, say, ext-block, would that work? BTW, is there any specific reason why LVM2/DM can't use /sys/block/* ? > (2) Device minor numbers can be quite large, and the 10-character limits > in dm/lib/libdm-deptree.c are too small. Would it be difficult to increase that? Thanks. -- tejun