From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nao Nishijima Date: Fri, 08 Apr 2011 14:07:41 +0000 Subject: Re: [PATCH 1/2] SCSI: Add a SCSI option for persistent device names Message-Id: <4D9F16AD.2090408@hitachi.com> List-Id: References: <20110405124946.7969.66796.stgit@ltc233.sdl.hitachi.co.jp> <20110405161454.GB885@kroah.com> In-Reply-To: <20110405161454.GB885@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Greg KH Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-hotplug@vger.kernel.org, Kay Sievers , James Bottomley , Jon Masters , 2nddept-manager@sdl.hitachi.co.jp Hi, (2011/04/06 1:14), Greg KH wrote: > On Tue, Apr 05, 2011 at 09:49:46PM +0900, Nao Nishijima wrote: >> This patch series provides a SCSI option for persistent device >> names in kernel. With this option, user can always assign a >> same device name (e.g. sda) to a specific device according to >> udev rules and device id. >> >> Issue: >> Recently, kernel registers block devices in parallel. As a result, >> different device names will be assigned at each boot time. This >> will confuse file-system mounter, thus we usually use persistent >> symbolic links provided by udev. However, dmesg and procfs outputs >> show device names instead of the symbolic link names. This causes >> a serious problem when managing multiple devices (e.g. on a >> large-scale storage), because usually, device errors are output >> with device names on dmesg. We also concern about some commands >> which output device names, as well as kernel messages. >> >> Solution: >> To assign a persistent device name, I create unnamed devices (not >> a block device, but an intermediate device. users cannot read/write >> this device). When scsi device driver finds a LU, the LU is registered >> as an unnamed device and inform to udev. After udev finds the unnamed >> device, udev assigns a persistent device name to a specific device >> according to udev rules and registers it as a block device. Hence, >> this is just a naming, not a renaming. >> >> Some users are satisfied with current udev solution. Therefore, my >> proposal is implemented as an option. >> >> If using this option, add the following kernel parameter. >> >> scsi_mod.persistent_name=1 >> >> Also, if you want to assign a device name with sda, add the >> following udev rules. >> >> SUBSYSTEM="scsi_unnamed", ATTR{disk_id}="xxx", PROGRAM="/bin/sh >> -c 'echo -n sda > /sys/%p/disk_name'" > > Also, where is the "real" program you have created to properly name > devices from userspace? You need that to properly test this patch, > right? > In the udev rule described above, notation “xxx” indicated by ATTR(disk_id) is scsi id given by disk. Then, when udev finds this rule, "/bin/sh -c 'echo -n sda> /sys/%p/disk_name'" indicated by PROGRAM is operated using xxx (scsi id) if udev find the disk with scic id xxx. Thus, persistent device name is assigned. I have tested this patch using the udev rule. and It works well. > thanks, > > greg k-h > Thanks, -- Nao NISHIJIMA Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., YOKOHAMA Research Laboratory Email： nao.nishijima.xt@hitachi.com