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Message-ID: <4E3278C9.7000703@hitachi.com>
Date: Fri, 29 Jul 2011 18:09:29 +0900
From: Nao Nishijima <nao.nishijima.xt@...achi.com>
To: JBottomley@...allels.com
Cc: Nao Nishijima <nao.nishijima.xt@...achi.com>,
linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
James.Bottomley@...senPartnership.com,
dle-develop@...ts.sourceforge.net,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
yrl.pp-manager.tt@...achi.com, axboe@...nel.dk
Subject: Re: [PATCH v2 0/3] Persistent device name using alias name
Hi James,
Could you review this patches?
Best regards,
(2011/07/22 19:59), Nao Nishijima wrote:
> Hi,
>
> This patch series provide an "alias name" of the disk into kernel messages.
> Users can assign a preferred name to an alias name of the device.
>
> A raw device name of a disk does not always point a same disk at each boot-up
> time. Therefore, users have to use persistent device names, which udev creates
> to always access the same disk. However, kernel messages still display the raw
> device names.
>
> My proposal is that users can use and see persistent device names which were
> assigned by they because users expect same name to point same disk anytime.
>
> Why need to modify kernel messages?
> - We can see mapping of device names and persistent device names in udev log.
> If those logs output to syslog, we can search persistent device name from
> device name, but it can cause a large amount of syslog output.
>
> - If we can use the persistent device names and can always see the same name on
> the kernel log, we don't need to pay additional cost for searching and picking
> a correct pair of device name and persistent device name from udev log.
>
> - Kernel messages are output to serial console when kenel crashes,
> it's so hard to convert device name to alias name.
>
>
> Of course, I am going to modify the commands using device name so that users
> can use alias names.
>
>
> How to use:
> 1. Build and install the kernel with this series, and reboot with the kernel.
>
> 2. Make a script of get alias_name
>
> [localhost]# vi /lib/udev/get_alias_name
> #!/bin/sh -e
> DEVNAME=`echo $1 | sed -e 's/[0-9]//g'`
> echo "ALIAS=`cat /sys/block/$DEVNAME/alias_name`"
> exit 0
>
> And you should set an execute bit,
> [localhost]# chmod +x /lib/udev/get_alias_name
>
> 3. Check disk's id
> Here is an example to get the serial id and the path of the device.
>
> [localhost]# udevadm info --query=property --path=/sys/block/sda \
> | grep ID_SERIAL=
> ID_SERIAL=0QEMU_QEMU_HARDDISK_drive-scsi0-0-1
>
> Some devices does not have the serial id. For such devices,
> you may use the device path.
>
> [localhost]# udevadm info --query=property --path=/sys/block/sr0 \
> | grep ID_PATH=
> ID_PATH=pci-0000:00:01.1-scsi-1:0:0:0
>
>
> 4. Write udev rules as follows
> (The user assigns "foo" to sda and "bar" to sr0)
> We use ENV{ID_SERIAL} or ENV{ID_PATH} (get by 3) to identify a disk.
> And to assign automatically an "alias name", we use ATTR key.
> If ENV{ALIAS} is empty, we use to get an "alias_name" by get_alias_name script.
>
> [localhost]# vi /etc/udev/rules.d/70-alias_name.rules
> SUBSYSTEM!="block", GOTO="end"
>
> # write alias name for sdX
> KERNEL=="sd*[!0-9]", ACTION=="add", ATTR{alias_name}="foo", \
> ENV{ID_SERIAL}=="0QEMU_QEMU_HARDDISK_drive-scsi0-0-1"
>
> # write alias name for srX
> KERNEL=="sr[0-9]", ACTION=="add", ATTR{alias_name}="bar", \
> ENV{ID_PATH}=="pci-0000:00:01.1-scsi-1:0:0:0"
>
> # make symlink
> ENV{DEVTYPE}=="disk", ENV{ALIAS}=="?*", SYMLINK+="disk/by-alias/$env{ALIAS}"
> ENV{DEVTYPE}=="partition", ENV{ALIAS}=="", \
> IMPORT{program}="/lib/udev/get_alias_name %k"
> ENV{DEVTYPE}=="partition", ENV{ALIAS}=="?*", \
> SYMLINK+="disk/by-alias/$env{ALIAS}%n"
>
> LABEL="end"
>
>
> 5. reboot
> After reboot, we can see alias name in kernel messages.
>
> [localhost]# ls -l /dev/disk/by-alias/
> total 0
> lrwxrwxrwx. 1 root root 9 Jul 1 21:21 bar -> ../../sr0
> lrwxrwxrwx. 1 root root 9 Jul 1 21:21 foo -> ../../sda
> lrwxrwxrwx. 1 root root 10 Jul 1 21:21 foo1 -> ../../sda1
>
> [localhost]# dmesg
> ...
> sd 2:0:0:0: [foo] sd_init_command: block=17382146, count=56
> sd 2:0:0:0: [foo] block=17382146
> sd 2:0:0:0: [foo] reading 56/56 512 byte blocks.
> sd 2:0:0:0: [foo] Send: 0xffff88007ab1a900
> ...
>
> Currently, the user must add the naming rule manually for new devices.
> In the future, it is appended automatically, as like NIC.
>
> Changes in v2:
> - Change alias_name string to pointer
> - Change alias_name writable to write at once
> - Drop procfs patch
>
> Best regards,
>
> ---
>
> Joe Perches (1):
> sd: modify printk for alias name
>
> Nao Nishijima (2):
> block: add a new attribute "alias name" in gendisk structure
> sd: [BUGFIX] Use sd_printk instead of printk
>
>
> Documentation/ABI/testing/sysfs-block | 15 ++++++
> block/genhd.c | 84 +++++++++++++++++++++++++++++++++
> drivers/scsi/scsi_lib.c | 26 ++++++++++
> drivers/scsi/sd.c | 30 +++++++++++-
> drivers/scsi/sd.h | 8 +--
> include/linux/genhd.h | 4 ++
> include/scsi/scsi_device.h | 8 +--
> 7 files changed, 162 insertions(+), 13 deletions(-)
>
>
> --
> Nao Nishijima (nao.nishijima.xt@...achi.com)
>
--
Nao NISHIJIMA
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., YOKOHAMA Research Laboratory
Email： nao.nishijima.xt@...achi.com
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