[PATCH 1/2] SCSI: Add a SCSI option for persistent device names in Kernel.
Nao Nishijima <nao.nishijima.xt <at> hitachi.com>
2011-04-05 12:49:46 GMT
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.
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.
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.