Re: [dm-devel] [RFC PATCH 0/3] sg3_utils: udev rules: restrict use of ambiguous device IDs

From: Douglas Gilbert <dgilbert@interlog.com>
To: mwilck@suse.com, Hannes Reinecke <hare@suse.de>
Cc: James Bottomley <jejb@linux.vnet.ibm.com>,
	linux-scsi@vger.kernel.org,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Franck Bui <fbui@suse.de>,
	dm-devel@redhat.com
Subject: Re: [dm-devel] [RFC PATCH 0/3] sg3_utils: udev rules: restrict use of ambiguous device IDs
Date: Mon, 27 Mar 2023 19:58:34 -0400	[thread overview]
Message-ID: <3f02a075-cc30-5584-704b-da88be1d6b31@interlog.com> (raw)
In-Reply-To: <20230327132459.29531-1-mwilck@suse.com>

On 2023-03-27 09:24, mwilck@suse.com wrote:
> From: Martin Wilck <mwilck@suse.com>
> 
> Most modern SCSI devices provide VPD page 83 with at least one highly
> reliable device identifier, like NAA Registered Extended or EUI-64, or
> the ata-id identifier. Other device identifier types have shown to be less
> reliable and possibly ambiguous. Ambiguity in particular is a problem with
> multipath-tools, which may group unrelated devices together in a multipath
> map, causing possible data corruption.
> 
> The device identifiers are used in two independent ways by the udev rules:
> a) to set ID_SERIAL for subsystems like multipath, and b) to create
> /dev/disk/by-id/scsi-... symlinks. Our udev rules have traditionally created
> symlinks for every device identifier obtained from either VPD 83 or 80. This
> may cause issues, especially on large installments with storage devices that
> exhibit the same identifier for many logical units. At the same time, these
> symlinks are rarely used.
> 
> Avoid using unreliable identifiers for setting ID_SERIAL, and don't create
> symlinks for these identifiers. Add a configuration method that allows
> users to easily re-enable these methods and symlinks if they need to
> (this might be the case on systems with legacy devices that are referenced
> in /etc/crypttab, lvm.conf, or the like). This is done by introducing
> environment variables .SCSI_ID_SERIAL_SRC and .SCSI_ID_SYMLINK_SRC, to
> control use of device identifiers for determining ID_SERIAL and for creating
> symlinks, respectively. Both variables can contain the letters "T", "L", "V",
> and "S" to enable T10-vendor ID, NAA local ID, vendor-specific ID, and VPD 80
> based ID, respectively.
> 
> Distributions can change the defaults for these environment variables
> to provide backward compatibility for their users, while offering users
> an easy way to change the settings.
> 
> I'm sending this as RFC, because I expect that not everyone will agree
> which identifiers should be enabled by default.

Lets see if anything happens. Applied as sg3_utils revision 1019 and
pushed to https://github.com/doug-gilbert/sg3_utils .

Didn't see any effect on an Ubuntu 22.10 when sg3_utils deb package
built and installed. No sign of 00-scsi-sg3_config.rules being placed
anywhere by Ubuntu. Does Suse install those rules?

Doug Gilbert

> Martin Wilck (3):
>    55-scsi-sg3_id.rules: don't set unreliable device ID by default
>    58-scsi-sg3_symlink.rules: don't create extra by-id symlinks by
>      default
>    udev: add 00-scsi-sg3_config.rules for user configuration
> 
>   Makefile.am                       |  1 +
>   scripts/00-scsi-sg3_config.rules  | 23 ++++++++++++++
>   scripts/55-scsi-sg3_id.rules      | 53 ++++++++++++++++++++++++++++---
>   scripts/58-scsi-sg3_symlink.rules | 46 +++++++++++++++++++++------
>   4 files changed, 109 insertions(+), 14 deletions(-)
>   create mode 100644 scripts/00-scsi-sg3_config.rules
> 

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